Possible missfire

Tiny
JUANLRANGEL
  • MEMBER
  • 1984 JEEP CJ7
  • 6 CYL
  • 4WD
  • MANUAL
  • 187,000 MILES
I left the lights on and had to replace the battery, now it hesitates intermittent as I’m driving, feels like a tug.
What do you think could’ve happened?
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Sunday, January 20th, 2019 AT 12:04 PM

6 Replies

Tiny
CJ MEDEVAC
  • EXPERT
Is the Jeep still "stock"?

Can you list any modifications that may have been done in the past?

Does it still have a mechanical fuel pump?

This seems to be strange symptoms, I'm wondering if this might be a coincidence with another problem.

How often are the "tugs" occurring?

Your turn,

The Medic
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Sunday, January 20th, 2019 AT 12:56 PM
Tiny
JUANLRANGEL
  • MEMBER
Installed new 258 engine about two years ago with a hig performance Weber 61670 carburator hotter spark plugs and wires.
I get a fuel smell when I let off the pedal while driving with the back window off.
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Wednesday, January 23rd, 2019 AT 5:59 PM
Tiny
JUANLRANGEL
  • MEMBER
And coil.
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Wednesday, January 23rd, 2019 AT 6:00 PM
Tiny
CJ MEDEVAC
  • EXPERT
The fuel smell is probably normal if your exhaust runs straight out of the rear.

I started kicking mine out of the side behind my rear driver's wheel years ago to eliminate what you are experiencing now (me and my passengers weren't fond of the smell either) See pics 1 and 2.

Have you added anything lately, around the time of the "tugging"?

Let's try to isolate this issue. Answer these questions please.

1) Have you tuned your rig using instruments- timing light and a dwell/ tach or vacuum gauge? Is it possible it has not been tuned correctly? See pic 3.

2) Have you been swapping jets around in your carb?

3) How long has it been "tugging"?

4) When do you notice it - during acceleration? Any speed? At the end of "winding up/ out"

5) Is it kind of like a hesitation, like when try to go and your carburetor is still cold and your Jeep is not nowhere near operating temperature? (Like it spits)

6) Is it a constant problem, does it go away (if so, when?), How often does this occur? (Seconds/ minutes/ after it a operating temperature?

Can you remove your breather and send me really good full pics of your engine, left side/ right side/ top.

The Medic
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Wednesday, January 23rd, 2019 AT 6:56 PM
Tiny
JUANLRANGEL
  • MEMBER
It started happening after I left the lights on and had to get a jump, so I now also replaced both battery positive and negative cables and it stopped doing it.
I am still concerned about the heavy smell of fuel coming in from the rear window when I slow down, it started doing it a few months after I got the rebuilt engine and had the new carburetor installed.
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Thursday, February 7th, 2019 AT 7:17 PM
Tiny
CJ MEDEVAC
  • EXPERT
I'm pretty sure that if you kick the exhaust out the side behind the rear wheel the fumes will diminish greatly.

As far as maybe your tuning making things richer, maybe we can tune yours a little better.

I'm going to link you to a post I answered about nine years ago.

This should be easy to follow, what I did was "converted" tuning my 258 over to a 304 (so the 304 guy could grasp what I was doing) So basically leave out the 304 parts!

https://www.2carpros.com/questions/jeep-cj7-1985-jeep-cj7-stalls-when-hot

Beings that this was written when I was a "newby", I feel sure I can explain things better should you run into something you don't understand. Keep us posted on progress!

I appreciate that you have returned and seem to have confidence in pulling your Jeep into our garage.

I'm right here if you need me!

The Medic
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Thursday, February 7th, 2019 AT 8:46 PM

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