My 2.0 86 Mighty Max is running really rough

My 86 mighty max it running really rough just finished engine swap and I'm trying to dial everything in but a place start looking on what could be making it run so rough. When its running the whole truck is shaking
Checked ignition it's good
Check compression 140 psi and up
I Check the vacuum lines there ok
The carb my need to be rebuilt or changed I have a new ca smog carb when I put it on it didn't do nothing for my truck but make it run the same but found it had a hole in a vacuum line when I pulled the motor
I'm also thinking it my be the catalytic converter cause the smell out the tail pipe is real strong and I can hear random puffs coming out the pipe

Catalytic converter could be a problem -- my 1986 2.6L California truck had two cats one in the exhaust manifold (completely blocked & now removed) and a 2nd cat in the exhaust pipe (it was ok clear) a PCV valve can cause crappy idle too...

Please read my 3 or 4 posts on this thread about engine running crappy: http://www.mightyram50.net/vbulletin...4796#post84796

Same with my truck it only has the cat in the exhaust pipe but I read the other post im the pcv valve its good, and the gas is only a couple months old but ill add some fresh gas and the timing I can't get it down cause its running rough I have to use the idle screw to keep it running and when I first start the truck up I have to give it gas so it can start or else it will just keep cranking

This timming is at 5 btdc

timing seems ok, the Haynes manual sats between 3-7 BTDC
http://www.mightyram50.net/d-50/Fact...-1983-1993.zip

When starting my (stock) 86 truck this works best:
COLD ENGINE~floor the accelerator pedal once & with foot off the pedal crank and start then pedal if needed (no matter what my truck has always had a history of rough running for a couple minutes when cold)
HOT ENGINE~floor the accelerator & keep it floored while cranking this works good for my truck

got spark at all the plugs?

Yes It's got spark I tested it by pulling the plug wires off and it started to misfire on each cylinder

did you check the timing with a timing light? im wondering if the timing is wandering when its running maybe.
when you set the timing do you put the icm into diagnosis/adjustment mode?

if thats all fine, is the engine visibly moving around? maybe bad or loose mounts?

During you engine swap, did you remove the distributor or timing belt? If so check that they’re correctly installed. Did you swap in a used or rebuilt engine?

I did check the timing with the light it was at 5° BTDC but I didn't put the ICM in diagnosis/adjustment mode I didn't know how but the mounts are fine I checked them before I put the engine in and it runs ok at higher Rpm like when the choke is on it just at lower rpm it runs rough but the carburetor is not at factory setting all the adjustment screw are messed with and the catalytic converter is good I tested the back pressure I'm think it might be a carb issue

read these threads
http://www.mightyram50.net/vbulletin...ing-on-my-4g64
http://www.mightyram50.net/vbulletin...ht=base+timing

Can my truck go into timing mode its a 86 also I didn't see nothing in the manual about setting my truck in timming mode

I did swap the head on this motor from a truck that been sitting for 5+ year but I cleaned it up before I put it on but the valves make alot of noise when it's running sound like all the lifters are making noise but this head has jet valve and I don't know if this could be part of the rough idle issue

Disconnect the vacuum hose form the distributor. BOOM! You're in "timing mode".

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Originally Posted by Fingers

Disconnect the vacuum hose form the distributor. BOOM! You're in "timing mode".

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Also take care to cap/plug that disconnected vacuum line at the carb side, so you won't have a vacuum leak complicating matters while you tune.

The term "timing mode" really applies more to the later injected trucks, which require shorting a specific connector to put the ECU into that mode for accurate adjustment of static timing.

Since you switched carburetors as stated in your first post and it made no difference, it may not be a carb issue (unless both were messed with). Check the cap and rotor for corrosion or cracks. Use an ohmmeter to check the ignition coil and spark plug wire resistance. It's more precise and reliable than a simple disconnect-a-wire test.
Also check EGR valve and again, the hose routing and connections for leaks. An EGR that doesn't close completely will cause rough idle. Same with a disconnected or miss-routed hose. You can use the propane method described in this blog, but do it outside to be safe:

Attachment 28293

The propane method is like the factory recommended procedure to adjust the carb mixture screw. Got a vacuum gauge or pump? It can also help diagnose vacuum leaks, valve issues and timing or carburetor setting faults as well as when adjusting the carb settings.

After A long time of think I finally realized the spark plug wires because I got them from amazon as a DIY spark plug kit but after I swapped the wires to the original one it run a long better but now that I got it run a little quieter I can hear some hissing coming from the left side where the battery is

Congratulations on your progress. Regarding the hissing, get a a one inch or so diameter hose or tube. With one end by your ear, move the other end near possible sources of the noise to isolate the sound.

Now that I got the timming where it need to be its running better with oem plug wire but it still running rough I check all the vacuum hoses with that hose trick but couldn't hear anything I did find a hose that you can hear hissing but I changed that hose with a brand new one and it still make noise but right now the rpm is around 1200 rpm if I try and lower the idle it just runs worse

have you checked the vacuum actuated equipment such as the EGR diaphragm, the vacuum advance module on the distributor? the vacuum actuator for the carb's secondary? these can all be checked to see if they hold vacuum, and if they don't that can be the leak you're looking for

The carb might be the problem because I messed with all the screws that you can adjust not knowing what they did still don't know what most of the do just know the mixture screw and the idle screw I'm thinking of finding somewhere that can rebuild the carb for me or try the new carb again

Andres483 keep chasing & you will find all the issues; it's probably more than just one thing...

These trucks are old the rubber is shot cracked and maybe leaking vacuum... Carburetor & distributor & fuel pump all have rubber diaphragms that most likely are cracked and full of holes... Make sure your battery passes a load test, it might be weak..? Get the timing adjusted at the proper RPM and have new non-ethanol gas new air filter(s) new fuel filter new or good PCV valve... Just keep tweaking and getting questions answered... Make sure all the bolts are tight for carburetor, exhaust manifold, intake manifold, my truck was missing 3 bolts...

Today, I took a Dremel tool with a small diameter sanding disk and polished the four posts inside the distributor cap and the rotor got polished too... Then I took electrical contact cleaner and shot blasts into the distributor followed by soft blasts of compressed air RESULT: dang truck is running amazing, no more miss & no more bog when pushing on the accelerator pedal...

Please share your progress :thumbup:

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Originally Posted by Mitsuzero

have you checked the vacuum actuated equipment such as the EGR diaphragm, the vacuum advance module on the distributor? the vacuum actuator for the carb's secondary? these can all be checked to see if they hold vacuum, and if they don't that can be the leak you're looking for

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The Egr valve under the carb is good it holds vacuum but the sub egr I think it want its called on the carb when I push the diaphragm up and put my finger on the vacuum hole it drops a little and then it hold but Got Damn the dis doesn't hold vacum

Here is a link to the 1987 distributor vacuum advance actuator that fit my 1986 truck and it might fit the distributor on the 2.0L engine as well... There is a Tel No. at the page bottom to contact Standard Parts Company & hopefully they can source the part...
https://www.standardbrand.com/en/ecatalog?partdetail=VC-268

That's what I found on my truck, the distributor vacuum advance diaphragm was not holding vacuum. You might have to buy a whole new distributor because I'm having a hell of a time finding a replacement vacuum advance

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Originally Posted by xboxrox

Here is a link to the 1987 distributor vacuum advance actuator that fit my 1986 truck and it might fit the distributor on the 2.0L engine as well... There is a Tel No. at the page bottom to contact Standard Parts Company & hopefully they can source the part...
https://www.standardbrand.com/en/ecatalog?partdetail=VC-268

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Thanks for the help but the vacuum advance on my truck it a little bit different the arm is curved on it but im going to try and rebuild it tomorrow and see what it does I took it apart already and it was so brittle

If you rebuild it could you let me know how you did it? I appear to be in the same boat as you, since we have the same issue with our distributors

CARBURATION TECHNOLOGY in Tacoma, WA Alan there will rebuild a vacuum actuator or give you advice via telephone ~ I was unable to login to his website perhaps because I am using a military connection as guest now ?

i was able to find the website, i'll give him a call

So after rebuilding the vacuum advance twice it still didn't want to hold vacuum so im just going to buy a remafactured distributor from my local parts store it's 160 and its a lifetime warranty in case it goes bad

Although hey didn't actually rebuild my vacuum advance, they were able to find an exact replacement for my 1986 2.0 g63b. my-classic-car-trader.com/distributor-vacuum-advance-rebuilding/. $99.00 plus shipping.

Alan at Carburetion Technology is the man that I would choose to rebuild the 2.0L vacuum advancer (during the covid shutdown he shared info over the phone to help me rebuild my Mikuni carb) his website link here: http://www.carbtech.us/service/


Good info guys thanks for posting I can't find a 2.0L vacuum advancer anywhere online 2.6L is available though ~ O'Reilly's has a $83.00 core charge for the old distributor IMHO it's almost worth just keeping it unless money is an issue ~ FWIW I cleaning my distributor cap contacts & rotor which made the engine run much better but it had 2 or 3 quick engine misfires at 65mph on the H3 freeway so luckily Napa Kailua had one cap & rotor on hand and the truck runs great now (lesson learned)
Hope you guys can get the parts you need & then post the source.
It might be worth a tel call to Standard Products to see if they can provide or source the 2.0L vacuum advancer.

Good Luck:thumbup:

I installed the new distributor and now it advances but when I had the truck idling I noticed the idle kind of fluctuates but when I tap the gas it runs smooth for a little bit and then it goes back to idling rough

How clean is the PCV valve ~ I think it only allows (crankcase gases) flow to the intake manifold & like a check valve no flow in the opposite direction ~ if you can locate an engine Trouble Shooting chart it will list the most likely cause of rough idle ~ don't be surprised if you end up having to learn A LOT and FIX a lot under that hood...

P.S. your truck is a 1986 Gen1 ?? Question, is the dome light inside the cab working & is the lens cover in good shape ?? If not then check out my thread in the Gen1 truck section ;^)

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Originally Posted by xboxrox

How clean is the PCV valve ~ I think it only allows (crankcase gases) flow to the intake manifold & like a check valve no flow in the opposite direction ~ if you can locate an engine Trouble Shooting chart it will list the most likely cause of rough idle ~ don't be surprised if you end up having to learn A LOT and FIX a lot under that hood...

P.S. your truck is a 1986 Gen1 ?? Question, is the dome light inside the cab working & is the lens cover in good shape ?? If not then check out my thread in the Gen1 truck section ;^)

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The pcv valve doesn't have no flow in the in the opposite direction but it does have flow going the other way but yeah I know this truck need some work but now I have time to actually work on it I just need help on what should be replaced and I know it going to take some time to fix everything

I installed the new carb I bought for my truck and to no surprise it runs the same. I am thinking the head is the problem now because I got it from a truck that was pretty much junk but thinking every thing would be ok if I just gave it a good clean but I didn't even check to see if the valve were closing properly and the engine that I got the head from had spun a main bearing and there was metal shaving in the oil pan so I think sending the head off to get rebuilt might be something I should do because when my truck is running the lifters are ticking like crazy there louder than the whole engine

Noisy lifters don’t necessarily mean the head needs work. More likely the lifters are gummed up or collapsed and just need cleaning. Try an engine flush or geezer101’s diesel flush method first. Or remove and clean them. You can also just replace them with new ones. Aftermarket ones are inexpensive. New or used, be sure to prime them with engine or diesel oil upon installation. After dealing with the lifters, then do a compression check. If it’s still 140+ as stated at the start of this thread, the head is probably fine.

Could the hydraulic lash adjusters need adjustment/cleaning I was looking at other threads and that might cause lifted noise too

Yes. They may need cleaning, but they have to be removed to inspect, test and clean. Since they're hydraulic, that can't be adjusted. Only the jet valves, which are mechanical, are adjustable. Once removed you should be able to compress the lifter slightly by hand. If there's no movement, clean or replace it. Also, look at the surface that contacts the valve stem. If it's pitted or worn unevenly, replace the lifters. You should be able to find a set of aftermarket lifters for $25 or less.

I think im getting the hydraulic lash adjusters and the jet valves confused there is a little bracket coming of the rocker and it has a nut and a spring on it is that a jet valve

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Originally Posted by Andres483

I think im getting the hydraulic lash adjusters and the jet valves confused there is a little bracket coming of the rocker and it has a nut and a spring on it is that a jet valve

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Yes, that's the jet valve with the small spring. Loosen the nut and turn the screw to manually adjust its clearance using a feeler gauge. The hydraulic lifter is recessed within the rocker arm end and it contacts the main intake valve. The lifter-main valve clearance cannot be manually adjusted. The hydraulic lifter automatically adjusts the clearance when functioning properly.
Here's what the lifter looks like:
https://www.amazon.com/Evergreen-LF5.../dp/B007P72X60
They're about 10-12mm in diameter and roughly 22mm long.

So after looking at the valve train the half of the hydraulic lash adjusters are stuck and the jet valves were off 3 were tight and 1 was loose but I want to know if it would be better to by new lash adjusters or try and clean the old ones

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Originally Posted by Andres483

So after looking at the valve train the half of the hydraulic lash adjusters are stuck and the jet valves were off 3 were tight and 1 was loose but I want to know if it would be better to by new lash adjusters or try and clean the old ones

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The answer depends on your budget, how much time you have and the condition of the old lifters. If the lifters have no obvious wear, cleaning is fine but takes time and effort. Buying new eliminates messing with the old ones, but is an expense. Whether you go with new or cleaned lifters, you'll need to remove the rocker arm assemblies. After loosening the cam caps, stretch cut off latex glove finger tips over the rocker ends to keep the lifters from falling out of the rockers and into the engine.

One thing, the lifters that feel stuck may be the good ones. Those you can easily compress aren’t filling with or retaining oil. So they will be the noisy ones.

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Originally Posted by FMS88

stretch cut-off latex glove finger tips over the rocker ends to keep the lifters from falling out of the rockers and into the engine.

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Note those should be nitrile latex gloves, the black/blue kind suitable for auto maintenance, chemicals, etc. Plain latex gloves (e.g. for medical use) will fall apart from exposure to oil.

The new HLA came in im going to install them this weekend I know I have to soak them in oil but is there anything else I should do before/after installing them

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Originally Posted by Andres483

The new HLA came in im going to install them this weekend I know I have to soak them in oil but is there anything else I should do before/after installing them

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Prime them to remove any air inside the lifters. Otherwise they’ll be very noisy until engine oil pressure forces out the air. When primed you shouldn’t be able to compress the lifter by hand.