Random Limp Mode Issue - Chit Chat

I didn't post this in the technical section b/c I'm not looking for help immediately, just wanted to see if anyone else had this issue and discuss it.

Ever since day one (Feb 2009), my car will go into limp mode and force me to pull over, shut the car off, wait a few seconds, restart. No codes logged at all. When it does happen, its when I'm about to go for it. The car had the saleen blower and tune in its stock form, then I had a JDM tune, then I had a local tuner tunes. In all cases, it has done it so I do not believe it is tune related necessarily unless its something in the factory part of the tune that make is never getting touched? And its random. I've run the car hard before back to back and it doesn't happen. Hasn't happened all summer. Yesterday I took the car out for about an hour and half. Was running well, got on it a few times no problem. On my way home, I went to go WOT and it does it. Struggle to get her pulled over, turn off, on, fine.

Its weird. When it happened the first time, Saleen had me send them the ECU and they reflashed it. But that never resolved it because I can't recreate it. It doesn't log anything. Happens like once or twice a year. Don't drive the car much and doesn't leave me any info to try to diagnosis it further.

Anyone else? Maybe just a random blip if I either hesitate with throttle or it just wasn't ready for it?

First thing that comes to mind that will put a throttle by wire car into limp mode would be a throttle body related issue. No codes when it occurs? Scan for codes with your handheld tuner. I would expect a code or two stored. You could try to do the relearn procedure for the TB assembly. IT may resolve the issue but not a guarantee. Check for binding TB blade, motor, gears, etc. Check for loose connections on the TB blade motor and TPS sensor. You can key on and Datalog the commanded TB position and actual position to see how they are corresponding to each other without starting the car. Observe throttle commanded against throttle actual as see if they are compliant. Observing the voltages on the TPS would be also advisable as there is redundancy in the TB system to protect the driver in the event of TB failures under normal driving.

Throttle body issues will generate a limp mode as quick as anything. Doing this and finding nothing will allow you to at least rule out one of the systems and move on to other things. Best of luck.

As RED above said, I would also have someone shake the wires when you are testing to make sure you don't have a wiring problem.

I would scan for codes when that happens and keep track of them.

I had a similar issue on my blown 05 that would do that after WOT pulls. Turns out, it was a simple fix as the hose connection kept coming loose and would cause the car to dump fuel like crazy and idle like utter shit.

Another option, do some data logs via dyno and send them to your tuner. They can pin point the issue with that information usually.

Any dash lights come on when this happens? ("wrench" CEL, or flashing theft, etc)

Scan for codes when it does it BEFORE you cycle the key. Are there any "pending" codes?

So to answer above: originally I bought a new MAF because Ford thought that might have caused the issue. I've wonder if it's the throttle body itself. I have taken the throttle body off a few times and sprayed it out with throttle body cleaner and make sure it's not oily(from the sc before I had a catch can). I did spray and clean it a few months ago. I have scanned with both my SCT x3 and my Palmer Performance laptop software. No codes, pending or hard. That's why it's weird. When it goes into limo mode, it does have a wrench in the dash.

Now I like the idea of scanning before I recycle the key. Normally it happens on the major roads so I'm more concerned with getting the car over safely and getting it running. But next time, I will pull over if I can and scan before I restart. Great idea.



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I also like the idea of having someone move the wires while I scan.

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I hate throwing parts at a problem without a diagnosis but perhaps pick up another throttle body and put it on? Used ones should be cheap enough now that it's not a current production model.

Yea I didn't do that back in the day because the stockers werent cheap. Maybe ill low-ball some eBay auctions.

When I did a search, I notice some people re-set their throttle body using the gas pedal. I've never done that. Some people said they do it every time they change tunes. Some said it's a placebo. I'll give it a shot.

Just curious what you guys think of this: with the key in the acc on position but not started, when I put the pedal to the floor the throttle position is 89%

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My latest datalog on a 1/4 mile pass shows Throttle actual @ 81.00% and the same for Throttle desired at WOT. Throttle off (idle) shows 5.10% actual with 5.07% desired as the car is slowing down at the end of the track - gas pedal fully released.

As I understand 80-82% is the norm at WOT. The 89% WOT actual may be your issue. The relearn function may resolve the issue...??? A swap out with a used one would be the quickest way to know in this case. Best of luck.

Thanks for the info. I'll try the reset, then a used throttle body

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I can make my car go into limp mode and have the wrench come on. And I'm positive it is my tune. And cycling the ignition fixes it. This happens if I set my idle lower than what the tune has set as base. But I get a code of "idle higher than expected P0506 I think it is. It actually idles lower than the setting. If I leave the idle speed alone, it never limped yet.

Bottom line, it could be something in your tune.

I would have thought so of the same issue hasn't happened since day one, across three different tunes. The throttle body is more likely the suspect than the tune at this point, I think.

Any of you guys running the cobrajet 62mm throttle body? I had planned to eventually upgrade to that anyway. Can I just slap that on? Since the MAF housing remains the same, it shouldn't require an immediate retune, correct? I just won't get the complete benefit until I do. Or is it gunna run shitty with it?

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Jeepngli said:

Since the MAF housing remains the same, it shouldn't require an immediate retune, correct? I just won't get the complete benefit until I do. Or is it gunna run shitty with it?

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I'm not a tuner so I won't act like I know the technical details, but I was told the PCM refers to a table to get values for getting throttle input to agree with blade angles and those values are different for each TB. So yes, you'll need a tune or I'm pretty sure the wrench light will come back.

Jeepngli said:

I would have thought so of the same issue hasn't happened since day one, across three different tunes. The throttle body is more likely the suspect than the tune at this point, I think.

Any of you guys running the cobrajet 62mm throttle body? I had planned to eventually upgrade to that anyway. Can I just slap that on? Since the MAF housing remains the same, it shouldn't require an immediate retune, correct? I just won't get the complete benefit until I do. Or is it gunna run shitty with it?

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ask the professional that you plan on buying the item from....assuming you are buying the device new. Your tuner would be able to answer that question for you as well.

Of course. I'm going to be switching tuners in the near future so I would always check with them. Just curious if any of you had experience.

Been busy the last few days, but I plan to do the throttle reset and see if I can reproduce the limp mode while data logging. Also watching eBay for a replacement. Thanks for the suggestions !

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Try 07Bandit. He had a stock TB for sale when I was looking for one but I bought from someone else instead. Looks like you guys are in the same state as well.