m20 Surging idle problem

[jc43089]

What would cause a surging idle on an m20?  Starts great, idled kinda high but steady until I put it into gear then it starts surging from about 1300-1800 rpm no matter what gear and even when back to park.  Take the oil cap off and it idles high and steady.  ICV, vac leak?

[B C]

check the throttle cable adjustment  including the accelerator cable and cruise control cable on the throttle body to make sure the throttle body is closing completely. Check for cracks in your intake boot and other vacuum leaks such as the dipstick tube, oil cap, and pcv breather tube. check the throttle position switch to make sure it is working.

[jc43089]

Excellent, thanks.  Didn't think it was anything major.  First thing I need to check is if there is enough fluid but 4hp22 trans no worky either, goes if coaxed in reverse but no forward gears.  Said it might have been driven from Madison to Platteville in first gear...  Probably shot?

[mkoepp]

Also check the temp sensor wiring/connection. I inadvertently left mine disconnected once and started it and what happened is what you are describing, high idle/surging. 

Mike

[jc43089]

Thanks, I will check that too.  There are some "custom" parts around the TB area so I am leaning towards a nasty intake leak.  Just need to get it to a storage unit until spring.

[mkoepp]

As for the 4HP22, I think it is shot. I had the same thing, no forward and reverse worked fine. What happens is the forward (A) clutch pak burns out. Not much harder to repair than a clutch on a manual. You will need to find a clutch pak from donor tranny. I rebuilt my whole transmission. It was that or the 5 speed swap. I know the autos don't get much credit but they are very good IMO. Key is to remember to NEVER rev the engine after the car has been put in gear. This is what kills the A clutch pak. I am glad I kept the auto in the 528e.

[RamRod E28]

I already have a donor 5 speed and my auto was the biggest turd ever only way to get going was to put through the gears manually so jc please do the manual swap...

[RamRod E28]

We can do our swaps at the same time

[RamRod E28]

Also check for an inline resistor on the coolant temp sensor... I had to turn my idle up until I found that to be the problem