Hot exhaust
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5th Wheeling
Joined: Aug 2020
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Hot exhaust
So last time I drove the truck was last Saturday. No issues. Go to take it to work today and it's missing like it's down a cylinder. Rev it up to 2k and its smooth held it there for maybe 30-45 seconds and let off. No more blub blub blub. BUT I started to smell heat. So I go out and hold my hand by the exhaust and the air coming out is bout hot enough to burn you. Last time this happened I had a broken plug wire. Made sure everything was connected . My exhaust dumps under the cab corner so it's shorter than usual.
Iv been a professional mechanic for 13 years but old stuff is new to me. But from what I know I either have a plugged cat, or I'm just super lean. It doesn't smell rich. Just hot as ****. Coolant temp is normal. I haven't messed with Timing or anything mechanical besides replacing my plug wires 2 months ago. So im kinda stumped. Any ideas?
Iv been a professional mechanic for 13 years but old stuff is new to me. But from what I know I either have a plugged cat, or I'm just super lean. It doesn't smell rich. Just hot as ****. Coolant temp is normal. I haven't messed with Timing or anything mechanical besides replacing my plug wires 2 months ago. So im kinda stumped. Any ideas?
FTE Legend
Joined: Nov 2015
Posts: 30,912
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From: Angier, NC
I was going to say issue with the cat if you have one still installed and it sounds like you do have one installed.
The cat would be working harder if you had 1 hole not firing as it would have loaded up with un-burnt fuel.
I would look into why it did not fire all holes.
Bad plugs or wire like you said. How old are either one?
Maybe the cap has a crack or a little dampness?
To check plug wires get a spray bottle with water.
When it gets dark open the hood, start motor and spray the plug wires from cap down to each plug.
If they are leaking you will see a lighting show from sparks going to ground.
Next time it has a miss shut it down and put a little water on the exh manifold by the head.
Water that evaporates by the head is firing, manifold still wet is not firing and not you know what hole to look at closer why.
Dave ----
The cat would be working harder if you had 1 hole not firing as it would have loaded up with un-burnt fuel.
I would look into why it did not fire all holes.
Bad plugs or wire like you said. How old are either one?
Maybe the cap has a crack or a little dampness?
To check plug wires get a spray bottle with water.
When it gets dark open the hood, start motor and spray the plug wires from cap down to each plug.
If they are leaking you will see a lighting show from sparks going to ground.
Next time it has a miss shut it down and put a little water on the exh manifold by the head.
Water that evaporates by the head is firing, manifold still wet is not firing and not you know what hole to look at closer why.
Dave ----
Lead Driver
Joined: Nov 2013
Posts: 7,174
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Most likely you've got one cylinder not firing properly, for reasons yet unknown. Raw fuel is being dumped in the exhaust, where it then burns off. Maybe a bad plug wire, as before? How did you quickly go from something simple like that to a plugged cat? Been reading Dave's new book?
Run a cylinder balance test. Engine warmed up, at idle. Note the RPM. Pull the plug wires one cylinder at a time. Use plug boot pliers so you don't shock yourself. The RPM should drop a uniform amount as each good cylinder is disabled. If you get no change for a cylinder, it wasn't doing its share of work.
You can also use an infrared thermometer. Engine at idle, check the temperature around each spark plug and adjacent exhaust manifold. The dead cylinder will be cooler than the others.
Once you identify the dead cylinder, the next step is to determine why. For a problem with one cylinder, the ignition system is the most likely culprit.
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5th Wheeling
Joined: Aug 2020
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So go figure I get home last night fire it up and it's running fine. Exhaust still hella hot. Maybe cuz i have it cat/muffler and 3 feet of piping to the front if the rear wheel? I dinno drove it this morning and it felt a little sluggy but it's a 42 year old truck lol . I donno maybe a partially clogged cat. I'll find out in a few months when I gotta smog lol
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oldblue89
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Aug 5, 2010 11:23 PM
