MAF Problem - O2 Problem - Wiring? Leaned Out Idle

[GofaST4life]

Im not even sure where to start. So here goes.

Getting the car running for the season. She was down for the winter doing a clutch install and a 20g setup with External Gate.

Everything was buttoned up and I went to start her for the first time.

She ran very rough. AFR was pegged at idle and she would stall out. This is on a completely stock fuel system and stock ECU.

My buddy Justin and I drained the tank to get good gas in the car. We also installed a new PCV valve as we found a TON of blow by, so much so that the turbo would stop spinning!

Problems we have found:
- The car will idle WITHOUT the MAF plugged in, AFRs around 17ish, its not a smooth idle, but she stays running.
- The car will die if you plug in the MAF = AFRs top out at 22.4 - We tried Justins MAF and had the SAME symptoms.
- We have a HUGE boost leak somewhere behind the throttle body. Cannot pinpoint it. I had the TB off for new gaskets and a new BISS screw.
- Also, the front O2 is not cycling - HOWEVER I have the wideband in the front O2 spot, and I have the Brown Wire (simulated narrowband) from the MTX-L wired to the ECU via Pin 76. THE car was running fine like this before she was parked.
- I believe I have an exhaust leak as well.
- The car throws various codes. Obviously for the MAF when its unplugged and the Front O2. When the MAF is plugged in, nothing is thrown.

Possible Ideas:
1. Maybe the Wideband O2 Sensor has gone bad? It only has 200ish miles on it.
2. Recheck all Grounds - Especially Pin 92 ECU Ground (both the MAF and O2 share this)
3. Recheck Plug Wires.
4. Check Coolant Temp Sensor.
5. Check all wiring that could have been messed with during install.
6. FIX ALL LEAKS (obviously this will be done)


What has me stumped is the fact that the car, even with the major boost leak AND the MAF unplugged, it runs super leaned out. When you would think, if would be running way to rich.

ALSO, I think this is a wiring issue or a ground problem, as I find it hard to believe that a perfectly running car would be parked and then have a bunch of sensors go bad for no reason.

Granted i'm basing the AFR off the sensor/gauge which could be bad.

I will post up more, it was a long night.

 

[92AWDHX40]

It seems a lot of things happen out of the blue, you never know.

 

[lil corb]

How is the condition of the ECU?

 

[GofaST4life]

As far as I know. The stock ECU is fine and the DSMlink ECU is fine. Both where pulled from running cars.

I checked the plug wires - All good
Also, I may have found something.

I was told to check everything with the Coolant Temp Sensor. I visually looked at it to make sure it was plugged in, then before removing it, I traced the lines back to the next connector. After a close look, there is an exposed wire on the rear of that connector leading back into the harness. The wire in question looks black, so it may be a ground.

Going to really investigate in a few.

 

[my dreamt dsm]

Not sure if this will help but the symptoms you're describing are similar to mine minus the maf problem. My MTX L is showing the e8 error code and my car is running lean at times and rich at times. O2 sensor is not my problem because it's brand new. The car will only run right if the e8 error code comes on. So sometimes I will have to turn the car on and off so the e8 error will show.

 

[GofaST4life]

Something is causing the car to run super lean.

The only reason the car idles when the MAF is UNPLUGGED is because when its unplugged the intake temp defaults to -40 degrees, thus telling the ECU to dump more fuel to warm the engine.
Theoretically, since more fuel is being dumped, the car runs and AFR or 16-17.

Then when I plug the MAF back in, it leans out hard and stalls.

The Coolant Temp Sensor is working fine and reading correctly.

On the other end, there is a major boost leak somewhere behind/under the throttle body. So in turn, a boost leak would cause it to run even more rich.

So confused.

 

[GofaST4life]

I have a huge boost leak at the throttle body.

It has to be down behind it. I cannot pinpoint its exact location.

I'm thinking something is seriously wrong at that location. For some reason the car isnt throwing any fuel during idle.

THUS - when you unplug the MAF or give it throttle, it runs much much better and the AFRs are in check bacause the car is getting fuel.

 

[ohlegend]

I am having a similar issue. No boost leak up to the throttle body. I think I am losing air somewhere behind as well. I am going to check tonight to be sure. Have you checked your shaft seals?

If I plug in my MAf it runs bad, unplugged it will idle forever. When my maf is plugged in, and I rev it, I have the same result as you. It will run and sound great.

 

[dugan33]

WOW. im shocked that we have such similar issues. Here's a video of what exactly im dealing with. I changed the motor and now im having this issue. I have stock side mount hooked up for now otherwise all my mods are the same as before the build. Let me know if you find anything out. i just ordered TB mounting side gasket and Ic pipe side gasket. Mine's a 90'. anywhere else vacuum leak can happen?

[ame=http://www.youtube.com/watch?v=u_8H5fW0WwA]1990 dsm 1g won't idle - YouTube[/ame]

 

[GofaST4life]

List of what im going to do next.

- Remove TB and make sure gaskets are not backwards.
- Re-install Stock Front O2
- Rewire Pin 76 and Pin 75 to stock.
- Fix all Boost leaks.
- Check to make sure im getting fuel at idle.

 

[dugan33]

I thought should know I resolved my issue changed gaskets and tightened my throttle cable. It was the throttle cable being too lose.

 

[ohlegend]

I also did the same thing. Tightening the throttle helped a bit.
I found an exhaust leak at my turbo inlet.
I believe my problem is the exhaust leak.
I just ordered some good gaskets... I will keep you posted.

 

[GofaST4life]

Its been stupid cold here, haven't had any wrench time.

I'm leaning towards my TB being the issue. I did a non-cruise install and gaskets over the winter. I think something is obviously askew at that location.

I will surely post back ASAP.

 

[dugan33]

I also did cruise delete. Thus, my cable issue ha.

 

[GofaST4life]

I also did cruise delete. Thus, my cable issue ha.

If you don't mind me asking, what exactly was wrong? My cable is pretty tight, not bound etc.

 

[miliman13]

Rebuild or replace your TB. Isolate your leaks by testing individual pipes, intercooler, BOV, ect....... Do one piece at a time, also check your compressor housing. You have to eliminate every leak 1st. Otherwise you won't make any progress, start with the path of least resistance and the most logical.

 

[GofaST4life]

Rebuild or replace your TB. Isolate your leaks by testing individual pipes, intercooler, BOV, ect....... Do one piece at a time, also check your compressor housing. You have to eliminate every leak 1st. Otherwise you won't make any progress, start with the path of least resistance and the most logical.

Doing that this weekend. I plane on removing the TB, checking to make sure the gaskets are correct and doing BLTs.
Also going to check my throttle cable as I did a non-cruise cable install over the winter.

I don't think my TB is bad, as it was completely fine before the winter. But we will see.

 

[ohlegend]

I replaced my leaky pacesetter header with the stock one, and got CEL P0135. Upsteam O2 heater sensor.
Still waiting on my temp sensors...and now a new o2 sensor.

 

[GofaST4life]

Got to work on the car a bit today.

Ripped off the TB to find that the TB to IM gasket was on incorrectly. Replaced it with a new one, on the correct way, bolted her all back up.

No more leak! And the car was running just fine at idle!

I CANNOT believe a boost leak created all these issues.

I had my wideband still installed and wired in. No CELs thrown.

I also swapped out the 20g for a 14b. When Justin and I where diagnosing, we found that the 20g would spin/spool on initial start up, but then stop spinning at idle revs. Going to look into having is possibly rebuilt or selling it.


I will be checking for more boost leaks as well as exhaust leaks before setting the car back up with DSMlink.

 

[ohlegend]

My throttle set screw was in too far. When I was idling, my throttle position was at 0%, when it should be at 2-3%.

 

[Dsmkauai]

This is why a boost leak test is such a important maintenance item for our cars guys! I regularly do them like a oil change or tire rotation, to be on the safe side! Glad you guys are figuring your problems out, another reason to double check your work sometimes !