can't get above 70 MPH?

Ok guys I have a serious question to ask.

I did tune up of the truck and it runs and sounds a thousand times better than when i got it home for the first time.

But one thing that is bugging the hell out of me is, when i test drove the truck down an old abandoned road I couldn't get the truck to climb above 70 mph!

Now I admit that i don't drive above 65 as I am alergic to speeding tickets here in the south. But i would like to have the peace of mind knowing that if I ever needed to punch it, that I had the power to do so.

main question is, is this normal for the stock carb? Is there a hidden governor that I am missing?

will this change when I get the weber installed?

Any advice on what is causing this, or way of fixing this would help incredibly.

I still think you have a vacuum leak, maybe in the advance for the distributor? My two cents.

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Originally Posted by royster

I still think you have a vacuum leak, maybe in the advance for the distributor? My two cents.

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But I don't any hissing that is evident with a vacuum leak...

Would a vacuum leak cause the truck not to climb above 70 MPH? I've never heard of that happening before.

Do you know about the cigar smoke trick to detect vacuum leaks? With the engine off, you blow cigar smoke into the vacuum line, and watch for the smoke to seep out at the leaks.

Two things: if it is a minor leak, you won't hear it at idle. At high rpm (highway speed) it would be most pronounced and of course, you wouldn't hear it.

Inufficient vacuum could indeed cause the spark advance to not work properly and not allow higher RPMs. This is just a suggestion, Frank

Hmmm I guess I'll have to check that out.
I will post an update later on today.

Shift into 3rd... (couldn't help myself)

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Originally Posted by LSR Mike

Shift into 3rd... (couldn't help myself)

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:)

A Viagra joke in disguise. Good one, Mike. If your truck remains at 70 MPH for more than 4 hours, see your mechanic...

Frank, as you know, my parts truck is a G63B 2.0. I never attempted to get it running, but in dismantling it, I removed that black spaghetti-covered carborator. Lots of electronic parts on there, and the number of vacuum lines on it boggles the mind. Perhaps the new Weber will solve the problem...I don't know, I'm no expert. In fact, I'm not much more than one of your cyber friends hanging around the garage tossing out ideas.

Better than listening to crickets? I hope so :)

I by no means endorse Scotty Kilmer, but this particular video was useful for me...perhaps it will help you.

http://www.youtube.com/watch?v=zMok2y05jNE

Well I swapped out all the vacuum lines for new ones and its still doing it. I will be changing the cap and rotor button next. I will post results.

Have you checked to see if it's getting wide open throttle?
I know it's a dumb question but that is the first one I see. Put a broom stick / brick/ small child, on the pedal and then look down the carb. Then turn the linkage some more by hand. If it opens up more then you need to make an adjustment. You don't want the carb to keep the pedal off the floor. You want to have just a tiny bit of slack or you can bend the linkage with your foot. Thats why the end of the cable is on a slider mount by the carb. I guess I can make a video in the mechanics tips and trick section, since many You Tuber's like my electric choke adjustment explanation.

Camoit's suggestion sounds better, except the small child part: a small child is likely to crawl off the pedal and thus give a false reading.

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Originally Posted by camoit

Have you checked to see if it's getting wide open throttle?
I know it's a dumb question but that is the first one I see. Put a broom stick / brick/ small child, on the pedal and then look down the carb. Then turn the linkage some more by hand. If it opens up more then you need to make an adjustment. You don't want the carb to keep the pedal off the floor. You want to have just a tiny bit of slack or you can bend the linkage with your foot. Thats why the end of the cable is on a slider mount by the carb. I guess I can make a video in the mechanics tips and trick section, since many You Tuber's like my electric choke adjustment explanation.

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Ok I checked that out and there is just enough slack in the line so it is not taught. The last thing to check is the cap and rotor. It looks like the original factory one on the there so I will be swapping them out on my next day off and test driving once again .

So how may miles are on it?
What is the compression test come back on it?
I don't remember how fast mine would go. But then again 70 is pretty darn fast in a death trap. It's fun to take people for a ride in my truck now. Because they think it's hauling ass. Just because it's loud, vibrates, and smell like hot engine and burnt fuel. Then you jump in a new car and it's all quiet and you are insulated from the speed and danger of driving. No wonder people drive like shit. They should put a big mettle spike right in the center of the steering wheel. That would solve all them problems.
It could also have a coil going out. The higher the RPM the more demanding the spark is. It might be getting week after 30 years of service.

here is what I did so far since I drove this puppy home:

1. Oil change: used Delo 400, substituted one quart of that with Riselone. Added the ZDP addetive. used Purolator One premium filter (No shitty fram for me!)
2. Changed all 4 spark plugs, using NGK v-powers. Gapped them to spec at .040
3. Changed all plug wires one and a time as to not mess up the firing order.
4. Used Lucas fuel treatment with every fill up (I noticed MPG and HP gain after the second fill up!)

Here is the probelm check list so far.

1. No Vacuum leak
2. Throttle is not loos nor to tight.
3. I will be swapping the distributor cap and rotor on Monday (my Day off) and speed test again.

Oh and the mileage right now is at 118,556

DO you have the right vacuum line connected to distributor so it advances correctly. Almost sounds like your distributor might not be advancing correctly. A good test is to remove the vacuum line at carb for distributor and remove distributor cap and rotor. Suck onto the hose end that removed from carb and make sure you see movement in the distributor. The advance vacuum mechanism in the dizzy should turn a bit at a reasonable vacuum as you test it.
If you have the stock air cleaner also, make sure there is a vacuum line going to the heat riser flap on top of air cleaner housing and that the flap inside the air cleaner is fully closed after being warmed up.
I had one experience with a car not getting to top speed and that was a 74 Toyota land cruiser. Though probably not your issue at all, but it's problem was a lack of oil being pumped to the head and we had to run a separate oil line to the rod tube. Very doubtful this is what is going on with yours.

Camoit asked if your getting full throttle also, the cables may be fine but is it open carb flaps completely and is choke fully open as well when warmed up.

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Originally Posted by BradMph

DO you have the right vacuum line connected to distributor so it advances correctly. Almost sounds like your distributor might not be advancing correctly. A good test is to remove the vacuum line at carb for distributor and remove distributor cap and rotor. Suck onto the hose end that removed from carb and make sure you see movement in the distributor. The advance vacuum mechanism in the dizzy should turn a bit at a reasonable vacuum as you test it.
If you have the stock air cleaner also, make sure there is a vacuum line going to the heat riser flap on top of air cleaner housing and that the flap inside the air cleaner is fully closed after being warmed up.
I had one experience with a car not getting to top speed and that was a 74 Toyota land cruiser. Though probably not your issue at all, but it's problem was a lack of oil being pumped to the head and we had to run a separate oil line to the rod tube. Very doubtful this is what is going on with yours.

Camoit asked if your getting full throttle also, the cables may be fine but is it open carb flaps completely and is choke fully open as well when warmed up.

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Hmm I guess I'll check the stock cleaner housing for that. And yes all the vacuum lines are going to where they are supposed to go. Now if it turns out to be the air cleaner, will an after market open air cleaner with K&N filter fix that issue. if I also use replace that hose with a K&N breather cap?

try and drive it with out the air cleaner and see if it helps before you spend money on that.

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Originally Posted by camoit

Have you checked to see if it's getting wide open throttle?
I know it's a dumb question but that is the first one I see. Put a broom stick / brick/ small child, on the pedal and then look down the carb. Then turn the linkage some more by hand. If it opens up more then you need to make an adjustment. You don't want the carb to keep the pedal off the floor. You want to have just a tiny bit of slack or you can bend the linkage with your foot. Thats why the end of the cable is on a slider mount by the carb. I guess I can make a video in the mechanics tips and trick section, since many You Tuber's like my electric choke adjustment explanation.

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What he said ^

These trucks are not the most powerful (or thrifty on gas for that matter) What they do well is just keep on running- Energizer Bunny type running. They just keep on running with minimal fuss.

On the interstate 70-75MPH you have to keep your foot on the floor just about.

I remember many years ago I took in on the highway to see what it could do.

I think I just barely got it over 80 after 15 minutes of trying to push the gas pedal through the floor. Must have come up on a downslope.

26 years and 346,000 miles later it runs the exact same way.

What they give up in power they more than make up with in heart.

Can't kill 'em...

Ok I checked for wide open throttle and it is correct. i swapped out the cap and rotor, and while I was in that area I noticed the PCV was clogged so I swapped that too.

Still same issue. can't climb above 70 . I guess i'll just have to live with it till I swap out the carb for a weber...

other than that the truck runs better than ever, no popping or ruff idle. MPG is good and gets up to 45 mph in a snap.

I'm thinking the stock carb's secondary is the issue and I am not rebuilding this thing!

My G63b 84 model ram 50 hits 85-90 easily on a flat road LOL. Gotta love a mikuni that is not computer controlled. And of coarse mine only has 33,000 miles on it. I could'nt dream of a weber as I have california emissions.

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Originally Posted by Kaos731

Ok I checked for wide open throttle and it is correct. i swapped out the cap and rotor, and while I was in that area I noticed the PCV was clogged so I swapped that too.

Still same issue. can't climb above 70 . I guess i'll just have to live with it till I swap out the carb for a weber...

other than that the truck runs better than ever, no popping or ruff idle. MPG is good and gets up to 45 mph in a snap.

I'm thinking the stock carb's secondary is the issue and I am not rebuilding this thing!

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Wise choice.

Rebuilding a stock carb would be as useful as probing for toe jam.

IIRC I got mine up to 85 or so.

Top speed is higher in 4th as opposed to 5th. LOL

LOL 85?! The speedo goes all the way to 115! This is false advertising if you ask me.

My goal is to make the truck use the full scale on that speedo! Weber , Headers, and magna flow muff should help with that, or get close. (I hope)

oh and this is an automatic with overdrive, so it is a 4 speed.

My old 2.0 and 2.6 would hit 100 pretty easily. I think you have a problem somewhere.

I have the same thing happening only it takes me a short bit to get to even 45, just has no power. and I got up to 76-78 earlier today but any kind of hill at all and I was dropping to 4th in hopes of staying above 55.then hope for down slope to get back to the speed limit. im feeling a 4g63t swap will be a must when I get my fall school loan. ive had mine for 2 days and I admit I love the thing but my friends golf cart could yank me around the yard probably. maybe a locker and some 4.10 gearing would help us. honestly I see the weber as a waste, if we cant get up to speed in a reasonable time now a carb swap isn't going to do much if anything other than throttle response in itself. my .2

OH Shit wait I just thought of something..:idea1:
Since I have automatic this truck should have a torque converter if I am not mistaken.

Could the torque converter be going bad, to cause this issue?

It definitely has a torque converter. If it was going bad, it would sound like slipping and higher RPM's without power. Two cents.

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Originally Posted by ram50bam

I have the same thing happening only it takes me a short bit to get to even 45, just has no power. and I got up to 76-78 earlier today but any kind of hill at all and I was dropping to 4th in hopes of staying above 55.then hope for down slope to get back to the speed limit. im feeling a 4g63t swap will be a must when I get my fall school loan. ive had mine for 2 days and I admit I love the thing but my friends golf cart could yank me around the yard probably. maybe a locker and some 4.10 gearing would help us. honestly I see the weber as a waste, if we cant get up to speed in a reasonable time now a carb swap isn't going to do much if anything other than throttle response in itself. my .2

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It depends on what you're looking for in the truck, what you have to spend, and what the truck has on it according to the odometer. They aren't a waste on a high mileage truck that came with a carb originally ...in fact it is only a matter of time before the Weber is the only viable choice you have.

The original Mikuni has a plastic body/throttle bore-what happens is that the shaft that the throttle blades are affixed to wears at the plastic body (bakelite actually) that causes an internal vacuum leak that cannot be fixed by rebuilding. Not only that, but the Mikuni cannot be tuned with jetting changes. Once you get a Weber set up properly, it's 'set and forget'.

If you really want more power any number of MPFI 4s, V-6s and small V-8s will fit in that engine bay- 3000GT V-6, 3800 Series II Buick V-6 (one of the best choices for combined power and economy IMO)...all kinds of choices.

Yank the motor and swap in one from a junkyard if you really want more power. The thing would be scary fast with the right V-8 if you did it right. Bullet proof 283 Chevy that will turn 7000-7500? You talk about FUN LOL :grin:...I would do that to a rust free body if life circumstances permitted.

That said- the Weber was not a waste for me. It was a Godsend.

When the original Mikuni finally went on mine, the truck could not get out of it's own way on the interstate. Slow lane with 4-way flashers going...40-45 MPH top speed...

Pay your money and take you're choice.

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Originally Posted by royster

It definitely has a torque converter. If it was going bad, it would sound like slipping and higher RPM's without power. Two cents.

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Would that sound like a "Sputtering" when I hit 70 MPH? Cause that's what I here when I do...:think:

No, I would suspect sputtering to be caused by a distributor problem...that elusive vacuum leak. If the internal diaphram is leaking, your girlfriend can still get pregnant.

Oh wait: different diaphram.

While I hear testimonies of the carborated trucks being "gutless wonders", you should still be able to get some "oomphfff" out of your engine. It sure sounds like a timing problem somewhere.

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Originally Posted by royster

No, I would suspect sputtering to be caused by a distributor problem...that elusive vacuum leak. If the internal diaphram is leaking, your girlfriend can still get pregnant.

Oh wait: different diaphram.

While I hear testimonies of the carborated trucks being "gutless wonders", you should still be able to get some "oomphfff" out of your engine. It sure sounds like a timing problem somewhere.

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LOL Damn it I should just drive this friggin thing the 8 hours up to you so you can help me! LOL

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Originally Posted by Kaos731

Would that sound like a "Sputtering" when I hit 70 MPH? Cause that's what I here when I do...:think:

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Here is my .03 cents- take it for what it's worth. If you have an original carb, I think it has given up the ghost.

Mine had that 'sputtering' too. The truck acted like two spark plug wires were crossed once it got really hot under hood. The hotter the motor got, the worse it ran. Once it gets really hot out (looks like you're in GA) it's really going to run like shit. This is what happened to me back in July 2007 with 280,000 miles and the original carb and no motor changes whatsover.

It is difficult to diagnose drivability problems over the internet, but tell us more about the truck's configuration as it sits right now. Original carb? Fuel pump? Odometer mileage? Need to know more, but if you have the original carb, I truly feel you about to enter the 'Weber World'.

That's my .03 cents.

P.S. You may have a distributor problem, but that depends on if the truck has sat for years w/o running for example. Some of the original components on these trucks last forever. I still have the original distributor on mine with 346K.

Give us the complete back story on the truck.

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Originally Posted by originalowner

P.S. You may have a distributor problem, but that depends on if the truck has sat for years w/o running for example. Some of the original components on these trucks last forever. I still have the original distributor on mine with 346K.

Give us the complete back story on the truck.

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And also tell us what the emissions laws are in GA...

so the carb swap could give us back the power and acceleration and get my truck past 55 in a normal time frame? is there any way of knowing for sure the carb is the problem? is there a cheaper alternative than the weber? seems expensive. also, every time I push in my clutch it revs a lil higher for a few seconds before dropping?

I'd be prone to listen to originalowner, particularly since the Voice Of Experience speaks, there.

:)

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is there a cheaper alternative than the weber?

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From what I've read by the experienced guys here on the forum, "cheap" ends up being "costs twice as much" over the long term. Their experience begs those who will listen to do it right the first time.

My own build thread speaks of admitting I have to do it right, and completely, the first time. That's how enduring and satisfying results come about.


Otherwise you end up paying an arm and a leg in parts
Attachment 8704

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Originally Posted by originalowner

P.S. You may have a distributor problem, but that depends on if the truck has sat for years w/o running for example. Some of the original components on these trucks last forever. I still have the original distributor on mine with 346K.

Give us the complete back story on the truck.

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Ok here is the back story.

I bought this truck off the second owner. he got it from his boss.
The truck was used as a work vehicle on a construction site here in georgia by the fairgrounds.

The second owner used it as a daily driver he changed out the following:

- Fuel Pump and filter (Upon inspecyion by me today, he lied when he said it was an electric in the tank. The shop just swapped the busted mechanical one with a newer one behind the carb)
- replaced front shocks and four new cheapo tires from Tires plus here in Georgia (195/75/R14)
- It looks like the regular maintenance wasn't done in a timely manner.

Ok when I bought the truck and drove it home here is what I have done so far:

1. Oil change: used Delo 400, substituted one quart of that with Riselone. Added the ZDP addetive. used Purolator One premium filter (No shitty fram for me!)
2. Changed all 4 spark plugs, using NGK V-powers. Gapped them to spec at .040
3. Changed all plug wires one and a time as to not mess up the firing order.
4. Changed the distributor Cap and Button.
5. Changed the PCV Valve as the one in the truck seemed to be the ORIGINAL factory one and it was clogged pretty bad.
6. Used Lucas fuel treatment with every fill up (I noticed MPG and HP gain after the second fill up!)

Now to clear up something. The truck does NOT run bad in fact it runs and sounds One THOUSAND percent better than it did when I first got it home. I do not have hesitation when I hit the gas it responds pretty snappy, not Fuel injection snappy but snappy none the less.

My only concern is that it will not climb past 70 MPH with out a very long straight away, as it starts to sputter if I mash the gas to get it past 70 quickly.

There are NO knocks or pings. It has Wide open throttle. It has ZERO vacuum leaks. Only noise that I hear is the exhaust blow-bye because the exhaust manifold may be cracked or it might have a blown gasket either at the block or where it connects to exhaust pipe flange.

So does that make a clearer picture for you guys. LOL

Oh and fas as Emissions laws go in GA...

The county I live in (Dodge, ironic isn't it) has NONE so i can run the smoggiest set up in the world and the law can do nothing about it. LMAO

Have you changed the fuel filter? Just tossing it out there. It's up in front of the tank or on the frame behind the driver.

the answer to that question is my previous post.

The fuel filter and pump were swapped for new by PO.

and there are 2 fuel filters from what I saw. one by the tank, and a smaller one next to the carb above the new Mech pump.

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Originally Posted by Kaos731

and there are 2 fuel filters from what I saw. one by the tank, and a smaller one next to the carb above the new Mech pump.

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Hmmmm...too much filtering, maybe. Like a clogged filter, it's okay at idle, but under demand for flow, two filters restrict the amount going out. Unless one of those filters is a return to the tank, I'd look into eliminating one of those filters somehow. Try it and see what the results are: you can always put one back.

I'd like to see members post their opinions about which filter to remove: my vote is the small one near the pump.

is the Emergency Brake on? (again, I couldn't help myself:grin:)

Did I catch "none COMPUTER Mikumi"? I would suggest checking your base timing. Computers will mess with your head (and the timing), but if you do not HAVE a computer base timing is sort of important. That mechanical advance plate in the distributor only moves a few degrees on a good day; if the base timing is off by several degrees it can affect your high end a great deal!! Cheers!

PS; I have an '86 2.6 with the Mik "brain box" carburetor, and on the day I brought her home from down state I was being good (my philosophy is money is for fun, not traffic tickys). Imagine my surprise when I glanced down to check the instruments and found we were proceeding at 87 MPH!! Could not tell from the ride... even with the 14 inch tires. That is something on Pennsylvania roads. I soon installed a cruise control.

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Originally Posted by ram50bam

so the carb swap could give us back the power and acceleration and get my truck past 55 in a normal time frame? is there any way of knowing for sure the carb is the problem? is there a cheaper alternative than the weber? seems expensive. also, every time I push in my clutch it revs a lil higher for a few seconds before dropping?

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No.

A Weber DGEV, Carter P4010 electric pump, and Holley 12-804 fuel pressure regulator and the related miscellaneous parts for the install will set you back around $500 bucks MAX if you do it yourself. The only cheaper alternative is to ride the bus. :shrug:

If you do an install as described in the 2nd Gen fuel pump thread you will end up with 2.9psi of fuel pressure (just below the Weber recommended 3psi max) and plenty of flow.

Source the pump and regulator from StreetSideAuto.com and the carb from Pierce Manifolds or Redline Weber in Cali.

I am obsessed with doing things with a view towards cost effectiveness ONCE. That is just the way I am. The Facet electric pump? and 2nd Gen electric fuel pump install threads tell you everything you need to know on this topic.

Do it as outlined and you will be able to drive the truck w/o folks honking at you and flipping you the bird. Just remember, they have a car payment and insurance 10X more than you. ;]

Kaos- I tend to agree with Royster that the motor is starved for fuel due to "over-filtering". Source a factory filter from Mitsu, they are like 5.00 bucks- that's all the fuel filtering you need... That said, I still think you will end up having to get a new carb- probably sooner than later.

20 years of writing service for a dealership group with every make under the sun showed me dozens and dozens of times that people will ignore sound advice to do it a "better/cheaper way" and they invariably ended up spending more than they should in the long run and had multiple headaches to boot.

Believe it guys. I can't argue with what I have seen with my own eyes.

The more I read stories about these trucks the more I think that people do 'repairs' because they think that what they are doing is some kind of magic wand to transform the vehicle into something that it is not. Or give it more power that nothing short of a motor swap will do.

They are what they are. Won't pull a greasy string out of a cat's ass. Or a sick whore off a piss pot. Bwahahaha:

But even so- you should still be able to keep up with modern traffic.

Brings to mind the guys in the 50s who still drove Model T pick-ups because they were so cheap to drive and own and you do all the mechanical work on the vehicle with a set of tools that fit in a fishing tackle box.

Another two copper coins for you; have you pulled one or two of your new spark plugs to check their color? What did the old ones look like? Cheers.

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Originally Posted by Kaos731

and there are 2 fuel filters from what I saw. one by the tank, and a smaller one next to the carb above the new Mech pump.

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Ah ha.. A new filter by the carb. But does the one under the rear look new? We have seen that trick before because they could not find it so just add one in and say it's new.

Give it a compression check and see what it's doing in there.

How have you gone with diagnosing the power drop out at 70? Have you tested the secondary vac actuator on the carb? It's as simple as removing the vacuum hose to the actuator and applying some suction to it and holding it. If the actuator rod stays put, its good. If not, well, it's got a split in the diaphragm. Sometimes the vacuum leak isn't a huge split in the diaphragm but enough for the unit to lose vacuum over a few seconds of throttle. Replacing it doesn't require the carb being unbolted from the manifold - it should be dead easy to swap it for a good unit. Hope this is helpful.

& the "in tank" fuel filter accessible thru drain plug