Another Idling thread

[Forbie15]

A few days ago my rpms have been acting weird. My car shakes more than it used to when I'm sitting still, my exhaust smells off, and when I shift into neutral, my rpms drop faster than they used to. They drop to about 100 or so, and if the car doesn't stall out and die, it climbs slowly back up to around 900ish. It still run terrible when its cold, but worse when its at temp.I get no CEL, and the light isn't burnt out. I've replaced spark plugs and crankshaft sensor so far. When I was idling, I disconnected my MAP sensor/IAC and nothing changed. Is it an IAC problem? I've been suggested that it could be a fuel pump/o2 sensor problem as well.


About 10min before I noticed a difference on how my car ran, I got half a tank of gas from a station I've never been to before. Possible water contamination? I already filled my other half with super premium gas and added a half bottle of Heet and it helped a little.

Any ideas?

 

[Wicked95AWD]

Sounds like you already answered the question.. I would also suspect those symptoms after getting some watered-down fuel. It might be easier to diagnose the problem if your profile had a little more detail. You mentioned that you unplugged your MAP sensor, are you running a 5 bar sensor and using an AEM EMS or something? Also, did anything else change before the trouble started aside from getting fuel from an unfamilliar source?

 

[Forbie15]

Sounds like you already answered the question.. I would also suspect those symptoms after getting some watered-down fuel. It might be easier to diagnose the problem if your profile had a little more detail. You mentioned that you unplugged your MAP sensor, are you running a 5 bar sensor and using an AEM EMS or something? Also, did anything else change before the trouble started aside from getting fuel from an unfamilliar source?

What kind of details would help? I got headers and cool air intake installed about a year or so ago, don't know the brands though. Every other component is stock.

How do I tell if my MAP sensor is a 5 bar that uses AEM EMS?

 

[Wicked95AWD]

Sorry, I think I just made this overly complex. I think what you are saying is that you unplugged the wire that connects to your MAF or airflow sensor, or did you mean that you unplugged the ISC (idle speed control) sensor on the throttle body? Either way they should both be plugged in at all times if you want your car to run properly. I thought you might have been talking about an aftermarket 3/5 bar MAP sensor. Some people add them to the intake system as an upgrade when making more horsepower than the stock mass airflow sensor can meter. However, in order to properly utilize a map sensor you would need a piggyback or standalone fuel management system like AEM or DSMlink. Regardless, It sounds like bad fuel to me. If that is the case all you can do for now is add some octane booster and fuel system treatment and drive until you get all the suspect fuel out of the system. If the problem still persists with your next tank of gas I would suspect a clogged fuel filter.

 

[Forbie15]

Sorry, I think I just made this overly complex. I think what you are saying is that you unplugged the wire that connects to your MAF or airflow sensor, or did you mean that you unplugged the ISC (idle speed control) sensor on the throttle body? Either way they should both be plugged in at all times if you want your car to run properly. I thought you might have been talking about an aftermarket 3/5 bar MAP sensor. Some people add them to the intake system as an upgrade when making more horsepower than the stock mass airflow sensor can meter. However, in order to properly utilize a map sensor you would need a piggyback or standalone fuel management system like AEM or DSMlink. Regardless, It sounds like bad fuel to me. If that is the case all you can do for now is add some octane booster and fuel system treatment and drive until you get all the suspect fuel out of the system. If the problem still persists with your next tank of gas I would suspect a clogged fuel filter.

Right, they are plugged in, but when we were troubleshooting it, we unplugged them to see if we could notice any change. My brother said that it sounded normal for a few seconds then it went back to crap (pulling the ISC). Hopefully it's just bad fuel. This weekend if the problem still persists, we are gonna check cylinder compression and replace the fuel filter, and if needed, the IAC.

I didn't know where any of these things are before this week. Leave it to problems to give you a crash course on engine components.

 

[Forbie15]

Alright, we removed the bad fuel in the tank and replaced the fuel filter, but the problem still persists, does that mean the IAC is next?

Thanks