So I believe I have found my issue as my truck is running much much better, still need to do the finish work to consider it done but I am in the home stretch. My truck ended up having clogged cats. Sometimes it would run well other times it wouldnt. I drilled two 1/2" holes in my cat and that fixed it so I could go up to 90% throttle with no hesitation or stuttering. I also replaced the TPS before I drilled the holes and that seemed to help some. My multimeter showed it probably needed to be replaced.

I know your cats are newer but it may be worth checking on them just in case. Sorry I cant offer much better advice. Hopefully you are able to get it figured out soon.

 

any oil in the coolant or coolant in the oil? any smoke? if so, what color? hold a piece of paper up close to the tail pipe, does it blow the paper away from the exhaust or try to suck it in? blowing out is good, sucking in would indicate a valve not closing properly or at the wrong time (stretched timing chain?)

 

I had the exact same problem and was blown away by the fix. Check out this thread

 

Ok. The problem is still around. I took the header off and got the crack welded (Thanks Cody Allen), I have re-installed the header and it is still doin the chugging. Altenator problem was a dash issue-that has been resolved.

What do you mean when you say you drilled 1/2" holes in your cats? Is it super loud?

Should I replace the IAC with a new one ( I replaced it with a used one originally)?

Should I cut the cats out to see if the problem dis-appears?

I need to try some more "quick" fixes, because I am supposed to be pulling a 30ft travel trailer 100 miles away next week!

 

Samsonite: I will try this when I get home this evening. I checked 5 and 6, but not 1 and 3. I will buy new wire seperators today and re-organize all wires.

ISSUE: Engine miss, spark knock, buck/jerk, surge and other driveability concerns may be caused by induction crossfire. This occurs because of improperly routed spark plug wires.

ACTION: If spark plug replacement is performed, the correct firing order and spark plug wire routing is essential to prevent the possibility of induction crossfire between cylinders. Refer to the following procedures for inspection of the spark plug wire routing and firing order. Properly reroute the spark plug wires if required.

Whenever a high-tension ignition wire is removed from a spark plug, the distributor cap, or the coil to perform a maintenance operation, Silicone Dielectric Compound must be applied to the boot before reconnection. Using a small clean screwdriver, apply a thin layer of Silicone Dielectric Compound on the entire interior surface of the boot. Do not apply compound to metal terminals.


FIRING ORDER

The firing order for 1987-1993 5.0Ls is 1-5-4-2-6-3-7-8. If #7 and #8, or #2 and #4 spark plug wires are routed next to each other at the separation bracket, an induction crossfire condition can occur.

The firing order for 1994 5.0Ls & all 5.8Ls is 1-3-7-2-6-5-4-8. On these vehicles the #1 and #3, or #5 and #6 spark plug wires must be separated to eliminate the possibility of an induction crossfire.

To eliminate the possibility of the coil wire becoming disconnected, route the coil wire under the spark plug wires at the distributor cap.

 

I seperated the wires and it is still not right. Idle fine at start up then begins missing after warm up (missing, chugging, hesitating.........whatever).

So now IAC replacement or holes drilled in the cats?

 

I may have missed part of this discussion, but I am keying in on this:

"Idle fine at start up then begins missing after warm up (missing, chugging, hesitating.........whatever)."

If the problem happens when the engine warms up, it sounds like it's having trouble in closed-loop operation. The last time I encountered something like this was with a MAF sensor that was not properly connected. So a failed sensor can do the same thing. Does your car have a mass-air sensor, and do you know its condition?

 

I checked the 02 sensor. The 02 sensor was so loose that it was only halfway threaded in. I pulled out and cleaned with carb cleaner and re-installed it. It ran better but still had the issue. I replaced the IAC with a brand new autozone special. Now the idle problem is completely gone, even if it is warm or cold or in gear or in neutral. Purrs like a kitten. The problem still exists when going down the road. So I ran the OBD 1 scanner with key on engine off and engine running. Here are the codes:
Tester said it is an 8 cylinder (yay)
33 - EGR Valve position error - it is not opening or closing properly
44 - Problem with smog system (its disconnected right now)
11 - system pass
53 - TPS- signal voltage is too high (indicating wide open throttle condition)
85 - canister purge solenoid circuit failure or transaxle problem or electronic control assembly (ECA) status: adaptive lean limit reached in fuel control program.
36 - I cannot find a code 36 definition
63 - TPS- Throttle Position Sensor signal voltage is too low.


Looks like the new tps is not working

 

when you say you replaced the IAC did you bother to take the throttle body off and clean it good? it doesn't take much build up in there to foul things up. get some throttle body cleaner (gentle enough to not remove the teflon coating) and a toothbrush and some rags and clean the hell out of that thing.

 

I have traced the problem to a short in the wiring harness. It is giving the code 53 on 4 different TPS units. I have parts truck that I am pulling the harness, computer and MAF sensor from.......... I will try to update on Sunday.

 

Sorry being late getting back into this. I just took a 1/2" drill bit and drilled a few holes in my last cat. I cut the other one off so I have barely any exhaust so yes, it is loud. I plan to put a muffler under there so I don't make the neighbors mad. That helped but hasn't been it.

I recently did a tune up, plugs, cap and rotor. I also got plug wire clips so I could try and keep the wires separate. After the tune up it ran great for a while. It seems like it is still temperamental but much better than it was. I am wondering if I need to do a better job routing my wires since sometimes after I hit a bunch of bumps it will change how it runs.

Hopefully you get it running well soon. I have been banging my head trying to figure out my issue.

 

"sometimes after I hit a bunch of bumps it will change how it runs"

I had this problem once as well; it got so bad that the engine started to lose power while I was on the freeway. But each time, after I stop and turn off the engine, it would behave just fine, until I hit a bump again. It could have been a loose wire, but it happened a couple of months after I replaced the fuel filter. So, I replaced the nearly new fuel filter again, and the problem went away completely. I guess either the fuel pump pushed something into the filter canister that would plug it up if shaken just right, or something inside the filter body failed and started to plug itself up, if shaken just right. I should have cut it open to see, but I didn't had the patience.

 

I am starting a new thread. The computer and harness pulled from the 5.0 maf truck has an AODE transmission instead of an E4OD transmission!!!!!! uggghhhhhhh!!!!