PCM too hot?
06-12-2007, 02:18 PM
#1
PCM too hot? What is the normal PCM tempereture in a F-Body?
When it's too much?
Is there some kind of safety-mode at a certain temp-treshold?
My problem: when the engine bay is hot (long racing, traffic...) my fuel trims go negative by -10% or so.
I checked everything
but there's nothing that can be related to this situation.
Is it possible that the PCM is getting too warm and acts weird?
Thanks!!!
When it's too much?
Is there some kind of safety-mode at a certain temp-treshold?
My problem: when the engine bay is hot (long racing, traffic...) my fuel trims go negative by -10% or so.
I checked everything
but there's nothing that can be related to this situation.Is it possible that the PCM is getting too warm and acts weird?
Thanks!!!
06-12-2007, 02:26 PM
#2
TECH Addict
iTrader: (10)
Join Date: Jun 2004
Location: Commerce Twp, MI
Posts: 2,918
Likes: 0
Received 0 Likes
on
0 Posts
Hmmm...I usually have the opposite problem (things go lean with higher underhood temps). Regardless, intake and engine coolant temps have a good deal to do with fueling calculations. It's not the PCM acting up.
06-12-2007, 05:15 PM
#3
In my setup I can install the IAT before or after the blower.
Beforeit's "cold" (as stock), after it's pretty hot.
No matter where the IAT is it goes rich...
Coolant: the fan settings are changed so that the coolant remains around 200-210F.
I insulated the MAF thinking it was picking up heat... no results.
The MAP couldmake strange things. but at idle it stays there at 29 kpas, no matter if the fuel trims are ok or not.
What else depends on underhood temperature?
Both banks are the same
If I let the engine cool down for 10 - 15 min the fuel trims go back to normal values
Sooo... it's difficult not to think it's the PCM
Beforeit's "cold" (as stock), after it's pretty hot.
No matter where the IAT is it goes rich...
Coolant: the fan settings are changed so that the coolant remains around 200-210F.
I insulated the MAF thinking it was picking up heat... no results.
The MAP couldmake strange things. but at idle it stays there at 29 kpas, no matter if the fuel trims are ok or not.
What else depends on underhood temperature?
Both banks are the same
If I let the engine cool down for 10 - 15 min the fuel trims go back to normal values
Sooo... it's difficult not to think it's the PCM
06-14-2007, 09:00 PM
#6
FormerVendor
iTrader: (9)
Join Date: May 2003
Location: Jacksonville, Fl
Posts: 1,573
Likes: 0
Received 0 Likes
on
0 Posts
When this high under the hood temp, rich condition occurs what is your pcm commanding? Is it still in CL, 14.63? These pcms are designed to operate in hell hole type conditions.
06-15-2007, 01:18 AM
#7
Originally Posted by Doc
When this high under the hood temp, rich condition occurs what is your pcm commanding? Is it still in CL, 14.63? These pcms are designed to operate in hell hole type conditions.
Something happens that causes more fuel to be injected, at the same time the PCM take it back changing the fuel trims.
Like a mechanical cause. More fuel pressure, or something like that.
The lower the load, the bigger is the correction the PCM has to do: at idle maybe -10%, mid load -5%, max load almost no changes.
But the fuel pressure is still the same (I have a gauge).
What else can mechanically cause more fuel to be injected?
Is it possible that it's related to the purge canister? Fuel tank?
The purge canister is continuosly flushed with fresh air that goes in the intake manifold, but this amount of fuel vapours is soooo small...
Another thing could be the MAF: but it's in a cool place and has an insulation to avoid overheating
