Cactus_Sam

Ok, I'm rather puzzled on this one. I AM a bit of a newb, as in I have BASIC knowledge of internal combustion, change my own oil, and do as much of the regular maintenance as I can on my own. I HAVE recently downloaded the service manual for my truck as well, so hopefully that will help for repairs/replacements too.

Problem:
Several months ago I began to notice what I believe was a VERY intermittent misfire (as identified by a friend riding along with me). This RARELY happened, and as such was not much of a concern to me (bad?).

Anyways, about 2 weeks ago (+/-) while driving home from a 200 mile trip, in my last mile or so the intermittent misfire turned into misfires left and right.

This went on for a couple days where when I would start the car, it would make a good bit of noise, there was no power (acceleration was practically nonexistant), it was just terrible. Additionally, after the engine would warm up, if I let off the gas it would quickly drop down to between 450-500 rpm for a period of maybe 3-5 seconds, often times sputtering out after that. After making several concerned phone calls, I, based off of recommendation, replaced the spark plugs and ignition wires.

IMMEDIATELY the misfire problem was gone, for the most part the engine idle seems to be back to normal, and the engine no longer dies at idle after warm up. HOWEVER, there is virtually NO power!

When I pulled the old spark plugs (I was using Pulstar "pulse plugs" that I bought a year or two ago, which probably have MAYBE 30,000 miles on them and I'm sure that's a generous over-estimation), which seemed to have what looks like a rusty-ish deposit on the arms, I noticed that one of them basically just fell apart in my hand into two pieces. I figured it was the culprit.

What seems odd though, is that if it was just the spark plugs, I can't imagine that two different spark plugs could have THIS drastic of an effect!

Also, I'm about half-way through the gas tank as the gas gauge reads right now, and I'm only at like 100 miles, which is god awful compared to the 150+ miles that it's usually at when it reaches the 1/2 way mark.

Attached are pictures of the spark plugs in case that helps with the diagnosis.

Other potentially pertinent information:
-recently replaced the left side tie-rod end, alignment seems to be correct as it does not wobble or pull any particular direction and the car doesn't rapidly slow down when I let off the gas.
-I put some fuel injector cleaner in this tank to try to wash out any muck that may have built up while there was apparently no spark getting to the cylinder that was not firing (3rd injector)

TNRabbit

FIRST: Read the sticky at the top of this section of the forum titled "Official 86-95 FAQ READ FIRST!"

1. Most common reason for low power is the pigtail that runs under the intake manifold from the Knock Sensor to the wiring harness. A break in it will render the timing to 0 degrees & power will DISAPPEAR.

2. Terrible mileage can usually be traced to an O2 sensor that needs replaced, but can be many other things as well. Miles of vacuum hose getting older & more brittle makes for a lot of possible vacuum leak potential.

3. Distributors wear out. Another possible reason for ignition problems & general bad power/fuel economy.

4. Ensuring GOOD connections on all the major power cables & GROUNDS is important to an engine that runs off an ECU. Check all sensor connections & specs as well.

Those will get you well on your way to finding your issues. There is literally NOTHING that hasn't been discovered & written about in the annals of this forum! Good luck!



...that would do it~

Cactus_Sam

I brought a coworker out into the parking lot this morning and he mentioned that it sounded like it's still misfiring. I would believe that the problems could be the result of only running on 3 cylinders, but any opinions are still much appreciated. I'll keep this updated as I think of more to add or get any more information from any techs/service centers that I talk to.

fierohink

If you had a total deadmiss in the cylinder with the broken plug it's possible that you washed the cylinder walls of oil and now have incomplete combustion, even though the plug problem has been resolved. Pull the plug from the cylinder that had he broken one and see if it is all coated in raw gas or if it looks normal. Raw gas = problem to fix, no gas = good.

Also did you possibly cross a plug wire? That would cause a miss.

Do you have a CEL on? If so, the computer can tell you codes that will narrow down your problems.

Aside from havig no power, how does the ruck run othrwise? Will it rev up easily? Does it have a smooth idle? Does the exhaust smell normal or does it smell a lot like gas or rotten eggs or sweet?

You could have a totally unrelated problem to the spark plugs like a clogged fuel filter.

More info for us allows us to help you better

Cactus_Sam

I will check on this and get back to you Pretty sure that I didn't cross them up, I was careful to try to replace one at a time, though I will double check to be sure Don't have one, though I'll try to get into a service bay and see what comes out Seems to run fine otherwise. Don't notice any staggering differences as fare as revving up. Haven't sniff tested the exhaust, though I'll be sure to report back on that as well.

Also, after some more thought, any likelihood that it could be a flat cam?

fierohink

If you hve the 4cyl, then your valve train is all mechanical i.e. no hydraulic lifters to collapse if they aren't getting enough oil pressure. So if it was a cam issue, you would have crappy performance all the time, imagine having a flat tire... bad all the time.

Cactus_Sam

See attached picture. Do you mean these pigtails? They were the only ones that I could find under the intake manifold. From what I could see, they looked to be in fine shape, couldn't see any cracks or kinks of any kind.I'll check out the distro soon, and have the ignition coil inspected as well. Otherwise, I couldn't see any cracks or anything in any of the vacuum hose that I could see (not that there ISN'T one that's bad somewhere), and as far as I can see, all cables and grounds look secure.

Pulled the #3 plug, it looked ever-so-slightly damp, but was not covered or dripping with fuel in any way. I pulled the #2 spark plug to compare, it looked exactly the same. Double checked all the wires and cross referenced with a circuit diagram in the service manual, all looks like it's where it's supposed to be. sometimes now it will drop back down to around the 500 rpm mark when idling, though after a rev or driving even a block it will go back to idling around 950 rpm.

Also, exhaust smells normal, no weird smell like gas, rotten eggs, sweet tinge.

TNRabbit

You CANNOT "look" at a connection & tell it is secure. Oxidation under the nut, etc. can interfere with the connection. you need to remove the three major grounds (batt to body, body to frame, frame to engine) then clean thoroughly with a connection enhancer such as DeOxit, then tighten back down securely.

Use a propane or MAPP gas torch (UNLIT!!) & pass it around all the hoses (including the two that go to the front diff) & listen for idle uo to indicate a leak.

Red Wheeler

Brake cleaner or carb cleaner works just as good if you dont have a torch handy.

Cactus_Sam

So, after running the propane around, the engine idle would jump up suddenly?

fierohink

Then you have either a vacuum leak or an intake leak that allowed the propane in to the motor. Do the test again very slowly and pay particular attention to when the idle jumps. This should narrow down where you need to focus your attention.

TNRabbit

I wouldn't say "suddenly"....it's a subtle increase in rpm....like a 200 rpm or so.

Cactus_Sam

Well, as it turns out, it was none of the above. Took it into a mechanic this morning to have it looked at. The timing chain jumped a tooth, and the plastic guides for the chain are essentially nonexistent now, which, I'm told, will continue to jump teeth if I don't get it taken care of.

He's quoting me $950 for the fix.

Thoughts?