Slight miss at idle, #1 plug is firing but clean

[formul8]

My '94 had a new opti and Autolite plugs installed right before I bought it. The injectors were checked for pulsing and they all came out OK.

I had to replace a bunch of parts because the car sat for a long time. I installed new AC DELCO premium wires.

It was missing before I even changed the wires. It is a slight "pfft...pfft...pfft" from the pass side tailpipe. There also seems to be an exhaust leak from the drivers side under the heat shield right after the converter.

I pulled plugs #1, 3, and 5 after driving the car for 100 miles or so. Plug #1 was totally clean and looked like it was firing, but almost no build up. It does not smell like raw fuel.

#3 & 7 had normal signs of firing with some carbon buildup.

Could the #1 plug being totally clean be the miss fire? The only thingI can think of is the injector is plugged up and not squirting enough fuel.

 

[Paul Higg]

Do you have an ammeter? Place it over each plug wire and read the amperage while it is running. You will know right away which plug is not firing. I do not know the exact amperage. I have been in the hospital for the last week. Wish I could help more. An ammeter is an easy way to troubleshoot since the wires carry a LOT of current. They should all be the same.

Paul

My '94 had a new opti and Autolite plugs installed right before I bought it. The injectors were checked for pulsing and they all came out OK.

I had to replace a bunch of parts because the car sat for a long time. I installed new AC DELCO premium wires.

It was missing before I even changed the wires. It is a slight "pfft...pfft...pfft" from the pass side tailpipe. There also seems to be an exhaust leak from the drivers side under the heat shield right after the converter.

I pulled plugs #1, 3, and 5 after driving the car for 100 miles or so. Plug #1 was totally clean and looked like it was firing, but almost no build up. It does not smell like raw fuel.

#3 & 7 had normal signs of firing with some carbon buildup.

Could the #1 plug being totally clean be the miss fire? The only thingI can think of is the injector is plugged up and not squirting enough fuel.

 

[formul8]

Thanks.

I should add that these Autolite plugs look like total cheap garbage....

I will swap in some better plugs tomorrow.

 

[Paul Higg]

Just had mine replaced with OEM's and it is running factory smooth.

 

[USA-1]

do you have access to a clamp on inductive timing light? with the engine running, clamp the pickup to the suspected wire (1) and see if the light is triggered. if it doesn't, the cylinder isn't firing and you'll need to research. 1st, try another plug. note, sometimes a fuel fouled plug will never fire so try a new plug. if it does trigger the light it it could be a problem internally. valve, ring, gasket, etc

 

[formul8]

I sold my timing light a few years back. Did not think I would need it again! :duh

The #1 plug does not smell fuel fouled and looks like it has fired, but is incredibly clean compared to #3 and 5. One of the Autolite plugs electrode isn't even lined up with the center electrode! Maybe the plug itself is bad?

I am going to pick up a set of NGK's today and see if that helps.

I am wondering if that may be the reason I keep getting DTC 43?

 

[formul8]

Swapped the junk Autolite plugs for Bosch Platinum Plus.

Idles much better and the slight miss is much better than it was, which leads me to believe that the #1 plug might have been defective.

 

[So Bay Vetter]

You might try checking the plug wires in the dark to see if they're arcing to a metal surface. Lots of sharp edges when you're replacing that stuff. It might be a scuffed wire shorting out. . . my 2X$.01

 

[formul8]

You might try checking the plug wires in the dark to see if they're arcing to a metal surface. Lots of sharp edges when you're replacing that stuff. It might be a scuffed wire shorting out. . . my 2X$.01

Wires are brand new. The old ones were arcing, though but replacing them did not seem to solve the problem.

 

[G Winter]

Haven't seen where you checked the ohms on the injectors.
Not sure on your yr but on most it is supposed to be about 16 ohms. My FSM says anything under 10 in no good. Even with low ohms you can usually feel the injector pulse but it seems they don't deliver full fuel volume.

Glenn

 

[formul8]

Haven't seen where you checked the ohms on the injectors.
Not sure on your yr but on most it is supposed to be about 16 ohms. My FSM says anything under 10 in no good. Even with low ohms you can usually feel the injector pulse but it seems they don't deliver full fuel volume.

Glenn

They were ohmed right before I bought it. Checked out fine.

I replaced the crapola Autolite plugs with Bosch Platinums and the engine runs way better. The idle speed in drive before was struggling at 500 or so RPM and with the Bosch's, it is 600-700.

I suspect the #1 plug was defective.