420A no mods - rough idle

[jsturgill]

Motor will not idle right!!!!

Car overheated from bad water pump. Caused the CPS to go bad. Replaced CPS and water pump. It now starts but will not idle right. Idles fine first minute or two then its like when the engine starts to warm up idle drops way down. If you do not give it some gas it will DIE!!! Seems to run fine as long as you keep the RPMS up.

Does this have anything to do with timing???? I had the timing belt off 3 times trying to get it just right. It was dark by the time i found out that i was having this problem so i could not recheck the cam gears to make sure they were still in TDC position.

Haynes manual says this may be caused by a blown head gasket to! really? How does a blown head gasket cause idle problems? I'm sure it needs one since it overheated but i've had to replace 2 on my other DSM but never had idle problems.

Basicly i'm tring to run down every other possible solution before i go taking the head off of it to replace the gasket... I plan on doing this but it will be a few more weeks. In the mean time i would love to at least get it back on the road.

Thanks for the help.

 

[Fotowntalon]

if your timing is dead on, you might want to check your TPS, IAC, and also check for any vacuum leaks.

 

[740 Turbo Brick]

Depending on how bad it overheated it may have warped the head or blown the head gasket..

 

[jsturgill]

Depending on how bad it overheated it may have warped the head or blown the head gasket..

Would a warped head or blown head gasket cause the idle to drop?

 

[740 Turbo Brick]

Would a warped head or blown head gasket cause the idle to drop?

It would lead to less compression in the cylinders, which means the car would have to struggle to run at idle, may get marginally better at a higher RPM. Do a compression test.