Hello everyone, I'm happy to find a place with such a huge amount of knowledge.
I've been having a serious problem with my truck for a couple of months now. It's a stock 95 DX 2WD with the 2.4 liter 4 cylinder. I have 277k miles on it and although most of those miles are highway, I have to admit I've driven it hard for the ten years I've owned it. Up til now I've been able to fix everything myself. No mechanics.
Bear with me, there's a lot of history and clues here.
A couple months ago the truck began giving me issues. It wouldn't run higher than about 2k rpm, then it would get better on it's own after some time. I replaced the TPS sensor as I'd done once before but this time it didn't solve the problem. After being nearly useless on the road I took it to my local dealer for a diagnostic. The dealer adjusted the TPS sensor and told me it was driveable. I only made it a few blocks before I was unable to make it up a hill. I brought it back and demanded that they finish the diagnostic they began. After another 3 days in the shop they told me that the noise from the fuel injector rail telescoped down the fuel line and disrupted the knock sensor on the back of the engine, thereby retarding the timing incorrectly. The physical cause of this mixup I'm told, was the aftermarket fuel filter I put on 8 years ago. I told them to replace the filter if that was really the issue. They declined.
What they did do before they came up with the B.S. diagnosis was test the fuel pump and ignition system. Everything passed. I couldn't really argue, because it did run at about 90%. I no longer have any faith in my dealer.
A day or two later the problem came back fully and there are a few distinct symptoms:
1) Inconsistent idle. It will idle at normal rpm and drop sharply for a moment. Sometimes it's enough to kill the engine, but most of the time it bounces back. Usually it drops to about 250 rpm.
2) While driving at any speed, the engine will stutter hard for a moment then regain normal rpm. Similar to the idle issue.
3) Every three or four weeks I will have a major episode. I'll be driving and the power will fade fast. I can't keep speed, I can't get out of the way of traffic and I have to pull over. If I floor the pedal, I can move, but no other position will maintain speed.Strangely, the idle will be perfectly fine. Eventually, after minutes or hours the episode will pass and I can resume driving.
4) At no time in any circumstance or episode has the computer given a code. The light is not out, when I replaced the TPS sensor, I forgot to plug it in before starting and I immediately got a check engine light. The dealer reset it, and I haven't seen one since.
Now, what I've done:
1) Spark plug wires. No change. The old ones were only a couple years old.
2) New cap and rotor. Also unnecessary, but worth a try.
3) New ignitor. It ran smoother, but no change in symptoms.
4) Used distributor. Again, smoother, but no change in symptoms.
5) Used ECU. (I started to suspect that no codes must have meant that the code giving piece was bad) Runs better, but no change in symptom severity or frequency.
6) Two different fuel treatments, first Heet for possible water in fuel, then Lucas for injectors. Absolutely no difference. Filling the tank has no effect on the symptoms.
I don't know what to do anymore. I suspect that the problem is electronic based on the "feel" of the symptoms. Sharp, inconsistent/random cutouts from the engine. I've done my best to keep track of the conditions under which these symptoms occur. I can't find any commonality to them. Hot, cold, wet, dry, turns, bumps, hills, time, engine cold, engine warm, length of trip, loaded or unloaded. I believe that there may be more than one issue here, but I can't think of what they might be and why I haven't been able to solve at least one of them yet.
Has anyone else seen anything like this? My truck must have at least 75k more miles in it if I can just solve this crap. Thanks.