Lexstang
09-15-2014, 07:50 PM
ok hopefully I explain this clearly.
About a month ago my car started this weird burp/backfire thing when you started it cold. It doesn't start, makes weird exhaust burp sound. Next time you crank it starts up. One night I noticed even with the radio off, I was hearing a whining from the speakers... So I googled it. With amazing consistency the forums said cam position sensor, or alternator diodes requiring a new alt. So a few days ago I bought a cam position sensor for 17 bucks, one bolt and one electrical connection and it was in. It seemed to help the starting problem some but still didn't seem 100%. So I knew I needed an alternator. In the meantime, the exhaust sounded like the heat shields were vibrating off the catalytic converter on my brand new BBK xpipe. I spent several hours getting car jacked up, checking for loose bolts, taking it out and checking the ceramic element inside, rebolting it, adjusting the exhaust pipe that was too close to a frame rail. It still did it just as bad so I was about to see if the ceramic element was not only intact but secure in the converter. I was not looking forward to giving bbk a crapton more money to send me a new xpipe to hopefully exchange under warrantee.
Today I went down to oriellys, pulled off the alt and had it tested on the bench. It promptly failed all tests, which I expected. They had a rebuilt in stock so I got it, and slapped it back in. No problem. Starting problem fixed! What I didn't expect, was the exhaust problem to be instantly gone too.. Now it makes sense to me but I would have never guessed the alt would fix it.
As best as I can figure, the alt was causing interference to the cam position sensor. But it wasn't only at startup. It was fooling the computer to add fuel as the exhaust valve opened, causing combustion in the exhaust headers and xpipe.. That vibrated the heat shield and would have ruined the cats in short order probably. Alt replaced, starting problem fixed, exhaust sounds awesome again. Now I can go back to getting compliments on it:)
Hopefully this will be helpful to someone else.
About a month ago my car started this weird burp/backfire thing when you started it cold. It doesn't start, makes weird exhaust burp sound. Next time you crank it starts up. One night I noticed even with the radio off, I was hearing a whining from the speakers... So I googled it. With amazing consistency the forums said cam position sensor, or alternator diodes requiring a new alt. So a few days ago I bought a cam position sensor for 17 bucks, one bolt and one electrical connection and it was in. It seemed to help the starting problem some but still didn't seem 100%. So I knew I needed an alternator. In the meantime, the exhaust sounded like the heat shields were vibrating off the catalytic converter on my brand new BBK xpipe. I spent several hours getting car jacked up, checking for loose bolts, taking it out and checking the ceramic element inside, rebolting it, adjusting the exhaust pipe that was too close to a frame rail. It still did it just as bad so I was about to see if the ceramic element was not only intact but secure in the converter. I was not looking forward to giving bbk a crapton more money to send me a new xpipe to hopefully exchange under warrantee.
Today I went down to oriellys, pulled off the alt and had it tested on the bench. It promptly failed all tests, which I expected. They had a rebuilt in stock so I got it, and slapped it back in. No problem. Starting problem fixed! What I didn't expect, was the exhaust problem to be instantly gone too.. Now it makes sense to me but I would have never guessed the alt would fix it.
As best as I can figure, the alt was causing interference to the cam position sensor. But it wasn't only at startup. It was fooling the computer to add fuel as the exhaust valve opened, causing combustion in the exhaust headers and xpipe.. That vibrated the heat shield and would have ruined the cats in short order probably. Alt replaced, starting problem fixed, exhaust sounds awesome again. Now I can go back to getting compliments on it:)
Hopefully this will be helpful to someone else.