Replaced DPFE, but it's still hitching!!!

[RentonRanger]

I've been suffering the dreaded bucking/hesitation/jerking at cruising speed (50-60 mph) and have tried several things to make it stop. O2 sensors replaced about a year ago, problem gone. Hesitation started again about six months ago so I replaced the plugs, problem gone again. Bucking started again about a month ago so I got a new DPFE. The hitching is about 90% better, but still there. Now what? Is there something that might be dirty or gunked up that I can clean? I just cleaned my MAF and K&N not too long ago, so I don't think that's it, but I can easily clean them again.

The only other thing I can think of in searching this and other forums is maybe my camshaft position sensor and synchronizer might be going bad but I don't have that chirping sound that goes along with a bad CPS. I'm not a big fan of replacing perfectly good parts, but I'm at a loss here. What else could cause this highway hesitation?

 

[martin]

When did you last change the fuel filter?

 

[Wicked_Sludge]

the engine will run fine without the CMP (cam position sensor). it will NOT run well without the CPS (crank position sensor). the CPS gives no audible warning before it fails.

you should swing by a local parts store and have them scan the truck for codes, just to see if anything is stored in the KAM.

 

[RentonRanger]

Fuel filter is a couple of years old. I suppose that could be it. I already tried to pull codes with my X-Cal2 and didn't get anything.

 

[mht95ranger]

What kind of audible warning will the cps give before it goes out?

 

[shadetree]

A bad throttle postion sensor will give this symptom. It gets a worn spot where it spends most of it's time. Common porblem on vehicles with cruise control.shady

 

[RentonRanger]

What kind of audible warning will the cps give before it goes out?

It's kind of a chirping sound.

A bad throttle postion sensor will give this symptom. It gets a worn spot where it spends most of it's time. Common porblem on vehicles with cruise control.shady

Well I don't have cruise control, but I do spend a fair amount of time in the 50-60 mph range.

 

[Wicked_Sludge]

What kind of audible warning will the cps give before it goes out?

the CPS gives no audible warning before it fails.

the CMP syncro shaft will sometimes chirp as it wears.

 

[snake]

Shoot a can of 44K in the thing and see if it straightens it out. It will clean the crap out of the injectors...

 

[Bent Bolt]

Since we're all guessing, I say have a look at the plug wires

 

[RentonRanger]

Shoot a can of 44K in the thing and see if it straightens it out. It will clean the crap out of the injectors...

Sorry for my ignorance, but what's 44K?

Since we're all guessing, I say have a look at the plug wires

Will do.

 

[dogboy]

My truck is doign this eaxct same thign for the past 3 or 4 months ( quite annoying). But mine does it at any speed if I get the throttle in just the wrong spot (a somewhat large spot...).

I've been told to check for intake manifold/ vacuum leak, dirt injectors, and the Throttle Position Sensor, fuel filter, and plugs/ wires. I've changed the fuel filter, and plugs, and the wires tested within spec (7k ohms resistance per foot if I recall) with no change.

I ran a can of Seafoam through a full tank, with no changes at all either. I am probably going to hook a vacuum gauge up to it tomorrow and see what it says (7-8 months ago, it read 18-19psi vacuum, or what ever you want to call it).

After that I am going to check/ adjust the throttle position sensor. I've been told you can adjust it, so I'm just going to figure out how to do that and see what it does.

 

[feellnfroggy]

My truck is doign this eaxct same thign for the past 3 or 4 months ( quite annoying). But mine does it at any speed if I get the throttle in just the wrong spot (a somewhat large spot...).

I've been told to check for intake manifold/ vacuum leak, dirt injectors, and the Throttle Position Sensor, fuel filter, and plugs/ wires. I've changed the fuel filter, and plugs, and the wires tested within spec (7k ohms resistance per foot if I recall) with no change.

I ran a can of Seafoam through a full tank, with no changes at all either. I am probably going to hook a vacuum gauge up to it tomorrow and see what it says (7-8 months ago, it read 18-19psi vacuum, or what ever you want to call it).

After that I am going to check/ adjust the throttle position sensor. I've been told you can adjust it, so I'm just going to figure out how to do that and see what it does.

It could be the TPS going bad. But when it does you will know it. There is no adjusting the TPS. It spins 180degrees based on the position of the intake butterfly. The DIS box can be a problem, In my truck it was the coil for the waste spark (2.3l) I have points 1 and 4 were bad and had to replace it. I still have problems. Check to see if the CPS is dirty. Buy a haynes manual to help with disassemblies and assemblies.

 

[snake]

Sorry for my ignorance, but what's 44K?


Will do.

Its some bad-ass injector cleaner- about $23 or more a can and only sold at stealerships and a few oil change places. Local mechanic turned me on to it, works like a mo-fo. Its supposed to be pure techron.

 

[RentonRanger]

Well, it seems to have worked itself out. It's running just fine now, no bucking or hitching at all! I'm thinking that maybe the PCM needed to "re-learn" the new DPFE readings and it just took a few days of driving to get it right.

I'll keep you posted if something changes...