Quick distributor question...

[5Tractorguy]

Trying to chase down a misfire on a V30 TBI 350. Have it narrowed down to the distributor (has new plugs, cap, rotor, wires, ignition modules, pickup coil, etc). What I'm wondering is, can the magnetism in this star looking piece on the shaft ever get "out of sync"? Maybe one of the poles is messed up and the pickup coil isn't "reading" it properly?

That's the only thing left that I can think of with this problem. I searched failing distributor symptoms, but those answers always point to rotor, cap, etc.

Any thoughts would be appreciated.

[kwmech]

Not really get out of sync, but they can fail. What about the coil itself, I recently had to replace mine in my suburban and it made a huge difference in driveability. Sometimes you don't notice things as they fail slowly

[ky-donzi]

The pickup coil can cause a really erratic mis, and hard starts in my experience. We had a heck of a time chasing it down in my sons car. Finally after replacing every other component we tried it and that was the issue. Good luck I know you are frustrated by now

[Just call me Sean]

Mine was misfiring because bad grounds caused the oxygen sensor to give false readings.

[5Tractorguy]

The ignition coil itself was replaced within the past year or so, ran the same with the old one too...

Pickup coil was done in Oct '18. From what I remember it made no real significant difference. Though the original was the one I changed out so it must've helped some.

Sean, over the years (8yrs) I have changed that O2 sensor about 3-4 times. Always ran better for about a year or two after then it would go back to it's bogged self. Last time I changed it, there was no change in how it ran and it stayed the same. We did add a bunch of extra ground cables to the engine, transmission and frame in case.

I've done every ignition part (except distributor body/shaft), sensor, module and vac line on this truck at least twice chasing this problem for years. Slowly eliminating all the symptoms and the last one left seems to be the misfire causing it not to advance the timing and run strong.

Going to order a brand spanking new distributor and give that a whirl. It's only $85... worth a shot for that.

[Just call me Sean]

I had to ground everything to the battery. I even had to ground the computer case to the battery.

[Pontiac1976]

I never run TBI distributor but as said bad connection or to much rust that part can make it bad or the coil if it got a leak/crack( bad connection ) gone bad from sitting to long or corrosion some time can be cleaned up.( bad coil power wires or connector.

[5Tractorguy]

Update: I went over the grounds in the truck this weekend. Cleaned up the hot stud on the firewall too (that black plastic junction block with 2 studs) and changed the ignition switch on the column.

Figured the switch might've had something to do with it. The starter solenoid has been clicking when trying to start the truck for a number of years now and the radio will cut out at random on rare occasions. Turns out the starter problem still persists with the new ignition switch. Radio not sure yet...

Replaced the starter too about a month ago with a brand new one, clicking problem was still there (will crank/start 1-3 tries in, sometimes without issue, sometimes with).

Anyways, figured the switch might have something to do with power/ground to the ignition system.

Have a new complete distributor and ignition coil on the way this week...

[Just call me Sean]

My S10 does that clicking thing all the time. My truck does it sometimes. My van did it a couple times then the starter died. All have been replaced with new.

[ky-donzi]

Oh, I forgot to say....those pick-ups also pulse the injectors. Has the truck ever died for no reason and then restart?

[5Tractorguy]

Originally Posted by ky-donzi

Oh, I forgot to say....those pick-ups also pulse the injectors. Has the truck ever died for no reason and then restart?

Did that this past Sunday. Fired and ran for about 3-5 seconds and died. I took off for the morning, came back and it fired right up.

Also died before I started this thread on the 14th. Driving home and it was like someone just turned off the ignition. Couldn't get it to restart, injectors weren't firing. Figured it was the ignition control module on the dist. Replaced that the next day and it fired up.

Could be a bad pickup coil since it's intermittent?

[ky-donzi]

98% sure that what it is especially if it wasnt fueling. I have had the pick up go out on two different vehicles.

one was a carb engine and we tracked it for months, seems like we would put a new part on (cap rotor, module, ign coil, ect) and it would fix it for a couple days. Finally replaced the pick up and fixed it!

the second time on a different vehicle we had a intermediate problem, this one was a tbi and involved a computer so it was more involved, but after noticing that it wasnt fueling and speaking with a mechanic he said it was the pick up coil. apparently the rotating pick up coil pulses the tbi injectors. problem solved again.

[Just call me Sean]

My pick up coil went bad and I had to pour gas down the throttle body to get it to start. Then I had to keep it above idle or it would stall and I would have to pour in more gas to start it again. I only did this to get it home. I guess the signal wasn't strong enough to fire the injectors at idle.

[5Tractorguy]

Thanks guys! Sounds like the pickup coil is the culprit...

New distributor will be here Thursday, so I'm going to swap the whole thing. Would have to pull the old one to change the coil anyways. Will check back in due time...

[5Tractorguy]

Alrighty, got the new distributor installed after Thanksgiving, along with a new coil and the neutral safety switch that mounts to the base of the steering column.

- No difference in how the truck runs with the new dist. and coil

- It did start quick and run smooth as silk when I had the timing advance wire unplugged. Granted the base was at about 15-20deg before I brought it down to 0, BUT it did start and run very smooth. Once I set the base and reconnected the wire, back to misfiring and such.

- Still has the clicking starting issue with the new neutral switch (not a big deal really, figured the switch would remedy since the truck still had the OEM switch).

- Drove this past Friday, still has a misfire upon startup, runs doggy, will not increase engine RPM after 2200 - 2400 rpm when depressing the pedal under load.

- The engine almost cut out on me again twice. Radio started to blip a few times then shut off entirely. Turned right back on after. Then the engine almost shut off, fell on it's face for 3-5 seconds and recovered. Like someone started to shut off the injectors. Got a bit shaky on the highway then evened out for the reminder of the ride (15min).

I'm at a loss here guys....
Seems like there is a bad connection somewhere in the harness or dirty power. I ohm'ed out the wires for the ICM, knock sensor, timing plug, no shorts. Started the truck and wiggled the harness everywhere, nothing happened. Something is causing the misfire, not letting it advance timing under a load and in turn hogs through fuel (8.5mpg). Swapping in a new/good used engine harness has crossed my mind...

[ky-donzi]

Defiantly Sounds like dirty power and it’s messing with the ecm.

[Nick_R_23]

You may have a failing diode pack on your alternator. While the truck is running, take a multimeter and set it to read AC (~) current. Put the red lead on the alternators 12V stud, and touch the black lead to the alternator body. You should not get any voltage readings, if you do, your alternator is introducing AC voltage into the system, which can definitely mess with the ECU and sensors.

[5Tractorguy]

Originally Posted by ky-donzi

Defiantly Sounds like dirty power and it’s messing with the ecm.

Originally Posted by Nick_R_23

You may have a failing diode pack on your alternator. While the truck is running, take a multimeter and set it to read AC (~) current. Put the red lead on the alternators 12V stud, and touch the black lead to the alternator body. You should not get any voltage readings, if you do, your alternator is introducing AC voltage into the system, which can definitely mess with the ECU and sensors.

You guys might be onto something... Nick, I checked the alternator yesterday with the meter on AC. The digital meter read anywhere from 1 - 4V each time I checked it. The analog meter, with the dial set to 15vAC, spiked the needle all the way up.

It's a remanned alternator that's been in the truck since dad restored it 11yrs ago. And it's always ran crappy from the get-go.

Got a brand new Delco on the way from Rockauto... Here's hoping AGAIN that this may finally solve it!

[400/400]

“- The engine almost cut out on me again twice. Radio started to blip a few times then shut off entirely. Turned right back on after. Then the engine almost shut off, fell on it's face for 3-5 seconds and recovered. Like someone started to shut off the injectors. Got a bit shaky on the highway then evened out for the reminder of the ride (15min).“

I had a similar experience in my ‘85 K20. Initially it was the odd misfire or turn signal gremlin. Then the radio would cut out or the truck would stall randomly. At 1st it would restart immediately, then sometimes it wouldn’t crank and I’d have to wait a while and it would fire right up.

So I did all the normal trouble shooting. Chased down every ground on the block and body and cleaned them. No change.

After a lot of frustration, looking around under the hood, I bumped the positive lead at the battery and saw it move. ( side post battery). I tightened the cable and never had another issue.

I learned that day to always start electrical trouble shooting with verifying BOTH battery connections are clean and tight.

[LT7A]

Stuff stuff like this is hard to run to ground...so to speak. I appreciate people taking the time to chime in. This is good info here.

[5Tractorguy]

Some new developments this week...

Got the new Delco alternator installed this past Wednesday. All went well with that.

Thanks for the tip 400/400, I checked the positive cable and it wasn't that great. Cable was moving around some in the post clamp and the other end going to the starter wasn't great either. So I made new 1/0 positive and negative cables with crimped on ends, ran the negative straight to the engine block with another cable going from there to the frame. Thing cranks like a son-of-a-gun now! Click-start thing is very minimal, radio only blipped once and that was it.

So, after all that, the truck still runs the same... go figure! Not as much ignition skip upon startup, still has hesitation, no power on hills, weak acceleration on highway, blows through fuel...

I did some digging around here this AM about timing and stumbled upon this post below from rfmaster from a few years back about setting the IAC. I had a feeling it might not be correct because if the truck wasn't warmed up fully, you put it into drive and begin rolling forward, the idle would jump up (would also do this rarely during regular driving).

So after I reset the IAC per his description, the engine immediately ran smoother when I re-started the truck. Took it for a quick drive and it made a significant difference. Still some hesitation upon take-off and when you lay into the pedal, but there is definitely more pep/power. Feels like the ECM is properly advancing the timing now...

I'll know more once I get it up on the highway again and/or go for a longer drive. I'm telling ya, if nothing else, I sure am getting familiar with the working of a TBI system!

Originally Posted by rfmaster

2) You'll need to reset IAC. ECM does not know position of the IAC so it needs to be reset after repair. To do this you need to put a jumper between pins A and B of the ALDL connector in the cab. This puts the ECM into ALDL test mode. Turn ignition key to run position (not start) and the IAC should drive completely closed. You should hear a buzzing noise from the IAC. If you have the winaldl up and running on your laptop, you should see the IAC went from 145 to 0. Now unplug the IAC connector. Turn the ignition key off. Remove jumper from ALDL plug. Start motor. If the idle is too low you may have to keep it running. On the front drivers side of the throttle body is the adjustment screw. It may be behind a silver plug. If so just use a nail or punch to poke it and remove it. Then use a #20 torx bit to adjust the idle speed to at least 100 rpm less then your warm idle speed. If 600 then set to 500 rpm. You are looking for the lowest consistant idle your motor will do. When set, turn off motor and reconnect the IAC. Done - ECM will now be able to control idle RPM.