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A mechanic friend and I pulled the plenum and replaced the coils on my '91 ZR1 on Friday. It rums great now but it has a high idle. Upon startup it revs to 3000 rpms and then settles down to about 1500 rpms. I think we may have misplaced a vacuum hose. If you guys would look at the attached pics and let me know if you see anything wrong I would greatly appreciate it. Thank you!
Easy way to test for hidden vacuum leaks is to use a portable acetylene torch, the kind that the plumber uses to solder copper pipes.
Start the engine and wait for the idle to settle down.
Then simply open the valve on the torch but DO NOT LIGHT it.
Just spray the acetylene gas around the plenum area and listen for the idle RPM to increase.
There is a rubber vacuum connector just behind and below where the throttle cables connect that can be a real bear to get to seal.
The PCV valve connector can be troublesome as well if it's gone soft.
It lives behind the plenum and is the top piece that connects the twin PCV valves.
You could have broken one of the pipes under the plenum, the plastic gets brittle with age and your motor looks like she's got quite a few miles on her.
Easy way to test for hidden vacuum leaks is to use a portable acetylene torch, the kind that the plumber uses to solder copper pipes.
Start the engine and wait for the idle to settle down.
Then simply open the valve on the torch but DO NOT LIGHT it.
Just spray the acetylene gas around the plenum area and listen for the idle RPM to increase.
There is a rubber vacuum connector just behind and below where the throttle cables connect that can be a real bear to get to seal.
The PCV valve connector can be troublesome as well if it's gone soft.
It lives behind the plenum and is the top piece that connects the twin PCV valves.
You could have broken one of the pipes under the plenum, the plastic gets brittle with age and your motor looks like she's got quite a few miles on her.
'Crabs
'90 ZR1 #792
Thanks crabs, I'll give that a shot. Right at 57,000 miles really.
my vote is for that thick curly one under the front part of the intake below where the throttle body is.... it always seems to pop off when positioning the intake back down.. use a stainless hose clamp on each end. it is tough because there is not a lot of room to work with under there but prop the intake up enough to get the clamps on and you will have peace of mind it won't leak my 2 cents
my vote is for that thick curly one under the front part of the intake below where the throttle body is.... it always seems to pop off when positioning the intake back down.. use a stainless hose clamp on each end. it is tough because there is not a lot of room to work with under there but prop the intake up enough to get the clamps on and you will have peace of mind it won't leak my 2 cents
Thank you wfot. I'm going to try and look at that today.
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high idle after plenum pull
