Rough idle - smooths out when I drive (going insane) Options

[97Supra]

I have never found a problem with an engine that I was unable to fix with some moderate thinking.. but with this 1.8L engine I have done the following:

Symptoms:

Car starts VERY FAST. Click vroom. Perfect. Idles 1200 or so to warm up, then drops to what appears to be factory setting around 750 or so. In park, or neutral the engine is vibrating but you don't feel it as bad. The moment you put it in a gear, R or D the entire car shakes to pieces. Touch the gas, and with a load the problem is magically gone until the next stop light... it never stalls. I just failed emissions for HC.. (unburned fuel... which made me think ignition system)


- plugs
- cap
- rotor
- wires
- coolant temp sensor
- egr check
- re-ground everything
- iac clean / check
- vacuum sensor check
- replace all vacuum lines
- checked for leaks anywhere
- set base timing to factory specs
- changed fluids
- changed motor mounts
- unplugged and plugged back in every sensor to no avail
- put on an entirely different distributor
- drained the gas tank and put in all new fuel

.. The only thing I can think of that I did not try is replacing the ignition coil in the distributor, it could be bad.. but the likely hood of both the old and newer distributors coils both being bad is probably slim... I'm going insane.

Now after messing with the TPS my idle wont go below 1,000 or so.. guess I put it back in the wrong position. Oh well, I'll figure that out later but is there anything I'm missing here? I've tried everything I searched google many times I can't even find anything else to check.

fuel pressure? Any ideas....

This post has been edited by 97Supra: Mar 1, 2011 - 7:05 PM

[97Supra]

I installed the new ERG today and that was a waste of $200 bucks... That didn't help anything. I then made a new negative battery cable, and grounded it in 2 places, that didn't help either.. the list is growing.

Getting back to the alternator theory, I grabbed my multi meter and at warm idle on the battery im reading way low around 12.4 or 12.5. off idle it's around 14.4 but it differs it's either one or the other all the time it fluctuates which is leading me to believe it's either faulty wiring to / from the alternator, or the alternator itself. If I wiggle the plug on the exhaust side of the alternator the car trys to stall.. it appears to be somewhat melted visually. I guess a good LOOKING alternator can still be a piece of junk.. perhaps

Anybody have any experience with such a thing? Is it going to be wiring, or the alternator? I'll try to figure it out tomorrow it's dark and cold.. till next time

This post has been edited by 97Supra: Mar 7, 2011 - 7:04 PM