diagnosis of a miss (1 Viewer)

[JohnnyFish]

My 80 has a miss that I was hoping to solve with a tuneup kit from witsend, but that didn’t do it. It does run better, but there’s still a miss. When I’m accelerating it surges once or twice a second as though one cylinder is only firing intermittently.
I’m thinking it’s a bad fuel injector, so I’ve run fuel injector cleaner through with no improvement. maybe the coil can’t cope with full spark on all cylinders.
Any diagnostic help y’all can offer? Thanks.

 

[60 toy ota]

My 80 has a miss that I was hoping to solve with a tuneup kit from witsend, but that didn’t do it. It does run better, but there’s still a miss. When I’m accelerating it surges once or twice a second as though one cylinder is only firing intermittently.
I’m thinking it’s a bad fuel injector, so I’ve run fuel injector cleaner through with no improvement. maybe the coil can’t cope with full spark on all cylinders.
Any diagnostic help y’all can offer? Thanks.

Any codes? What year?

 

[BILT4ME]

My 80 has a miss that I was hoping to solve with a tuneup kit from witsend, but that didn’t do it. It does run better, but there’s still a miss. When I’m accelerating it surges once or twice a second as though one cylinder is only firing intermittently.
I’m thinking it’s a bad fuel injector, so I’ve run fuel injector cleaner through with no improvement. maybe the coil can’t cope with full spark on all cylinders.
Any diagnostic help y’all can offer? Thanks.

Check your engine and body ground cables for good solid clean connections.
Check your wiring harness by the EGR, open it, inspect for bares and shorts, rewrap and insulate.
Consider having you injectors cleaned or replaced.

 

[JohnnyFish]

Any codes? What year?

‘96 with 190k miles
no codes right now. Occasionally it’ll throw a common EGR code that clears itself.

 

[elhombre]

Need more info. What did you change out?

Assuming you did spark plugs, what did the old ones look like. Did one of them stand out as really crudded up or a different color?

Did you change out spark plug wires? Cap? Rotor?

Wiring harness (mentioned earlier) is a good place to look too. Sometimes the harness gets messed up and when the engine torques to one side while accelerating, the wires get stretched, or separate, or short out a little causing a miss.

A bad injector usually leaks and the unburnt fuel will show itself when the computer tells you an O2 sensor is "bad". Messing with the injectors is down near the bottom of my list of possibilities when getting this fixed. Not to say it isn't a bad one, just there are other causes that should be checked first. The spark plug in the offending cylinder will look different than the other 5.

Go to Walmart and get a few more bottles of Techron fuel additive and run it through the gas tank a few more times . Definitely can help, it's cheap, and it won't hurt.

 

[JohnnyFish]

Need more info. What did you change out?

Assuming you did spark plugs, what did the old ones look like. Did one of them stand out as really crudded up or a different color?

Did you change out spark plug wires? Cap? Rotor?

Wiring harness (mentioned earlier) is a good place to look too. Sometimes the harness gets messed up and when the engine torques to one side while accelerating, the wires get stretched, or separate, or short out a little causing a miss.

A bad injector usually leaks and the unburnt fuel will show itself when the computer tells you an O2 sensor is "bad". Messing with the injectors is down near the bottom of my list of possibilities when getting this fixed. Not to say it isn't a bad one, just there are other causes that should be checked first. The spark plug in the offending cylinder will look different than the other 5.

Go to Walmart and get a few more bottles of Techron fuel additive and run it through the gas tank a few more times . Definitely can help, it's cheap, and it won't hurt.

Thanks! Very helpful thinking.

I changed out the plugs, wires, rotor and coil wire. The old plugs' electrodes were eroded to points, but I don't remember one looking oilier or wetter than the others.

i took one picture then chucked the old plugs

 

[ppc]

The old plugs' electrodes were eroded to points

Those plugs are not worn to a point, the old plugs are Iridium plugs that have a different style of tip.