My 88 has been running rough as of late with low idle speed and hesitation. I decided to check the plugs I replaced about 7000 miles ago. Each one was ash white, I couldn't tell any difference between all 6, indicating a lean mixture. I checked for vacuum leaks couldn't locate any, then I hooked a vacuum gauge up at different locations and got 18 inches of vacuum. I am not sure if that is a good or bad reading.

After this, I decided to check the timing. I jumped the right connectors and hooked the light up and waited till it was warmed up completely. I found the timing mark was over 20 btdc, I estimated because it was off the scale. I adjusted the distributor to the proper 10 btdc and what a difference I could feel and hear. Strange that distributor bracket had scoring on the exact same place I had moved to get 10 btdc. Someone obviously didn't know what they were doing.

I took it out for test drive, I noticed improvement immediately and the pinging was way less (almost gone completely) and power was better thru out. Tomorrow I plan on checking compression and replacing all tune up components. I am a little concerned that from running hot,may valves may have damage. I hope the timing fixed the hot plugs.

I'm idling smooth at 800 RPMs but I have noticed that my timing mark moves about 2 mm advanced every few seconds, is this normal?

 

Seems that my vacuum is good but I found this, I will redo my vacuum gauge test using this information http://www.imperialclub.com/Repair/F...auge/index.htm

 

If your timing is jumping around, that's USUALLY an indicator of a worn distributor.

 

Thanks, I will see about the distributor after I get the ignition tuned up again. I found some arcing burns in the rotor cap. Also my vacuum gauge fluctuates 1"hg at the same time the timing jump. It's amazing how much a vacuum gauge can indicate engine health.

 

I'm coming to the conclusion my distributor or my timing belt is bad. I pulled the plugs they are worn to about .0050 I put them in at .0035, with just 7-9000 miles on them. At least they are even and look the same, white ash. I replaced the cap and rotor, after allowing it to warm up the timing is still jumping. Took the new cap off and white tracks from the spark on each contact. After all this I am back at square one, rough idle not as bad but I have a new clicking noise, which I think is from the distributor. I can rotate the distributor' signal rotor about 1-2mm, no vertical or side to side play. It seems that this play is making the timing mark jump and possibly the clicking noise. I think the new cap amplifies the clicking because it is more noticeable. I may also have a weak spark.

Does the distributor have a replaceable gear sprocket?

 

After reading some articles on th web, it seems that a little rotational play with the signal rotor is normal. It must be the timing belt, I believe it has never been replaced.

 

The trouble was a dirty intake from air cleaner to throttle plate, just sticky nasty goo. I cleaned all out and sprayed some MAF cleaner. still has a slight lope but almost completely gone. I should have looked there first.

 

Just want to add, the TPS had a weak spring so it was not returning all the way to the idle setting. I replaced it with a new one and now have no loping at idle.

 

Meaning...you did all this troubleshooting and diagnosing without even checking for DTCs first(or at any point?).

You would have had a code 51(minimally) telling you the TPS IDL circuit was an issue. And who knows what else?

BTW, I run my 3VZ-E with the ignition timing @ ~23° BTDC. Idles smoother than silk like that too. And the TPS was dirty/gummed up is a far more likely scenario than the spring becoming "weak". They can usually be cleaned internally to restore them to proper working order. That's what I did with mine, and it's still working perfectly after 24 years in service

 

Didn't notice a code at first because it flashed normal, only when I reved up to 1000+ did it give the 51 which is still there last I checked. My engine didn't run good that far advanced it runs great at 10-12 BTDC, this also cured all pinging. I wasn't able to get proper readings trying to adjust the TPS. It also had a dead spot at 3/4 throttle, maybe it just needed cleaned like you say but it sure seems a lot weaker than the new one. Anyway, I may not have trouble shooted the same as an expert mechanic, but my engine is running great with no hesitation, no more loping, the timing mark doesn't jump anymore and has noticeable increased power. I can accelerate uphill in 5th where it used to lose speed. I don't think I did too bad of a job.

 

sounds like a good self-diagnoses