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Been chasing this for awhile.
Car usually starts fine but within a few minutes it starts to miss when at idle and eventually will die. Lately there have been hard starts (usually after a cold, wet night) resulting in the same idle problems.
Once on the road, it runs fine at speed (above 1,000 rpm) but will miss & die when I let up on the throttle at a light or even as the car decelerates (not always but often). The misfires and hard starts are usually accompanied by a rich mixture indication on my O2 readout. If I keep the RPM above 1,000 to 1,500 at a stop light, it will continue to run but still has a miss sometimes.
Over 3,000 rpm there is a very pronounced miss as well which I initially attributed to a bad intake hose. Thought I found the problem when I did a starting fluid spray test and got a blip when spraying around the Turbo-to-Intercooler hose which I replaced. No joy, all symptoms are still present.
Emissions are WAY off the mark, all indicators (CO, HC & NOx) are high with NOx being in the stratosphere. The only reason the car EVER failed emissions in the past was due to a dying cat pushing the NOx just over the limit, CO & HC have never been a problem, until now. The emissions problems probably indicate misses while running that are covered up by the speed.
Did an ignition tune-up last summer (Cap, rotor, plugs, wires, etc).
Thought the symptoms pointed at ignition and there WAS one lonely code present which pointed at an intermittent CPS which I replaced. No joy. Code has NOT reappeared.
Swapped out a few ignition parts including the power stage and cleaned all the connectors I could find. No joy.
Have NOT tried the MAF nor the O2 sensor yet and am starting to lean toward the O2 sensor which is aftermarket but only a year old. Oh, and I cannot find any vacuum leaks.
Am I on the right track?
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1999 E320-200K 1994 F150 (awaiting a new engine) 1989 560 SL-180K 1994 945T (daughter's)-312K 1986 242Ti (awaiting a B230FT transplant) 1968 GT500KR (under slow restoration) 2007 HD Nightster (son's ride)
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