doc

Recently, my '87 has been doing two different things than normal. 1) the engine is running lean at WOT, and 2) the tranny will not up-shift @ the usual RPM at WOT.

I know its running lean due to a wide band O2 sensor. At WOT, I see high 13s and low 14s, like 13.8 to 14.3... And the engine is hitting the rev limiter set in the Eprom chip.

Is there any connection between these two events?
What are the possible root causes of the WOT lean condition?
What are the possible root causes of the tranny not up-shifting at WOT?

It seems like the ECM is not going into Power Enrichment mode even though I have the pedal to the floor!!! I did a scan at WOT:
RPM,,BLM,FTC,eng load,,IPW,,MAF,,,,,,,,,,,,,,KR,Timing
4772, 128, 15,, 244,,,,,8.2msec,246 gm/sec,1*, 36.4*

EDIT: the TPS voltag is 4.41V, the Eprom for %TPS for WOT is 70% (what ever that means?)

RBob

iTrader: (1)

Odds are that the TPS voltage at WOT is too high and the ECM is ignoring it. This will prevent the ECM from going into PE mode along with creating a default TPS% value.

RBob.

doc

My TPS is saying 4.41V,,, I am assuming that thats above 70%,, that would put me in PE mode. RBob, I do not understand your reply. How can the TPS voltage be too high?

EDIT: I can set the idle TPS at 0.62V, I think that it came out to be 0.54V at idle after changing to the HSR.

2nd EDIT: I measured the TPS with key on, it read 0.54V. I changed it to 0.62V, then checked the full throotle TPS and its at 4.54V...

RBob

iTrader: (1)

There is something goofy in the way GM handles the TPS in the TPI '7165 ECMs. This has happened to others in the past. The ECM thinks that the TPS voltage is too high.

And in response ignores the TPS and stays out of PE mode. No code is set which makes it more difficult to diagnose. The first time I heard of this it was driving the guy nuts. It was here on the diy_prom board several years ago.

One thing you can try is to hook up the scanner, key-on, engine-off, then observe the TPS volts and percent as you slowly move the go pedal to the floor. Then watch that they track and don't do anything funny.

OTOH, it may be that the throttle isn't opening all the way and the 4.41V TPS value is too low for PE mode.

Also, check the log file for the commanded AFR. That will tell you whether the ECM is going into PE mode.

If would also be helpful to put the TPS% value into the ALDL data stream. In place of something equally useful (sarcasm alert) such as the EGR or CCP value.

RBob.

doc

Concerning the TPS% in the ALDL data stream: I am simply using an old Autoxray 240 that I have had for 12+ years. I am even still "burning" Eproms like I started out back in 1997 (or so). I still use a UV eraser. I think that it is time to upgrade. Time to join the 21'st century.

doc

I have checked the working of my TPS. It is now set at 0.62V closed throotle and slowly increases in voltrage, up to 4.54V... No skipping or jumping. I have no idea how the ECM would have a problem with too high voltage from the TPS and because of that, not go into PE mode.... I am totally stumped right now. Please help!!!!!!