International Full Size Jeep Association
Home Forums Reader's Rigs Tech Library Trail Stories FSJ-List
International Full Size Jeep Association  

Go Back   International Full Size Jeep Association > Tire Kickin' > General FSJ Discussion

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 02-22-2012, 05:10 PM
Ofeargall's Avatar
Ofeargall Ofeargall is offline
Member
 
Join Date: Feb 11, 2012
Location: Dallas, Oregon
Posts: 77
Idles low, runs rough at 1/4 throttle, goes great at 1/2 throttle

After getting fuel today, my rig started running weird. At idle it's barely running. But, coming off the light it spring to life. Then, while holding speed it misfires and runs rough. But if I put my foot into it, runs awesome!

What's the deal? I'm running an Edlebrock intake and carb. It smells lean when idling too. Any ideas?
__________________
1979 Wagoneer 'Wilma'
Reply With Quote
  #2  
Old 02-22-2012, 07:25 PM
FSJ Guy FSJ Guy is offline
 
Join Date: Mar 20, 2005
Location: Colorado
Posts: 10,062
Smells lean?? I could only smell rich running....

It seems lean because it probably is. When you stomp on it, the accelerator pump is giving it a shot of gas which allows it to run (slightly) better but after that's done, it goes back to being lean.

Did it just start being a problem or has it always been an issue?
__________________
Ethan Brady
1987 Grand Wagoneer, slightly longer than stock.

www.bigscaryjeep.com

Don't mess with me. I once killed a living hinge.
Reply With Quote
  #3  
Old 02-22-2012, 07:53 PM
serehill's Avatar
serehill serehill is offline
Gone,Never Forgotten.
 
Join Date: Nov 22, 2009
Location: Mesquite Texas
Posts: 8,622
Could be bad gas

Or maybe a vacum leak.
__________________

80 Cherokee
360 ci 727 with
Comp cams 270 h
NP208
Edlebrock performer intake
Holley 4180
Msd total multi spark.
4" rusty's springs
Member, FSJ Prissy Restoration Association

If you can't make it better why waste your time. No use repeating the orignal mistakes. I'm to old to push it that's why.
Reply With Quote
  #4  
Old 02-22-2012, 07:57 PM
FSJunkie's Avatar
FSJunkie FSJunkie is offline
The Nigel Tufnel of the FSJ world.
 
Join Date: Jan 09, 2011
Location: Not The Hot Part, Arizona
Posts: 3,994
Does it only run well if you are actually moving the throttle open? Or does it run well at heavy load with the throttle held open steady?

If it's the latter then I think the power valve has gone bad or stuck open making it rich.
At light throttle and idle the engine needs a leaner mixture, but because the power valve is enriching, it runs poorly. Once you step on it, the engine needs more fuel anyway, and that is the time when the power valve would be open, so it runs fine then.

If it's the first one then it's running lean. Probably a plugged passage in the carb.
__________________
'72 Jeep Wagoneer Custom, 360 V8

I love how arguements end as soon as Ristow comments. Ristow is right...again.

Last edited by FSJunkie : 02-22-2012 at 08:01 PM.
Reply With Quote
  #5  
Old 02-22-2012, 08:09 PM
serehill's Avatar
serehill serehill is offline
Gone,Never Forgotten.
 
Join Date: Nov 22, 2009
Location: Mesquite Texas
Posts: 8,622
Really

Quote:
Originally Posted by FSJunkie
Does it only run well if you are actually moving the throttle open? Or does it run well at heavy load with the throttle held open steady?

If it's the latter then I think the power valve has gone bad or stuck open making it rich.
At light throttle and idle the engine needs a leaner mixture, but because the power valve is enriching, it runs poorly. Once you step on it, the engine needs more fuel anyway, and that is the time when the power valve would be open, so it runs fine then.

If it's the first one then it's running lean. Probably a plugged passage in the carb.

Did you read the thread? I don't think Edlebrocks have PV's do they ??????
__________________

80 Cherokee
360 ci 727 with
Comp cams 270 h
NP208
Edlebrock performer intake
Holley 4180
Msd total multi spark.
4" rusty's springs
Member, FSJ Prissy Restoration Association

If you can't make it better why waste your time. No use repeating the orignal mistakes. I'm to old to push it that's why.
Reply With Quote
  #6  
Old 02-22-2012, 08:17 PM
FSJunkie's Avatar
FSJunkie FSJunkie is offline
The Nigel Tufnel of the FSJ world.
 
Join Date: Jan 09, 2011
Location: Not The Hot Part, Arizona
Posts: 3,994
Quote:
Originally Posted by serehill
Did you read the thread? I don't think Edlebrocks have PV's do they ??????
I wouldn't know, I'm not an aftermarket parts type guy. If it does have a diaphram type power valve, it's what I would first suspect for rich running. Mixture needles might be pulled out all the way if it has them, who knows..... But I suspect something is making it too rich and it doesn't sound like a choke.
__________________
'72 Jeep Wagoneer Custom, 360 V8

I love how arguements end as soon as Ristow comments. Ristow is right...again.
Reply With Quote
  #7  
Old 02-22-2012, 08:21 PM
Ristow Ristow is offline
 
Join Date: Jan 20, 2006
Location: The Great Googley Moogley Midwest.
Posts: 17,104
probably bad gas. sticking a fill nozzle in the fill hole usually doesn't blow powervalves and pull needles out of jets....
__________________
Quote:
Originally Posted by Hankrod
Ristows right.................again,




Quote:
Originally Posted by Fasts79Chief
... like the little 'you know what's' that you are.




Quote:
Originally Posted by Fasts79Chief
I LOVE how Ristow has stolen my comment about him ... "Quoted" it ... and made himself famous for being an ***hole to people. Hahahahahahahahahha!


→ Where the kids hang out...

fsjbuilder.org come for the mindless chat,stay for the hand drawn emoticons.

It's like you're unraveling a big cable-knit sweater that someone keeps knitting...and knitting...and knitting...and knitting...
Reply With Quote
  #8  
Old 02-22-2012, 08:25 PM
bruner1981jpce's Avatar
bruner1981jpce bruner1981jpce is offline
350 Buick
 
Join Date: Apr 23, 2011
Location: San Jose, CA/ Chico, CA
Posts: 1,410
Bad gas would depend on how long it was sitting, right? I would suspect plugged fuel filters or maybe a slightly leaky fuel pump. Just my .02. I had a similar problem and these fixes helped me, but i'm running a 258 with a carter BBD
__________________
Andy
'81 Cherokee Laredo W/T 258/Weber 32/36 DGEV/HEI/176/208 AMC 20/Dana 44 3.31 gears
Status: Storage Miles: Less than 140K (as of the talk with the original/previous owner) "The Jeffrey"

Build Thread: http://www.ifsja.org/forums/vb/showthread.php?t=151814 New pics: 5/18/12
Reply With Quote
  #9  
Old 02-22-2012, 08:37 PM
serehill's Avatar
serehill serehill is offline
Gone,Never Forgotten.
 
Join Date: Nov 22, 2009
Location: Mesquite Texas
Posts: 8,622
no it wouldn't

Quote:
Originally Posted by bruner1981jpce
Bad gas would depend on how long it was sitting, right? I would suspect plugged fuel filters or maybe a slightly leaky fuel pump. Just my .02. I had a similar problem and these fixes helped me, but i'm running a 258 with a carter BBD

Quote After getting fuel today,

Is how he got the bad gas
__________________

80 Cherokee
360 ci 727 with
Comp cams 270 h
NP208
Edlebrock performer intake
Holley 4180
Msd total multi spark.
4" rusty's springs
Member, FSJ Prissy Restoration Association

If you can't make it better why waste your time. No use repeating the orignal mistakes. I'm to old to push it that's why.
Reply With Quote
  #10  
Old 02-22-2012, 08:52 PM
bruner1981jpce's Avatar
bruner1981jpce bruner1981jpce is offline
350 Buick
 
Join Date: Apr 23, 2011
Location: San Jose, CA/ Chico, CA
Posts: 1,410
Quote:
Originally Posted by serehill
Quote After getting fuel today,

Is how he got the bad gas
ohhhh.... right. leave it to me to not see that
__________________
Andy
'81 Cherokee Laredo W/T 258/Weber 32/36 DGEV/HEI/176/208 AMC 20/Dana 44 3.31 gears
Status: Storage Miles: Less than 140K (as of the talk with the original/previous owner) "The Jeffrey"

Build Thread: http://www.ifsja.org/forums/vb/showthread.php?t=151814 New pics: 5/18/12
Reply With Quote
  #11  
Old 02-22-2012, 09:02 PM
serehill's Avatar
serehill serehill is offline
Gone,Never Forgotten.
 
Join Date: Nov 22, 2009
Location: Mesquite Texas
Posts: 8,622
I wished i never missed anything but that is a good way to get it probably water.

It could be trash. That was a dead give away. A lot of people wouldn't catch it & a lot of stations get away with it because no one complains. Kind of like restaruants. I've seen guys replace the entire fuel system & still have the same problems because they never got rid of the bad gas. Just drive it out & refill & it will probably go away.

Edlebrocks don't have Power valves & power valves only effect lower rpm. So it wasn't that. It could be other issues but it is probably just that simple.
__________________

80 Cherokee
360 ci 727 with
Comp cams 270 h
NP208
Edlebrock performer intake
Holley 4180
Msd total multi spark.
4" rusty's springs
Member, FSJ Prissy Restoration Association

If you can't make it better why waste your time. No use repeating the orignal mistakes. I'm to old to push it that's why.

Last edited by serehill : 02-22-2012 at 09:18 PM.
Reply With Quote
  #12  
Old 02-22-2012, 11:38 PM
Ofeargall's Avatar
Ofeargall Ofeargall is offline
Member
 
Join Date: Feb 11, 2012
Location: Dallas, Oregon
Posts: 77
More details... This has never happened before. Aside from blowby and a little smoke on a warm restart, it runs great.

I don't know if this would have anything to do with it, but the gas station attendant (can't pump your own gas in Oregon) did the ol inverted nozzle trick and crammed $50 in really super fast.

One other thing, I have 2 tanks but only one filler hole, not sure how that works...

Also, I replaced my tranny mount yesterday and removed the crossmember that has some sort of fuel line part mounted on it. Could moving that around caused a problem?

Last thing, I did notice the problem just before getting gas. We had just driven into town and were in a 35mph zone holding steady.

It runs best under a load.
__________________
1979 Wagoneer 'Wilma'
Reply With Quote
  #13  
Old 02-23-2012, 08:07 AM
serehill's Avatar
serehill serehill is offline
Gone,Never Forgotten.
 
Join Date: Nov 22, 2009
Location: Mesquite Texas
Posts: 8,622
ya that changes thing although we can only suppose.

With this age vehicle you could have broken cracked some fuel lines moving the older rubber aroung. That would react like this. This could be either at the rear or front I would check all your lines very closely. Sounds like an overall hunt of the systen is in order. Good luck.
__________________

80 Cherokee
360 ci 727 with
Comp cams 270 h
NP208
Edlebrock performer intake
Holley 4180
Msd total multi spark.
4" rusty's springs
Member, FSJ Prissy Restoration Association

If you can't make it better why waste your time. No use repeating the orignal mistakes. I'm to old to push it that's why.
Reply With Quote
  #14  
Old 02-23-2012, 11:39 AM
Ofeargall's Avatar
Ofeargall Ofeargall is offline
Member
 
Join Date: Feb 11, 2012
Location: Dallas, Oregon
Posts: 77
Shifting to low causes the problem

Okay, so I let the rig sit overnight and it fired up and ran like a champ this morning. Drove into town (9 miles), no problems. Drove through town, no problem. I had to drive up a steep, bumpy driveway so I shifted it into low (the transfer case and the tranny - just for giggles), got to the top of the first steep section and shifted the tranny back into drive. It did great.

But, when I got to a second steep part of the hill, I dropped it into low rather suddenly. I meant to go into 2 but overshot when I hit a bump. The rig lurched under the compression and started doing the misfiring with even throttle and low idling. I drove it back home in regular hi-range/drive mode and it's still running rough under light load.

Looking back on yesterday, I drove the rig in a similar manner (shifting to low on the tranny but not the t-case though). In fact, I drove up the same driveway... Maybe I need to not go up my friend's driveway!

If I rev it in the driveway, it runs rough at all RPM. Putting a load on it is the only thing that causes it to run properly.

If I've got two inline fuel filters, I'm not sure how I could get anything into the fuel system to cause this. And, if it was bad gas or a clogged line, then it would run poorly under a load as well, right?
__________________
1979 Wagoneer 'Wilma'
Reply With Quote
  #15  
Old 02-23-2012, 02:31 PM
FSJ Guy FSJ Guy is offline
 
Join Date: Mar 20, 2005
Location: Colorado
Posts: 10,062
If you put the transmission in gear and rev the engine against the transmission (with your foot on the brake so the truck doesn't move), does it run better or still run as rough as it did with "no load"?
__________________
Ethan Brady
1987 Grand Wagoneer, slightly longer than stock.

www.bigscaryjeep.com

Don't mess with me. I once killed a living hinge.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Holley Pro-jection/TBI Conversion questions Spectre General FSJ Tech 9 07-22-2005 09:34 AM
runs rough cold steve schufer General FSJ Tech 11 09-17-2004 01:28 PM
runs great til attach vac advance arter General FSJ Tech 1 03-15-2004 05:31 AM
Idles great but put it in gear and runs like snot 88BattleWagon General FSJ Tech 19 05-25-2001 04:45 PM
Runs great, dies, and won't start again!? tamarack General FSJ Tech 11 10-25-2000 01:35 AM


All times are GMT -6. The time now is 10:25 AM.


Powered by vBulletin Version 3.5.4
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
corner corner