Rough idle and leaning out

[speedypro2003]

So I've been having this problem for some time now with my msp and Im running out of ideas. I've replaced my coils, plugs, wires, cleaned my egr, new maf, new injectors and the problem continues.

What my car does is at idle after it gets warmed up it will lean out to around 16 afr and almost stall out. Then run ok then back to lean. It also has a misfire that you can clearly hear at idle and when cruising at highway speeds you can hear and feel in the car. Also when I go into boost at WOT my afrs read lean at 14 and after a second it will drop to normal around 10.9-11.2. im not currently throwing a CEL but when I did it was for cylinder 3 misfire. Another thing is at idle if I stay steady on the throttle at say 2000 rpms it will fluctuate like crazy and stumble but after 3000 rpms it seems fine.


Im starting to think it might be a wiring issue somewhere but im not sure. Any help would be awesome Id like to drive my car at some point this year...

Forgot to mention it pulls perfect vacuum and compression test was dead on.

 

[hornsfan10609]

No CELs? Could be a primary 02, dirty maf or a defective plug wire. Are the plugs gapped to .028"?

 

[speedypro2003]

Plugs are brand new and gapped, new maf and no current cels only had one for cylinder 3 misfire.

 

[hornsfan10609]

Double check the wire for that coil and possibly swap the coil, if its is telling you cylinder 3 is misfiring...

 

[njintau_fsd]

Also check the fuel injector connectors. For the longest time, the A/F ratios would go out of whack after warmup eventually causing a single cylinder misfire. Turned out one of the injector connectors had worked itself loose, causing that injector to fire unreliably. Also, check for boost leaks and cracks in your intercooler piping and couplers (if you have the stock pos plastic pipes, this is a must!) I had issues with overly lean or rich operation (it was actually too high or low for my wideband to read at times) and it was really noticeable after warm up. Turned out I had two holes in my pipes: one past the MAF and one past the cool-side outlet of the turbo.

 

[speedypro2003]

Fuel injectors have all been replaced as well as new orings, new coil packs and plugs as well. I have a full custom FMIC and as stated in the original post I am pulling perfect -21 vacuum.

 

[hornsfan10609]

Just because they were replaced does not mean the new parts are good. Double check all the connectors and maybe re-seat the coils and wires. Plugs can be bad out of the box as well. Single-cylinder misfires are usually the easiest to diagnose.

 

[njintau_fsd]

The holes that I mentioned were in my aluminum pipes btw (I also have a custom FMIC) and I also had perfect -21 vacuum. In the case of the hole past the turbo, essentially the lower radiator hose clamp was so close to it that it vibrated through the pipe. I don't know how the other hole happened but my guess is either it was road debris or something from the engine bay punching through it. So check your pipes, its even possible that its leaking at one or more of the couplers.

Also, given that you just changed the injectors, that's an even bigger reason to check the connectors. Its possible that either you didn't press them down well enough or one or more of them just worked itself loose due to engine vibration.

 

[speedypro2003]

Ran a full diagnostics on my car and its showing that even at 2500 rpms my ecu only thinks its running at 809 rpms. Did a voltage test on my TPS and its reading as a failed unit. So ill be replacing that this week sometime. I once again checked all of my injectors and they are fine. The diagnostics showed EGR working properly as well as my IAC and MAF. So it appears everything is pointing at my TPS at the moment. Ill keep you guys posted.