on an 88 F-150 4x4 with a 300. This problem has been with it for a little while but it has finnaly started to get annoying. It also seems to be more noticable when cold.

It will have a bad hesitation or stumble in it. more prevelent at lower rpm. whenever I shift gears, it will always shudder and stumble a bit before picking up. it does it on all gears. it also seems to do it under lite throttle too, but not quiet as bad.
It seems to be less noticable when under a load. like once I change gears and it startd to stumble, if I accelerate hard it will just stumble breifly then smooth out. same thing if I shift right before taking a hill. once I hit the hill and give it more gas, it smooths out.

at cruising speeds (55+) it does just fine.

The EGR valve is blocked off. (alluminum between it and intake)

I have replaced the coolant temp sensor and the Air charge sensor. both are well within the norms.

Any ideas?
Thanks.

 

Try changing the fuel filter, because it is often overlooked and a fuel delivery problem could be your culprit. Clogged fuel filters make the problem seem like a dirty injector which is kind of what your problem sounds like. If after changing fuel filter there is no change, check your fuel pressure at the schrader valve with a fuel gauge, ($40 at auto store) or you can run injector cleaner/seafoam in gas tank and seafoam through brake booster line. If still doing it pull spark plugs and check for fouling. A mechanic once told me that the problem like you described was the egr, but he was wrong, and you have yours blocked off. See if the engine is missing at all too, another mechanic caught it missing with my old truck, I had the same symptoms. It was the fuel filter.

 

I have the exact same problem. The mechanic changed the egr, the sensor,cleaned the fuel filter, checked all of the plugs and wires , ran some b&g fuel treatment, changed trans filter and fluid, ran some type of conditioner in it, cleared the codes on it. I still have the same problems? After a month at the shop and 850 dollars later. The check engine light comes on and gos off? After my wife and my dog my truck comes next, but after driving it to a local store I'm so frustrated with it I want to drive it off a bridge. This problem has gone on for almost 2 years now WTF.

 

Check/replace the gasket between the throttle body and the intake manifold. There was a tech bulletin about the gasket being sucked in. While the throttle body is off, look at the idle air control valve on top of it to see if it is sticking.

 

I had the codes checked today. It read that the egr was sending sinals? I just replaced the egr and the sensor????? I t has less then 100 miles on it. The check engine light comes on when I give it any thing more then part throttle. then it goes off.

 

I had the codes checked today. It read that the egr was sending sinals? I just replaced the egr and the sensor????? I t has less then 100 miles on it. The check engine light comes on when I give it any thing more then part throttle. then it goes off.

 

AAron and dr run 2 bottles of Heet and 2 bottles of ISO HEET Don't do anything else
just dump it in the tank with whatever is in there 3/4 1/2 and run it until 1/8 tank
and refill with fresh fuel another of heet and some marvel mystery oil to hopefully stop
any rust in the fuel system. You could also pull off the fuel filter and fill it with Heet
and turn the motor over a couple turns to get the heet up into the fuel rail and let it
sit for 10 minutes or so to grab any water off the injectors!! Try to keep the fuel tank
filled to prevent condensation build up and run a bottle of iso heet every other oil
change as a preventative.

 

i would throw a vacuum gauge on it, verify that you have no vacuum leaks, and also double check your timing.

 

I had what sounds like the same problem a while back. Thought fuel filter, then read the directions for changing it, and figured starting with the plugs would be easier. Boy was I glad I went that route.
Plugs #2,4,6 were ALL loose. They looked like hell too, so I changed all 6 and the wires since one of the plugs ripped off the metal plug from the boot. Worked great ever since.

 

I'd give the timing a bump and see if that helps. I'm not sure if 88's had a DPFE sensor, but I would check that out too. My 96 was throwing EGR codes and it turned out to be the DPFE, not the EGR valve itself.

 

i had the same problem. check the timing gears. they might be worn. i changed mine and wa-la no more hesitation

if the gears are worn that would cause it to hesitate when you get on the throttle because the chain has to make up the distance between the chain and the gear. once your on it and dont let of to much it wont hesitate cause it is already in contact with the gear

 

Redwing58
The 300 doesn't have a timing chain.

 

well i know it has a fiber timing gear......little bit of a brain fart....
still it still will have wear and cause the hesitation