DFBonnett Posted November 12, 2004 Report Share Posted November 12, 2004 I'vee been chasing a misfire at idle in my '93 Eldo 4.9 for some time. It is progressively worse as the engine reaches higher operating temperatures such as in traffic in warm weather. It is also progressively more noticeable as more load is put on the engine such as putting it in gear or turning on the A/C. Plugs, wires, cap rotor, coil, injectors, FPR, pump pressure, etc all check out OK. THose parts have all been replaced or tested according to the FSM. No codes. Can an ignition module begin to fail slowly producing these kind of symptoms? I know they can have intermittent failure due to heat and produce a no start condition. I'm out of ideas and would rather not wait for a precipitous failure to fix this. Any guidance would be most appreciated. Link to comment Share on other sites More sharing options...
DFBonnett Posted November 15, 2004 Author Report Share Posted November 15, 2004 Bump... Link to comment Share on other sites More sharing options...
JasonA Posted November 15, 2004 Report Share Posted November 15, 2004 In my experience, an ignition module that's failing would show up as a "no start" after a hot soak, like you mentioned. I've never heard of one breaking down while driving or anything like that. Jason(2001 STS, White Diamond) "When you turn your car on...does it return the favor?" Link to comment Share on other sites More sharing options...
Logan Posted November 15, 2004 Report Share Posted November 15, 2004 Check the front lower engine block ground near the starter. Common for that ground to get funny. The ignition modules can suffer from green corrosion on the pins. The pick up coils can often get green also. Could be a bad PCM messing up as the PCM warms up. You can try tap testing the PCM while the car is running....a stall or a burp while tapping would indicate a bad PCM. Logan Diagnostic LLC www.airbagcrash.com www.logandieselusa.com www.ledfix.com www.ledfix.com/yukontaillightrepair.html www.ledfix.com/ledreplacements.html www.ledfix.com/j42385toolrental.html Link to comment Share on other sites More sharing options...
adallak Posted November 15, 2004 Report Share Posted November 15, 2004 Could be a bad PCM messing up as the PCM warms up. You can try tap testing the PCM while the car is running....a stall or a burp while tapping would indicate a bad PCM. While I was replacing a failed heater core I noticed all the computers are very close to the heater and would get pretty warm partucularly in the summer.... I decided to remove the glove box and probably the lid to cool down the PCM and BCM if they start acting up. Last summer I had non-starts several times when the engine was hot (200 plus). I think the aged wires and connections are the culprits. Looks like corroded connections are much more vulnerable to excessive heat. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
DFBonnett Posted November 16, 2004 Author Report Share Posted November 16, 2004 Many thanks for the replies and suggestions. I'll get busy on further diagnosis this weekend and will post the results. Again, many thanks. Link to comment Share on other sites More sharing options...
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