Intermittent idle/throttle problem

Tiny
RUSTY AVEN
  • MEMBER
  • 2006 FORD E-SERIES VAN
  • 5.4L
  • V8
  • 218,000 MILES
I drove my van the other day and parked it to do laundry. After I went to leave and when I started the van the idle starts to surge fast and slow up and down. As I drove it the idle stayed at least 1,000 rpm even at idle. I parked the van for a bit and started it again and It ran fine then and for a few days. Tonight I had parked it and when I started it again it ran really rough and threw an open wrench light. I moved it to flat ground and turned it off after it sucked a lot of gas and smelled really rich. I let it sit for a bit then tried it again and it ran fine again. I turned it off and contacted you guys, help? Lol
Saturday, April 6th, 2019 AT 11:34 PM

10 Replies

Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello,

This sounds exactly like a vacuum leak. I say this with extreme confidence because my car has a 4.6L engine in it which is essentially the same engine, yours just has a little bigger heads on it. When you have a vacuum leak the idle will "search" up and down at idle. The rich gas smell you are smelling is because the upstream O2 sensor is falsely reading a lean condition in the bank with the vacuum/intake leak and is trying to compensate for this by adding extra fuel to the bank.
A good way to check for an intake/vacuum leak is to get a propane torch. Crack it barely open so that propane is barely coming out. Make sure it is not lit. Start your vehicle and let it idle. Move the torch around the air intake duct, the throttle body, the intake manifold, all vacuum and Evaporitive Emissions (EVAP) lines. When the intake/vacuum leak is found, the engine will pick up as the propane is introduced into intake and burned into the combustion chambers. Please do this test and get back to us with what you find out.

Thanks,
Alex
2CarPros
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Saturday, April 6th, 2019 AT 11:54 PM
Tiny
RUSTY AVEN
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  • 10 POSTS
No propane and forced camping. Out in Malibu. What about the really rough idle?
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Saturday, April 6th, 2019 AT 11:56 PM
Tiny
RUSTY AVEN
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  • 10 POSTS
It was also running in limp mode with the open end wrench light on bit. No other lights or check engine light.
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Saturday, April 6th, 2019 AT 11:58 PM
Tiny
RUSTY AVEN
  • MEMBER
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Thanks Alex.
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Saturday, April 6th, 2019 AT 11:59 PM
Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello,

You can also do the same test with a spray bottle of water, just that the engine will bog down instead of rev up. I like the propane way because when I was going to school that is the way Honda of North America taught me to do it. I have included a link below for you to go to:

https://www.2carpros.com/articles/reduced-power-limp-mode

Please go through the guide and test for intake/vacuum leak and get back to us with what you are able to find out.

Thanks,
Alex
2CarPros
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Sunday, April 7th, 2019 AT 5:31 AM
Tiny
RUSTY AVEN
  • MEMBER
  • 10 POSTS
It is not all the time. Can a vacuum leak be intermittent?
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Sunday, April 7th, 2019 AT 8:42 AM
Tiny
RUSTY AVEN
  • MEMBER
  • 10 POSTS
The electronic throttle control light came on and the van went into limp mode. I shut it down and after awhile restarted it and it ran fine. Not sure its a vacuum problem. More TPS? Maybe or AIC?
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Sunday, April 7th, 2019 AT 8:48 PM
Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello again,

No, a vacuum leak would not be intermittent. I have included for you a diagnostic troubleshooting guide for your vehicle's Electronic Throttle Control System in the diagrams down below. It will call for you to use a multimeter, so I have included a link below if you are unfamiliar with how to use one.

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Please go through the troubleshooting guide and get back to us with what you find out. This is probably going to take care of the whole ball of wax as well, because your original complaint would also be caused by this system malfunctioning.

Thanks,
Alex
2CarPros
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Monday, April 8th, 2019 AT 12:55 AM
Tiny
RUSTY AVEN
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  • 10 POSTS
Hey Alex, sorry it took so long to reply. I was able to finally get to a friends house to diagnose the problems. I pulled the throttle body off and cleaned it and re-calibrated it as per video instructions. I found out with Fords, if you disconnect the battery the throttle body needs to be calibrated again. So continued on trying to do the testing you sent but it didn't make sense between the instructions and application. Also my truck is drive by wire, no cables or linkage, so I am at square one. Checked the vacuum, cleaned the PCV, which was rattling, not clogged, couldn't find the EVAP canister, ran around the engine block, no leaks. It still has a miss with no code, frustrating.. Any better tests for the sensors? Is key on or off? Where can I find information for thorough tests. Haynes manual says refer to electrical diagnostic manual for this truck?
Any help is appreciated. Thanks
Rusty
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Wednesday, May 8th, 2019 AT 6:10 PM
Tiny
STEVE W.
  • MECHANIC
  • 14,108 POSTS
The E and F-series in that generation in particular have a known issue with the TPS on the throttle body failing. There have been multiple updates to them over the years with the latest ones supposed to fix the problem. They are a bolt on replacement with the newest version being a box shaped part. When they start to get glitchy they can cause limp mode as well as running issues.
The miss with no code should be visible if you have a scan tool that can view mode 6 data in the generic OBDII mode. IE you just use the machine in generic mode, not using the vehicle specific mode. Fords are kind of quirky that way on many scan tools.
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Sunday, May 12th, 2019 AT 4:55 PM

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