DanInOttawa

'92 f22a1, stock motor, 300k miles

History:

• Problem started with rough idle at cold start-up, would chug/stutter, would last briefly and go away once warm.
• Period of rough idle got progressively longer
• Then started bogging, hesitating, stuttering, kind of like a mis-fire, under load.

Current:

• No CELs ever thrown for this problem (CEL works, as it came on when running with EGR disconnected as diagnostic)
• Rough idle is worse the colder the engine or outside temps get
• Once car is warm, very little idle problem
• Bogging, stuttering, hesitation on acceleration is worse the colder the engine is
• Hesitation, stuttering is worse the greater the load (e.g. if I'm in 3th but should be in 2nd, it is worse the lower the rpms and the greater the strain)
• Almost all hesitation disappears around 2500rpm
• Car will stutter to 2500, and then will seem to 'catch', shoot forward and accelerate normally with no hesitation
• Occasional stutter/miss when cruising (e.g. 3000+ rpm), but infrequent in comparison to when under load
• Acceleration problem is not consistent in severity, almost always there to some degree, but sometimes much worse than others. Usually improves with increased operating temps
• Number 1 spark plug is darker than the others (looks a little cold/rich) the other three look great.

Things tried (not necessarily in this order):

• New NGK wires and plugs;
• New cap and rotor (generic aftermarket);
• JY coil;
• JY EGR valve;
• JY underhood fuse/relay panel (more for another issue);
• Smoke vacuum test (no leak detected);
• Compression test (all cyl good and consistent)
• Cleaning EGR passages while valve was off (not the right way by pulling plugs, just with TB cleaner while reving, they were done right about 125k ago);
• Cleaned TB with spray cleaner;
• Cleaned IACV;
• Adjusted FICV;
• Disconnected and blocked vacuum and electrical control for EGR, run w and w/out check engine w valve disconnected;
• Listened to injectors w screwdriver, seem to be ticking fine
• Multiple coolant bleeds;
• Mulitple ECU resets;

Would love opinion on a few of these thoughts that I've gathered by researching:

1. If it was the O2 sensor, would it not be ok at cold start-up due to being in open loop?
2. Since the problem is worse w cold, I've kinda ruled out EGR ports being clogged as the problem, could they be causing the problem even when cold even thought the system should only kick in when warm? Except if the valve is sticking open, which it seemed not to be on both the original and the one that I switched in (although this was a visual before plugging it in, is it possible that the EGR solenoid would fail forcing it open when operating?)
3. Have doubts about fuel pump delivery/filter being the issue, due to temp dependency
4. If it was something electrical (dizzy, ignitor, battery, ground), would it not be temp independent, or at least not be affected by the temps as much as what I'm seeing?
5. If it was ring related, wouldn't that have shown up on the compression test?
6. Kinda have my doubts about a blocked cat, but would warming it be enough to increase efficiency to the point where flow would improve? Why the 2500 rpm threshold if this was the case?
7. ECU?
8. Valve lash (was done about 100k ago, but maybe fell out of spec since then)?
9. any other thoughts on what it could be or opinions on the above or other ideas would be much appreciated!

DELuth

1. Disconnect the sensor and retry. Simple to eliminate.
2. EGR will not open in park. If you suspect it is not fully closing, loosen the two nuts and slide a business card under the valve to block the ports. Tighten the nuts and recheck.
3. Actually, a fuel problem seems likely. Possibly clogged injector screens or low fuel pressure.
4. Doesn't sound like ignition to me either since you are getting more of a bog or hesitation rather than a miss. I wouldn't rule it out though.
5. Yes. Your engine is probably fine.
6. Nope. A clogged cat will get worse as RPMs and temps increase.
7. Unlikely, but always a possibility.
8. Not the problem.
9. ECT sensor, IAT sensor, MAP sensor, BARO sensor (inside PCM), vacuum leak

A look at the data list would probably show the problem right away and eliminate most of those checks. That doesn't help you much since you probably don't have a scan tool.

DELuth

LOL, "data list"! I just saw the year! Ignore the last sentence!

holmesnmanny

OP, with the car completely and totally cooled down, take off the two prong connector that is located under the distributor and use a multimeter to test for ohms on the sensor that that connector came off of. I got one from Walmart for about $20 that is autoranging. It should read around 2000 to 2500 ohms or so. Write down your reading. Then completely warm the car up and let it idle. When the fans have cycled on twice, shut off the car and take another reading.

It should now read 180-250 ohms or so. Write down that reading and report back.

Like the previous guy said you can rule out the oxygen sensor by disconnecting it and running without it.

Even if the oxygen sensor is not the culprit you can still test it by finding a safe and quiet place to accelerate your car and punch it at wide open throttle while in 2nd gear for 5 seconds, then immediately brake to a halt. If it throws a code for it then it's bad. However, if it hasn't been replaced yet it would be wise to just replace it with a new Denso model. Don't by Bosch as they only make junk oxygen sensors.

oxygens sensors do get lazy for effectiveness while still not throwing codes.

jrepko18

My car has this same problem and i do know i have a vacuum leak

jrepko18

Just realized this post is 4 years old let me know if you fixed it and what it was please so i can get mine done