Intermitten miss

[Darrell J]

Hello everyone.

I was hoping for some help.

I have a 1992 Chevy Sliverado 4wd, 5.7 v8.

I rebuilt the motor back to stock specs.

I now have an intermitten miss in the engine when it's idling and up to rpm.

It's not backfiring throught the TBI, it just sounds like it "stumbles" when it misses. No pattern or consistency to the miss.

I've replaced the roto cap, roto button, plugs, and plug wires.

I'm up for any suggestions, thanks!

Darrell

[NEUMANNZZ]

I assume base timing is at zero degrees.

egr valve sticking open?
distributor drive gear worn?

does it miss with est wire disconnected(timing bypass)

[Darrell J]

The est wire is disconnected. (the automatic vacuum advance adjusting wire)
I have the distributor loose so I can turn it to adjust the timing.

No matter where it is on the timing it still intermittenly misses.

How would I check to see if the distributor drive gear is worn?
How do I check if the egr valve is stuck open?

[NEUMANNZZ]

the drive gear shouldnt be knife edged(sharp as a knife)
like this when new:
http://images.search.yahoo.com/image...sigb=13b3kuqt9

remove and clean egr valve.
cycle egr valve manually with screwdriver to see if its sticking.
to test egr valve remove vacuum hose to it. apply vacuum with mityvac hand pump, to see if diafragm holds vacuum. can also cycle it that way, instead of manually with screwdriver.

is timing erratic with est wire disconnected?

have you isolated any cylinders or is it all cylinders?(remove spark plug wire one at a time)

[Darrell J]

ok I checked the drive gear, sharp as a razor and looks good.

timing is consistant as far as I can tell.

I think it's all cylinders, erratic, no one in particular not working, at least what I can find.

is the EGR valve just above my finger to the left, in this pic?


also noticed that when the engine gets hot, say after running down the highway for about 40 min it starts to miss even more!

[DennisTA15]

The dizzy gear shouldn't be razor sharp, and yes that is your EGR valve (just above your finger, to the left).

[Darrell J]

Ok, it's not RAZOR sharp but it's not dull ground worn down either.

[Darrell J]

EGR is fine.

now after it cooled off, I started it again and it's missing even worse! ARGH!

I'll recheck the timing on it first.

[Sparkee]

I had a similar problem on my old K1500, problem ended up being a bad pickup coil in the distributor. The pickup coil only runs about$10-15, but you have to completely remove the distributor from the engine and disassemble it to replace the coil. Have a good one!

[NEUMANNZZ]

you can ohm out the coil and pick up coil. 500-1500 ohms. shouldnt be short or open.

[mattkx125]

did u ever figure out the problem? i have a 94 k2500 454 that has the exact same thing ive replaced egr already. so far it seems people have fixed the problem by replacing the distributer which would be inline with the coil, pick up coil. if u fix it post how u did! thanks

[Darrell J]

Ok, just got back from my hunting trip,(no didn't take the truck, wouldn't run :) )

so now back to working on the truck and problem.

How do you OHM out the coil and pick up coil. Or a more basic question, WHERE is the coil and pick up coil? a picture would be very helpful to me on where it is and what to do.

[Darrell J]

Is this the coil?
Where is the pickup coil?

How and what do you test on it with a volt meter?

[mattkx125]

i believe that is the ign coil. the pick-up coil is located in the distributer!

[NEUMANNZZ]

The pick up coil has two wires that plug into the ignition control module. disconnect it. put a red lead on one wire and the black lead on the other wire. multimeter set to ohms. 500-1500 ohms.
for the coil: see figure 5
http://www.angelfire.com/realm2/84ca...coil/coil2.htm

[Darrell J]

Ok I cannot find anything that looks like my distrubitor at that link, am I missing something?

Here's another pic of my distributor

[NEUMANNZZ]

pickup coil is the round rusty thing on top,
ignition control module is the black plastic thing, underneath and to the side of it.

[Darrell J]

THANKS! I'll take it apart tomorrow and have a look at it! test it too!

[Darrell J]

ok put the ohm meter to the pickup coil, red on one side black on the other of the two plugs that come out of the distributor. The ohm's read 0, showing ? that there is a complete circuit? and this is good?

[NEUMANNZZ]

you have to disconnect the pick up coil wires from the ignition control module. between 500 -1500 ohms. if it reads zero ohms its shorted and bad. or if its open its bad.