sudden loss of power/bogging/surging???

[bentley james]

hi all new to the site and have a major problem with my mitsi… So first a little info, I own a 1992 Mitsubishi mighty max/ 2.4L gas engine/ 5rspd manual tranny. so last night on my way home from 1.5 mile work as I was roughly traveling at a merry 60 mph I started climbing the hill on my way home from work and the first thing I noticed was my exhaust was what seemed to be twice as loud and a lot deeper than normal and I was losing power. now mind you the hill I speak of is more like an ant hill with an approx long gradual grade. I take it to and from work daily with absolute ease until now. once I got it home I let it idle to get a better listen and at idle it seems to studder almost like if you were to unplug a plug wire, the extra loudness of the exhaust was still there also. I did notice a stronger smell of fuel too. at first thought I thought I might have a plug wire come loose but they were all still securewly fastened.. just thought id get a little insight before running out to the parts store and panic buy aa bunch of needless stuff. should I start with plugs and wires or what should I start with. Im not a professional but I have had thius truck long enough to know most of the time its something small and simple you should check first.. any feedback is much appreciated.

[Giovanni89]

Welcome to the forum! I would start by pulling the plugs and just taking a look at them. Are they normal, are they all sooty and rich, is just one sooty and rich, is one extra clean... If you have a compression checker, it couldn't hurt to check while the plugs are out.

[SamuelRock]

I have had a plug die on me back when I was younger and did not know so much about mechanics. I took it to the dealer as the truck was less than 10 years old at the time they told me the computer was bad and it would cost just over 2k to repair it..

I was like no freaking way, one thing I was good at was electronics so I opened the computer up and looked for any issues and came up empty handed! I searched the local junk yards and located a replacement ECU and guess what, Same Shit! I was about to pull the motor and replace it when my buddy was like man lets just change the plugs and wires and see if it gets better, mind you the current set of plugs and wires was less than 6 months old. Well we did the plugs first and as soon as I hit the key you could tell that it was running better. I was so pissed at the dealer, I have never taken a vehicle back to a dealer since! That was 24 years ago the way I look at it is at least I don't have to pay my self to miss diagnose something, now days with the internet you can find information on how to fix any thing.

As Giovanni89 said Check your plugs, Even if they all look good replace them they are cheap.

If you drove through some deep water you may have gotten some of the electronics under the hood wet I have seen the trucks completely stall out when this happens.. Time will fix this you gota let it dry out..

Another thing I have seen is the fuel pressure regulator takes a shit and your not getting enough fuel pressure. A quick way to test this is to pinch off the return line and see if the performance returns. The return line is the one that has the spring clamps on it.. I will take a photo if there is enough light when I get home to show you what one the return is, if I cant get it tonight I will do it first thing in the morning..

Good luck hopefully you get her back on the up and up soon!!

[geezer101]

A leaking exhaust will cost you power. Seeming you've also noticed it got louder, the 2 may be connected. Check under the truck and have a look at the clamps and flange gasket etc.

[royster]

I wonder if it's a clogged catalytic converter? That would certainly cause these symptoms, though I wonder why it would come on suddenly?

[claych]

^^This.+1
O/P,
Simple Diag,
Install a vacuum/ pressure gauge on the TOP centerport of the throttle body.
Take reading at idle.(baseline)
Rev engine , reading should drop( from baseline) then increase .
No increase & steady drop = exh restriction --- catalyst, collapsed pipe, muffler baffle failure.

[bentley james]

I wonder if it's a clogged catalytic converter? That would certainly cause these symptoms, though I wonder why it would come on suddenly?


was completely out of nowhere, ran great on the way to work then on the way home it hit and by the time i was at the top of the hill i had went from 5th cruizing at 65 to 3rd struggling to maintain 40mph

[bentley james]

like i said before im mot a pro lol shade tree mechanic at best.. lol. can one of these guages be picked up at a CARQUEST or autozone if so i will pick one up as i get new plugs and wires

[bentley james]

it ran fine on the way to work that day and then on the way home as i started over the hill it began losing power and getting louder almost sounded like someon was trying to muffle it with their hand kinda sound.. anyway by the time I hit the other side of the hill I had went from cruising comfortably in 5th gear doinf 65 to 3rd struggling to maintain 40mph

[geezer101]

They're just the ordinary engine vacuum gauges you'd install as an accessory gauge in the cab. It actually wouldn't be a bad idea to have it permanently installed as it's a handy guide to maintaining economy and will give you a warning that something is up with the engine. A mechanical gauge is the easiest gadget to fit - only need to hook up the backlight to the dash circuit and run the thin vac hose through the firewall to the barb on the intake.

[bentley james]

only gauges I could find are boost/vac gauges

[geezer101]

If you suspect the exhaust - put your hand over the exit of the tail pipe and feel what the output pressure is like (actually try to block it off with your hand). If you kill the engine quickly, you're on the right track. I've only experienced a collapsed cat converter once and it was a PITA to diagnose.

[85Ram50]

To test the CAT if you have a point and shoot temp gauge warm up the truck and take the temp at the front and the back of the CAT. The temp at the back should be a lot higher than the front.

[claych]

^
A good thought, one caveat however, works well with severely restricted catalyst not so well with partial failures.
Also the reflective surfaces at the test points must be cleaned, or false readings will be obtained.
(I have seen as much as 325 degF variance by a thin film of dirt,pipe oxidation, etc)

bentley james,
HERE (http://www.mightyram50.net/vbulletin/showthread.php/4974-Using-Vacuum-Gauge-to-Diagnose-Engine-Problems) is a great link BradMph posted on vacuum gauge diag.
Download, unzip, click on gauge, all of the gauges are animated with explainations.

[xboxrox]

Hello James B,

Test your catalytic converter the easy way: https://www.youtube.com/watch?v=qJTmddbOxMk (3 psi MAX back pressure)

I have zero mechanical knowledge and can't fix anything without breaking it first; but try this:

Spark Plugs -- REMOVE & INSTALL ONLY ON A COLD ENGINE & USE PLENTY OF ANTI SEIZE ON THE THREADS (WHY..?)
Spark Plug Wires -- REMOVE & INSTALL ONLY WITH THE SPARK PLUG TOOL DESIGNED FOR THIS JOB (NAPA HAS...)

My truck likes 91 octane gas & fuel treatment to keep cleanliness in the fuel system & lubricate cylinders...

:thumbup:

[bentley james]

So a quick update... Changed the plugs. The back 3 looked fine, the first one was soaked dripping oil. Changed all 4 anyway. Started it up symptoms are still there and it smoked ALOT. It's always smoked a little on cold starts and a little more as the we ather gets colder. Using the smoke to my advantage I did find an exhaust leak where the header bolts to the down pipe of the exhaust. Haven't had a chance to fix that yet but this is what concern's me.. I tried reading the check engine codes with an analog multi meter and all it gave me was a steady sweep. Tried clearing codes and reading again and sane thing.

[geezer101]

There is something up with #1 piston and/or combustion chamber. This could mean bad rings, bore damage to #1 cylinder, a crack in the combustion chamber - or an easier fix like valve stem seals. Most Mitsu oil consumption issues revolve around bad valve stem seals. Compression check to tick the rings and bores off the list. Valve stem seals have a life of about 10 years before wear and tear or age takes them out. If the engine has been regularly serviced and had good quality oil and/or additives used every service, it can extend the life of the seals (and pretty much everything else...)

[Giovanni89]

x2 on the compression test. If #1 is low, the head is coming off.

[xboxrox]

Can valve stem oil seals be replaced without taking off the head..? <--- assuming the compression test is a PASS no need pull head, right? What a big job that would be, best of luck to you 'n your truck bentley james

:helpsos:

[royster]

Can valve stem oil seals be replaced without taking off the head..?

Absolutely. I've done it. You DO have to remove the valve train. There's a trick of taking out the spark plug, and moving the piston almost TDC...then you stuff rope into the cylinder. Once that's done, you crank the motor so that piston is snug up to the top. The rope holds the valves in place while you remove springs and keepers.

[geezer101]

That's one way. The other is similar to roysters' method but instead, use a threaded adapter to screw into the spark plug hole and pressurise the combustion chamber with a shop compressor. I actually watched a video this week where a guy on youtube went through his procedure on his Mighty Max (not the most articulate fella but he got down to the bones of it) -

https://www.youtube.com/watch?v=dIGq_9q0aGU

*WARNING - VOLUME IS SET TO EAR BLEEDING ON THE INTRO. He really needs to spend more time on editing and audio.

OR the magic rope trick...

https://www.youtube.com/watch?v=B8WTTfkyW8g

*Not a Mitsu engine but the process is similar.

2 guys, 2 different engines, 2 different techniques - no formal training or special skills. If they can do it, you got this :thumbup:

[claych]

Absolutely. I've done it. You DO have to remove the valve train. There's a trick of taking out the spark plug, and moving the piston almost TDC...then you stuff rope into the cylinder. Once that's done, you crank the motor so that piston is snug up to the top. The rope holds the valves in place while you remove springs and keepers.

^^^
Lol in my case I realized 5 'shop rags' could be 'stuffed' into an 18mm plug bore ( oil as the lubricant)

Humble Apologies Sir.

[claych]

royster ,
??? your health ???

[royster]

Doing okay :)