Cobra Manifold / Fast Idle

FLM Fan

FLM Fan

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Fast idle!
Did a search on this issue and found some similar problems but not all had solutions or the fixes didn't fit.

We just put the Cobra manifold on my 98 Mark CE. Also installed an Accufab throttle body and a JLT Performance Ram Air Intake (modified to fit) and tuned it on the Dyno.

The idle was up and it took a long time for the engine to return to a normal idle speed after blipping the throttle. About a half hour of running time and I got a CEL. We ran the code and it indicated the IAC. We changed the IAC and the problem continued.

The engine ran high idle until the IAC was unplugged and then it would return to normal.... but then it would give the code.

Before I have them start trying to correct this with the tune, thought I'd ask out here and see if anyone has another idea.

BTW... we did check for vacuum leaks all over the engine.
 
i had the iac problem with my intake, but i didnt do the intake swap. problem went away after i changed it out, but only after 2 CEL's. i have yet to get another check engine(4 months). from what i have read, some people use the iac that goes with the cobra intake... or was it the mark iac, maybe one of those will solve the idle issue. i have also read that people solve this issue with the tune. maybe try using the mark TB(upside down of course) and see if that improves anything. could be a few differenet things. just some ideas....
 
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might check with one of the sct tuners, such as lonnie.

If I remember correctly the stock intake manifold and the cobra intake manifold have "different volumes"... the PCM uses manifold volume figures for alot of the engine controls, idle stability and other areas that will affect performance.

looking in my SCT pro racer I can see the second gen manifold volume is different that the first gen manifold volume.. one could assume the second gen manifold volume wouldn't be the "same" as the cobra intake.

...just a thought from the far side.
 
More than likely they have something in the programming not setup correctly. Let them work it out. Tuning a Mark isn't anything like a Mustang they will find out. Have them check for vacuum leak also.
 
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Are the IAC ports in the Accufab throttle body the same as factory? If they are bigger/smaller it could also effect the idle, that is if they are indeed in the TB.
 
J said:
Are the IAC ports in the Accufab throttle body the same as factory? If they are bigger/smaller it could also effect the idle, that is if they are indeed in the TB.
Click to expand...

No, the IAC mounts on the front, right of the manifold and the vacuum line runs into the JLT CAI.
 
Ok...thats what I was wondering. Sometimes they stick the IAC valve on the TB or on the intake.

You say the vacuum line runs to the CAI? What vacuum line?
 
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