i am posting this for a friend that has a 99 sierra 1500 4.3 V6 single cab it will start up everytime but will idle at 500 rpm and be ...

99sierra1500 · by **99sierra1500** [OP] » Dec 08 2011, 6:50pm

i am posting this for a friend that has a 99 sierra 1500 4.3 V6 single cab

it will start up everytime but will idle at 500 rpm and be really shaky but wont stall, rpms moving up very slowly, will drive but wont go that fast and will start to feel like no tranny is there. Once in gear it will idle really rough if not on the gas and will eventually stall i will try to post a video from my phone but not sure if it will work.

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ASTE25 · by **ASTE25** » Dec 08 2011, 7:19pm

Kinda sounds like a clogged catalytic converter. The thing is, a plugged converter is more likely a symptom of another problem. If it does turn out the converter is plugged, of course it will need replaced, but you should make sure the truck does not have a problem that caused it to plug (such as a misfire condition).

wheeler82 · by **wheeler82** » Dec 08 2011, 8:18pm

could be a number of things...convertor is deffenent possibility, my buddy had a bad convertor on his monte carlo and you would have swore it had a slipping tranny really acted wierd...any check engine lights?? etc...

99sierra1500 · by **99sierra1500** [OP] » Dec 08 2011, 9:39pm

i just checked now and it started really rough and wouldnt go above 2k (even at wot) and just stalled and no CEL, do you guys know of anyway to check the cat without going to a shop?

ASTE25 · by **ASTE25** » Dec 09 2011, 2:11am

You can have a helper sit in the vehicle and rev the engine. You stand by the tail pipe and feel if the proper amount of air is coming out (be careful, it will be hot). If you think it is not flowing enough, you can unhook the exhaust before the converter and run it long enough to see if it will idle and run (rev up) normal (of course it will be loud as hell).

wheeler82 · by **wheeler82** » Dec 09 2011, 2:14am

ASTE25 wrote:You can have a helper sit in the vehicle and rev the engine. You stand by the tail pipe and feel if the proper amount of air is coming out (be careful, it will be hot). If you think it is not flowing enough, you can unhook the exhause before the converter and run it long enough to see if it will idle and run (rev up) normal (of course it will be loud as hell).

yeah absoultly....you can also start it and with it running in PARK...reach under near the converter and it will be throwing off noticiablly more heat than the rest of the exahust, but it really sounds like that could be the problem.