MPFit

Thanks for the update. I’m following because I’m having exact same problem on my 4.9.
im replacing the dizzy and will let you know if it works. I’ve checked out all ignition components and the SPOUT voltage test fails every time. I’ve done everything I can but swap out the stator / pickup. Since it’s an original distributor I bought a new Cardone to get truck running then I’ll replace old pickup in the OEM dizzy for a spare if it works out

TTurner

I'm definitely hoping that works for you. I really feel like that is my problem on my truck. I am also running the original distributor and while the truck does not have a ton of miles 145K ish it is 30 years old.

TTurner

Update... Ok so today I finally got the block off plate installed on the EGR to verify nothing was getting by and at first it acted like that was the fix but... I know better than that LOL! After about an hour to 2 hours of letting it run and cycling the motor, temp wise, it definitely fell right back to its old issue. I pulled the EGR again to verify that the block off plate did not "burn" through, in other words, I verified it was still intact and it was.

Pulled engine codes again and got:

KOEO (O)- 34
KOEO (C)- 34
KOER (R)- 34, 42, 77 (which was because I didn't do the wide open throttle test, trying to not **** the neighbors off)

So now what? Distributor??? O2 Sensor???

MPFit

I’m putting the New dizzy in today and will let you know how it works out. Have you by chance ran the ignition tests from the haynes if you have one? My issue is a low voltage spout causing exactly what your symptoms are. I had a code 42; but it comes and goes. It could be from the misfire caused by preignition / detonation. Also- you can pull off your EVP and test it. Haynes describes that as well. Another way to test is to tape the stick of the evp all the way down to and run a test again to see if it changes anything. That should show the computer the egr valve is fully open when the stick is down. Unfortunately I think the code that gets thrown for this could be the 34. But worth a shot.

TTurner

So I think I finally made some forward progress today. I went and bought a distributor with the full intention of ripping the old one out. Well in one final check of everything I found some bad burn spots on the terminals in the cap and on the rotor, the rotor also had a couple very small rust spots. SO..... I sanded everything to make it smooth and started the truck and it seemed to run smooth. So with that being said I went and bought a new cap, rotors, and plug wires. I found one wire that was questionable so I replaced them all. This brings me now to the new thing it is doing.

So it doesn't seem to have the dead miss/stumble anymore but if I hold the throttle at constant rpm it does seem to surge a few 100 RPMS. It is not a drastic change when it happens seems to be fairly subtle. Could this be the O2 sensor? Only reason i ask is because of the 42 code which is showing system rich.

MPFit

Awesome. I did not throw the New dizzy in; may not even have to- I retested ignition and have a bad coil (odd because it passed when the issues started). With something to actually go on I’m going to replace and see where that lands me. Still have a low voltage to Spout however. Not sure what that means yet but I’ll worry about what I can fix now first.

vjsimone

"Do All Scheduled Maintenance Prior to Troubleshooting"
A tune-up goes a long way in resolving suspected issues....
Play in the Dizzy shaft can give you issues with your Rotor and Cap.
How are your plugs?
Glad to see you are making progress.....

vjsimone

O2 sensors do not last forever, if you don't know the age, you should replace it.

TTurner

What would be considered unacceptable play in the dizzy? and are you referencing like the rotor being able to move?


I just want to make sure I understand what you are talking about because you can wiggle the rotor a decent amount. Enough that I am kind of curious as to the condition of the teeth on the bottom of the distributor.


Havent pulled plugs I would hope they were good... I was shocked by the rotor and cap because they were not old at all and hardly had any actual miles on them. I WILL check the plugs though and get back to you.

TTurner

Thanks for that I am getting very suspicious of that sensor lately.