Afr With Bigger Turbo (hx35/40)

[waxer52]

I have narrowed down my problem, (at last0, it now idles fine with afm voltage at 1.2v, tpr voltage at 4.6v.

My wideband sensor is giving a lean reading due to a missfire on one of the cyclinders (no.2 I think), i removed all the spark plugs and no.2 looks fairly light while the rest of the plugs are fairly black. Could it be lean on one cyclinder or rich on five?

When I have the car running and I slowly rev the engine up to about 3000rpm you can hear the miss very distinctly.

I have wasted spark with msd coils and i have spark at all cyclinders

I have fuel at all cyclinders

Iac valve clean as a whistle (solved my bad idle)

Fuel pressure is good

Anyone know what my next step is to solve this.

Forgot to say that when I try to start it when warm I have to fully depress the throttle to get it to start.

Edited November 28, 2009 by waxer52

[R31Nismoid]

I still don't understand why people modify the factory coil setup which will do 400rwkw without even blinking... just brings more issues of reliability and something else to diagnose.

anyway...

If NO.2 is light on then it would be lean. I would be skeptical of the other 5 being the issue.

I'd say you have a issue with the aftermarket ignition, perhaps connection? Bad coil?

[waxer52]

I had issues with the standard coil so I went to wasted spark, maybe it was a bad choice but as for the moment I have a good strong spark at all plugs.

If you think its cylinder 2 that is lean there could only be one cause and that is not enough fuel, what is the best way to test for this?

[Cjmartz2k]

Try swapping injectors around and see if it the problem follows the injector.

[waxer52]

I have now swapped no.2 injector with no.3 injector.

When i have the car running i can remove and injector plug and you can hear the engine misfire. I have done this for each individual injector and they all seem to be firing as the misfire gets worse when removed.

The same happens with removing spark plug leads. Misfire get worse when removed individually.

Dont know what to do now, I have checked for vacume leaks and cannot find any, but the only way cyclinder 2 could be lean is if it was drawing extra air somewhere.

Think I might have to get a garage man to look at it.

[winstonusmc]

perform a boost leak check on this. As nothing changed except the turbo, this should not affect idle AFR at all. On the Power FC, do you have O2 control disabled? If not, it still could be a leak. Just pop a plug on the inlet of the turbo and pressurize the piping and check for leaks, could be a leaky compressor housing or some boost piping.

To put this in perspective, I was tuning my MAFs this past weekend. After installing the new stretched out rubber piping for the 80mm MAFs I left the vent pipe off the valve cover by accident. At no load and 2000rpms, I was running 14.2 AFR. At idle I was running 18 AFR. Put the hose back on and the AFR steadied back to 14.5 AFR, which is what I was shooting for. End of story, so check for leaks.