josh A8 |
06-20-2013 07:41 PM |
engine runs very rough
1999 A8, just started today without warning. sounds like a very bad misfire. VCDS says it's cylinder 4. I changed out the plug and the coil. no difference. swapped the ECM with a good spare. no difference. fault codes are P300 & P304 for the misfires, and the third is a P1690 electrical malfunction relating to the MIL (check engine) light not working. doesn't come on when the key is turned, or after starting. I know it was working before this. I scanned the car about a month ago and it was fine. the car can not be driven over about 20 mph, at which point it shakes violently. I've been through every relay I can find. pulled them and reinserted. nothing makes a difference. all fuses I've checked are ok. this happened one other time. I unhooked the battery for an hour, and it cleared up. that was last fall. it's been a-ok till now. tried the unhook battery deal too. no luck. what would make the MIL light malfunction ?
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