Sounds like you never had the crank relearn done after using JB Weld. That is a mistake. Obviously you don't have much of a misfire if it took 7 miles to come on - so is it a real misfire you can feel? Or are you just relying on the scanner to tell you there is no problem. At this point I don't know if problem is crank sensor moving around, or if something in your distributor is wrong.
If it was mine, I would be putting in a new distributor, cap, and rotor - and installing a new timing cover. Then have the crank sensor relearn done and see where you are at then. Life's too short to jack around so much with too many unknowns (and that is exactly what you have). Sorry!
+1
Also, have your crank sensor clearance checked and shim as necessary before the relearn.
I haven't solved this but one the SES light went out and truck ran fine.
Working on issues decided to address the exhaust leak on the passenger side
Found this Passenger side on the left. Notice the damage on the ball flange. Undamaged driver side for comparison A close up and the was a crack on thr #2 cylinder header tube and where the 3 tubes came together After welding and ceramic coating
I replaced the distributor after it jumped time for the 2nd time. Summit replaced it without issue.
This past weekend I decided to fire the parts cannon at the problem. I purchased an AC Delco fuel spider based on a 1.5% difference in fuel trims between cylinder banks. Also two hard starts.
When I pulled the upper manifold I found this Evidence of leakage at cylinder 1 which had the most misfires. Leakage at Cylinder 6 the second worst misfire frequency
The upper manifold was down tight as shown I guess that one is tight The evap purge solenoid the ears are crushed. Also one of the 10 hold downs was gone so I guess extra torque was needed
I had a unbroken upper manifold and extra stud and so hopefully there will be an improvement.
After starting the truck runs better but number 1 and number 4 still have misfires.
The truck is getting a case relearn done.
One basic thing to try that I don't think I've seen mentioned-pull the plugs and temporarily drastically reduce their gap. I'd try .030" or a little better. What this does is greatly reduce the voltage the ignition system must attain before a spark jumps the gaps. In turn, that temporarily hides problems in the secondary side of the ignition system (coil, cap, rotor, plug wires, plugs). If the misfire goes away or greatly improves, focus on those components. If it does not, then the problem is likely fuel related, vacuum leak, or a mechanical sealing issue.
V8449 I agree with you but I have replaced the plugs, plug wires, cap and rotor, distributor and the ignition coil.
The distributor had a cracked ear and could only be corrected to -9.7 CMP retard
the cap and rotor had some corrosion and 25k miles.
there were a couple of plug wires which had leaned against the header.
a new ignition coil was installed last August when this issue prevented a case relearn after a timing chain change.
Each time I have fixed an actual problem but now I am thinking it the upper manifold leaking vacuum, the damaged purge valve solenoid or a bad IAC valve
Ok, you may be fine then. If it was my vehicle I would still do it as an easy test. 60 thousandths is a pretty wide plug gap and it will put a significant strain on the voltage-containing ability of all secondary components. You wouldn't be the first to have a defective new ignition component. Coils are particularly suspect in recent years.
Ok, you may be fine then. If it was my vehicle I would still do it as an easy test. 60 thousandths is a pretty wide plug gap and it will put a significant strain on the voltage-containing ability of all secondary components. You wouldn't be the first to have a defective new ignition component. Coils are particularly suspect in recent years.
This is one way to get a look at spark strength but another method is a proper spark tester and look for 1" of strong blue spark at the plug end of the wire(s). Also you can do a drop cylinder test while on each wire. Less drop in RPM = something wrong with that cylinder, then you go further for spark/fuel/compression.
I didn't see anything wrong with the plugs when I had them out for the header removal and reinstall. Yes I realize one can be gas fouled and not appear all that different.
What I need to find is how the EVAP Purge Solenoid works as the line came off without messing with the clip. I haven't seen when it opens and closes but I half remember or so I think.
The misfire is more prevalent at idle especially when cold and when climbing hills. I am thinking replacing the EVAP Solenoid purge valve is a good idea to make sure the upper plenum is on correctly and has no vacuum leaks. Probably replace the clip for the hose at the same time.
I didn't see anything wrong with the plugs when I had them out for the header removal and reinstall. Yes I realize one can be gas fouled and not appear all that different.
What I need to find is how the EVAP Purge Solenoid works as the line came off without messing with the clip. I haven't seen when it opens and closes but I half remember or so I think.
The misfire is more prevalent at idle especially when cold and when climbing hills. I am thinking replacing the EVAP Solenoid purge valve is a good idea to make sure the upper plenum is on correctly and has no vacuum leaks. Probably replace the clip for the hose at the same time.
One way to determine if you have a vacuum leak is to look at your fuel trims. If you have positive trims at idle that become less positive at 2500 RPMs then you may have a vacuum leak. Under that scenario the truck is running lean and the ECM is adding fuel to compensate but as your raise The rpm the vacuum leak becomes a smaller percentage of the total engine air intake. Let me know if you want to pursue this.
11-10-2020, 12:20 AM
