I'm experiencing a hesitation while accelerating under a load. It usually occurs while I'm either in third or fourth gear at about 3000 rpms. If I let off the gas it will stop immediately. I seem to notice it more when cold, sometimes it drives perfectly. It has not thrown a CEL and doesn't have any codes stored. I've had it checked out by mechanics and they can't simulate the hesitation, but it happens to me all the time. It has new plugs, wires, and fuel filter. It also had upper and lower intake manifold gaskets replaced. I'm not sure what to try next.
Is fuel pump pressure within the manufacturer's specs? Have you checked for other vacuum leaks?
November, 2, 2013 AT 4:48 PM
The mechanics I've took it to checked the fuel pressure. They were happy with the reading. I've tried to look for other vacuum leaks. I sprayed carb cleaner around the engine and listened for any difference in idle. No difference. I haven't spotted any bad lines. Any particular ones I should look at?
November, 2, 2013 AT 4:52 PM
No specific ones. I am trying to eliminate things. If it is the original engine, have you checked compression?
November, 2, 2013 AT 4:57 PM
No I haven't. This problem is very intermittent. Sometimes the vehicle will run perfect.
November, 2, 2013 AT 5:03 PM
Then compression most likely isn't an issue. I need to think about this one.
November, 2, 2013 AT 6:07 PM
Okay. The hesitation is very much noticeable when the vehicle is cold, once warmed up not so much if at all.
November, 3, 2013 AT 10:54 AM
Without being there, the only think I can think of is dealing with the ambient temp switch. IT tells the computer the coolant temp and from that, the computer adjusts fuel mixture. On a cold start, it could be running lean. Also, back to the compression. As steel heats up, it expands increasing compression. To confirm that isn't an issue, you may want to check it.
November, 3, 2013 AT 3:05 PM
Okay I will do that. I drove the truck for a few hours today. It didn't make a difference whether the truck was cold or warmed up. Under loads or at freeway speeds it would buck and jerk. I couldn't power through it either. I'm getting worse gas mileage as well. Still no CEL.
November, 3, 2013 AT 6:19 PM
You know, the "NO CEL" has me a bit confused. Usually if there is an electrical problem, a misfire, sensor issue. It shows up. I really question the fuel pump pressure. If there is an issue with the fuel pump, usually the CEL will not come on. Are you able to check it yourself? It could even deal with the fuel pressure regulator.
November, 5, 2013 AT 10:13 AM
I checked the fuel pressure myself. 65psi running or off with key on. I have noticed that if I disconnect the battery an hook it back up my truck will run perfectly for a while before hesitating again.