Any Tips on Tune Up?

[DJWAMI]

Yesterday I purchased a 94 Mighty Max, with the 2.4L. It runs, drives, and stops. It appears to be either misfiring or just idling kind of rough. On a cold start it will die without a little bit of throttle input, but stays running once warmed up. While driving, everything is normal, but at idle I can tell something just isn’t right. Today I’ll be changing the spark plugs, wires, distributor, and ignition coil. Beyond that, I’ve seen some similar issues where people believed that either the O2 Sensor or the Coolant Temp sensors were the issue with their idle problems. Any inputs on that?

[charger_john]

Welcome to the ram 50 & mighty max club.
I’m not familiar with fuel injection, sorry, others might help. But I think you’re doing the right things to start. Are you really replacing the distributor? or just the cap & rotor?
If your problem persists after you do the above, the next thing I would do is take out the injectors and have them ultrasonic-cleaned. Dr. Injector in Federal Way is a good shop for that.

These are all necessary maintenance items anyway. If the problem still exists after that, then a bit more diagnostic knowledge would be needed . . . . .

Good luck ~ John in Kent, WA.

[85Ram50]

Go to member introductions thread and read the top sticky. That should cover most of what you need to know.

[geezer101]

Hi and welcome to mightyram. An EGR clean out has been known to help with rough running. Ignition coils break down after 10 years so replacing it will help restore engine efficiency. Sounds like you are going to service the ignition system so that will remove some possible issues. Also do a OBD-I code check on the ECU to see if there are any error codes lurking in it. Could be a bad O2 sensor as well We have a section on how to set the ECU into diagnostic/tune mode which will allow the ECU to accept a new tune once you've replaced the serviceable ignition components and adjust the timing.

[DJWAMI]

Thanks for the info guys! I made a new thread, as the problem has gotten worse.

Today I put on the new distributor, wires, and spark plugs, and now the engine will die while idling, hot or cold. Only runs if I keep the throttle on. I tried cleaning the EGR valve, which appears to have done nothing. Tomorrow I’m going to replace the O2 Sensor, and see if it makes any difference. I’ll also attempt to replace the ignition coil, although the stupid screws holding it in place may be seized up, it’s gonna soak in penetrating oil tonight but I’ll see how it goes tomorrow.

[geezer101]

It sounds like you haven't grounded the diagnostic/tune wire in the engine bay so the ECU will accept the new tune. Have you followed this? -

http://www.mightyram50.net/vbulletin...th-ECM-control

[finalfighter]

check your ecm before doing anything else! what your are describing sounds like blown caps.

[Can1991Ram]

check your ecm before doing anything else! what your are describing sounds like blown caps.

Mine did exactly that with blown caps.

It is AWFUL to pull the ECU but take you time and it will come out.

Open the ECU and look for cap that are bulged up or leaking. They can leak from the top OR bottom and wipe out the traces on the PCM.
If it have done they you can either have it repaired or you will need to replace it.

My truck has had AT LEAST 3 ECU failures due to caps. I installed the third ECU that was a repaired ECU and now it runs VERY well.

The caps will have an X on the top. look for those to open up (venting) or bulging.

My coil also failed. I replaced it.

I pulled the EGR and soaked it in carb cleaner. BIG difference.

I pulled seafoam into the engine through the vacuum hose on the back of the intake... it helped.

[DJWAMI]

Hey guys, so I got the timing adjusted after installing a new distributor, which was a pain in the ass (I don’t have a timing light). I DID ground the Timing Plug, so good there. It runs now, but not well. I suppose I’ll check on the ECU tomorrow, but beyond the ECU, what else could be causing the misfire? It’s definitely still misfiring.

I've replaced the entire ignition system minus the ignition coil (the screws are completely seized up and three of them stripped as I was trying to get them off).

I was going to replace the coolant temp sensor but they sent me the wrong one. I’m considering putting a new O2 sensor in, but there’s an exhaust leak as well so I don’t how much that would really do.

I cleaned out the EGR Valve, and swapped the TPS.

So I guess, beyond the ECU and ignition coil, would there be any other culprits for the misfire?

[geezer101]

If you are stuck without a timing light, you can try a dynamic tune (but then you need a tach meter to monitor the rpm's) Don't go throwing parts at it, you will be better off getting error codes from the ECU. Timing might still be off, then there's low compression, mis-gapped plugs, arcing in the distributor cap or the cap not sitting right. A bad temp sensor will cause a fuel delivery problem (stuck in open/closed loop) Combustion chambers might be carbon'd up as well.

[DJWAMI]

If you are stuck without a timing light, you can try a dynamic tune (but then you need a tach meter to monitor the rpm's) Don't go throwing parts at it, you will be better off getting error codes from the ECU. Timing might still be off, then there's low compression, mis-gapped plugs, arcing in the distributor cap or the cap not sitting right. A bad temp sensor will cause a fuel delivery problem (stuck in open/closed loop) Combustion chambers might be carbon'd up as well.

For the time being, buying a tach or a timing light isn’t an option. I’m fairly confident that the timing is okay now. As far as “throwing parts”, it’s got A LOT of miles on it, and based on the amount of seized bolts and the general condition, I’m going to assume it’s very unlikely that anything on this motor has ever been replaced, so a majority of what can be replaced is going to be.

I already have a new O2 Sensor so it’s going on whether it fixes the issue or not, though I doubt it will. I wanted to do the coolant temp sensor, but I’ll have to wait for the shop to order me a new one since they gave me the wrong one. I’ll also be doing the ignition coil, as soon as I can manage to get it off the bracket, as it’s completely seized on there and the screws have stripped.

I spent around 18 hours total between two days working on the timing, and it’s running as good as it possibly can all things considered, but the misfiring persists.

I appreciate the advice, but like I said, I’m looking at issues beyond timing now, since I would be very surprised if there weren’t any other glaring issues on this rust bucket

[finalfighter]

can you post a picture of your engine bay? if the ecm checks out fine than its most likely the maf sensor. your o2 and coolant sensors can be bad and it will still run fine. ive tested with my truck, actually makes more power. i recently replaced my reman maf after it failed with a generic ebay maf and im pretty impressed to say the least.

https://www.ebay.com/itm/METER-MAF-A...53.m2749.l2649

this is the one i purchased. you need to replace plate the holds the cones in with the one off your truck. i believe i had to file down 2 spots on the old plate to make it fit. took less than 5 minutes todo. ive also logged what the ecm was doing with my data logger and can say these mafs are suitable replacements. i bought a spare one two have on hand sense i have 2 trucks and cant fine parts in the yard that often anymore.


also, are your timing marks lined up as shown in these picks?








ill upload a pick of my plug wiring also in a little bit.

[SubGothius]

the screws are completely seized up and three of them stripped as I was trying to get them off

On that tangent, get some Free All penetrant (O'Reilly carries it lately) and a JIS* screwdriver or bit set. Hozan or Vessel brands are good and widely available online. I like my ball-grip Vessel with swappable bits, even came with Pozidriv bits that came in handy for assembling Ikea stuff.

Philips screws/drivers are designed to cam-out as a torque limiter for ease of assembly without stripping threads, but this can lead to stripped heads with repeated dis/reassembly.

JIS screw heads look similar but differ, being designed for a more secure fit between the screw head and driver bit; these often (but not always) have a dimple on the head, so that's a dead giveaway you've got a JIS screw, which is pretty much all of them on these trucks. A Philips driver bit engages these even more loosely than a proper Philips screw head, further contributing to head strip-out.

Nearly anything assembled outside the US will be using JIS or equivalent screws, so having the proper driver/bit will help enormously. Better yet, a JIS driver bit also works better on actual Philips screw heads, and a JIS screw head stripped by a Philips driver/bit may still be recoverable with a JIS driver bit.

*Technically superseded by DIN 5260-PH/ISO 8764-1, but outside the industry ppl still call them JIS anyway as they're nearly-enough identical, and only these newer successor standards are readily available anymore anyway.

[DJWAMI]

can you post a picture of your engine bay? if the ecm checks out fine than its most likely the maf sensor. your o2 and coolant sensors can be bad and it will still run fine. ive tested with my truck, actually makes more power. i recently replaced my reman maf after it failed with a generic ebay maf and im pretty impressed to say the least.

https://www.ebay.com/itm/METER-MAF-A...53.m2749.l2649

this is the one i purchased. you need to replace plate the holds the cones in with the one off your truck. i believe i had to file down 2 spots on the old plate to make it fit. took less than 5 minutes todo. ive also logged what the ecm was doing with my data logger and can say these mafs are suitable replacements. i bought a spare one two have on hand sense i have 2 trucks and cant fine parts in the yard that often anymore.


also, are your timing marks lined up as shown in these picks?








ill upload a pick of my plug wiring also in a little bit.

Thanks for the photos, yes my marks were all aligned and I managed to get the timing set yesterday, just have other issues to button up in the engine bay

[DJWAMI]

On that tangent, get some Free All penetrant (O'Reilly carries it lately) and a JIS* screwdriver or bit set. Hozan or Vessel brands are good and widely available online. I like my ball-grip Vessel with swappable bits, even came with Pozidriv bits that came in handy for assembling Ikea stuff.

Philips screws/drivers are designed to cam-out as a torque limiter for ease of assembly without stripping threads, but this can lead to stripped heads with repeated dis/reassembly.

JIS screw heads look similar but differ, being designed for a more secure fit between the screw head and driver bit; these often (but not always) have a dimple on the head, so that's a dead giveaway you've got a JIS screw, which is pretty much all of them on these trucks. A Philips driver bit engages these even more loosely than a proper Philips screw head, further contributing to head strip-out.

Nearly anything assembled outside the US will be using JIS or equivalent screws, so having the proper driver/bit will help enormously. Better yet, a JIS driver bit also works better on actual Philips screw heads, and a JIS screw head stripped by a Philips driver/bit may still be recoverable with a JIS driver bit.

*Technically superseded by DIN 5260-PH/ISO 8764-1, but outside the industry ppl still call them JIS anyway as they're nearly-enough identical, and only these newer successor standards are readily available anymore anyway.

Theyre stripped bad, I’ll be drilling them out today and replacing them