First off, I have a 2001 C5 with 75k miles. It has been modified by East Coast Performance in NJ with their N/A cam package. It comes with a comes with a cam, performance springs,titanium retainers, ported throttle body, ported oil pump, 160 therm, double roller timing chain, etc, with a full dyno tune. It also has a Vara intake, AAR long tube headers (who makes these can't find info), and a full Borla exhaust. The car made 400 RWHP on a Dynopack dyno. Here is the issue now. I have the car for a week. It runs great and is a blast to drive, but coming up to stop signs it sometimes will go under 500 RPM but will then catch itself and get back up to ~1000 RPM range. It will also do this at start up some times. If I shut down, and restart, it fixes itself. I also noticed that the car smells rich sometimes. It hasn't been doing it consistently, but I would like to fix this before it becomes a problem.

Is this the initial signs of a MAF going bad? I tried pulling the wire from it and it did lower the RPM when off, and went back to normal when re-connected. My idle problem doesn't always happen so I am not sure this is the best test. Is there anything I could do to test it, or could this be something else? Thanks for all the help.

 

You should probably talk to them.

Is the check engine light coming on, or are you checking the codes to see the P0103?
The reason I ask is, tuners who tune in speed density mode purposely (within the tune) fail the MAF sensor, which puts it in SD mode, and doing so sets the P0103.


Since you have an 01, physically unplugging the MAF (even if it is purposely disabled) is not a good idea since your 5 wire MAF sensor also incorporates the IAT sensor, which is still a very vital input device to the PCM, even if the MAF is disabled.


Your description sounds like a classic case of poor tuning of a cammed car, not so much a component malfunction.

 

Y2Kvert4me,
Thanks for the reply. The check engine light is not coming on. I am guessing I will have to call ECS and find out what is going on. I thought it was weird that it would show the code, but not give me a check engine light or anything else. Thanks.

 

Pete,

This may seem overly simple, but was a new K&N style filter put on too? Or, was your existing one recently removed and cleaned? I've seen over oiled filters cause problems like this - basically the excess oil accumulates on either the MAF wires, or the ACT sensor and causes them to have readings that fall out of range, creating idle or driveability problems.

Again, its a simple thought, but it could be part of the problem. Just clean them with an electronics cleaner, or a MAF cleaner if you have some.

Kurt

 

I was actually thinking the same thing. I don't think I have anything that is MAF or electronics specific, though. I do have carb & choke cleaner (advance auto version) and I do have brake cleaner. Would either of these be ok? I don't want to screw anything up, but I didn't see anything like those at Advance when I was there yesterday. Thanks.

 

If it's an ECS tune, it's probably in speed density mode.

The MAF has been purposely failed within the tune, the MIL enabler has been turned off for MAF codes. This is why no check engine light, yet the P0103 is there when you check codes. (A P0103 would normally trigger the check engine light on).

Other than the IAT sensor, the MAF is only there for decoration right now, it is doing nothing. The PCM is determining incoming airmass solely by MAP and the VE table.
With enough work and logging, SD tunes can be perfected, but when they're not perfect, can be fussy, especially when climate changes. The MAF sensor is a very good compensator for baro and weather changes, and helps the car run more consistently no matter the weather.

SD tunes have their place and applications, but there really is no good reason NOT to run the MAF sensor on a typical h/c car. Tuners like to do it because it's less work for them, and customers think "speed density" sounds cool and exotic.


A custom tune on a heads/cam car is something rarely ever perfected on the first try. Might run 100% perfect when you leave the shop...but after 100 miles when fuel trims have settled in and some weather change, it might not seem as great.
Tuners know this, and most have no problem making minor changes later on to better dial the car in and eliminate the mannerism annoyances like what you are experiencing. Talk to ECS before attempting to fix a component that isn't even functional in the eyes of the PCM.