Just dynoed today and have a high A/F. Motor is stock with 141,000 and a few mods. SAE Torque=295.2 SAE HP=257.1 A/F 3200rpm 13.4 then has a sharp drop down to 12.0@3600 and then a steady fall to 10.2@5900rpm. Checked f/p regulator and no sighns of gas leaks at the vacuum line. Have not checked fuel pres to see if I have any fuel injectors leaking down. If anyone has had this problem please let me know.

Thanks, Mike

 

You could start with a clean MAF.

When were the O2's changed? They could be lazy and thus your BLM's to be off and cause you to be off at WOT.

I am sure there are many other suggestions from others.

Ben

 

Thanks Ben for the reply, I have cleaned the MAF and used sea foam. How long does it take for the pcm to go into open loop after the car is started? When I had it dynoed the guy would start the car and instantly run the dyno and shut the car off between dynos. If the car is still in closed loop when the dyno is run could that cause it to run that rich?

Thanks, Mike

 

hmm...

thats hella rich... i was running at 11.8 and 12.5 (jerking around)

car should go closed loop (run PCM tables dunno if its called open or closed) as soon as u go WOT... or you might need a little tune

i got my car tuned after the dyno from madwolf, i have to take it to the dyno place again, to see what i get for af

 

No!

The PCM operates in "closed loop" at part throttle/low-to-moderate loads. When you go to WOT, it enters "power enrichment" (PE) mode. Closed loop is still "enabled", but the PCM ignores the O2 sensor feedback. It uses the BLM's from Cell 15 if it was adding fuel, and sets a new "target" A/F ratio, based on rpm and coolant temp. In the stock programming, the target A/F ratio usually works out to around 11.7:1. So, 95Z28QFZ's results aren't necessarily so unusual. Going as rich as 10.2:1 would indicate a problem though, possibly with sensor input, or excessively inflated BLM's. A scan of the system under load would probably help identify the problem.

 

i've been owned

thank you very much

 

OK Cartman (from South Park).

Anyway, The last BLM in a particular cell would be used in PE even if it hasn't achieved closed loop yet. It takes my car at least 3 minutes when I am warmed up to close, BTW.

Just a note on BLM's, I found mine to be inaccurate throughout a particular cell (15) because we are using over 1/2 of the full usable MAF table from idle to WOT within 1 cell. The computer does not have much of a chance to compensate at the higher MAF readings because it never sees these in closed loop (non PE) mode.

Just something to think about. I calibrated mine before my dyno and I was off by 7% at the high end. After calibration, I was dead on my AFR.

GL to you.
Ben