car starts cutting out/popping/backfiring at 4800 RPM

[amc91z]

long story short, i just acquired a 99 eclipse that was my brothers (who just passed away). The problem is that the car starts cutting out/popping/backfiring at 4800 RPM and will not pull any higher than that. I ran the code that was showing and it said the coil was bad. Replaced with a new coil but it didnt change at all. A shop in virginia recently put in a replacement engine from a wrecking yard and i think it may have been doing this before the old engine let go so i dont think it has anything to do with the new engine. It is a 2.0/auto non turbo car. I really just dont know where to start with these cars...Any help or advice is appreciated!
Adam

 

[Defiant]

This is the range in which used-up spark plugs and wires show their age. Replace.

 

[poonman]

i would start with your o2 sensor

 

[amc91z]

It has new plugs and wires on it from when the engine was put in. If it were the o2 would it have a CEL? It has has o2 problems before from what i remember my brother telling me, so that may be it...i was just thinking it would have a code...Thanks for the quick replies!

 

[throwedgsx]

Check your plug gap. My guess is plugs or wires

 

[poonman]

sometimes a cel wont come on at all if its just not enough to set it off but enough to make the car messed up. But for the cell you should have 2 different cels one for each bank.

 

[mentalTSiAWD]

I've encountered exactly what you describe in my wifes 420A car everytime(yes, more than once) a plug wire fails. Really, swap out your plug wires. Also you can make sure there's no moisture in the spark plug well.

 

[amc91z]

well, pulled the plugs to replace them and the cam cover gasket was leaking down into them...so i've replaced cam cover gasket, plugs, wires, and coil...Its still doing the exact same thing. Should i try the o2 sensor next? If so, which one? Any other help is greatly appreciated!!!
Adam

took the car and had it scanned again today...still showing the same codes.
P0351 Ignition Coil A Primary/secondary circuit malfunction
P0352 Ignition Coil B Primary/secondary circuit malfunction

When we got the coil, it had a different plug in on it so i took the old coil off the car and took it in and it was one off of a neon, they said the coil was the same but just a different pigtail on the harness. So
I got the neon coil b/c it plugged in. I then checked the wires to the coil and it has been cut and wired back together...someone had wired a neon harness to it...so i re-spliced the 3 wires and still the same. I did find out that is you rev the car in park, it pulls pass the 4900 RPM, but there is a slight stumble when it hits it, but pulls right pass it. I am at a loss with this car and about ready to pull my hair out.

what should the stock fuel pressure be?

Thanks,
Adam

well, everyone that has looked at the car thinks its the ECU but i cant seem to find one anywhere to replace it. I've found a couple on ebay (of all places)...their vehicle description matches everything about my car, but i pulled my ecm and the part #'s dont match. Is it possible i have the wrong ecu in my car now? The one in my car now is


3191AC
Chrysler P/N: p05293191ac 0529
module S/N: t59eh0549a6339 17:29:29

How can i find out if this is the correct one for my car. Could it possible be out of a different car with a lower rev limiter?
Thanks,
Adam

 

[wises4057]

do you see a drop in fuel mileage? I would think if your front o2 sensor is going out, then its probably causing a little lower fuel mileage as well...but then again, the issue at hand could/should be causing fuel mileage loss as well. I would start with the front o2 sensor first, because I believe the rear o2 sensor is for emission purposes only.