Idle Problem

[skofroth]

I have a 1991 NA that has been converted to a TT. I've had this car for about 10 years now,
it's been an on-again, off-again project for all that time. Now... it's on-again.

My most pressing issue is that I just can't get the car to idle.

So far:
Pulled the engine, did a rebuild, then converted it from NA to TT and all that that entails.
I have the Chrome ECU. Wish I could hook to a laptop for data logging,
but from what I understand, I would also need the $170 device from
Tactrix in order to do this (am I wrong?). I only put about 50 miles on it
when I did all this about 10 years ago. I have just tinkered with it from
time to time over the years, now I'm seriously trying to get it to run.

Did the vac reduction.

Researched and fully examined all relevant areas dealing with
TPS - Throttle position sensor
CAS - Seems good, no identifiable issue.
IAC - Cleaned, looks good, appears to be functioning correctly.
Vacuum leaks (where did those come from!)
Plugs (properly gapped) and plug wires just replaced.

Replaced valve stem seals last week. That was fun. Put in
a new fuel pump at the same time. All timing marks aligned
properly when I put it all back together with a new timing belt.

The car will run at this point as long as I keep the RPM's up and
over aprox. 1100 -- the car just refuses to idle. When goosing the
throttle, letting off of the gas triggers some backfiring, not much,
but I can hear it. Letting completely off of the gas results
in the car dying after a few seconds.

I have a basic OBDII reader, but it is not showing me anything definitive
as to a problem. I would very much like to hook a laptop with EvoScan
up to this thing, but the only way I can tell that this will work with the
Chrome ECU is by buying the $170 Tactrix adapter - and, as I'm sure
many of you can relate, I've reached a point where I'm tired of throwing
money at this car.

Could it simply be a timing issue? I've tried adjusting the crank angle
sensor. The result of this was a reduction in backfiring, but not complete
elimination. I just bought a timing light yesterday and will try it out
to see if that shows me anything I don't already know.

Is there any other way to get EvoScan functioning with the Chrome ECU
other than to buy that adapter?

Anyone else have such a nasty problem with just getting the car to idle?

Thanks in advance. Scott

[99 vr4]

That is the only way... tactrix cable.

Just one thought, did you unplug the MAF to see if that helps. A bad MAF will cause a variety of issues. Unplugging it puts the car in limp home mode with static fuel tables and ignores the air volume.

Also, you need to check the entire intake system for leaks. Pressure test your intercoolers if all else is ok. I have seen many an idle issue caused by a leaky air hose, usually the connection at the throttle body works loose under boost. Any air intake leak will cause it to run lean and not idle.

Sent from my SAMSUNG-SM-G920A using Tapatalk

[skofroth]

Thanks for the feedback. I'll be looking into that next.

[skofroth]

Turns out my biggest problem was lack of sufficient fuel pressure. Put in a new Spectra pump and the car is running very well. That being said, it is just one of many things I've done to get this car running right. I'm sure all steps mattered. Clean air filter, cleaned and calibrated throttle position sensor, set timing with CAS, replaced fuel filter, removed/cleaned/tested injectors, replaced plugs and wires, cleaned throttle, set the idle... That hits all the main points. Car is running quite well (for now).