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Re: engine miss and CEL (long) Posted by Ari [Email] ![]() ![]() In Reply to: engine miss and CEL (long), Roger Hyman, Tue, 27 Mar 2007 22:45:47 Members do not see ads below this line. - Help Keep This Site Online - Signup |
I'm inclined NOT to replace the O2 sensors. Those are likely symptoms, not causes. If the engine misses, you'll get a blast of raw fuel out the exhaust and that will throw the O2 sensors off for a little bit. And the O2 sensor doesn't control that much fuel flow.
Compression doesn't sound quite right, either, because it wouldn't explain an intermittent. But compression tests are quick and easy to do, so it couldn't hurt, in case there was a sticky valve or carbon buildup in one cylinder.
The threeplaces that come to mind for me are the MAP sensor, the CPS and the fuel pump/relay. Forced to guess, I'd go with CPS. I hate throwing parts at things, but the only effective troubleshooting of a CPS that I can think of would be to put an oscilloscope on the output and see if the waveform was flakey. That requires equipment and skill that a lot of shops don't have - they just swap out parts. The MAP sensor is next. Given that the fuel filter had some impact, given lots of time and money to troubleshoot, I'd do a fuel pressure and fuel flow test. But if the engine runs OK at high load/RPM, you've probably got decent flow and pressure.
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