Friends GN running ruff

[EVIL]

I haven't checked it out yet and don't have any scan tool readings but he brought it to his mechanic and this is what he said.

When he puts a key in the DLC which puts the computer in bypass mode the car runs great.
They have swapped out computers with a known good one and there was no change.

I'm not sure what that means.

Any suggestions would be great before i take a look at it.

Also from what I remember his cigarette lighter was shorting out last year and i couldn't hook up a scan tool to check for codes and such.

D

 

[EVIL]

Here is some info. Hopefully enough to generate a response.

The car starts backfiring when you give it gas even with no boost.
We the A&B connectors are connected with a key, like when you look for codes, the car runs fine like nothing is wrong.
My friends mechanic has changed the
crank sensor
cam sensor
ign control module
knock sensor
MAF
ECM
The car still backfires.

I got some readings today with the car idling.
02 voltage = .35 - .52
02 cross counts = 16 - 28
TPS = .40
MAF = 5
INT 147 - 158
BLM = 135
LV8 = 27 - 29
IAC = 34

There are no codes.

D

 

[Dunebilly]

could the cam sensor be 180 degrees off?? that was what happened to me before

 

[Dunebilly]

the car was running like the plug wires were all mixed up

 

[EVIL]

I could go and set the cam sensor myself to make sure.
But even with the A-B connected under the dash and the car runs perfect?
Would it still run that good if it was the cam sensor?

D

 

[psycho6cyl]

I would look into cigarette lighter short first. The aldl wires and cigarette wires look to be in the same place. It's definitely weird. Tried for checking codes w Eng off? And how did you guys figure out when you check for codes it runs good? Maybe your friend or his mechanic was fooling around there and did something? Just seems odd..

 

[EVIL]

I would look into cigarette lighter short first. The aldl wires and cigarette wires look to be in the same place. It's definitely weird. Tried for checking codes w Eng off? And how did you guys figure out when you check for codes it runs good? Maybe your friend or his mechanic was fooling around there and did something? Just seems odd..

I did not try to check for codes with engine off.
There was an issue with the cigarette lighter. I'll tell the mechanic to check it out.

D

 

[EVIL]

How would the short in the cigarette lighter make the car back fire? and when A-B is connected it runs good?
I'm curious?

His lighter had issues a few years ago and someone fixed it.
The car ran fine. Strong too
I'm not sure if it was messed with again before it started back firing.

D

 

[psycho6cyl]

It probably has nothing to do with it but. I like to tackle problems one at a time cigarette lighter would be easiest and I figured maybe when digging for that you come across another wire touching or something. Who knows how the lighter problem was "fixed".

 

[EVIL]

Ok thanks

D

 

[gunslinger]

By jumping the pins on the DLC, you're putting the computer into "service mode". It only looks at major inputs and goes to base timing and I think it batch fires the injectors.
Try unplugging the cam sensor with it running to see if it clears up. Check the data stream for erratic MAF, coolant temp, air intake temp, etc, and see where the O2 is reading when its running rough.

 

[John Larkin]

Does he have a DirectScan cable hooked up? If those cables go too deep onto the ECM connector, the car will run barely run for some reason, at least mine does this.

 

[John Larkin]

Backfiring means it's rich. The IAC is a little high which tells me it is trying to compensate for the richness by requesting more air.

I don't know if those O2 cross counts are good or not. Maybe O2 sensor suddenly went bad. Can he borrow yours?

 

[EVIL]

No direct scan. O2 sensor? WOW I can't believe we overlooked that one.

In the next few days I'll go thru all this advise and post a result.

thanks guys.

D