OK, I've been chasing this gremlin for some time now and not sure what to do now. I've posted about this before and gotten some very useful information, but the problem persists. The short of it is that the car starts and runs fine until closed loop. The instant the computer goes closed loop the the injectors get cut back and the engine goes extremely lean for about a minute or two, and then clears up and runs fine. This is just part throttle crusing between 35-45 MPH. I've checked and replaced a bunch of stuff with no luck, so I'm back to thinking it may be programing again.

Anyway, I was wondering if someone could look at a Datamaster log for me and tell me what I'm missing.

For history, I've had the battery and Alternator checked, replaced the injectors and checked the fuel pressure, replaced O2 sensors, installed a Delteq ignition system, and even replaced the computer. Also, the computer is not showing any codes.

OH, and the mods are EM long tube headers Random Tech cats and Corsa cat back, AFR190 heads, LT4 Hot cam, and SLP intake.

Thanks
Kerry

 

You can send the datamaster log to me at: gbc93@adelphia.net

 

kerry you can send a copy to me as well:

tjwong@qwest.net

 

Just checking back in, I sent you guys an email. I haven't had any more time to look at it yet, maybe this weekend.

Anybody else wanna take a look?

Thanks
Kerry

 

I looked at your Datamaster file. I saw a couple of things. First, your TPS volts look low. I think they should be in the .50 to .60 range. Second, your LT BLM's indicate that your running really rich in most cells. You may want to verify that TPS volt spec and remove some fuel from your tune. Also if you have an aftermarket throttlebody without a bypass air hole you may need to add one to improve the BLM splits you have at idle.

 

I haven't received your file yet.

 

Thanks 93Blackrose,
The LT BLM's are rich, because I was trying to richen it up to make it stop going lean. Check out what happens just before and just after the computer goes to closed loop. Now that I think about it, maybe I'm making it worse by richening it. Maybe if I lean everything out it will try to richen when it goes to closed loop. Heck I'm willing to try anything at this point. Thoughts?
It is interesting about the TPS low voltage though. I have a Holley 52mm TB and when I first installed it the computer threw a code of TPS low voltage, so I ovaled the holes in the TPS so that I could adjust it and that took care of the code. I guess I can adjust it some more, do you think that will help?

Yeah, I know about the split BLM's, the TB is a piece of junk. I did drill the bypass hole and I adjusted the TB blades to closed them down. However, when I went to drive the car the TB blades would hang and not close all the way when I would let off the throttle, so it would idle at 1800 RPMs until I tapped the throttle and make them slam shut. I've torn the thing down at least a dozen times trying to fix that problem. It is actually opens and closes smooth as silk when the car is off, but start it up and put a vaccum behind the blades and sometimes they will close and sometimes they wont. So, my solution was to crack the blades open a little bit and live with split BLMs til I can get another TB.

tjwong, I must have mistyped your email address, I just sent you the file again.

Thanks guys
KH

 

Do you still have the stock throttlebody? If so, I would put it back on and see how things look from there. I have heard of so many people having problems with aftermarket throttlebodys. If you do not have a stock throttlebody, check ebay from time to time and pick up a used one.Then send it off to David Koldos dkoldos@ameritech.net and he will bore it out to 52mm and do a sealed roller bearing throttle shaft upgrade. David does excellent work and alot of people have had great success with his throttlebody conversions.

 

OK, I found my old TB and put it on. Same problem, only now it's slow.

Do you think maybe the O2 sensors are not coming online quick enough. They are fairly new from NAPA. Anybody had any problem with these?

 

Well, I think I finally fixed it. It turns out it was the O2 sensors! I went to the dealer and bought new GM sensors and it runs perfect now! I started buying stuff from NAPA because the stuff at Autozone was junk, Oh well. The sensors I got from NAPA are made by Bosch. They would probably work fine on a stock engine, but with a modded engine and programming they just don't seam to react quick enough.

Thanks guys for all your help.