Gm 3800 driveability issue

**toneloc60** · 12-31-2006, 10:29 AM

I'm trying to play over the phone auto doctor for a friend of mine. He's working on an '02 Regal with a 3800. The car idles fine, but at 2000 rpm it starts pinging. The knock sensors are picking up the ping, then pulls timing. It pulls a total of 12 degrees.
The engine wont rev over 2500 rpm, and the car can not build speed over 25 mph. The computer is picking up misfires on all cylinders, but cylinders 2 and 6 are registering the most.
Thinking it may be injector problems, he swapped 2 and 6 for 1 and 3 but noticed no change.
He and I have started to suspect the problem may be in either in the fuel filter, or even in the fuel itself. I've told him to call the gas station the owner of the car last filled at and change the fuel filter. He's also going to fill a small clear jar with fuel from the inlet line from the fuel filter to check the fuel for any noticeable contaminates.
On a call back to the car owner, she had even questioned whether it could be a problem from someone tampering with her fuel. So, I think we may be on the right track.
I'm hoping someone here may be able to come up with some ideas on this in case we're off base.

**0rion** · 12-31-2006, 10:51 AM

Has he checked the fuel pressure yet?

**toneloc60** · 12-31-2006, 10:55 AM

yes, fuel pressure is good. However, he has not yet checked flow. I told him to check that as well.

**autotrix** · 12-31-2006, 02:10 PM

Could have gotten some bad gas, maybe has water in it. Most major fueling stations will pay for any diagnosis that finds the gas at fault to avoid lawsuits.
What do the plugs look like? Coolant or oil fouled?

Finding out which cylinder it is dropping could help, possible ignition module or coil pack...

**toneloc60** · 12-31-2006, 02:45 PM

Plugs are in good condition. Have switched coil packes around, but no improvement. Plus, the two worst misfiring cylinders are not fired from the same coil.
I will advise him to check the ignition module for possible problems.

**bigrondownhiller** · 01-03-2007, 09:56 AM

how many miles on the car?

**toneloc60** · 01-03-2007, 10:11 AM

There were 75,000 on the car. However, the problem has been figured out. There was too much back pressure in the exhaust due to a clogged catalytic converter. All is well now. Thanks though.