oldred95

I can't seem to nail down these wild AFR swings I keep having. It all seems to be temperature related. I can have the AFRs dead on at 14.7 and then the next day it will go all over the place. The MAT sensor does help but it seems to me like there needs to be a %correction vs Manifold temp table to adjust how much the MAT is able to correct based on the actual Manifold temp. The MAT/CTS Blend multiplier vs airflow table doesn't seem to do what I'm needing. The MAT is 100% in control of fuel correction. Before enabling with CTS fuel correction it was even worse. Like I said when I datalog and correct the fuel trims for a given day and temperature it works great at that temperature but when it gets hotter or colder (ambient temp) it wants to be either rich or lean, usually way lean. Any ideas? This is even using the MAF and I'm having all this trouble and I'm in open loop. Full open loop with it commanded to 14.7 across the board except at 90-100 KPA which is 13:1.

dimented24x7

iTrader: (2)

You might want to make sure that you are not running in speed density. If your error codes aren't enabled, the PCM can still go into speed density if there is trouble with the MAF sensor. With MAF, its virtually immune to air temp changes, so the IAT isnt used at all. The CTS is only used to control the desired AFR based on engine temp. The only time the IAT will be used is if its optioned, an the PCM is in speed density. In that situation, the PCM uses the IAT to generate a blended air temp term for the inverse air density lookups.

pandin

Running a stock 2000 325 LS1. The only indication that the MAF was bad, was when the battery died. After installing new battery the ECM had a hard time finding the right tune. It would stall on idle, took 5 min to straighten out.

Months later, engine running fine, and still no check engine anything, installed a new MAF (cheap Ebay) and no change at idle, so left old one in the truck. A month later installed new starter and after hooking the battery up, it did that same start and stall unless you held the gas.

Installed the new MAF/IAT and what a difference. Started and ran at idle on the first start. I even unhooked and rehooked the battery to be sure.

Easy idle on first start, just turn the key, no peddle.

oldred95

Are you referring to Error 17, MAF signal lost? If so it is checked. I'm almost positive its running off the MAF sensor.

18436572

This may not have anything to do with your problem but my car is a drag that I bracket race so consistancy is most important. I put a pot in place of the MAT sensor and mounted it in the dash. This gave me a fuel adjustment right on the dash plus it keeps the MAT at a consistant temp.

va454ss

iTrader: (1)

Have you tried closed loop?

oldred95

No. I imagine it would be able to adjust some to compensate for the lean condition but there shouldn't be a lean condition in the first place. I've checked my intake routing for leaks and can't find anything. Don't believe there are any vacuum leaks anywhere. I even tried my spare MAF sensor and it does the exact same thing.