toddk911

Well, it was nice weather this weekend so I did a detail and that included an engine degrease. Yes, I know. But I was careful not to let anything get wet that shouldn't and let it dry etc.

So after that I go for a drive and notice the exhaust seems louder and feels/sounds like a small block chevy and boost is very slow to build and hold.

I didn't get a chance to get under and look for exhaust leaks but is there any way this could be something from washing the engine and not an exhaust leak?

If it is an exhaust leak, that is audible and affecting performance, I would assume it has to be somewhere between the headers and WG right?

Tom M'Guinn

Sure you didn't just get you ignition / rotor wet and cause a slight miss?

toddk911

I didn't feel a miss it wass just very slow to boost and noticeably louder exhaust tone.

Could it have been a bunch of small misfires??? lol

rlm328

Knock a vacuum line off maybe.

toddk911

Possible, but have a noticeable change in exhaust sound.

toddk911

Ok, no exhaust leaks. Def seems like either vac leak and running very rough and exhaust is pulsing, like a small block with a hot cam.

Vac is reading about 16 when hot at idle when normally about 20.

Did a quick pressure check and did not notice any leaks. Also for as rough as it is running I would expect a very noticible leak. Bypassed the ISV and idle shot up and vac did as well, however it still ran rough and slow spool, etc. So didn't fix the problem but I guess my ISV is bad??

However, when re hooking up the ISV to intake hose when it was on, but still some vac leak before getting the hose on all the way, it seemed to idle like normal. ???????

Although, I noticed my narrow band was dithering but most of the red/yellow lights were noticable at once when norally to fast to see. Didn't get a chance to get the wideband readout.

Also I pulled the maf plug and a few times it made no difference???? So sounds liek bad maf/sensor but then repluged and pulled again and then noticible difference and then stall.

Chicken or the egg: Vac leak causing rough running or rough running (maf-a/f issue, etc.) causing the vac to be lower to keep from stalling??

I guess the best comparison is putting in bigger injectors and then tuning after. Until it is tuned for them the car runs very rough.

Ideas?

rlm328

Check your O2 sensor connection at the back of the engine. Although it only comes int play when the engine is idling it would be easy to eliminate

toddk911

Yep, unplugged it and did not help.

I am looking towards the maf now. as a couple of times when testing I unplugged it and no difference as the car should have noticable changed or stalled. Then unplugged again and then it did change and stall.

However the voltage read outs for the maf sensor on my SAFC2 seemed ok.

Black51

Are you guessing your injectors might be bad or something? Otherwise why consider changing to bigger injectors?

toddk911

No, i was saying that it is running as if I had put in bigger injectors but did not tune for them; just as an example to describe how it is rough running, etc.

Actually now I am leaning towards the DME.

I hooked up the lap top and zetroninx showed maf just fine but crazy read out on rpm, like 228K rpm, lol. Also no graphic display of the rpm like normal.

Also, a/f is flat line reading of full rich.

But both rpm and a/f would periodcially jump and have graphs like a heart monitor. lol

Maybe some water leaked down into the DME or DME connections, etc.

Chris White

Could be just a shorted sensor due to too much water. If the coolant temp sensor was shorted it would make the DME go to a rich condition.

Drive it for a while a see if the heat dries it out.

toddk911

Hey Chris!

Well maf is fine and DME swap did not fix. It has been about a week now and should be plenty dry but I am leaning towards your route of a sensor being bad or shorted, etc. and that is causing ultra rich which is then causing low vac just to keep it from stalling so no issue of a leak.

And now the temp gauge seems ok. lol

However, this still has me confused:

"I hooked up the lap top and zetronix showed maf just fine but crazy read out on rpm, like 228K rpm, lol. Also no graphic display of the rpm like normal."

And this makes me think speed/ref sensors but they are both fine and dry and only a few years old.

I am pretty much out of ideas. Only other thought would be fpr/dampener ???

Or what else could cause a full rich condition across the rpm/load range?

Tom M'Guinn

You say the zeitronix shows the maf is fine, but you also say it is running rich everywhere. What is the wideband air-fuel ratio at idle and while cruising down the road at light load?

toddk911

Idle reads full 9.6 rich. So it might be worse than that but not able to show richer than 9.6. Even light jabs at the throttle causes popping and backfire so it is RICH.

I didn't get it on the road with wideband as it running so bad it is hard to really drive it but I can try. If i ease on the throttle it will sound ok and rise up the revs but if i hit the throttle quick it pops and back fires, and stumbles etc.

Can you get a normal maf voltage (.8 or so) at idle etc. but the maf still be bad?

Rogue_Ant

MAF numbers sounds ok... Test your temp sensor. There is one sensor for the gauge, and one for the DME - test the DME one. The strange RPM reading could just be a bad connection from the Zeitronix. Is your tach jumping around? If not, then I would say that reference & speed sensors are fine...
You pulled the plugs, correct? What did they look like? If you are running that rich, it should be obvious, and they will foul out soon.