2008 GT Bogging Intermittently

[Deerhunter4]

I’ve had the car for a couple of months and about 2k miles. The issue is noticeable in all gears (manual transmission) below 3500 rpms. Sometimes the car runs great and at the next stop light it has nearly zero power below 3500 rpms. It has about 135k miles right now. Since I bought the car I’ve changed plugs, air filter, fuel filter, cleaned throttle body and MAF sensor. I installed a canned SCT 87 tune just to check but the issue exists both stock and tuned.

If I clear the KAM or change tunes it runs great for a while but the issue always returns. It seems worse on warm days and when the car is fully up to operating temp. It is not a misfire and feels to me like a fueling issue. The only code I’ve ever got was P0115E which is what led me to cleaning the TB.

I’ve read that bad catalytic converters could cause similar symptoms but how would I diagnose bad cats? Anything else I can look for? Cam position sensor maybe?

The car is completely stock. It idles perfectly smooth and doesn’t make any odd noises? When it’s running good it makes full power at all RPMs. When it’s bad it only makes power at high rpms. It bogs and slowly builds rpms and then feels like a nitrous shot was added if that makes any sense.

Any help or ideas would be greatly appreciated! Thanks.


Sent from my iPhone using Tapatalk

 

[bujeezus]

Clogged fuel filter? Mine was pretty bad at 60k miles.

 

[Deerhunter4]

Clogged fuel filter? Mine was pretty bad at 60k miles.

I wish. I just changed the fuel filter after reading that it could cause similar symptoms. A test drive directly after I changed it showed no improvement.

I read something about air bubbles in the fuel system caused by a faulty pump but I’m trying to figure out how to troubleshoot that as a possible cause too.


Sent from my iPhone using Tapatalk

 

[bujeezus]

Maybe a poor ground causing intermitent fuel pump operation? Sorry man, just throwing things out there.

 

[Deerhunter4]

Maybe a poor ground causing intermitent fuel pump operation? Sorry man, just throwing things out there.

Thanks. That’s a good thought. These are the type of ideas I was looking for. I’ll check the obvious places.


Sent from my iPhone using Tapatalk

 

[Deerhunter4]

Another idea I just had...could the computer be pulling timing due to knock (real or false?). One thing I haven’t tried is a tank of premium fuel. Any thoughts on this idea? Could a knock sensor be giving a false reading and the computer compensates? I have no idea if this would be as noticeable as what I’m experiencing. I may hook up my OBD and see if I can log timing.


Sent from my iPhone using Tapatalk

 

[Derf08]

What is a P0115e code? P0115 is the engine coolant temp sensor code...

it could the cmcv plates are malfunctioning. At rpms below 3500-4000 the pcm controls them. At higher rpms or WOT they are supposed to be fully open. If they are sticking, it will feel like a bog because it’s choking the motor out.

There is a motor on the back of the intake that controls them.

Another thought is a vct solenoid is dirty or failing and hasn’t tripped the CEL yet.

 

[Dino Dino Bambino]

When it’s bad it only makes power at high rpms. It bogs and slowly builds rpms and then feels like a nitrous shot was added if that makes any sense.

That rules out a fuel delivery problem and clogged cats right away. However I think Derf08 might be on to something about the charge motion control valves. It's frightening how quickly they get gunked up with dried up oil from the crankcase even on a low mileage engine, so they could be stuck in the open position. That could cause the symptoms you've described.
If that's indeed the problem, the solution is to delete them and get a custom CMCV delete tune.

 

[Deerhunter4]

Thanks guys.

It’s actually P115E FORD - Throttle Actuator Control Throttle Body Air Flow Trim at Max Limit

I’ll read up on CMCV. I’m completely unfamiliar with what these are. I did notice a fairly large amount of oil coating inside the intake manifold when I removed the TB for cleaning. I’m not sure if that’s normal or not either.

I can say with confidence that at full throttle the car runs perfectly. I’ve made several 0-100 runs and other than my poor shifting the car is pulling hard all the way. If that rules out fuel pump and cats I’m happy.


Sent from my iPhone using Tapatalk

 

[Deerhunter4]

Well after reading up on the CMCV issues I believe this could be what is causing my difficulties. I’m going to look into deleting these for sure. I’ve got a tuner I just need a custom tune and I’ll order some delete plates. Can’t hurt to at least give this a shot.

Edit: I do have the ability to adjust the canned SCT tune to delete the CMCV so at least I could install the plates and try the canned tune without a need to buy a custom tune. This would at least only cost me for the delete plates. Cheapest I’ve found so far is $279. I’m going to keep searching.


Sent from my iPhone using Tapatalk

 

[Deerhunter4]

Drove about 50 miles today and the car ran perfect. It’s been about 100 miles since I cleaned the TB and reinstalled the stock tune with no hiccups. I’m not complaining but wish I knew what was causing this issue. I report back if the issue returns. I drive about 75 miles a day so I’ll know something is better if it doesn’t happen on tomorrow’s commute.


Sent from my iPhone using Tapatalk

 

[Snake52]

Deerhunter,
I have been having pretty much this exact problem for a few months now, and I had a hell of a time finding any reference to it online. I read through these forums all the time for fun, but this is the first time an issue was directly related enough to me to post on it.

I have a 2011 GT, and just like you described, below 3500 RPM or so I get strange bogging, then I get full output very abruptly above those revs.
Your last post mentions that things seem to be running well now. Did you actually end up installing the CMCV deletes, or did you just clean out the TB and go back to a stock tune?

 

[Deerhunter4]

Deerhunter,
I have been having pretty much this exact problem for a few months now, and I had a hell of a time finding any reference to it online. I read through these forums all the time for fun, but this is the first time an issue was directly related enough to me to post on it.

I have a 2011 GT, and just like you described, below 3500 RPM or so I get strange bogging, then I get full output very abruptly above those revs.
Your last post mentions that things seem to be running well now. Did you actually end up installing the CMCV deletes, or did you just clean out the TB and go back to a stock tune?

I haven’t ordered the delete plates yet and ever since I removed and thoroughly cleaned the TB and reflashed to stock tune the car is running great. It’s been about 300 miles since then and all is well for now. I’d done this previously but I only wiped down the TB the first time. This time I spent some serious time getting it squeaky clean. If the issue comes back I’m going to order the delete plates and go that route. Since it’s running good now I’m not going to touch anything.


Sent from my iPhone using Tapatalk

 

[teeje]

When my car was completely stock, I had an issue with the ac drain condensation dripping into the o2 sensor connectors and that caused my problems. Stupid as hell but good idea to check.


Sent from my iPhone using Tapatalk

 

[Deerhunter4]

When my car was completely stock, I had an issue with the ac drain condensation dripping into the o2 sensor connectors and that caused my problems. Stupid as hell but good idea to check.


Sent from my iPhone using Tapatalk

Dang! I’ll have to check that.

After about 500 miles since my last issue I noticed a slight hesitation again today. This seems to be a repeatable cycle now. If I reset the KAM or retune it runs good for about 300-500 miles the gradually gets worse again. After about 1000 miles it is down on power so bad it’s hard to drive but a reset or retune and it’s good.

On another note I did have my alternator go out this week so I was hoping that might have had something to do with it but I guess not.

The saga continues...


Sent from my iPhone using Tapatalk

 

[01yellerCobra]

There was a time my Expedition had a weird issue with losing power. It would be fine, then suddenly it couldn't get out of it's own way. It was random though. Almost got me killed getting into traffic a couple times. It turned out to be a flaky MAF sensor. Replaced it and all was good again. When it starts getting bad try unplugging the MAF. See if it acts any better.

 

[davidjurss1]

One thing that will help, is an oil catch can. It may not solve the immediate problem, but it'll prevent oil buildup in the intake further down the line. If you decide to go that route, pick up the driver side catch. You can throw one on the passenger side, but it doesnt produce enough to worry about. When I replaced my intake and throttle body, I noticed both were gunked up pretty good with oil. Added a catch can to my build, and havent noticed any issues.

 

[Deerhunter4]

Thanks guys. I’m still troubleshooting this issue. Right now everything is good.

I’ve been watching throttle position on my monitor. Is it normal for commanded throttle position to fluctuate like 30% while cruising on flat ground. I had the cruise control set on 70 mph on level ground with no wind and the readings were jumping from 25-55%. Seems excessive to me but I can’t find any info to back up my gut feeling.

I’m still leaning towards something that the computer controls (like the throttle) because if I retune or clear the KAM it runs good.


Sent from my iPhone using Tapatalk