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Discussion Starter · #1 ·
Good Day all. Had to replace an injector on my son's 2000 300M. Replaced the injector and set the plenum back down, hooked every thing back up and once it started it would idle at no less than 2000 rpm's. The plenum gasket is new and the the seals on the rear egr tubes are new but when I put my hand over the throttle body, there was almost no suction. I have lifted the plenim and took ma peek to see if the gasket moved and it was still in place. Any body have any idea's.
 

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1966 Crown Coupe, 2016 200 S AWD, 1962 Lark Daytona V8.
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Big vacuum leak somewhere.
A spray bottle of water to test seam and joint integrity is useful. The sound and engine speed should change when the leak sucks water.
 

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Discussion Starter · #3 ·
An update to this situation. There is now vacuum at the throttle body (might have somehow missed it the 1st time) and I sprayed some carb cleaner around the base of the plenum with no change in engine speed or tone. It has not displayed any codes. Got me and my buddies stumped.
 

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Make sure that the blue rubber seal hasn't fallen off the EGR tube as it was being installed.

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Discussion Starter · #5 ·
Make sure that the blue rubber seal hasn't fallen off the EGR tube as it was being installed.

View attachment 85610
Both seals are in place and the clips have been replaced. Was thinking maybe while my son was manhandling the plenum, some junk fell in the area of the AIS motor and it isn't closing as it should. Any thoughts?
 

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Check all vacuum hoses that connect to the upper intake manifold. Make sure no attaching nipples cracked / broken. Make sure all hoses intact and not cracked and oppositve end of vacuum hose is attached properly to its individual device. Leak at power brake booster hose can cause serious vacuum leak and raise slow idle speed.
 

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Discussion Starter · #8 ·
Check all vacuum hoses that connect to the upper intake manifold. Make sure no attaching nipples cracked / broken. Make sure all hoses intact and not cracked and oppositve end of vacuum hose is attached properly to its individual device. Leak at power brake booster hose can cause serious vacuum leak and raise slow idle speed.
Good thought. My son has a tendency to think brawn over brains and could have easily pulled or broke something.
 

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Discussion Starter · #9 ·
Good thought. My son has a tendency to think brawn over brains and could have easily pulled or broke something.
This morning I plugged all the vacuum ports started the engine with the same result. Pulled the IAC and checked the ohms and came up with 51.4 on the outer pins and 54.2 on the inners. Since I can't find the specs, is this thing junk or in the money?
 

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The IAC can't be tested with an ohmmeter. Any readings would be inconclusive.
Plug the electrical connector back into the IAC and hold it in your hand. Have a helper turn the ign key from off to run.
The pintle should cycle out, then in.

A light layer of carbon is normal. If the pintle tip and its seat is heavily coked up, the IAC position has to 'adapt' to its new position to keep RPM within bounds.
 

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Chiltons and Haynes leave a lot to be desired. Used factory manuals are the best deal.
 

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Discussion Starter · #13 ·
Thanks. That is good to know. So, not everything in this Haynes repair book is to be believed.
Checked the IAC as you suggested with zero reaction. Does anybody have an idea how I can check to see if the IAC is bad or ECM has gone south? The book I have is worthless as far as a procedure for this kind of check. Thank You in advance for any help the community can give me.
 

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Just a thought, I had that problem way back when and ended up pulling each vacuum hose not off the manifold but the opposite end like the brake booster, cruise control, etc. Just plugged the end and listened for a change.
 

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The only way I have ever done an IAC/PCM diagnosis is with a capable scan tool. There are tests and commands that can be used to see if the PCM can control and the IAC can react.
If this fast idle just began after the intake manifold/fuel rail/injector service, I'm pretty sure you are dealing with a vacuum leak.
I would pull things back apart for a look.
 
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Discussion Starter · #16 ·
The only way I have ever done an IAC/PCM diagnosis is with a capable scan tool. There are tests and commands that can be used to see if the PCM can control and the IAC can react.
If this fast idle just began after the intake manifold/fuel rail/injector service, I'm pretty sure you are dealing with a vacuum leak.
I would pull things back apart for a look.
I've had the plenum off twice to see if anything moved and came up with nothing. And, tried spraying carb cleaner around the base of the plenum and got no change. Still bugs me that the IAC didn't react as suggested. Just a thought, can I plug that IAC into my 99 LHS and try the same test without harming that ECM? Around here, scan tools are as hard to find as virgins after prom night.
 

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The Rockauto website shows 1999 and 2000 3.5L use the same IAC part number.
 

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Discussion Starter · #19 ·
Tried the test and found out the IAC is dead. We'll get a new one and see where it goes from there. Unfortunately, it gonna take 3 days to get one. One of the few bad things about living in the middle of nowhere. Updates as they happen.
 

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Discussion Starter · #20 ·
Tried the test and found out the IAC is dead. We'll get a new one and see where it goes from there. Unfortunately, it gonna take 3 days to get one. One of the few bad things about living in the middle of nowhere. Updates as they happen.
HELP! Just installed a new IAC and checked to see if would move before I cranked it and nothing happened. Am I looking at a bad ECM?
 
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