[BuckyBoy]

We have a 93 Blazer that seems to be skipping. We replaced the fuel pump to get the thing to run, and it has sounded this way the entire time it has been running. To try to get rid of the skipping we replaced the plugs, wires, distributor, some gaskets, maf sensor because of a code it was throwing, fuel filter and a few other parts.
When it is up to cruising speed on the road it runs smooth, but when taking off or idling you can hear the skip if that is what it is in the exhaust. Is this even a skip or something else we should look at?
We just ran some seafoam through it earlier and tons of smoke came out like it was supposed to, but it didn't help the problem.
The car was sitting for a while before we decided to work on it. Since we replaced all the parts, it has had <50 miles on it. Would just driving it a while help?
Any suggestions are appreciated.

 

[kidney_bean]

Hmm...it almost sounds like a problem with the timing and/or spark advance. How did you set the timing when you replaced the distributor? Are you sure the new distributor is in properly (not off by 1 tooth or 180 degrees out)? Has the skipping changed since replacing any of these parts?

 

[BuckyBoy]

Well, I didn't actually replace the distributor. We had a mechanic do most of the diagnosing.

 

[kidney_bean]

Well, I didn't actually replace the distributor. We had a mechanic do most of the diagnosing.

Did you have the work done at a shop, or just have a friend who happens to be a mechanic work on it? Either way, do you know if the timing was checked after they installed the distributor? Also, was the replacement distributor new, reconditioned, or used?

 

[Bitter]

sounds like a misfire under load. could be a number of things, but probably spark related. make sure that the coil is good and distributor is working correctly. this isnt one of the engines with the distributor on the front of the engine under the waterpump is it?

 

[kidney_bean]

this isnt one of the engines with the distributor on the front of the engine under the waterpump is it?

I take it you mean the LT-1 that had the photo ring trigger...just like the cross-fire injection on the mid-80's Corvettes, it sounded like a really cool idea...:ghey2:

 

[BuckyBoy]

Did you have the work done at a shop, or just have a friend who happens to be a mechanic work on it? Either way, do you know if the timing was checked after they installed the distributor? Also, was the replacement distributor new, reconditioned, or used?

It was a friend of my dad, but he has his own shop.
I'm not sure if he checked the timing because he would always talk to my dad about what he did. I am 99% sure the distributor was brand new.
I just ask my dad and he said "I am sure he checked the timing."

Also, the motor is a 4.3L Vortec. The distributor is not below the water pump.

Would a hole in the exhaust pipe cause this? There is a nice little chunk out of the pipe, but it is right at the end of the exhaust. But, you can also feel the skipping when you first take off so IDK if it would be that hole causing it.

 

[Bitter]

I take it you mean the LT-1 that had the photo ring trigger...just like the cross-fire injection on the mid-80's Corvettes, it sounded like a really cool idea...:ghey2:

yep, thats what im talking about. theres a vacuum vent system on them that often fails causing corrosion inside of the unit. replacement is the only way to repair it, a tell tale sign is corrosion on the pins where the 4 wire connector goes into the unit, on the top left looking from the front of the car at the engine.

we just did one on a police caprice that had similar symptoms, but when it got hot it would also misfire...but not as bad as under acceleration. when the new one is installed make sure the vacuum vent system is connected correctly, its diagramed on the underhood sticker.

 

[Bitter]

It was a friend of my dad, but he has his own shop.
I'm not sure if he checked the timing because he would always talk to my dad about what he did. I am 99% sure the distributor was brand new.
I just ask my dad and he said "I am sure he checked the timing."

Also, the motor is a 4.3L Vortec. The distributor is not below the water pump.

Would a hole in the exhaust pipe cause this? There is a nice little chunk out of the pipe, but it is right at the end of the exhaust. But, you can also feel the skipping when you first take off so IDK if it would be that hole causing it.

its not the exhaust leak, its probably a spark issue, a weak spark will cause misfire under load.

 

[BuckyBoy]

its not the exhaust leak, its probably a spark issue, a weak spark will cause misfire under load.

is there anyway to check that or is there something i would have to replace and see if the problem goes away?

 

[Bitter]

you can check the resistance of the primary and 2ndary coil of the ignition coil and replace the cap and rotor. it would help to see if its always one cylinder missing or if the misfire moves around.

 

[BuckyBoy]

you can check the resistance of the primary and 2ndary coil of the ignition coil and replace the cap and rotor. it would help to see if its always one cylinder missing or if the misfire moves around.

we replaced the cap and rotor already. i have no clue how to go about check the coils, but even if i did, i dont think i have the tool to do it.

 

[kidney_bean]

I don't recall it being mentioned, but have you checked it for codes? That should always be one of the first steps on a fuel injected engine that isn't running right...

 

[kidney_bean]

we replaced the cap and rotor already. i have no clue how to go about check the coils, but even if i did, i dont think i have the tool to do it.

You just need an ohm meter (any multimeter has that function)...just check the resistence...specs should be in a repair manual, but there shouldn't be an open circuit on either coil...

 

[BuckyBoy]

I don't recall it being mentioned, but have you checked it for codes? That should always be one of the first steps on a fuel injected engine that isn't running right...

The only code was caused by the MAF sensor. Now everything is clear.

 

[kidney_bean]

Well, I'm still in agreement with Bitter thinking it's a spark problem, but just out of curiosity, when's the last time you checked the air filter?

 

[BuckyBoy]

You just need an ohm meter (any multimeter has that function)...just check the resistence...specs should be in a repair manual, but there shouldn't be an open circuit on either coil...

Alright, I will give that a shot.
When you say there shouldn't be an open circuit on either what do you mean? When I check the meter it should be the same the entire time.
I'm sure this is the stupidest question so far, but I just wanna be sure. I check the reading with the car running right?

 

[BuckyBoy]

Well, I'm still in agreement with Bitter thinking it's a spark problem, but just out of curiosity, when's the last time you checked the air filter?

We haven't messed with the air filter. We had it completely off at one point and it didn't help the issue.

 

[kidney_bean]

Alright, I will give that a shot.
When you say there shouldn't be an open circuit on either what do you mean? When I check the meter it should be the same the entire time.
I'm sure this is the stupidest question so far, but I just wanna be sure. I check the reading with the car running right?

NO! You have to remove the coil from the circuit (unplug it). I forget how the coils are on that car, but you should have a small connector that provides power and ground for the primary coil (you'll need to find a schematic to know which are the right terminals)...there should be some resistance (check the manual for the specs)...if there is no continuity, then the coil has a short. Also check the secondary coil resistance as well...

 

[Bitter]

car off, unless you want your hair standing on end.


if you had a scope you could do alot more