Jeep is lurching - JeepForum.com
 
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post #1 of 12 Old 04-08-2021, 08:57 AM Thread Starter
Bedlam_YJ
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Hey guys,


Been a while but I'm back looking for some help with troubleshooting a new issue.

Recently, my Jeep has started lurching. Almost like its losing fuel and trying to die on me. Think like instead of a steady stream of fuel its getting 'squirts'. The lurching seemingly only occurs when the Jeep is moving and usually in 4th gear around 2200-2300 RPM. Thats by no means a 100% accurate diagnosis, just an observation. Sitting in neutral and revving makes it act normal. Give it less throttle when it happens while driving and it goes away so long as you don't throttle back into the 'problem zone'. Trying to throttle through the problem zone and it wants to stall the engine. If I can manage to get past the point where it acts up, without killing the engine (like coasting downhill), and it drives like normal. I got past the problem this morning without pulling over and it was fine the rest of the drive into work, though I could feel it want to do it again briefly after I stopped for coffee.



Fuel filter was replaced last week and the carb was rebuilt last week as well. Soft and hard lines under the hood were checked yesterday when I replaced the fuel pump and looked good. The only fuel related part that hasn't been replaced is the sending unit in the tank. Given all of this, I'm left suspecting it might not be exclusively fuel related but I'm not ruling it out yet.

The distro rotor and cap, and plug wires were were all Team Rush upgraded about 4 years ago. Coil is less than 2 years old. Plugs were replaced yesterday when the fuel pump was replaced. Old plugs had slight scaling on them, but nothing out of the ordinary. Scaling was of a good color and not indicative of overheating or fouling.

I'm asking to see if any of this is ringing any bells for you guys. Surely someone has had this happen to them before. Most of the searches I've done have returned results for newer Jeeps and problems with sensors and whatnot. Fortunately, my Jeep is a little too old for such luxurious points of failure!


Send help, plz. A week and a half ago this issue left my Jeep stranded on the side of a busy highway and me walking 8 miles home during rush hour.

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post #2 of 12 Old 04-08-2021, 10:32 AM
bruinjeeper
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Check your codes.

I had a TPS issue do the same thing. Ground clean up and tighten and wire loom relocation fixed it.

The code would only pop up sporadically. Hence, I believed it to be a wiring issue as replacing the TPS had no effect.

~YJOTM MAY '16, JULY '19~


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post #3 of 12 Old 04-08-2021, 10:58 AM
EABiker
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I just fought a similar issue on my 89 4 banger. The symptom would come and go, I went through the fuel system, since that made sense, and I got things running better overall, but the intermittent issue was still there. I ended up replacing my ignition control module, and so far, so good.
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post #4 of 12 Old 04-08-2021, 11:37 AM Thread Starter
Bedlam_YJ
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Quote:
Originally Posted by bruinjeeper View Post
Check your codes.

I had a TPS issue do the same thing. Ground clean up and tighten and wire loom relocation fixed it.

The code would only pop up sporadically. Hence, I believed it to be a wiring issue as replacing the TPS had no effect.
It's an '87, there is no TPS. There are also no codes, as this is pre-OBDI and OBDII. There is no CEL on the dash light cluster, so I can't use the Renix-era trick with counting CEL flashes. My only options are the expensive Snap-On tool or getting my hands on the factory tool for diagnostics.



Quote:
Originally Posted by EABiker View Post
I just fought a similar issue on my 89 4 banger. The symptom would come and go, I went through the fuel system, since that made sense, and I got things running better overall, but the intermittent issue was still there. I ended up replacing my ignition control module, and so far, so good.
Ignition module was replaced back in January, thinking that was going to solve a separate issue I was having with the Jeep having trouble starting up again after being driven, but that's probably carb related as it still persists even after replacing the module. I still have the old module so I guess I can splice that back on and see if this issue goes away, though this particular issue arose at the end of March and the new module has been in since January.
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post #5 of 12 Old 04-08-2021, 11:58 AM
CJ7 Trasher
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So its a carburated engine? What engine?
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post #6 of 12 Old 04-08-2021, 12:31 PM Thread Starter
Bedlam_YJ
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Quote:
Originally Posted by CJ7 Trasher View Post
So its a carburated engine? What engine?
It's all in the profile, 4.2 258 I6. It's effectively a CJ without being called a CJ. The carb is a Weber 32/36. None of that flying saucer Carter nonsense.
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post #7 of 12 Old 04-08-2021, 02:42 PM
93YJ4FUN
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Timing advance vacuum hose?

Carb Float level?

Accelerator pump?

Here's a thread on something similar:

https://www.jeepforum.com/forum/f8/c...r-pump-907450/

Last edited by 93YJ4FUN; 04-08-2021 at 02:48 PM. Reason: Added Link
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post #8 of 12 Old 04-08-2021, 04:16 PM
bruinjeeper
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Quote:
Originally Posted by Bedlam_YJ View Post
It's an '87, there is no TPS. There are also no codes, as this is pre-OBDI and OBDII. There is no CEL on the dash light cluster, so I can't use the Renix-era trick with counting CEL flashes. My only options are the expensive Snap-On tool or getting my hands on the factory tool for diagnostics.
Apologies.

That doesn't display when i look at JF on my phone.

~YJOTM MAY '16, JULY '19~


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post #9 of 12 Old 04-08-2021, 04:46 PM Thread Starter
Bedlam_YJ
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Nothing quite like stalling out 5 times on the way home from work a little while ago. Accelerating in 1st and 2nd gear is fine, but as soon as its shifted into 3rd and throttle is given it bogs down and I can hear the spray in the carb, and then it dies. Sometimes I can pump the gas and keep it alive, but most times it ended up with me coasting on the side of the road while I turned the key to get it going again. Trying to shift past 3rd into 4th, or shifting from 3rd into 4th does the same thing. 4th to 5th too.


The last time it happened before getting home, I sat idling on the side of the road for a minute or so and then when it was clear, jumped back on the road and it gave me no more problems for the last 3 minutes of the drive.

Quote:
Originally Posted by 93YJ4FUN View Post
Timing advance vacuum hose?

Carb Float level?

Accelerator pump?

Here's a thread on something similar:

https://www.jeepforum.com/forum/f8/c...r-pump-907450/
Vacuum hoses should be fine, I sprayed them down with soap mixture and saw no bubbles. They don't look cracked or worn and don't feel brittle. The only vacuum lines left in the Jeep are only the ones required for it to run.

Anything carb related is kind of beyond me. The rebuild kits from Redline only come with the gaskets, some of the smaller screws/pins/jets and a few other bits. Nothing that had me adjust anything with the float, save for the brass plunger that rides on top of it. Even then, I'm positive I didn't bend the tab and accidentally adjust the float level while installing the new plunger, so float level is the same as before the problem started.
I don't recall if the kit came with a replacement accel. pump or not, as I don't remember installing a new one. It's most likely that it did not. Either that, or I am in serious need of glasses.

Quote:
Originally Posted by bruinjeeper View Post
Apologies.

That doesn't display when i look at JF on my phone.
No worries. I figured it was something like that, I just gave the extra info so it was there and no one tried to give the same answers. I'll preface subsequent topics with the pertinent information next time! My bad!


EDIT:
The rebuild kit did in fact come with a new acceleration pump. I missed it in the large bag because it was sandwiched in between the pages of the direction and parts list. Luckily the trash company didnt pick up our garbage today since I had to dig the box out to double check.
The new pump is on and I'm getting ready to attempt a run to get some food and gas. Hopefully, nothing explodes!

Last edited by Bedlam_YJ; 04-08-2021 at 06:55 PM. Reason: Added new information under EDIT heading
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post #10 of 12 Old 04-09-2021, 09:40 PM
SevenSlotAddict
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I found the Weber, while a good swap, is the most finicky carb I ever dealt with. My last YJ had one and it constantly gave me issues. I finally sold the Jeep on but I was looking into replacing the Weber with something more user friendly. Once a Weber is tuned properly, they run great but require constant attention. That was my experience anyway.


Hope your work today solves your issuer. If it does, it only reinforces my views on Webers.
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post #11 of 12 Old 04-11-2021, 06:57 AM
93YJ4FUN
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Did that fix the problem? Enquiring minds want to know lol
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post #12 of 12 Old 04-11-2021, 08:37 AM
Boojo35
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What you are describing is a fuel starvation issue. Your carb bowl gets low enough that your Jeep begins to only deliver fuel with each pulse from your mechanical fuel pump. Sometimes these give you a clue by having fuel leaking or a residue around the little hole in the body of it. Sometimes the fuel goes into the crankcase also through the lever area that is driven by the camshaft. It is most times a bad fuel pump but if you have a cracked line sucking air or a clogged tank sock for example you can get the same symptom. Also, a fuel tank that does not vent correctly. The last possibility that I can think of is vapor lock which is basically your fuel boiling.

I worked on carbureted vehicles daily once upon a time. Kudos to you. Your description of what it does and when it does it is awesome. I am very very confident in what you need to chase and what you will find when you do. This is one of those moments where being old pays off. A fuel pressure test is your friend right now.

If you cannot fix it with a hammer then it has to be an electrical problem.
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loss of power , Lurching forward , stall issue

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