Well, my 2001 Supercrew 5.4l with about 65k miles started having some hesitation/shuddering under light load. Noticed it first on a road trip using the cruise control going up slight hills. If I accelerated a little harder it would go away. It got much worse after I got home. Anyway, rolling along at 40-50mph going up a slight rise, as you give it gas it really shudders bad.

So, I had added something to the gas to clean the injectors. Also got to thinking I may have gotten some bad gas on the interstate. Oh yeah, check engine light came on while I was putting load on the engine in the driveway (in gear, brakes on, wheels chocked). So what I did was to replace fuel filter, air filter, pcv valve, and add seafoam to get rid of moisture in gas. Also filled up tank with fresh gas. Oh yeah, cable off battery for 30 minutes to clear code (yep, should have found out code first). Still seems to do it, but not as bad.

One extra piece of info, I had the tranny fluid serviced before the long road trip. Fluid level is good now.

Any hints? Where to start next?

thanks,
Rusty

 

Are you sure it's the engine shuddering and not the tranny? No real reason to think it'd be the tranny, but since it started right after you got the tranny serviced, seems a little fishy.

One other thing it could be is your O2 sensors. They'll make your engine shudder under moderate load too and since your truck is a 2001 and only has 65k miles on it they might be all gummed up with carbon. Just a thought.

Have you run a full talk of gas through it since you Sea Foamed it and added the injector cleaner? Sometimes that cleaner takes a while to work. If it's not too severe, I'd run it a while and see if it continues. If it does and you get a SES light they you can get the code read and see what's up. Post the code up on here and I'm sure that someone can tell you what it means. Good luck.--DIY.

 

Tranny was my first guess, figured it was the torque converter seeking, but I'm noticing it runs a little rough idling at lights. Just did the seafoam today, so I'll put some miles on it. It was bad when we had some cold weather last week and it will be cold again next week.

Also, at it's worst it was really bad. Almost bucking. Another thing. I did the tranny service, drove for a week, then did a road trip from Austin to Phoenix. No problems until halfway back to Austin. So call it 3k miles before any symptoms.

 

Try cleaning the mass air meter with electonic cleaner (spray). It can cause all sorts of symptoms. It's located in the Zip tube ( main air inlet tube) right behind the air cleaner. Just seperate the tube from the air cleaner box and you will see the meter inside. Don't swab it or touch it just spray it real good with the cleaner. It just takes a speck of debris to get stuck on the metering portion and it will give you fits. Just a thought. Good luck

 

Well, I put some miles on it and have tried the cleaner on the sensor suggestion. One thing I've noticed is that it is fine when the engine is cold (like overnight) for the first few miles. After that the problem shows up. Haven't been able to get the check engine light to come on again. It is also definitely missing. I did clean under the hood and thought I was careful, but now reading some of the other threads about water and the COPS I am strongly suspecting that now. The guys that did the tranny service spilled some fluid and I cleaned it up.

So, how do I diagnose which coil it is if the engine light doesn't come on? Buy one and swap? I only cleaned one side of the engine compartment so I know where to start.

thanks,
Rusty

 

Oooh. Yup, water and COP's don't mix real well. To find the one that's missing, if you can get it to miss for a little while, turn the motor off and start pulling plugs. If you compare the 4 plugs (you said you know which side to start on) The one that's darker and possibly even damp with fuel, is the one that needs to be replaced. Coils have a way of getting weak when they warm up and I'mm betting that's the ticket. Good luck.--DIY

 

Well, we had some warm weather and after reading some of the other threads about missing and poor idle, I used one of the other suggestions to get it to show the check engine light and did some hard starts in 2nd gear. 10 minutes later it was lit up and off to the AutoZone. Misfire on cylinder 6. New plug, coil, anti seize and off to home. An hour later of frustrating body manipulation and contortion, I had it back together. Runs great.

Thanks for all the comments and help.