Misfire and no power....

[sgosa]

I checked the exhaust temps at the entrance and exit of the Cats. They were within 15-20 degrees or so. Is that a reliable way to check them?
I checked that the coils are firing.
I checked the injector harnesses with a noid light. All were good.
Last night unplugging some of the injectors seemed to effect the idling. Today none of them being unplugged affected it at all. It idles very rough. Just barely staying running. I felt sure last night that I was going to find a bad injector today. And I guess that’s still a possibility. But at this point I’m not sure.

 

[sgosa]

If the cats were clogged to the point of causing this much of an issue, would it sound like it has an exhaust leak under the hood? It’s got that steady poofing sound when idling. That’s a silly way of describing it but I’m sure y’all know what I’m referring to.

 

[Scottydoggs]

manifold to cats would be much hotter then the post cats pipes. if you drive it at night, when its good and dark, you can drive it somewhat hard, then pull over to see if they are glowing red.

best way i can describe a clogged cats sound is a vacuum with a full bag, it wants to suck in, but it cant any more.

you can also remove both front o2 sensors and run it. yes your making exhaust leaks, but that lets the back pressure off if the cats are clogged, and it should run better, sound like crap, but run better.

when was your last tune up? if recent what plugs you use?

 

[sgosa]

manifold to cats would be much hotter then the post cats pipes. if you drive it at night, when its good and dark, you can drive it somewhat hard, then pull over to see if they are glowing red.

best way i can describe a clogged cats sound is a vacuum with a full bag, it wants to suck in, but it cant any more.

you can also remove both front o2 sensors and run it. yes your making exhaust leaks, but that lets the back pressure off if the cats are clogged, and it should run better, sound like crap, but run better.

when was your last tune up? if recent what plugs you use?

I replaced the plugs and wires this weekend. I used Taylor wires and AC Delco plugs.

 

[89Suburban]

I checked the exhaust temps at the entrance and exit of the Cats. .

No check the exhaust manifold exits at each cylinder head. If there is a dead cylinder it should be cooler than the others.

 

[sgosa]

Probably a dumb question. But does it need to be at full operating temp to check them all? I would think so but I’d rather ask and know.

 

[sgosa]

I checked the exhaust temps at the point of exit at the head. Seems like a wide range to be honest. Almost makes me doubt my thermometer is working properly.

Driver side
front cylinder 287
second cylinder 347
third cylinder 333
rear cylinder 311

Passenger side
front cyl. 288
second cyl. 214
third cyl. 210
rear cyl. 186.

 

[Kraig]

If you had a dead cylinder on a cold (not warmed up) engine, you’d have an exhaust passage just above room temperature.

 

[Kraig]

When you say the cat con temps are within 15-20 degrees—they’re hotter at the aft end than the front, right? That would indicate they’re working.

 

[sgosa]

Yes sir.