Swapped in two different computers today, and still the same running rich problem with the tip in and part throttle hesitation and stumble. >: I'm about fed up at this point.

Here's my thoughts: Car's running RICH, very rich. Stumble and hesitation at tip in and part throttle when quickly rolling to wide open, which I believe can be attributed to the over rich condition causing a misfire. If I smoothly rev it will barely do any stutter. If I tap it or stomp on it, that's when I get the stutter and hesitation. Only under relatively quick throttle movement.

PCM - Nope, tried 3 different ones, two known to be good.
EGR - Seems fine, diaphram easy to move. Would this cause a rich condition in the first place???
TPS - .92 at idle, 4.65 at WOT. Possibly going out?? Could a failing TPS cause the stumble at tip in and part throttle under quick movement due to the computer thinking it needs more fuel than necessary??
Opti - Nada. Put a new one on myself. Works fine, same problems as before.
Plugs - NKG TR55, brand new, look fine.
Wires - Taylor OVC kit. NOT Arcing, NOT burned. Only 1 1/2 years old with about 2000 miles.
Tune - Alvin (PCMFORLESS.COM)and I did about 6 chips so far, and the problem remains.
Fuel Injectors - Brand new SVO 30#. Don't know how to check those or I would.
Fuel Pressure - 42 PSI at IGN On and Idle. During stumble and stutter, goes up to about 46-50. After it breaks through the stumble, comes back down to about 38ish.
Fuel Pressure Regulator - Haven't checked, don't know what to do again.
Oxygen Sensors - Fine, checked on a scanner and datamaster.

Did I miss anything?? Any inputs? Sorry about the double post but I figure this information would be more useful.

 

how can the 02 sensors be fine with the car running rich?

 

Should I say O2 millivolts. The sensors were showing fine, and the problem is present in open loop also, ruling out the oxygen sensors since they're not picked up until the car is in closed loop.

 

what do the both upstream 02s read in closed loop?

and what do the BLM's read or LT fuel trims read at closed loop?

 

check the fuel regulator:
pull the vaccuum hose off and check for fuel leakage

check the air/fuel ratio with MAF sensor unplugged.

 

Lol, sorry guys, this is a 93 car. No MAF, No differentiating O2's. Just the old school non-heated O2's.

I'm going to pull the vaccuum hose off of the regulator tomorrow. Should fuel leak out of the regulator if it's bad???

 

yes

 

Well, just gave the old pressure regulator a check. Took off the vaccuum off the regulator, no fuel leakage. I did a double check of the fuel pressure.

Ignition on, car off: 43 PSI
Car running: 38 PSI

Didn't stutter on me amazingly enough. I'm kinda starting to lean towards the possibility of the O2 sensors, since on the 93's it doesn't take too much time at all to heat them up and kick the car into closed loop.

Sound like a possibility??

 

while engine running, what are the LT or BLMs reading on both banks after about 3 min. of idling??

 

I'll get back to ya tomorrow on that one. I'll hook up datamaster again and see what shows.

 

Ok, did a datamaster log.

On an interesting note, the car was FINE when it was first started and cold.
Once it started to warm up, less than a minute later basically, the symptoms
started to appear. The longer it ran the worse it got, until it was "normal
crappy ops."

Once it got into closed loop at about 350 seconds is when things get
interesting. The right STerm counts kept pushing all the way to 1 and
hovering around 1-10. Not right?? But why would this cause a problem in
open loop???

If anyone wants to see the log, let me know and I'll email it to you. Thanks for everyone's help!!!!

 

send it over here. lt1ramair97@yahoo.com

 

Sent, thanks!!!!

 

I had/have a similiar problem. Installed a new opti and new coil the car ran great w/out the problems described in your post. Then the new coil died and threw the old one back in Accel. Now I have the described problems you mentioned. At least in my case I know it's the coil and I noticed you've checked everything and no mention of that. Could that be your culprit as well? 93 also w/ LT's.

Hope you find your problem. No fun chasing bugs all the time.

 

Well, the coil is brand new. It was part of my Accel 300+. I do have an old MSD coil that's fine that I can swap in, but could that really be the problem???

Something else I've noticed in my searches is the ICM mod. Looking at things now, the car is FINE when it's first started and cold. After maybe a minute at most, it starts to have the problem. I'm wondering if I do the spacing out mod if that may take care of it???