I read the thread with the 4.9 miss, and I'm not sure if I have the same problem.

This just started a couple days ago.

While driving a constant speed (around 35-60), if I maintain that speed, my motor will start missing and chugging. It also feels like it retards the timing. The other day it wouldn't take off from a slow roll after slowing down for a red light. Then it snapped up and went. Also yesterday, it completely shut off and back on for a split second, causing a nice neck jerk.

When it does the above problem, at constant speed, I can punch the throttle, and will come back online, for about 5 minutes, then do it again.

 

pull codes, check the timing with a light, tune up with new wires, plugs, cap and rotor. replace fuel filter and check the fuel pressure

 

Yea, going to do that today. Also check my TPS.

 

ok, so the volts jump around on my TPS, but only just off of idle. I figured that was a problem, because it was so hard to barely give it gas off idle. But I don't think that is my highway problem.

 

lowest Ohms I got was 799, then it would jump around to 900-850-880 ETC before settling back at a nice 850 and slowly climb up.

 

PULL CODES

 

will see if there is any tomorrow, ran out of time today.

 

Ok, so update time.

Only code was O2 sensor reads always lean.

I've already replaced it before this started, so I don't think that is the issue, unless it went out already.
Now I have replaced the engine temp sensor and TPS.
I've cleaned out the intake, and used a can of Sea foam. Fixed a really bad exhaust leak. (loose header collectors) Still doing it. Although, I noticed today that my temp was up slightly hiher then it has been, and when it did that, the problem went away, but then my check engine light came on.

Is it possible that the T-stat is opening too soon? Also the light is already gone.

 

Bump, still need help

 

you need a 194* stat in there so you might change out whats in there for something new. they are cheap insurance

 

Yea, I think I will

Althouh I do think I might have narrowed down the problem. I got to thinking while driving home yesterday, and I have come up with this might be fuel related.

I disconnected the fuel pressure regulator, and it seems the problem has gotten a lot better. For the first time ever, i can smell the raw fuel-lol So I think that either my front pump is going out also and/or the reg is bad.

 

Ok, changed the fuel reg, and still not fixed. I'm at a loss on what to do next.

 

Ok, so I picked up a t-stat today. I also still think my pump might be the problem, but I don't know till i replace the known bad one.

 

ok, still need help

Replaced t-stat, and no luck. in fact it runs cooler now >.<

 

Good luck. I have a similar problem and in spite of shooting a parts cannon at it, I'm no closer to a solution.