Low Idle Speed

[zedhead]

Been fighting a low idle speed for a while.

 

1998 LOBW- Engine warm, it idles at 2-300 rpm in gear, foot on brake.

 

I've cleaned the IAC, new TPS set to .5v throttle closed.

 

I need to clean the TB, But, I doubt that will give 400 RPM idle speed.

 

Any idea's??

[Scoobywagon]

Have you plugged in a scan tool and what did it tell you about the running condition of the engine at the time?

[wtdash]

What is the idle speed in Park (assuming this is an AT)? If it's normal could be trans/TC issues.

 

What's the history of the engine? Did the low idle follow a major service - e.g. Head gasket, etc?

Td

[zedhead]

I just got done with a Head Rebuild, both heads had the valves ground, surface shaved, valve lash set. New OEM HG's. New timing belt, idlers, water pump.

 

But this problem was occurring before the head work. And continues after. I was hoping the head rebuild would have cured the problem, but..

[wtdash]

?What is the idle speed in Park (assuming this is an AT)? If it's normal could be trans/TC issues.?

[zedhead]

Around 350-400 rpms in park

[Scoobywagon]

350-400 in park is also low. Plug in a scan tool and see what fuel pressure looks like.

[Jim Ma]

I just got done with a Head Rebuild, both heads had the valves ground, surface shaved, valve lash set. New OEM HG's. New timing belt, idlers, water pump.

 

But this problem was occurring before the head work. And continues after. I was hoping the head rebuild would have cured the problem, but..

 

Check the EGR valve and check all the hoses for leaks. Check all hoses going

to intake manifold for carbon block. there is a small pipe going from the EGR

valve to the intake check it.