Rough Idle, dies on occasion

[R. Buckley]

i have an issue that is fairly new with my chevy. recently the idle has been very rough, to the point it feels like a vibrating chair when in drive and at a stoplight, however, in park it feels normal. from time to time the truck will die when im at a stoplight and go to take off (normal levels of acceleration). truck only has 81,000 on the ticker, engine has 40,000 (gm goodwrench crate 350). edelbrock carb, and intake, new fuel filter. any suggestion are appreciated. and if any more information is needed for diag. i will be happy to provide it.

 

[Skweegle89]

Has it had a tune up in that 40,000 miles?


Sent from an old rotary telephone.

 

[PrairieDrifter]

Sounds like you might have a cylinder missing? It would idle fine with a miss but with the load of being in drive at a stop would cause it to bog down and die possibly, and you said it vibrates bad so that's why I would say it's a miss. My .02 cents

 

[MadOgre]

i have an issue that is fairly new with my chevy. recently the idle has been very rough, to the point it feels like a vibrating chair when in drive and at a stoplight, however, in park it feels normal. from time to time the truck will die when im at a stoplight and go to take off (normal levels of acceleration). truck only has 81,000 on the ticker, engine has 40,000 (gm goodwrench crate 350). edelbrock carb, and intake, new fuel filter. any suggestion are appreciated. and if any more information is needed for diag. i will be happy to provide it.

I would bet my ass lol that you have a lockup torque converter staying locked up. Could be a wiring issue. Could be a bad torque converter.

 

[R. Buckley]

It has had a tune up, about 10,000 ago.

Tranny and torque converter are pretty new too, is there any way to farther diagnose the TC? Or a way to check and see if it's locking/unlocking properly?

My initial thoughts were maybe a miss too. This weekend I was going to pull the plugs and check them, and pull the carb and give it a thorough cleaning. It looks like it could possibly be gunked up form my cursory inspection.

Anything else I should check gents?

 

[MadOgre]

@chengny

@HRPC

 

[MadOgre]

Do you know where the wiring and TC switch are on your truck ?

 

[R. Buckley]

Do you know where the wiring and TC switch are on your truck ?

no i dont, its a 700r4 though, if you wouldn't mind pointing me in the right direction.
once ive found them can i disconnect the switch? or put a new one in?

 

[chengny]

To be sure that the TCC is not being energized at inappropriate times (and causing the transmission to be locked up while at low speed/stop conditions), you can disconnect the power supply in any number of places. If you are not familiar with all the components and what they look like/are located, the easiest thing to do might be just pull the plug at the transmission casing. It is shown here in several views:

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Or if you'd rather not crawl under the truck, here is the wiring diagram (for a system with an EGR bleed) showing several more options for disconnecting the power. A non- EGR bleed system is similar - there is just no bleed valve:

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[R. Buckley]

Awesome, great pictures. I'll get that plug disconnected and report back.

 

[R. Buckley]

Got it disconnected at the transmission and it seems to have helped. Is it safe to drive it with that disconnected for a while to either confirm or deny that is the problem?

 

[MadOgre]

Got it disconnected at the transmission and it seems to have helped. Is it safe to drive it with that disconnected for a while to either confirm or deny that is the problem?

Yes but avoid driving in 4th (OD) gear. If your problems disappear then you know it is The Torque converter locking up that is causing the issue. Then well troubleshoot the system.

 

[R. Buckley]

Rodger. I'll give it a few drives to confirm and report back

 

[R. Buckley]

so after a few miles of driving around town and on the outskirts, that seemed to fix the issue. not only is the rough idling and dying gone but the obnoxious squeal that i used to have when backing into a parking spot disappeared too (i had originally credited a weak power steering pump with this issue), so im not not sure if that is a coincidence or if that is also related?

should i replace the switch on the transmission case itself? or should i perform other troubleshooting steps?

thanks for the help!

 

[MadOgre]

Im working with a fresh PC so my pictures are gone lol.
@chengny

There are a few spots that could be the issue.

the cut out switch at the brake pedal

The TCC switch on the firewall

and the vacuum hose connecting from the TCC switch to the carburetor.


It is totally safe to drive around with the wiring disconnected until you get this sorted out just stay out of OD.