2003 can't maintain idle, bad random misfires

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tjp74

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I've spent hours searching through number of forum posts but can't seem to find the answer.

It's actually been few month since my 2003 started developing random misfire issue. But it only happens at idling. Once car moves, it pulls smoothly and strongly. Never an issue so I delayed looking into the issue. Then, it has progressively gotten worse. Another thing I noticed, when I start the car first time in the morning, RPM shoots up to like 2-3K, stays there for 10 seconds at least then drops down only to start misfiring. So excessively long and high initial RPM upon cold start is another issue. Figured it's a vacuum leak.

Then about 2 weeks ago, misfiring has gotten so worse, car would stall at idling. I can give it a bit of gas and maintain 1-1.5k RPM but as soon as foot is off the gas, engine sputters and dies. I also hear popping sound... like backfiring sound during idling.

Here is what I've tried. I have another D2, 2004 that needs valve lifters replaced. Otherwise it's a perfect engine, idles and runs smoothly. So I took all intake stuff... top manifolds, map sensor, idle control valve, EGR valve, SAI vacuum hoses, intake hoses, ignition coil and plug wires from 2004 and swap them on to the 2003 in question. Absolutely no improvement. What I didn't replace is spark plugs and fuel injectors. But I can't imagine spark plugs.. which looked just fine would cause engine to just stall.

So I eliminated ignition as being a problem. May be the fuel injector issue? should I check the fuel pressure? can any of this issue cause stalling and misfires at idling but engine runs fine above idling RPM? It has good power... and runs smoothly with no hesitation or misses what so ever. I kind of regret not swapping the fuel injectors while the top manifold was off. Code indicates multiple cylinder random misfires, basically 1 through 8. But no other code detected.

Or could a slowly dying crank position sensor cause issues like this? I can see that a dead CPS would cause engine to not even start so it's not dead yet.

I need help deciding what to do next... CPS or Fuel injector or possibly fuel pump? or try swapping the ECU from 2004?
 

joey

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Never swap an ECU unless you have the computer to reprogram the system.

I have seen corrosion in the ECU connector or even in the Fuse Block that can cause weird issues.
 

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