misfire, idling & under load, but not decelerating

[quikveedb2]

my car has some hesitation & misfires taking place both at idle and under load. it is pretty consistent.

so far i've run seafoam both through the intake and in the gas, replaced the plugs last fall, and checked them again recently, they all look good and have good, normal color &are correct gaped. i pulled & cleaned the dizzy cap & rotor. the rotor was a bit dirty & very corroded but it's nice & shiny now, but noticably a bit worn as is the rotor. after all this i started the car and it ran the same but started a bit easier. i disconnected the 02 sensor & the car ran great for about a minute and a half, long enough for me to pull it out for a test drive, but within 100 feet the misfire returned, at first random, but then the further i went it became as consitent as ever.

now the misfire continues, but strangely the car seems to hit on all cylenders when decelerating/engine braking (weird). i'm thinking maybe something in the fuel delivery, i can hear the pump buzzing when the car is running, i'm sure the fuel filter needs replacement as it seems the PO did no maintenance whatsoever. also i've been getting code 1233 (wot switch) for a while, but haven't gotten around to adjusting the tps to see if i can eliminate the code. but the misfire is across the r3v range, not just under wot. thoughts? also, car dies with afm disconnected. i was thinking clogged injectors but as i mentioned the plugs were all colored well and the car got seafoamed. at the moment i'm stumped...any m20 gurus care to chime in?

[Devil Inc]

Possible coils leads?

[quikveedb2]

you mean the 2 wires that run to the coil? the ground wire insulation was rubbed off and frayed on 1 side when i checked it, and has been rewrapped. should i check the length of those for more wear spots?

[Devil Inc]

You might, not sure, I had something similar happen, car would start fine. Then upon starting to move it, it would misfire and die.

[quikveedb2]

no dying going on really, the car is drivable, starts fine, idles a bit low, but it's underpowered as though missing on 1 cylinder, and only under load and at idle. if i engine brake and then give it a little gas, it'll accereate as normal, but the miss returns almost as soon as the engine recieves accelerator input.

[Devil Inc]

I'd say get that fuel filter and tps, checked.

[quikveedb2]

iirc the tps is just basically a 2 position swtich, so i don't see why a misadjustment to the switch would cause the problem would occur anywhere between closed or wot position. could be wrong on that, though. fuel filter is a possibility i supppose, maybe it is causing enough restriction that the engine is not getting enought fuel across the board, but as i mentioned before the plugs looked like they were getting enough gas and are colored well, and the power loss is more of a misfire feeling that a general lack of power. i'm going to replace it regardless, it needs to be done.

[Devil Inc]

Just a general check of the connection, maybe.

[SpecM]

take off the VC and make sure all the rockers are intact.

compression test too, maybe?

[Finn]

Similar situation

I have similar situation (Unfortunately I haven't resolved it yet). I started the car and individually pulled the plug wires to see if I was getting a consistent spark. The cylinder which is suspect to be misfiring (used to miss only during idle, but now misses under any amount of throttle) had a weak and inconsistent spark. The plugs are relatively new and appear fine, the wires, cap and rotor are all new as well. Any ideas? I need to get the car back into daily use and but I only have a place to work on it during the weekends. I will pull the cap off again to see if it has any strange wear, but really am at a loss. Thanks!

[jlevie]

If you have one plug with a weak spark as compared to the others, you have a bad plug, bad distributor cap, bad ignition wires, or possibly a bad DME.

[Finn]

The issue is that the same miss occurred before and after the replacement of the cap, rotor and plugs. And was not resolved be the new ignition wires which were purchased later.

[thereisnoyun]

check your engine ground.

[Faviolosky]

it may sound weird, but a FPR can be bad and putting too much or too little fuel in.

[Finn]

it may sound weird, but a FPR can be bad and putting too much or too little fuel in.

I have swapped out the entire fuel rail, injectors and FPR from an engine which ran, but this did not solve the problem.

check your engine ground.

I'll have to try this.

I am beginning to wonder if the timing belt is stretching. I have no idea when is was replaced. I checked the compression, but the suspect cylinder wasn't that much lower than the others (although it was lower). I'll do a valve adjustment when I put in a new timing belt, as well.