Sunday, December 14, 2008

Car trouble

Running the support group at RTI, my ears peak for a debugging challenge. This time it is not about our Data Distribution Service or about a networking problem of an embedded system. My debugging challenge is about my 1998 Honda Civic EX (154K miles). 

The first sign of a problem showed up about three weeks ago. The check engine light came on as my wife stated the car in the morning. It started rough. The error code indicated a misfiring of cylinder 1. Once started and idling the car sounded and felt okay. Also when driving on the highway the car did not show any trouble. 

After a compression check, we did a major tune up (overdue) : oil change, new spark plugs, new spark plug wires, new distributor cap and rotor. All in all, all common electrical components were replaced. 

Two days later, the check engine light came on again. Again cylinder 1 was misfiring. My mechanic suggested to swap fuel injectors 1 and 2 to verify if the fuel injectors needed to be replaced. No change: still cylinder 1 was misfiring. 

A new distributor ruled out the distributor. The timing belt was changed around 90K miles. If the timing belt were the culprit one would expect to see all cylinders misfiring. (Unless the ocmputer saves only the first error code, and not those of all cylinders). 

My car has a VTEC engine. The valve timing is variable through a VTEC solenoid. This boosts the car power at lower and very high RPMs. My mechanic found a used VTEC solenoid to test. Again, no change: the check engine light came on at the first cold start. Low oil pressure could also affect the VTEC, but my mechanic believed this was not the case. 

I have since switched mechanics. My old  wasn't too interested in working on it. He kept me waiting a full day for a 10 minute job to swap the VTEC solenoid. He was horrible running calls, even to tell me the part was in. When you feel that he doing you a favor repairing your car, it is time to move on. 

One more data point: exhaust fume check shows clean burning. 

I am out of ideas. Anyone has a clue what might be going on? 

My new mechanic believed it could be a miniscule leak of the head gasket leaking coolant, or from a fuel injector. Either leak likely to be so small that it only shows up briefly at start up. He recommended not to worry about it and drive the car regardless. 


Kevin said...

The system can report multiple misfire codes. Misfires are detected by monitoring crankshaft speed.

I would suggest checking the injector wiring harness, especially for bent or retracted pins that might be intermittent, and check for cracked hoods that might admit moisture into the injector's wiring connectors.

Good luck.

Anonymous said...

It sounds like you need to call Car Talk on NPR .I bet if you call they will ask you about you name.