89 K5, Misses after Warmed Up??

[Glen1978]

Bought a 89 K5 from a guy other day and it drove great on test drive. AFter I bought it and headed home it started to miss once it was good and warm. Not doing it that I can tell at idle, granny gear or first but you can feel it in 2nd and 3rd. It feels like a fuel filter is bad......like you can let off a little and it will pick up. Fuel filter is new and fuel pressure checked out good at 13/14 psi. Im waiting on parts to come in tomorrow. AC Delco wires, plugs, cap and rotor. Anything else I should check? Check engine light works and is NOT on......checked for codes as well. All I got was 3x12 which shows clean. Truck is all stock 89 TBI.

 

[diesel4me]

May be the ignition coil is dying after it gets hot...seen some that work fine cold,then they lose voltage to the plugs once they get hot..and it'll show up under load more than sitting there idling...spark gets weak,and blows out under higher compression when you lug the engine down..

 

[Glen1978]

Well I took off stock cap/rotor and it had some build up so I sanded and cleaned that. Put it back together....same thing. I pulled off the coolant temp sensor plug and same thing. Im hoping the tuneup parts fix it. After that my guess was the same.....coil breakdown.

 

[jekquistk5]

Coil or ign module. Those two things break when they get warm

 

[Glen1978]

Went ahead and ordered the coil and ICM and will be here next Monday at latest. Be good insurance in my opinion. All AC Delco stuff. Will do the tuneup. Plugs/cap/rotor tomorrow when that stuff gets here and see what happens.

 

[jekquistk5]

Went ahead and ordered the coil and ICM and will be here next Monday at latest. Be good insurance in my opinion. All AC Delco stuff. Will do the tuneup. Plugs/cap/rotor tomorrow when that stuff gets here and see what happens.

Make sure you use the heatsink compound when you put the new ICM in.

 

[dyeager535]

Went ahead and ordered the coil and ICM and will be here next Monday at latest. Be good insurance in my opinion. All AC Delco stuff. Will do the tuneup. Plugs/cap/rotor tomorrow when that stuff gets here and see what happens.

Should have bought a whole new distributor. The pickup coil can cause all sorts of issues, and distributor has to be removed to replace it. Cheaper to get a distributor (granted, not Delco) complete than the components. May consider keeping the others as spares.

EGR may be a culprit as well, you can unplug the EGR solenoid it to test. You'll get a CEL, or should, but it will not affect performance.

 

[Glen1978]

Make sure you use the heatsink compound when you put the new ICM in.

Any info on this? First Ive heard of it.

Should have bought a whole new distributor. The pickup coil can cause all sorts of issues, and distributor has to be removed to replace it. Cheaper to get a distributor (granted, not Delco) complete than the components. May consider keeping the others as spares.

EGR may be a culprit as well, you can unplug the EGR solenoid it to test. You'll get a CEL, or should, but it will not affect performance.

yeah possibly but I wouldnt put aftermarket in there. Only ACD or Delphi in the ignition/electronic department for this guy. There is a reason why old Chevys are still running up and down the road.

I pulled the plug wires and plugs in preperation for the new parts to get here tomorrow. The wires looked good but when I pulled on them all but one wire came apart at the boot. The plugs were all tan but some had some corrosion on them. I have a feeling the tune up is gona fix this thing.....least I hope so. Mainly glad I had good fuel pressure. I did NOT want to pull that tank.

 

[dyeager535]

You do realize that you are most likely going to get *chinese* parts, right? Last few boxes of Delco components I got (fuel pumps) were Chinese.

Not saying the Chinese can't make things properly, just takes QC effort. If it isn't China, Mexico or Taiwan. NOS stuff will be US stuff of course.

Just going to put this out there....if you are going to dig into the distributor, replace the pickup coil. That will leave you stuck on the side of the road, guessing what the problem is, unless you've got a multimeter with you.

 

[Glen1978]

You do realize that you are most likely going to get *chinese* parts, right? Last few boxes of Delco components I got (fuel pumps) were Chinese.

Not saying the Chinese can't make things properly, just takes QC effort. If it isn't China, Mexico or Taiwan. NOS stuff will be US stuff of course.

Just going to put this out there....if you are going to dig into the distributor, replace the pickup coil. That will leave you stuck on the side of the road, guessing what the problem is, unless you've got a multimeter with you.

Well I canceled the order on the ICM. No point in spending money on that where if I ordered a new dizzy it would have a new one in it. Rockauto has a reman AC Delco dizzy for $252. Where else should I look if I wanted to buy new? What brands? MSD or anything like that or stick to stock type stuff? thanks guys.

 

[dyeager535]

Well I canceled the order on the ICM. No point in spending money on that where if I ordered a new dizzy it would have a new one in it. Rockauto has a reman AC Delco dizzy for $252. Where else should I look if I wanted to buy new? What brands? MSD or anything like that or stick to stock type stuff? thanks guys.

Honestly while I don't like it, a chain auto parts store complete distributor with lifetime warranty probably has the same components as any other non-Delco ignition parts you'd buy, and with the warranty, you pull it out and swap with them when/if it fails. I had to use a non-Delco pickup coil in my truck last go-round, and it's been fine the last couple of years. Of course that means nothing, aftermarket parts are entirely a crap shoot. Having new spares is good, but I honestly prefer a known-good used part over a new one in most cases...don't know if it's worse today than it was long ago, but new parts out of the box seem pretty prone to failure.

That's me, I understand that, but I firmly believe that you are better off diagnosing and replacing what is known bad, vs. expecting new parts to be good out of the box. FWIW, the aftermarket distributor parts seem to be pretty decent, I've not heard of massive failures. The ICM is the most common failure, but it's also the one that needs heat sink paste under it, and I suspect many failures of new ICM's are user error.

 

[jekquistk5]

I went to a yard and pulled a dizzy for $8.00 wth a delco icm. The used delco was way tighter than the msd knock off I bought.

 

[Glen1978]

The Blazer only has 117k on it and the shaft feels tight as a nuns butt. Ill put the tuneup stuff on it tomorrow and see what it does. I have a coil on the way as well so will add that later in the week if the tuneup doesnt fix it.....then go from there.

 

[dyeager535]

The Blazer only has 117k on it and the shaft feels tight as a nuns butt. Ill put the tuneup stuff on it tomorrow and see what it does. I have a coil on the way as well so will add that later in the week if the tuneup doesnt fix it.....then go from there.

The "tightness" of the distributor isn't normally the issue. It's typically the ICM or Pickup Coil, just the amount of effort required to replace the pickup coil tends to make it more time effective to replace the whole distributor, particularly if you don't trust all the other components. Add up a cap, rotor, ICM, and pickup coil and depending on where you get the distributor, it will be less than the combination of parts.

Low mileage indicates it was either only driven short distances, or sat a lot. Sitting seems to be pretty hard on the pickup coil, mine was pretty corroded when I took it out, and the truck sits for weeks at a time.

 

[Glen1978]

Well got my tuneup stuff in today minus the rotor (thanks to the USPS) , got the plugs and wires on and it wouldnt crank. I had it in my head that the the cylinders were 1-4 on driver side and 5-8 on pass side.....woops. Been awhile since I messed with a SBC. Got that straight and she runs like a new one. The dizzy cap was my culprit I believe. After closer inspection the contacts were pretty worn. So now that it runs great its time to move on to other stuff. I appreciate each and every one of yalls help.

 

[jekquistk5]

Glad it was that simple.