1990 TBI misfire/popping exhaust

[cbrown5385]

My 1990 TBI just started having a bit of an issue. It idles and Revs in the driveway fine but but some times while driving I’m getting almost a misfire/ popping from the exhaust. I’ve started it up and unplugged vacuum from the EGR and I had no change in idle no rough idle not stalling not. No change at all really. Can anyone point where I should be looking or what’s I should be looking into

 

[gmbellew]

My 1990 TBI just started having a bit of an issue. It idles and Revs in the driveway fine but but some times while driving I’m getting almost a misfire/ popping from the exhaust. I’ve started it up and unplugged vacuum from the EGR and I had no change in idle no rough idle not stalling not. No change at all really. Can anyone point where I should be looking or what’s I should be looking into

EGR is closed at idle. so unplugging the vac to EGR doesn't do anything at idle. manually opening the EGR, or using a mityvac to open the EGR, should cause it to bog at idle.

I'd hit up the fuel and emissions manual and look at the "symptom" charts for backfire and misfire. I think section 2 has the symptoms charts, separate charts for backfire and misfire

you haven't recently changed the plug wires?

 

[cbrown5385]

EGR is closed at idle. so unplugging the vac to EGR doesn't do anything at idle. manually opening the EGR, or using a mityvac to open the EGR, should cause it to bog at idle.

I'd hit up the fuel and emissions manual and look at the "symptom" charts for backfire and misfire. I think section 2 has the symptoms charts, separate charts for backfire and misfire

you haven't recently changed the plug wires?

I did new plugs and wires when I put headers on it the end of last year then it sat all winter ran good first few days once out for spring then started the issue. I did NOT do a new cap or rotor at that time though

 

[Ricko1966]

Wait until after dark spray the cap and wires all the way to the head,with salt water out of a spray bottle. Look for lightning.

 

[gmbellew]

I did new plugs and wires when I put headers on it the end of last year then it sat all winter ran good first few days once out for spring then started the issue. I did NOT do a new cap or rotor at that time though

might double check to make sure you have the firing order correct.

 

[fast 99]

Those distributor caps can crossfire internally.

We only use Delphi. More expensive by a lot. This is not a place to buy a bargain part.

 

[gmbellew]

Those distributor caps can crossfire internally.

We only use Delphi. More expensive by a lot. This is not a place to buy a bargain part.

yeah, inspecting the cap excess carbon is a good idea. and I agree on not skimping on ignition components!