Engine Load at Idle [Archive] - GrandAmGT.com Forum

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jack-pot
09-17-2009, 09:55 PM
Just scanned my 2000 Alero 3.4 today and the engine load at idle was 22% and the long term fuel trim was -19%. i know both of them are supose to be close to zero. just wondering if anyone has ran into that or know what might be wrong?
thanks

Malaclypse
09-18-2009, 06:25 PM
The Engine load parameter is pretty arbitrary. 22% sounds pretty normal.

The -19% fuel trim is a bit of an issue. You're running quite rich appearently.

AaronGTR
09-18-2009, 10:55 PM
There's always going to be some load on the engine. Even at idle with the trans disengaged it still has to turn all the accessories, flywheel, torque converter. The only thing I'd really be worried about is the -19% fuel trim. I'm assuming it was the long term? Might have a problem with the pressure regulator, or maybe a dirty/sticking fuel injector.

jack-pot
09-19-2009, 12:56 PM
Thanks yeah it is long term fuel trim. Ive checked the FPR and that was fine. havent pulled the injectors to see anything there. could a bad o2 senosr cause such a rich condition?
Also with the scan tool hooked up i noticed the map sensor pid for vacuum was only reading 9in of vacuum, thought that was crazy. tried a different map sensor but still the same 9in of vacuum. checked the vacuum port and its pulling 18in vacuum, can any other sensors cause the map to read wrong?

AaronGTR
09-19-2009, 06:20 PM
Thanks yeah it is long term fuel trim. Ive checked the FPR and that was fine. havent pulled the injectors to see anything there. could a bad o2 senosr cause such a rich condition?
Also with the scan tool hooked up i noticed the map sensor pid for vacuum was only reading 9in of vacuum, thought that was crazy. tried a different map sensor but still the same 9in of vacuum. checked the vacuum port and its pulling 18in vacuum, can any other sensors cause the map to read wrong?


Well, a bad O2 sensor can cause a rich or lean condition, but you wouldn't know it from scanning since the O2 sensor is what controls the fuel trims. You'd need a wideband O2 to compare it too.

What scanner are you using that shows in/Hg from the MAP sensor? It must convert the number for the pid because the MAP usually just sends the pcm a voltage signal that corresponds to a Kpa number in the pcm. My scanner will show either MAP voltage or Kpa, since most tables in the pcm that use the MAP are referenced in Kpa. 9 in/Hg does sound low, but about the only thing I can tell you is my boost/vac gauge usually reads 16 in/Hg when my MAP sensor is showing high 50's Kpa on my scanner at idle. I have a cam though so my vacuum is lower than normal. No idea what 9 in/Hg equals in Kpa, but if your MAP is reading that and you're getting a different reading with a vacuum gauge on the manifold I would def say there's a problem with the MAP. There shouldn't be anything else that would change the reading of the MAP. It is on a common vacuum line though. I forget what else is on that line (mine's been changed for so long)... you might want to try hooking the MAP with a vacuum line to the UIM all by itself?

jack-pot
09-20-2009, 08:30 PM
Im using a MAC scanner. Ive looked at data from other vehicle and they read the correct vacuum, cant figure out why mines incorrect, might have to check the wiring, maybe a bad wire?
thanks so far