My 2.0 86 Mighty Max is running really rough

[Andres483]

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

[xboxrox]

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

[Andres483]

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

[Andres483]

This timming is at 5 btdc

[Mitsuzero]

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

[xboxrox]

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

[tortron]

got spark at all the plugs?

[Andres483]

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

[tortron]

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?

[FMS88]

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?

[Andres483]

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

[tortron]

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

[Andres483]

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

[Andres483]

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

[Fingers]

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

[SubGothius]

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

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.

[FMS88]

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:

Propane Trick.docx

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.

[Andres483]

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

[FMS88]

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.

[Andres483]

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

[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

[Andres483]

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

[xboxrox]

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

[Andres483]

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 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

[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