91 hesitation/miss/backfire

[kbsbkb]

I am still having problems with my 1991 royale. When accelerating from a stop or trying to accelerate easily while driving without kicking the trans down, the car has a hesitation or a possible miss, and will sometimes backfire through the intake. If I floor it when this happens, it will take off and run fine. Also, this is a intermittant problem, it doesn't do this all the time. The car starts and idles fine hot or cold. I have recently replaced the fuel pump and filter, O2 sensor, ignition module, coil, and plugs. The ignition module had the green goo running out and I thought replacing it would solve this problem, but the car ran great for a day or two and then started acting up again. I have not replaced the plug wires (delco) because they are not very old. I have also checked the MAF sensor and TPS with a voltmeter. The car will usually run fine when first starting out cold and the problem is worse after the engine heats up. Fuel pressure seems to be fine. Anyone have any ideas? Could the plug wires be the problem? Any help would be appreciated.

[razr_88]

does your check engine light come on? If so, what are the trouble codes?

[kbsbkb]

The check engine light has never came on, however I did check the codes and found no codes stored. (code 12 only) Also, I checked the resistance on the plug wires, #1, 3.75k, #2, 7.08k, #3, 6.15k, #4, 6.05k, #5, 7.26k, and #6, 6.99k. Are these readings OK? If not, could this be the problem?

[razr_88]

bad wires are probably not what is causing this if it is backfiring through the plenum. maybe a crossed spark plug wire or perhaps the timing chain or gear. A bad cam sensor or mag should cause a code, as should a crank sensor problem. i don't know what to tell you. maybe a moderator could give some advice?

[kbsbkb]

Sorry that I haven't reply in so long, but I finally have gotten the problem fixed. I talked to a mechanic (30+ years experience), who suggested flushing the fuel injection system, since I had replaced just about everything and he had seen similar problems with these engines. After flushing the system, the car still ran about the same. I took the car back to the mechanic and after checking various things and scratching his head for almost two hours, he pulled the spark plugs and found that one had a hairline crack in the ceramic. He replaced the plugs and the car now runs like new. Keep in mind that the plugs had been recently replaced with ACDelco parts from Autozone. My mechanic told me that the plugs had probably been dropped or otherwise mishandled at the store before I bought them, he has seen this before. So, I probably replaced alot of parts that were still OK, but like I said the car runs great now. Thanks to everyone.