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2004 f-150 4.6L Rough Idle and stall

Predator support for Ford gas vehicles

Moderator: mikel

Post Mon Jul 20, 2009 4:12 pm

Posts: 11
U7151 f150
v.9r04
Univ Rev2
2004 F-150 4.6L Automatic

My engine is stock. I installed the predator 93 octane tune. When I first installed it sometimes the truck would stall when I stopped and did not place it in park. Also it did this when I shifted into reverse. I got a check engine light. I can't remember the trouble code (P ????) "Idle control air speed lower than expected". Also got another code saying something like "OBD test did not finish" or something to that effect. If it comes up again I will post it exactly. After a few weeks it stopped doing this but recently while on a 500 mile road trip it started again. Any idea what may be causing this? I read somewhere that it could be MAF sensor, and also that it could be throttle body problem. Do I need a custom tune? Any suggestions for a few more HP or MPG? I have been considering a cold air intake and electric fan. Is it worth it? what about throttle body or TB spacer?
Last edited by rdub76 on Mon Jul 20, 2009 4:14 pm, edited 1 time in total.

Post Mon Jul 20, 2009 4:13 pm

Posts: 55016
Location: DiabloSport World Headquarters

Do you have any other mods on the truck?
Mike Litsch
Powerteq Customer Service Manager
Diablo Tech support by phone:
561-908-0040x4
M-F 8:00 AM to 5:00 PM EST

Post Mon Jul 20, 2009 4:15 pm

Posts: 11
K&N air filter thats it.
U7151 f150
CalID: OKQ6A2
v.9r04
Univ Rev2
2004 F-150 4.6L Automatic


Posts: 55016
Location: DiabloSport World Headquarters

rdub76 wrote:
K&N air filter thats it.
Just a filter or a CAI?
Mike Litsch
Powerteq Customer Service Manager
Diablo Tech support by phone:
561-908-0040x4
M-F 8:00 AM to 5:00 PM EST


Posts: 11
Just a filter in the stock intake system.
U7151 f150
CalID: OKQ6A2
v.9r04
Univ Rev2
2004 F-150 4.6L Automatic


Posts: 55016
Location: DiabloSport World Headquarters

Interesting.
Try adding 5% to the global MAF curve.
Mike Litsch
Powerteq Customer Service Manager
Diablo Tech support by phone:
561-908-0040x4
M-F 8:00 AM to 5:00 PM EST


Posts: 11
Ok I adjusted the MAF curve +5%. Rewrote the tune. Still idling a little rough and stalled once when I was backing into a parking space. Seems like this happens more often when I'm turning the steering wheel while in reverse. Also check engine light came on again.
Code: P0506 "Idle Air Control System RPM lower than expected". Also code: P1000 "OBD system readiness test not complete". Does this info help? Do I need to give it a little more runtime to adjust?
U7151 f150
CalID: OKQ6A2
v.9r04
Univ Rev2
2004 F-150 4.6L Automatic


Posts: 1145
uninstall the predator and return the truck back to stock settings and see if it persists. This will help to identify if it is a tuning issue or an air cleaner issue or dirty MAF sensor. If you have a dirty MAF for some reason you can clean it with MAF sensor cleaner that is available at your local auto parts store.

If the problem persists with the stock tuning and clean MAF sensor, then you have another issue with your truck that is not tune related. Next step would be to put the stock air filter back in. I dont know why a simple panel filter would cause your issue but it is one more way to deduce the issue. If after returning the filter to stock the problem still persists, then you need to have it looked at professionally.


I am not a real fan of aftermarket fans for trucks as cooling is very important for trucks while towing. Factory electric fans are designed much better.

TB spacers are hit or miss for improvements of torque or fuel mileage. I have seen instances when they work and also vehicle applications when they didnt.

What is your idle speed? a rough idle and steering wheel turning indicates a low/weak idle. When you turn the steering wheel during low speed driving, it is more strain on the motor such as backing up out of parking space with very little or no throttle input. This may indicate a dirty MAF sensor as the sensor measures incoming air and correlates that with the electronic throttle to coordinate a smooth idle that doesnt stumble. If either, the MAF sensor or the TB are dirty, then it can cause idle issues. Check for any grease buildup on the Throttle body ( with the engine off) and clean accordingly.

Do you have any coolant usage? If you have coolant usage but no visible leaks than it could be a head gasket seal going bad and you are burning small amounts of coolant and causing a rough idle.


Posts: 11
Thanks concoursd, I'll try that. I looked at the MAF sensor and it doesn't appear to be dirty but i'll try cleaning it anyway. I haven't noticed any coolant usage. the exterior of the throttle body is clean, actually the whole engine is as clean as I've ever seen one and I don't clean the engine, I hardly ever even wash the truck. I keep all the maintenance up to date. If this persists I'll have it looked at professionally.
U7151 f150
CalID: OKQ6A2
v.9r04
Univ Rev2
2004 F-150 4.6L Automatic


Posts: 11
I cleaned the MAF sensor with CRC MAF sensor cleaner. New air filter in. I haven't restored the original tune yet. When in park the idle fluctuates between 450 and 670 RPM and the spark advance fluctuates between 16 and 33 deg. I will update this with any changes as soon as I restore the tune.
U7151 f150
CalID: OKQ6A2
v.9r04
Univ Rev2
2004 F-150 4.6L Automatic


Posts: 11
Restored original backup tune. Still idling a little funny but idle and spark advance are more consistent. Also I forgot to mention that when I had the 93 performance tune installed I was running 92 octane on the last fill up but it has been doing this with 93 oct anyway. It still has 92 in the tank but I plan on filling up with 87 later today.
U7151 f150
CalID: OKQ6A2
v.9r04
Univ Rev2
2004 F-150 4.6L Automatic


Posts: 1145
If it is still idling funny and the stock settings have been reinstalled than it is not tune related.


Posts: 11
I am waiting on the trouble code to pop up again but it is still stalling in certain situations when idling. I think it mat be the idle control solenoid or idle air control motor. It did this once before and that was the problem I believe but it was still under warranty then so i didn't worry about it much. Does anyone know where I might find online schematics or repair manuals for free?
U7151 f150
CalID: OKQ6A2
v.9r04
Univ Rev2
2004 F-150 4.6L Automatic


Posts: 55016
Location: DiabloSport World Headquarters

Mike Litsch
Powerteq Customer Service Manager
Diablo Tech support by phone:
561-908-0040x4
M-F 8:00 AM to 5:00 PM EST


Posts: 1145
I am not sure if the electronic throttle vehicles have an idle air bypass valve anymore. The bypass valve was used for cable operated throttles. Usually the computer controls the opening of the throttle body for idle control but I could be wrong.

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