Express & G-Series Vans Offered in both a full size van, or a large box truck, the Express is the modern GM workhorse

Chevrolet Express
Platform: GMT Van

1988 G20 running bad after tune up.

Thread Tools
 
Search this Thread
 
Old September 17th, 2017, 1:47 PM
  #1  
CF Active Member
Thread Starter
 
jimmydriver's Avatar
 
Join Date: Dec 2011
Posts: 140
Received 2 Likes on 2 Posts
Default 1988 G20 running bad after tune up.

Last weekend I put new plugs and wires on my van and it runs worse now than it did before. Rough idle and sluggish. A few months back a put a new cap and rotor on it and those were Accel high performance. I also replaced a couple of rotten vacuum lines too. Since my cruise control is dead I got rid of the diaphragm and rolled up the vacuum line and harness. I plan on pulling plugs to check their gap. I'm stumped.
Old September 17th, 2017, 4:43 PM
  #2  
CF Monarch
 
kevinkpk's Avatar
 
Join Date: Jul 2011
Location: kevinkpk
Posts: 5,917
Received 138 Likes on 130 Posts
Default

Did you correctly place the spark plug wires to the proper plugs, and follow the firing order on the distributor cap?
Old September 18th, 2017, 11:18 AM
  #3  
CF Active Member
Thread Starter
 
jimmydriver's Avatar
 
Join Date: Dec 2011
Posts: 140
Received 2 Likes on 2 Posts
Default

As far as I know I did. I did check to see if the old wires were ran the same as the diagram I downloaded before I took them off. I would think if I had even 2 wires in the wrong place it would be backfiring.
Old September 18th, 2017, 3:26 PM
  #4  
CF Monarch
 
kevinkpk's Avatar
 
Join Date: Jul 2011
Location: kevinkpk
Posts: 5,917
Received 138 Likes on 130 Posts
Default

I'd strongly suggest you recheck the plug wires
Old September 22nd, 2017, 10:46 PM
  #5  
CF Active Member
Thread Starter
 
jimmydriver's Avatar
 
Join Date: Dec 2011
Posts: 140
Received 2 Likes on 2 Posts
Default

So you're saying if 2 wires are on the wrong plug it will still run without back firing? As soon as the weather cools back down here I plan on taking the 4 plugs back out I just put in and rechecking the gap. I don't plan on driving it much until then. I'm going to look for the firing order on the manifold in the event that this isn't the original motor. I've looked online for spark plug wiring diagrams They all show the same thing.
Old September 23rd, 2017, 9:56 PM
  #6  
CF Veteran
 
canucklehead's Avatar
 
Join Date: Dec 2012
Posts: 1,584
Likes: 0
Received 6 Likes on 6 Posts
Default

When you changed the vacuum lines did you do the vacuum advance? Yours has a carb right?
Re check you plugs to be sure, and then make sure there is no shorting. ie they are routed properly.
You can use a plumbers torch to let a little propane out near the intake manifold and use it to look for vacuum leaks.....if the idle goes up, you have a leak.
Old September 24th, 2017, 1:10 PM
  #7  
CF Active Member
Thread Starter
 
jimmydriver's Avatar
 
Join Date: Dec 2011
Posts: 140
Received 2 Likes on 2 Posts
Default

I didn't see a hose for vacuum advance. No carb. It has TBI.
Old September 24th, 2017, 2:39 PM
  #8  
CF Veteran
 
StanVan's Avatar
 
Join Date: Jul 2008
Location: Harrisonburg Virginia
Posts: 1,306
Likes: 0
Received 13 Likes on 13 Posts
Default

Vacuum is produced at the intake manifold, regardless of whether it has a carb or fuel injection.
Old September 24th, 2017, 10:23 PM
  #9  
CF Veteran
 
canucklehead's Avatar
 
Join Date: Dec 2012
Posts: 1,584
Likes: 0
Received 6 Likes on 6 Posts
Default

Does putting a litte gas in the throttle body help or are we just talking spark and timing olnly? (could it be a fuel issue by some coincidence)
Old September 25th, 2017, 10:03 AM
  #10  
CF Active Member
Thread Starter
 
jimmydriver's Avatar
 
Join Date: Dec 2011
Posts: 140
Received 2 Likes on 2 Posts
Default

Originally Posted by canucklehead
Does putting a little gas in the throttle body help or are we just talking spark and timing only? (could it be a fuel issue by some coincidence)
I don't think so. Back in January I replaced cap & rotor and all 4 spark plugs on the passenger side. It made a huge difference. A month ago I was digging through my tool chest and came across the other 4 new spark plugs so I went a nd bought new wires installed the 4 new plugs and all the new wires. Now it runs like crap. It's getting gas.



All times are GMT -5. The time now is 3:55 PM.