CEL / TCS lights on, then off for a while, then on, etc.
 

Hi,

On my '01 Accord EX V6 Sedan in the past 13 months, the Check Engine and TCS lights have come on for a few driving cycles and turned off. Usually, the TCS light is the first to turn off and the CEL follows after a few cycles. No visits to Autozone for free Check Engine Light check.

When I consistently use BP gas in a certain part of Central MD, the CEL turns off after 1 or 2 cycles. When I use gas in a different part of Central MD, I can sense a difference in drivability (and gas mileage) before the lights flash on. I can use 7-11 gas and gas in PA (10% Ethanol) without issues.

The car drives perfectly fine, 27 MPG on hwy w/o AC and 23 MPG mixed driving with the AC on full blast. Just placed new Yokohoma Avid Envigors up front. Note, timing belt has never been changed - $800+ where I live.

Bad gas? Coincidence? Thanks.

SolEX01

Its hard to guess the problem.

Even if the CEL is turned off, I would get the codes read at an Autzone to get an idea of the problem.

Followup....
 

Followup:

On 8/10, I paid a visit to AutoZone who connected their scanning equipment to the car and found the following stored codes (CEL remains off):

P0401 - EGR Flow Insufficient
P0505 - Idle System Malfunction

The car runs perfect - quiet idle and 28 MPG on 2 recent tanks of gas.

Thanks in advance for any suggestions. :)

The P0401 is the code I would try to repair first, since that is more common. That is caused by a clogged egr port. Google 99-085.pdf. The second link from just answer shows the repair procedure.

Once you fix that the P0505 may go away.