2008 F150 idle surge

Timothy Diagnostician Raleigh, North Carolina Posted   Latest  
Question
Driveability
2008 Ford F-150 XL 4.2L (2) 4-spd (4R75E)

Looking for insight into an idle surge problem on a 2008 Ford F-150 4.2l. It came in with a p0304, p0316, after a few tests I found low coil secondary voltage output was the cause of the misfire. The clips on the intake manifold runner control had also broken off and were replaced. The problem occurs only at idle, and causes the engine to surge while in gear at idle. It feels almost like a dead miss, but has no indication of misfire in mode six. Fuel trim is slightly elevated on the opposite bank from the misfiring cylinder (+15) and drops (+11) when raised off idle. Vacuum leaks have been checked from lower manifold to all vacuum ports, piece by piece. Oxygen sensor counts are normal and respond to fuel enrichment. Injectors have been test fired and are all functioning normally. Cranking and running compression is in range with little to no variation, cam lift measured at the rocker arms is normal. Vacuum is normal and stable. Secondary ignition is normal, plugs and wires are new and oem, with good spark at the plug. Throttle is clean and tps values are nominal. Any insight would be welcome.

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Michael Mobile Technician
Clinton, Utah
Michael Default
 

Sounds like a stretched chain or VVT issue. This is not a "real" fix but if you have access to HP Tuners you can bump up the idle or make some minor adjustments to get it to run better. Had a Ford with 4.6L about that year with similar issue. Threw everything at it and finally used Hp Tuners to adjust. That fixed it.

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Steve Owner/Technician
Mankato, Minnesota
Steve Default
 

That is a good tool to look at the settings even if you don't buy the credits to change them.

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Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony Default
 

Hi Timothy: Try not to overlook the fuel. I understand that you've had warmer weather than us but if your fuel has changed,... This would be the opposite of what is described in the link but the result can be the same. youtube​.​com/watch?v=L-hMn4… A quick tangent if you don't mind. Years ago, Ford had an issue with the plenum bolts breaking on a particular engine We used to call…

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Timothy Diagnostician
Raleigh, North Carolina
Timothy Default
 

Remember it well the grommets on the intake bolts would shrink and allow the gaskets to leak with cold engine. Unfortunately the new design eliminates the gaskets.

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Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony Default
 

Hi Timothy: The point I was attempting to make was about the fuel blend and ambient temperatures. As you probably know, LTFT is used as part of cold running strategy. The tangent about the flash was to illustrate that LTFT was changed for that reason. (I'm assuming that the fuel trims noted by you are STFT.) P0136 is generally thought of as a misfire while the engine is still cold. Is there a…

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Tanner Instructor
Wellford, South Carolina
Tanner Default
 

What is the idle speed? Any time I have any type of surging the first thing I like to do is clean the throttle body really good to eliminate a problem caused by a sticking throttle plate or a low idle. Once that is done reset KAM. Then drive and after up to operating temp if the vehicle is still doing it let me know what fuel trim is for each bank.

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Timothy Diagnostician
Raleigh, North Carolina
Timothy Default
 

The throttle has been cleaned and actual is very close to requested rpm. There is slight movement from throttle in response to rpm shift/surge. Scope reads the response is after rpm drop. Reset kam, fuel trim remains the same.

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Lorenzo Diagnostician
Collinsville, Oklahoma
Lorenzo Default
 

I had a similar issue on a 4.2L, did everything you did and cleaned egr ports. Turned out to be a slightly bent rod on a number 4 cylinder in my case. Compression was normal during cranking tests. But when measured with engine hot and running at idle it was​.​about 30 psi lower than any other cylinder. Keep us posted on fix.

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Timothy Diagnostician
Raleigh, North Carolina
Timothy Default
 

Sounds like a promising lead. I'll give the running compression another try. The first time I did the running compression test #4 was low. Ran it a second time and it was normal. I just assumed it was an anomaly.

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Brian Instructor
Parma, Ohio
Brian Default
 

Sometimes I have been burned by the "anomaly"! the little differences in testing as long as I am not making errors in testing can lead to the right next step. let us know!

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Justin Mobile Technician
Herriman, Utah
Justin Default
 

Dumb question but did you make sure the ac compressor was off. The reason I ask is I found a compressor on a ford that caused idle surge/vibrations due to a valve that had come loose. Use IDS or similar scan tool function and watch power balance. It was only felt in gear at idle.

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

Good find! I've never had a compressor open to see inside.

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Justin Mobile Technician
Herriman, Utah
Justin Default
 

Thanks. If you listen to my haters they will tell you I’m a hack. A hack that somehow just finds and fixes problems.

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

Well, you "hacked" open that compressor, for sure....LOL I gotta remember to open one up, one of these days. The cars are so old here that we are usually getting remans, I think, so it is usually a core situation. I don't do much r&r anymore, but I will fer-sure ask the GST to hold the next old one for a look-see. Thanks again for the great photo. I "see" more stuff on iATN and here some…

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Dominick Technician
Bernardsville, New Jersey
Dominick Default
 

Hey go back,, got to be missing something! EGR stuck slightly open, vacuum leak caused by a solenoid opening at idle with engine running only maybe?

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