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Hi, 2003 9-5 Linear wagon with 146,000 miles. I am just about to admit defeat on self diagnosing an engine bucking that starts about 5 minutes into the trip and lasts for only a few minutes after which the car runs fine. No codes or check engine light. Doesn’t appear to matter if at idle or highway speeds though my daily commute rarely allows for an extended period of 50+ mph, mostly 20 miles of stop/go in congested traffic. Fuel supply and trim appears to be fine, no problem in starting, the engine will rev without hesitation while the bucking is occurring but the bucking will resume after the RPMs settle back down. Some vacuum leaks have been found but fixing them has not helped.
Early in the diagnosis cycle a suspected dodgy DIC was plugged in that didn’t improve on the bucking and after a week or so did result in a P1312 CEL. After clearing that code and swapping back the”good” DIC all the OBDII monitors have since run to completion with no new or pending codes. It did take about two weeks for the CAT monitor to run to completion, the downstream O2 sensor output voltage is jumping around quite a bit so the CC is probably getting weak. On a lark I plugged in one of the OEM MAF sensors E-Euro is selling cheaply, to no effect.
These parts have been replaced over the last 2-3 years:
- MAF
- PCV check valve
- Most vacuum lines
- DIC
- Fuel pump
- CPS
The car goes to my Indy for annual inspection in about 10 days, then it becomes his problem.
Thanks in advance for any ideas,
tim
posted by 108.2.1...
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