High RPM Problem, assistance please. - Forums at Modded Mustangs
 
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post #1 of 8 Old May 30th, 2013, 12:16 AM Thread Starter
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Exclamation High RPM Problem, assistance please.

Hello gentlemen,

I have had a problem for the past several weeks with my 04 GT and I still have not found my solution to my high rpm's. Two weeks ago I had a shop install a new aluminum intake manifold to replace my stock one that had cracked. I had not experienced any idling problems until after the intake manifold had been installed. Since then, I have had the car dyno'd, tuned with a 93 racing tune as well as a 91 street tune, replaced the IAC and TPS and I have a new EGR on the way. I have had my shop recheck all the wiring, tubes, and bolts to be sure everything was put back in the correct position and torque.
The problem is when I start the car, the rpm's shoot up to 2000 RPM and hold there for about 3 seconds, after that they drop back to 1300 RPM until lowering down to the correct 750-850 RPM range at an idle. This occurs even after the engine has been warmed up for several minutes/driving around for a bit. When shifting the RPM's stay around 2000 RPM & will not lower until the car has come to a stop for several seconds. In the lower 3 gears I have no need to apply the gas, as the car seems to do it itself - attempting to reach 2000 RPM. I have an SCT tuner and I have checked out the RPM's and the computer is telling the car to idle and maintain it's correct RPM level (not referring to the 2000 RPM level, but the level that the RPM should be at).
If you have any questions about my problem please ask as I can provide videos and/or more information. If the EGR does not fix this problem, I am planning on replacing the PCV. Any suggestions will help if you have experienced a similar problem. I do not want to take it to the FORD DEALER, but I will if I cannot find a solution by the end of this summer. Here is a picture of the engine bay;


Thank you for your help!
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post #2 of 8 Old May 30th, 2013, 12:20 AM Thread Starter
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Originally Posted by sam.k19 View Post
Here is a picture of the engine bay;


Thank you for your help!
Here is another view point.
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post #3 of 8 Old May 30th, 2013, 12:24 AM
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Sounds like your IAC valve to me. Its probably the most common problem on these cars. Ive went through about 3.

Also is that a typhoon intake you had put on?

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post #4 of 8 Old May 30th, 2013, 02:12 PM Thread Starter
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Originally Posted by KevinJ99GT View Post
Sounds like your IAC valve to me. Its probably the most common problem on these cars. Ive went through about 3.

Also is that a typhoon intake you had put on?
I just replaced the IAC yesterday and it helped the idle but it's still not functioning as it should.
The typhoon intake is made by Professional Products. I purchased it through American Muscle.
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post #5 of 8 Old May 30th, 2013, 02:22 PM
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Sounds like a vacuum leak to me. With everything replaced I can't really tell you where exactly it is or could be. Did they use new gaskets?


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post #6 of 8 Old May 30th, 2013, 02:23 PM
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Things to check:

Make sure the throttle cable is not binding and holding the throttle open (there should be some slack). It is not uncommon for aftermarket upper plenums and manifolds to place the TB higher and further to the passenger side as compared to the stock units, this can often make the throttle cable routing a bit finicky.

Also make sure the throttle stop screw is properly adjusted--here's how. Make sure you disconnect the battery for 5-7 minutes after making any changes to the stop screw.

One last thing would be to load the stock tune; reset the KAM and let the engine idle for 15 minutes); and see how it behaves. Some custom tunes change IAC and virtual dashpot settings that can interfere with idle control.

Actually resetting the KAM and letting it idle for 15 minutes may be something to try before doing anything else.

Here is how to test the IAC, I know you said yours was new, however it won't hurt to make sure it is also working properly...

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post #7 of 8 Old May 30th, 2013, 09:09 PM Thread Starter
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Quote:
Originally Posted by Nito2v View Post
Sounds like a vacuum leak to me. With everything replaced I can't really tell you where exactly it is or could be. Did they use new gaskets?
I didn't hear, nor did the shop hear any hissing or suction sound coming from the hoses but I can double check them when I get home.

New gaskets were used on the intake manifold.

---------- Post added at 07:09 PM ---------- Previous post was at 07:05 PM ----------

Quote:
Originally Posted by cliffyk View Post

One last thing would be to load the stock tune; reset the KAM and let the engine idle for 15 minutes); and see how it behaves. Some custom tunes change IAC and virtual dashpot settings that can interfere with idle control.

Actually resetting the KAM and letting it idle for 15 minutes may be something to try before doing anything else.

Here is how to test the IAC, I know you said yours was new, however it won't hurt to make sure it is also working properly...

What are you referring to when you mention KAM?
If you are referring to the Camshafts I plan on purchasing a set of stage II in the near future, perhaps new heads as well but that is undecided.
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post #8 of 8 Old May 30th, 2013, 09:54 PM
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KAM is the Keep Alive Memory, it is where the PCM stores learned data like idle air trims. fuel trims. etc. Disconnect the battery for 5-7 minutes to clear the KAM...

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My Mustang
SOLD! - 2003 GT, UPR X, 24lb/h injectors, Magnaflow, 180° stat,
PP 70mm TB & plenum, Ralco RZ_flywheel, RAM HDX clutch, 3.73s, 262 rwHP/305 lb-ft.

new ride - 1998 SL500, 5.0L 32V 326/347 HP/tq
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