328is backfire

m_mac · 09-24-2008, 11:55 AM

i have a 1997 328is the engine backfires wont idle and the cats get red hot

can anyone tell me the problem?

Jeron · Jeron's Garage

Plugged cats?

Way too rich?

m_mac · 09-24-2008, 01:50 PM

cats are not plugged looks like its dumping fuel cats breifly cought fire!!!

m_mac · 09-25-2008, 09:04 AM

could this be a computer problem??

Jeron · Jeron's Garage

Seems unlikely. Do you have a check engine light?

I'm just guessing but I'd start with injectors.

Manolito · 09-25-2008, 09:33 PM

If this car had a timing belt driving the cams rather than a chain, I would suspect that the belt had slipped and the cams were out of time. Has the head been off?

Having the VANOs fail and fully advance the cams would screw up you idle, but should not be as bad as you describe.

Are both cats getting hot? If so, the problem is affecting all cylinders (or at least one in front and one in back).

I would start with a compression check. If compression is bad across the board, I'd pull off the cover and look at the cam timing. If compression is bad on only some of the cylinders, you will likely be pulling apart a lot more than covers.

m_mac · 09-26-2008, 08:38 AM

Quote:

Originally Posted by Jeron

Seems unlikely. Do you have a check engine light?

I'm just guessing but I'd start with injectors.

No check engine light, but i have been told that the o2 sensors could be at fault does that sound right?

m_mac · 08:45 AM

Quote:

Originally Posted by Manolito

If this car had a timing belt driving the cams rather than a chain, I would suspect that the belt had slipped and the cams were out of time. Has the head been off?

Having the VANOs fail and fully advance the cams would screw up you idle, but should not be as bad as you describe.

Are both cats getting hot? If so, the problem is affecting all cylinders (or at least one in front and one in back).

I would start with a compression check. If compression is bad across the board, I'd pull off the cover and look at the cam timing. If compression is bad on only some of the cylinders, you will likely be pulling apart a lot more than covers.

Yes both cats get REAL hot, will check compression this weekend. to my knowledge the head has not been off. Thanks.

m_mac · 10-01-2008, 07:57 AM

Checked compression all is fine. what about the o2 sensor, possible???