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post #1 of 6 (permalink) Old 07-27-2014, 06:24 PM Thread Starter
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Acceleration problems

New commander owner here, 06 4.7L K&N CAI 101,xxx miles. Starts, idles, and drives great while driving normally. When I hit the gas while driving and the RPMs go over about 3000-3500, it loses power and jerks. Drives great otherwise, and no other issues. was kind of thinking weak fuel pump, but some advice would be great. Thanks
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post #2 of 6 (permalink) Old 07-28-2014, 09:35 AM
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1st check for stored DTC in the PCM. DTC=Diagnostic Trouble Codes. Search Youtube, you can watch a short video on how to do the Key Dance that will read out the stored DTC in the display on the dash. Likely your problem is represented in those DTC's.

Although you can't rule out the fuel pump, this is one people often jump to conclusions to as a cause, you'd "likely" have other symptoms if its the fuel pump to include the engine barely starting and idling shortly after it starts to fail.

TPS, ignition or even the MAP sensor is more likely IMO, but that would be wild guess on my part. Again, look up those DTC's, and fix those DTC's.

Doing tune-up/periodic maintenance items if they are due (especially if they are overdue) can help, maybe even fix it, at the very least eleminate those items as a possible cause. And its NOT a waste of money, because you're vehicle needed it anyway. New plugs, new ignition wire/boots for the coils, air filter, etc.

Oh, you've got the K&N Filter, we'll clean it and re-lube it instead of replacing it.


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post #3 of 6 (permalink) Old 07-29-2014, 01:04 PM Thread Starter
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Thanks for the reply! Pulled the codes using the key dance (handy little feature BTW), and got p0016 (crankshaft/camshaft position sensor). Not really sure why the check engine light didn't come on though but whatever... How do I find out which one is bad? My mechanical know-how I would rate as probably a 4 out of 10. I just had head gaskets replaced about a month ago (by an awful shop I might add took them 6 WEEKS to get it done) , not sure if that makes any difference or not. Ideally I'd rather fix it myself as im a little jaded right now about shops.
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post #4 of 6 (permalink) Old 07-30-2014, 10:18 AM
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Oh Geez, you're the one that posted about sync'ing the Cam/Crank Position sensors on another thread.

This code would mean that either the cam and crank timing is off mechanically, or a bad Cam or Crank position sensor.

A bad crank position sensor most likely would cause the engine to NOT run at all.

A bad cam position sensor most likely would cause the engine to NOT run at all. Its poossible your year 4.7L has a wasted spark ignition, if that is true, the PCM would make a 50/50 guess at the phasing of the motor on each start up, if it guessed right for that start up the motor would run fine, but if it guessed wrong the motor would run poorly. The idle and low speed driving would be horrible if this was true, and only some startups NOT all.

Or you crank/cam timing could be off, if it was retarded, you'd have better idle/low speed driveability but worse High RPM power, opposite if it was advanced. That would cause the code P0016 to be thrown.

The 4.7L is chaing driven timing gear, it is extriodinarily unlikely that chain drive skipped a tooth. Chains break and the motor doesn't run. They stretch, but the 4.7L has tensioners for that, and if one of the tensioners broke, you would be hearing noticeable engine noise.

If the cam gear or cam had been removed and reinstalled incorrectly, it is possible it could be out of alignment.
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Originally Posted by paulio View Post
...I just had head gaskets replaced about a month ago (by an awful shop I might add took them 6 WEEKS to get it done) , not sure if that makes any difference or not. Ideally I'd rather fix it myself as im a little jaded right now about shops.
The 4.7L is an Overhead Cam engine, meaning you have to remove the cam and timing gear to pull the head to replace the gasket.

Hmmmm, and the shop doing the job ended up NOT impressing you as a compentent organization?

What do you think might be the most likely cause of your DTC P0016, perhaps an incorrectly aligned cam/timing gear during reassembly?

Have you had this problem since you've gotten the vehicle back from the shop?

Less than reputable Dealer's and Shop's can do a "Tilt and Slip" job when replacing headgaskets. Instead of removing the head properly and cleaning the surfaces properly, and then re-assembling it all properly; they just disassemble everything enouth to be able to tilt the head up a bit, with the cam and timing gear still assembled, slide the old gasket out and slide a new one in. It can be done in a lot less time doing this horrible shortcut, but NOT only will the new gasket NOT seal as well and fail early, it is easy to damage the cam/timing gear or get the cam/timing gear to skip a tooth and be out of alignment.

NOT saying they did a "Tilt and Slip" job, its just as likely the mechanic did the gasket change properly and then messed up the timing gear alignment or the tensioner install.


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post #5 of 6 (permalink) Old 07-30-2014, 02:28 PM Thread Starter
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My hunch is that they didn't align something right when they put it back together. I don't think did that "tilt and slip" job you described because after 4 weeks of them having it I called to see what the hell was taking so long, and they said the heads were at the machine shop getting resurfaced. Any guesses on what im looking at price-wise to have a shop look at it?
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post #6 of 6 (permalink) Old 07-31-2014, 12:32 PM
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Quote:
Originally Posted by paulio View Post
My hunch is that they didn't align something right when they put it back together. I don't think did that "tilt and slip" job you described because after 4 weeks of them having it I called to see what the hell was taking so long, and they said the heads were at the machine shop getting resurfaced. Any guesses on what im looking at price-wise to have a shop look at it?
If you have had the problem since you picked the vehicle up from them, then it is extremely likely they didn't finish the job properly and mis-aligned the cams/crank.

They should fix their mistake for free.

I don't know how to confirm the cam/crank timing on the 4.7L, other than pulling off the timing chain covers and checking the marks are aligned, that would be several hours of labor at least if NOT in a dozen hours. Once all that is off, it should only be another hour or less to align the timing marks.

Perhaps there is another way to confirm the timing, you can ask another shop and see what they qoute you to check the cam/crank timing. Maybe there is an inspection port, maybe a shop has the tools to check #1 piston TDC, align a timing wheel on the crank and put a mic gauge on the intake lifter in a short of enough time it wouldn't cost much to have them check that way.

But the code P0016, engine symptoms are telling you that the cams are likely unaligned. Its NOT likely the Cam/Crank position sensors, and a shop just did a job where they had to remove, replace and re-align the timing gear. It looks very likely they didn't align the timing gear properly when they did the job.


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