What to do?
Change the 02 sensor...did that! Stays about 600-800Mv
Change the CTS...did that!
Reset the TPS...did that!
Change the MAP...did that!
It runs ok when it is cold but as soon as it goes into closed loop the BLM bottoms out at 108!
Oh yeah....no codes!
Anybody think of anything else?

 

Miswired hotwired cooling fan shorting out on the body?

 

Are the injectors stock? Is the car modified at all?

 

I have increased my injectors to 24#. Do I have to reprogram the prom or is there another way to get rid of running rich(besides NOS)?

 

Totally stock!

 

Have you verified the timing? Plugs/wires ok?


May want to verify that the prom is orignal.

 

Oh ya. I did put a new chip in that is said to have an aggresive fuel curve. That could be it.

 

My guess is it's something ignition related- on the side of the engine with the O2 sensor. The ECM is basically blind to the other side. Either a fouled plug, or bad wire, or a cracked cap, or incorrect ignition timing. One or more cylinders are not burning the fuel properly and the unburnt mixture is going right out the exhaust.

How does the car run? Does it hesitate, feel sluggish, or miss at any particular RPM/load?

My only frame of reference for BLM's bottoming out is when I had a corrupted EPROM- and the ECM did not flash a code on it either.

 

I would start with an injector leak down test. Install a fuel pressure guage. Clamp off the fuel return line. Pressurize the fuel rail (just turn the key on, no need to start the engine), your fuel pressure should peak, then drop to what ever your fuel pressure regulator is set at. If if is stock this will be about 45PSI. Your fuel pressure should hold for about 10 minutes with minimal leak down (5-10 PSI). If the fuel pressure drops rapidly, you have a leaking injector. Hense the rich condition.

 

can a spark plug be to loose? I only hand tightend them in since I can't get a wrench on them. I have seen though a method with some rubber hose stuck on the top of the plug.

 

Uh...forgot to mention did the timing thing.
Did the inj. leak thing.
Also did the vacuum test....steady! (18in.)
And also no miss, just sluggish.
I will change the ECM & Eprom next.
Hopefully I will find it there.
Thanks for the input.

 

Well, so much for that, changed the ECM & prom ...no help same thing!
And now someone else called me about another one ('92 GTA) with the same problem....Grrrr.

 

Don, what about your MAT sensor? Is it relocated?

The MAT greatly affects the calibration. I found on my car (I had relocated it), that I too was running BLMs in the 108s and the colder it got, the INTs got dangerously low.

This was about 3 years ago and one of the reasons I got into eprom burning.

I then "tuned" the engine to run "128/128" in closed loop and everything was fine. Then it got really cold one night and my BLMs dropped faster than the share price of a "Dot Com".

I then started to monitor it and found that as the temps increased that it caused the BLMs to rise. So I then hooked up the MAT in the plenum (I had left it there) and noticed that my BLM/INTs changed again. Worst, heat soak could cause problems AND if the ambient air temp was below around 40*F, the EGR wouldn't kick in and until the plenum "heated up" enough would run really rich.

Solution: For stock MAT locations - decrease the EGR enable temp. It does not correspond to any of the regular algorythms. I found this only be extensive testing that around 40*F caused it to disable and the stock MAT on a cold motor without a functioning EGR will run too cold for the MAT tables and run too rich.

Better solution - install a reloacted MAT and redo the MAT tables (as well as lower the EGR enable temp). The stock location with the tables are very difficult in my opinion to get a good consistent fuel range. A relocated MAT with modified MAT Tables works MUCH better and more consistent (on a naturally aspirated engine).

 

Glenn, how did you modify your MAT tables? What did you do to them? Ever since I relocated mine, I've dropped the inlet air temp by almost 100° and I'm trying to figure out how to take advantage of it.

 

Ruptured diaphram in the FPR? Pull the vacuum line and smell for gas.

 

I see you made a post on the DIY Prom Board and I've posted my MAT tables for you.

For any others looking to modify their MAT Table because of a relocated MAT, go here.

https://www.thirdgen.org/techbb2/sho...hreadid=173101

I will say that I found that once properly setup, my relocated MAT with the modified MAT Table works much better than the stock MAT sensor and table.

 

Ok boys, get your pad and pencil out and take notes on this one in case any of you run in to this again.
After exhausting every avenue searching for the clue I measured the ohms of each injector. Bingo...one on each bank had 3 ohms instead of 16. After disconnecting those two and adding a couple of used injectors to the wires ( to keep everything in balance) the BLM and the INT values came back to normal (127-130).
Running on six cylinders it actually ran smoother.
So.......I ordered a new set (not taking a chance on some going bad later) I will be installing them next week.
That's all for now....good lesson learned. (And a lot of time involved)
:lala: :lala: :lala:

 

Installed the injectors today ...GTA runs sweet again.
Thanks for all the input

 

sweet. Now jack it up like a mother and go kill some rustnags!