Engine Skipping when Accelerating

[Nibsey]

This is really beginning to drive me crazy. I have an '02 XLT that starts like a champ and appears to idle just fine. When warmed up, if I go up a hill (accellerate) or start from a stoplight, the engine will make a "pop/skipping" feeling at about 3500 rpm. This goes away once I get up to cruising speed. It only happens when I'm accellerating - and usually around that 3500 rpm mark. I've also noticed that the car is pretty sluggish when trying to pass cars on the freeway, etc.

I've changed the plugs, wires, coil, replaced the MAF, ran several cans of injector cleaner and still have this little skip. If in park, I can give it tons of gas and can't replicate the skipping. It only appears to occur when its in drive. Thoughts?

I don't know if this is at all related, but when I replaced the MAF and had the battery disconnected, the car ran great immediately afterward. Then after about 30 mins of driving, the skipping problem returned.

I was leaning toward replacing the TPS but wasn't sure if that's only an issue for high/low idle issues. Could a bad TPS cause a slight misfire feel during accelleration? No error codes are being registered.

Thanks in advance for any advice!

 

[rrgone]

Have you ever replaced the fuel filter? I once had one of those start to cause a hesitation under acceleration and running uphill. It was partially plugged up with gas crud.

I would think that a TPS issue would set a code, but I'm not sure. Good luck.

 

[chris2002]

In my case I thought I had a miss but it turned out to be the clutch packs in the rearend slipping. You can change the fluid and add the friction modifier. They would slip under heavy acceleration. The also slip and bind during tight slow turns. Just a thought.

 

[Black92LX]

I have the same problem and I have chocked it up to it being the Auto 4x4 kicking in.

I did the brown wire mod and when I am running 2wd the problem is gone and I have much better acceleration.

 

[jwright4]

try unhooking your 4x4 control module (behind the glove box, black box) and test it out. Same thing was happening to mine.... the 4x4 control module was bad. the module was trying to engage the AWD

 

[Black92LX]

try unhooking your 4x4 control module (behind the glove box, black box) and test it out. Same thing was happening to mine.... the 4x4 control module was bad. the module was trying to engage the AWD

how much is a new module?

 

[jwright4]

around 170 from fordpartsdirect.com they will need the vin though for production date. make sure u unhook the harness from the module though first to test it out.

 

[shadowless127]

my truck does this but in higher rpms like 4500+

 

[Nibsey]

Mystery Solved

Well I figured this one out thanks to the help of those of you who got me looking into 4x4 issues... I replaced two tires about 3 months ago (which is when this all started going down). Apparently, while I replaced two tires with exactly the same ones as were on the truck, the difference in tread depth was enough to cause my 4x4 to think it was slipping, and therefore would constantly engage/disengage the 4x4 on it's own (hence the bumping I was feeling on accelleration). Now I have two choices - pay $300 bucks for two new tires to match the new ones I just put on (but personally, the two I'd replace don't REALLY need to be replacfed), OR simply disconnect the 4x4 control module. I'm leaning toward the latter.... Thoughts?

 

[stuartr]

I have been having this same kinda skipping feel under a load like nibseytalked about. But my Mounty is AWD. I also put 2 tires on the rear new with the 2 rears sorta wore. Would this same issue happen to a AWD? I am in need of tires anyway. I hope this does the trick. I also thought about the fuel filter. Not sure what my problem is. I Hope I can get it fixed. Thanks for the help.
Stu

 

[stuartr]

bump

 

[skysthelymyt]

Change the whole fuel rail. Same thing was happening to me and after the fuel rail was changed, no problem at all and drives great. Hope this helps.

 

[Sedition]

The AWD system gives you hell when the tyres have a different overall size or pressure. I thought I would run slightly less pressure in the rear one day, it started doing the same thing your describing. In the 4x4 Auto mode, the truck will detect this difference in tyre speed through its abs sensors as slip and send more torque to the slower turning wheels.

Even torque distribution with slightly different overall sizes causes binding in the drive train. This binding action is what you feel as power loss.

In answer to your question; Yes this does happen to an AWD system when different tyres are turning at different speeds. You see, something else has to "slip" in the drive train to prevent binding but the AWD system binds up electronically to prevent wheel slippage.

Evening up your tyres will eliminate the skipping feeling.

 

[stuartr]

Thanks a bunch guys!
Sedition, are you saying AWD as in All Wheel Drive or Auto 4wheel. Mine is All wheel drive. I was wondering if that is what you were saying. I need tires anyway. So hope that fixes the problem
Sky, how hard of a job is the fuel rail and how much $$? It sorta seems like a fuel issue, not sure though. I thought about putting a fuel filter on tomorrow and trying that. BTW was the fuel rail giving you a CEL code?
Stu

 

[stuartr]

Doing a little reading on the net found this site.
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=18
Really this section:
Mismatched tires or using improper inflation pressures for all-wheel drive and four-wheel drive vehicles can also result in immediate drivability problems. Some Control Trac equipped vehicles in 4Auto mode may exhibit a shutter on acceleration and/or a noise from the front driveline and transfer case while driving. Some all-wheel drive and four-wheel drive vehicles may exhibit axle windup or binding while driving. Some four-wheel drive vehicles (manual or electronic shift) with a two-wheel drive mode may refuse to shift "on the fly" into 4x4 Auto or 4x4 High at highway speeds.

I don't think mine has control trac though. I guess the AWD system would be a form of this?
Stu

 

[skysthelymyt]

Thanks a bunch guys!
Sedition, are you saying AWD as in All Wheel Drive or Auto 4wheel. Mine is All wheel drive. I was wondering if that is what you were saying. I need tires anyway. So hope that fixes the problem
Sky, how hard of a job is the fuel rail and how much $$? It sorta seems like a fuel issue, not sure though. I thought about putting a fuel filter on tomorrow and trying that. BTW was the fuel rail giving you a CEL code?
Stu

With injectors, probably between 80-120. With labor and parts maybe between 200-250. It requires a special tool to remove the fuel supply line.
And yes, it was throwing codes. Every time I tried to pass someone it would throw a code and it was extremely sluggish. It felt like the computer was cutting a cylinder out. Mine threw a code for misfire on #3 cylinder but we did all that you could to it but no luck and then we found out that the fuel rail could give a false code for another injector or cylinder so when I got the rail changed, then my problem stopped. The cost might actually be less than that.

 

[Sedition]

Yes I mean ALL WHEEL DRIVE. I was only reffering to the switch on the dash in the earlier post when i mentioned "4x4 Auto" Sorry for any confusion.

 

[stuartr]

Thanks a bunch guys. I am going tomorrow to look for some tires. It would be great if that done the trick. Thanks for the help I thought that is what you meant sedition, just clarifying.
Stu

 

[stuartr]

Well got the tires on today. It didn't take the shutter out. I guess a fuel filter is next, but it is snowing here so not today!
Stu

 

[Sedition]

hmmm.... lets do a stall up test on your truck. What this will do is determine wether or not your automatic transmission is slipping.

1) start truck.
2) check hand parking brake applied.
3) apply foot brake, hard!
4) shift trans into D.
5) apply full throttle for 3 seconds whilst looking at RPM.
6) lift your foot off the gas.

It should rev at 2600RPM without sounding any alarms. What does your truck rev at while performing this task?