Will die when Idel drops too fast

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Dec 31, 2010 | 06:40 AM

jrodtaclet

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Will die when Idel drops too fast

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Hello, and thank you. Here is the problem I have on my 90 f150 4.9. 5 speed with 100k miles. The truck runs nice and smooth however when the RPMs drop too fast it will die. Example: I'm driving 55mph at 2000 rpm and put it in neutral approaching a red light, the truck will die as the rpms drop too fast. However if im driving and slow down to less than 1000Rmps. I have no issues. So when Im driving and I'm approaching a stop light, I just brake until my rpms are below 1000 an put it in neutral so my truck will not die, is not a major issue but im sure there is a fix for it. <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com

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Dec 31, 2010 | 07:19 AM

rla2005

Fleet Owner

Joined: Oct 2005

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From: Kentucky

The most common cause of your issue is a dirty/faulty Idle Air Control (IAC) solenoid. It is attached to the side of the throttle body. Do a search on IAC, this subject is brought up every single day on this forum. Long story short it can be cleaned, but many times it is a short term fix. A replacement may be in your future.

Look here for reference: Ford Fuel Injection » Idle Air Bypass (IAB)

Jan 10, 2011 | 01:32 PM

jrodtaclet

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I have replaced the IAC and is still doing the same thing.

Jan 10, 2011 | 04:09 PM

jv2290

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From: North Central Ohio

Quote:

Originally Posted by jrodtaclet

I have replaced the IAC and is still doing the same thing.

Could be a stuck EGR valve or a fault in the EGR system. If it's stuck or not closing all the way it's like a vacuum leak. I've had 2 trucks that have done that. You can try pulling the vacuum line from the EGR and plugging it to see how it works. Your check engine light will be on but it won't hurt anything.

Last edited by jv2290; Jan 10, 2011 at 04:12 PM. Reason: Spelling

Jan 10, 2011 | 04:42 PM

jrodtaclet

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Thank you, my EGR vaccum hose is disconected, this is the only way my turck runs great. I notice that my truck only has an issue once it warms up. Is not a big issue as I've learn to slow down before I put it in neutral. Thaks

Jan 10, 2011 | 05:21 PM

jv2290

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Joined: Nov 2010

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From: North Central Ohio

Quote:

Originally Posted by jrodtaclet

If it's only when it heats up it could be the ECT (Engine Coolant Temperature Sensor) located on the water outlet.

Heres a link with info on that. Ford Fuel Injection » Engine Coolant Temperature Sensor (ECT)

Jan 10, 2011 | 06:53 PM

rla2005

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Joined: Oct 2005

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From: Kentucky

Quote:

Originally Posted by jrodtaclet

So now we have a little bit more to the story. If you had added that tidbit of info initially it could have saved you some $$$ and time. Until you resolve your EGR system issue, you will have the side effect you started this thread with.