Lumpy when cold
05-01-2019, 10:13 AM
#2
RL Community Team
Rennlist Member
Rennlist Member
Is your idle elevated when you first start it, like it's supposed to be, or is it idling at the same RPM it does when it's fully warmed up?
05-01-2019, 11:20 AM
#3
It idles at the same 800 rpm whether it's cold or hot it's certainly not noticeably elevated, what is likely to be the culprit that's causing this?
05-01-2019, 11:46 AM
#4
RL Community Team
Rennlist Member
Rennlist Member
In a 997 of the same vintage, the air temp sensor is integrated into the MAF. If the MAF fails, the air temp circuit in the MAF, or the ground wire to the MAF, it will exhibit this behavior. If it doesn't get the temperature info, it doesn't enrich the mixture for the cold start (think old school with a carburetor and the choke off), but once warmed up it runs fine.
The question is where does the Cayenne get the temp reading that determines the cold start protocol - could be from the MAF or maybe from a coolant temp sensor. Someone more familiar with the Cayenne will have to chime in on that part.
Do you have a tool where you can read what the car is seeing for intake air temp as that might also give you a clue.
The question is where does the Cayenne get the temp reading that determines the cold start protocol - could be from the MAF or maybe from a coolant temp sensor. Someone more familiar with the Cayenne will have to chime in on that part.
Do you have a tool where you can read what the car is seeing for intake air temp as that might also give you a clue.
05-01-2019, 12:05 PM
#5
In a 997 of the same vintage, the air temp sensor is integrated into the MAF. If the MAF fails, the air temp circuit in the MAF, or the ground wire to the MAF, it will exhibit this behavior. If it doesn't get the temperature info, it doesn't enrich the mixture for the cold start (think old school with a carburetor and the choke off), but once warmed up it runs fine.
The question is where does the Cayenne get the temp reading that determines the cold start protocol - could be from the MAF or maybe from a coolant temp sensor. Someone more familiar with the Cayenne will have to chime in on that part.
Do you have a tool where you can read what the car is seeing for intake air temp as that might also give you a clue.
The question is where does the Cayenne get the temp reading that determines the cold start protocol - could be from the MAF or maybe from a coolant temp sensor. Someone more familiar with the Cayenne will have to chime in on that part.
Do you have a tool where you can read what the car is seeing for intake air temp as that might also give you a clue.