1988 Jeep YJ bucking while driving

Tiny
GRIZZLY93
  • 1988 JEEP YJ
  • 213 MILES

Ive got a 1988 jeep YJ with the 258 6cyl. And the ax 15 5 spd that I swapped in place of the peugeot POS tranny. Its been running really smooth lately up until tonight on my way home from work. It has done this a few times prior but would always stop after about 20 seconds or so, but it did it the whole way home. Commonly does it after I hit a puddle, or when its raining but it was dry today. Wanted to see if anyone else out here has had a similar problem and what they did to fix it.

it will respond smoothly to the gas when its in neutral but once I put it in gear and hit the gas it seems to just die than itll pick up and slam the entire jeep back and forth, similar to riding a bull or something. Definately causes a rough ride, and wont accelerate any faster than 25-30 or so.

any ideas? Im stumped.

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Wednesday, March 7th, 2012 AT 2:12 AM

17 Replies

Tiny
FIXITMR
  • MEMBER

Sounds TOO lean.

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Wednesday, March 7th, 2012 AT 2:40 AM
Tiny
GRIZZLY93
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I put in a weber 38 in place of the stock carter BBD which was in need of replacement. And with that it called for a fuel pressure regulator, so I ordered one as welll as an inline gauge to test the accuracy of the regulator, well one of them is inaccurate. Weber suggested 2.5 PSI so I got it set to that on the regulator and the gauge only reads 1.5 psi. It reads that regardless of what I set the regulator at. Do you think it could be from that? Or the fuel/air misture set on the carb?

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Wednesday, March 7th, 2012 AT 2:47 AM
Tiny
FIXITMR
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You could force choke partially shut and try it?

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Wednesday, March 7th, 2012 AT 2:59 AM
Tiny
GRIZZLY93
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What would forcing the choke partially shut do in terms of testing it? Im not really following.

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Wednesday, March 7th, 2012 AT 3:09 AM
Tiny
FIXITMR
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Richen the mixture.

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Wednesday, March 7th, 2012 AT 3:22 AM
Tiny
GRIZZLY93
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Okay got it now. Duh. Lol. Would the mixture be different from neutral to being in gear?

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Wednesday, March 7th, 2012 AT 3:31 AM
Tiny
CJ MEDEVAC
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GRIZ

I HAD A WEBER DGEV INSTALLED ON MY CJ 5 PRIOR TO USING THE O2 SENSOR, OFFY INTAKE AND NOW 4 BBL HOLLEY 390

THE ONLY THING I HAD TO GO ON WAS THESE DRAG STRIPPERS OPINIONS AND ATTEMPTING TO "READ MY SPARK PLUGS"

THIS WAS A PROGRESSIVE CARB---ONE BBL UNTIL YOU GOT INTO IT, THEN THE 2ND BBL WOULD OPEN

I HAVE SPENT OVER $200 ON JETS AND CRAP FOR THE DGEV

I STRIPPED OUT 2 OF THE SCREW HOLES ON THE LID TO THE JETS, I WENT IN AT LEAST ONCE A DAY MESSING WITH IT. THE O2 THING MAY COULDA HELPED ME A LOT, IF I HAD KNOWN ABOUT IT

I WANNA KNOW SOMETHING, DOES THIS WRANGLER HAVE A RETURN TO THE TANK LIKE A CJ, USING THE 3 T. IT FUEL FILTER OR SIMILAR? MECHANICAL FUEL PUMP?

THIS IS MY THOUGHT ON YOUR DEAL. WITH INFO I HAVE NOW

ONLY BUCKS AT HIGHER SPEEDS?

AS IF FUEL BOWL IS RUNNING OUT?

FLOAT ADJUSTED RIGHT?

CHECK FUEL PRESSURE STRAIGHT OUT OF THE PUMP--NOT AS IT FLOWS THRU THE SYSTEM. THIS WILL LET YOU KNOW WHAT THE PUMP IS CAPABLE OF

MAKE ABSOLUTELY SURE THAT CRAP HAS NOT ENTERED YOUR REGULATOR, AND HAS IT STOPPED UP (BLOW BACKWARDS THRU IT, OR REPLACE IT IF YOU SUSPECT CONTAMINATION) AND THE K. NOB IS IN THE "POPPED UP" POSITION WHEN YOU HAVE IT SET ON A PRESSURE

HOW DO YOU KNOW FUEL PRESSURE? I HAVE A SMALL FUEL PRESSURE GAUGE ON MINE EVEN THOUGH IT PULSATES, THE HIGHEST IT READS IS THE PRESSURE BEING GENERATED

IF YOU HAVE A RETURN LINE, CAN YOU PINCH IT WITH PLIERS SLIGHTLY, TO BUILD PRESSURE REARWARD FROM IT?

IF THIS WORKS, MAYBE INSTALL A RESTRICTIVE BUSHING SHOVED INTO THE RETURN RUBBER HOSE---FOR INSTANCE, AN EXPENDED.22 CASING DRILLED OUT TO A SPECIFIC SIZE (EXPERIMENT), THAT WILL ALLOW FLOW, BUT BACK-PRESSURE AT THE SAME TIME?

OR EVEN INSTALL A SHORT TUBE YOU CAN SQUEEZE DOWN TO MAKE A SLIGHT PERMANENT RESTRICTION, MESS UP? SIMPLY REPLACE THE SHORT SECTION

OK---SHOOT DOWN MY THEORIES!

TELL ME YOU NEED ALL OF THESE WEBER JETS AT A REDUCED RATE, I SOLD THE CARB TO SOME POOR SOUL LONG AGO

WITH THE HOLLEY, MY STUFF IS AVAILABLE MORE LOCAL

THE MEDIC

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Wednesday, March 7th, 2012 AT 5:01 AM
Tiny
CJ MEDEVAC
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I MEANT TO ADD IN--ON BOTH OF MY JEEPS I HAVE THE SAME REGULATOR. ONLY MR. JEEP HAS THE LITTLE INLINE GAUGE.

I FOUND THAT THE REGULATOR IS PRETTY ACCURATE OWN ITS OWN, THE DIALED IN READING IS DARN CLOSE TO THE GAUGE READING.

WITH WILLY, 3.5 PSI IS WHAT THE CARB REQUIRES

IF I TURN THE REGULATOR ANY LOWER, AT HIGHER SPEEDS. IT BUCKS!

WHAT IS HAPPENING IS THE FUEL BOWL IS NOT GETTING ENOUGH FUEL INTO IT. ITS GETTING USED UP FASTER THAN REPLENISHED. THE FLOAT IS DOING NOTHING 'CEPT DANGLING, IN HOPES THAT FUEL WILL RAISE IT UP!

WITH THE BOWL BEING SO LOW, THE FUEL LEVEL IS NOT FILLING THE VENTURIES TO THE PROPER LEVEL. THE FUEL SORTA NORMALLY KEEPS THE VENTURIES REALLY CLOSE TO "SPILLING"---THEN AS AIR (VACUUM) RUSHES BY THE VENTURI THE FUEL "MISTS" FROM THEM (LIKE A PAINT GUN NOZZLE) THIS IS WHERE AIR/ FUEL MIXTURE BEGINS IN A CARB

IF THE FUEL IS LOW IN THE VENTURI----THE RUSHING AIR (VACUUM) HAS A REALLY HARD TIME S. UCKING THE FUEL UP AND OUT OF THE VENTURI.

KINDA THINK OF HOVERING YOUR STRAW REALLY CLOSE TO YOU SOFT DRINK THE S. UCKING THE STRAW---YOU GET SODA!

THEN BACKING OFF A BIT MORE, NOW YOU CAN'T S. UCK HARD ENOUGH TO GET THE SODA INTO THE STRAW

IF YOU PULL THE CHOKE, THAT IS IF YOU HAVE A MANUAL CHOKE! THIS MAY MAKE SUCTION GREATER, AND IT MAY PULL ON THE FUEL A LITTLE HARDER (S. UCKS THE STRAW HARDER) THIS IS NOT A FIX, BUT IF THE BUCKING SORTA SUBSIDES A LITTLE, TAKE IT TO THE BANK, FOR SOME REASON (PUMP, RESTRICTIONS, NOT ENOUGH BACK PRESSURE FROM RETURN LINE, INCORRECT CARB ADJ, ETC.) YOUR BOWL LEVEL IS TOO LOW

THE MEDIC

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Wednesday, March 7th, 2012 AT 5:43 AM
Tiny
FIXITMR
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Mixture should not be different, just workload. Lean is ok withno load but fails undr load.

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Wednesday, March 7th, 2012 AT 7:03 PM
Tiny
GRIZZLY93
  • MEMBER

I turned the regulator up to 3.5 psi and it ran fine. Its weird though because it was running just fine for 2 months before this. It hasnt done it in awhile.

Medic, maybe ill do the O2 sensor piece on this one also since its my daily driver. Give me a better idea of my driviong habits and the efficiency of them. Might solve my 12 MPG.

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Wednesday, March 7th, 2012 AT 7:50 PM
Tiny
CJ MEDEVAC
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ONCE YOU GET YOUR JETS MATCHED WITH YOUR NORMAL DRIVING SPEEDS AND THE POWER VALVE SELECTED TO TAKE OVER WHEN THE VACUUM DROPS DOWN (REALLY READ THE "SCIENTIFIC TUNING THING I SENT A LINK TO) YOUR CARB WILL PERFORM SO MUCH BETTER AS FAR AS "AVERAGE AIR FUEL MIX" FOR WHATEVER SPEEDS YOU DRIVE.

BEING THAT A CARB CANNOT MAKE CORRECTIONS OR BE SET TO GIVE A PERFECT MIX WHEREVER YOU HAVE THE ACCELERATOR PEDAL POSITIONED TO, YOU CAN GET IT WORKING AT ITS PEAK IF YOU GET ALL OF THE FACTORS DOING THE BEST THEY CAN DO. WITH THE AIR/ FUEL GAUGE ON YOU WILL SEE "LEAN MOMENTS" AND YOU WILL SEE "RICH MOMENTS". YOU ARE STRIVING FOR IN-BETWEEN (STOICH, OR NEAR THAT) 14.7:1 AIR/ FUEL MIX IS PERFECT.A CARB CANNOT HOLD THAT, A COMPUTERIZED CAR CAN GET CLOSE.

I HAVE MINE JETTED FOR BEST PERFORMANCE AT 55 MPH ON FLAT GROUND. AT 55 MPH THE YELLOW LEDs ARE BOUNCING ALL OVER STOICH

PULLING A SLIGHT HILL, IT GOES RED (LEAN), IF I TOUCH THE PEDAL IT MAY COME BACK TO YELLOW, WHEN I "PEDAL A BIT MORE" THE VACUUM DROPS, THE POWER VALVE KICKS IN AND IT GOES GREEN (RICH)

AS FAR AS AROUND TOWN, IT STAYS RICH MOST OF THE TIME. BUT NOT AS RICH AS DOING THIS BY "WORD OF MOUTH"--IMPOSSIBLE TO READ PLUG CUTS (COLOR)---OUT OF THE BOX (WAS WAY TOO LEAN W/ MY HOLLEY)

I HAVE WENT FROM 15 MPG (BBD JEEP CARB) NOW TO 18 MPG W/ MY 4 BBL HOLLEY. DRIVING SENSIBLY.I TRIED FOR YEARS TO GET PAST THE 15 MPG MARK WITH EVERY GADGET SAID TO HELP, I AM NOW SATISFIED WITH MY RESULTS, THE O2 WAS THE ANSWER TO GETTING THE "BURN" PEAKED OUT. MY ON DASH VACUUM GAUGE ALSO KEEPS YOU AWARE OF THE HEAVY FOOT, KEEPING THE NEEDLE HIGH, KEEPS THE MPG UP!

THE MEDIC

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Thursday, March 8th, 2012 AT 12:33 AM
Tiny
CJ MEDEVAC
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LETS SEE IF ANY OF THIS STUFF AIDS YOU

THIS 1ST ONE IS EXTREME, THERE SHOULD BE ABSOLUTELY NO WOBBLE AT ALL...NOT EVEN A LITTLE

http://www.youtube.com/watch?v=1z2XpvyCknY

WATCH HIS AXLE---IT SHOULD NOT TURN UNLESS THE HUBS ARE LOCKED.....ARE YOURS STUCK IN THE LOCKED POSITION?

BELOW--SEARCH OUT THE BEST VIDEO SIMILAR TO YOUR SET UP THAT YOU HAVE ON THE YJ (I DO CJs, SELDOM MESS WITH A WRANGLER)......USE YOUR REPAIR MANUAL AS "LAW"--VIDEOS MAY NOT BE PERFECT EXAMPLES----HERE'S SOMETHING THAT COULD BE SIMILAR WITHOUT ME WATCHIN' ALL OF THE VIDEOS

USE DIFFERENT SEARCH WORDS, YOU MAY FIND A BETTER VIDEO....SEARCH BOX IS AT TOP OF THE VIDEO.....DON'T FORGET TO LOOK AT THE SUGGESTIONS DOWN THE SIDE OF THE VIDEOS.......WHEN THE "GIRLY ONES" POP UP---STEER CLEAR, YOU WON'T GET YOUR WORK DONE!

http://www.youtube.com/results?search_query=HOW+TO+REPLACE+FRONT+WHEEL+BEARINGS+ON+A+JEEP&oq=HOW+TO+REPLACE+FRONT+WHEEL+BEARINGS+ON+A+JEEP&aq=f&aqi=&aql=&gs_l=youtube-reduced.12...2133.26510.0.29445.45.45.0.30.30.0.237.2110.2j12j1.15.0.

OK THIS ONE IS ABOUT TIE RODS----LOST MOTION SHOULD BE CHECKED ON ALL STEERING PARTS

http://www.youtube.com/watch?v=so0vL-ZOwY8&feature=related

http://www.youtube.com/watch?v=so0vL-ZOwY8&feature=related

I USUALLY GET SOMEONE TO TO TURN THE STEERING WHEEL BACK AND FORTH--LIKE A 1/4 TURN OR SO (THE SLACK AREA) WHILE I WATCH STEERING JOINTS FOR SLOP---EVEN A LITTLE BIT OF SLOP IS TOO MUCH!

REMEMBER "MORRIS 4X4s KNOWLEDGE BASE" HAS YOUR REPAIR MANUAL ONLINE---FOR YOU TO LOOK AT ANY TIME....YEAR CLOSEST TO YOURS SHOULD BE IT

http://www.jeep4x4center.com/knowledge-base/index.htm

KEEP ME INFORMED

THE MEDIC

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Monday, April 30th, 2012 AT 2:45 AM
Tiny
GRIZZLY93
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http://www.youtube.com/watch?v=7UvXD4OgRX4

found this one off of your links. this is nearly identical to the noise that im hearing. only louder, im sure because of being under the weight of the vehicle and stress of the turn. ive been pricing them, and to eliminate the work ill probably order the whole hub assembly with new bearings in them.

Thanks again Medic. ill have to record my tie rods in the same fashion as the youtube video. the yj doesnt have locking hubs, round 88 they had a hard on for vacuum lines, so the front hubs are vacuum actuated when the t-case is shifted into 4wd, all other times they are free. unless other modification has been made to change the system. but mine is still stock.

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Monday, April 30th, 2012 AT 3:09 AM
Tiny
CJ MEDEVAC
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YA ON THE HUBS----SOMETHING LOCKS 'EM---SEE IF IT COULD BE BROKE OR STUCK. THUS ONE SIDE OF THE AXLE MIGHT TURN, WHEN IT SHOULDN'T

AS FAR AS GETTING RID OF FAMILY MEMBERS (JEEPS)

TALK MOM INTO GETTING RID OF DAD--KEEP THE JEEPS

DAD IS NOT AS SYMPATHETIC IN MOST CASES---MOM IS MORE "WRAPPABLE AROUND YOUR LITTLE FINGER. LEAST THAT WAS THE CASE WHEN I WAS GROWING UP. LOL!

I SORTA STARTED OUT WITH NOTHING, AND STILL HAVE MOST OF IT LEFT!

WE KEPT DAD REGARDLESS, HE WAS A FORD MAN, I WAS NOT ABLE TO GET MY 1ST JEEP TILL I JOINED THE ARMY, WENT THE AIRBORNE RANGER ROUTE, AND WAS FINALLY ABLE TO BUY IT "MY DREAM"."PAP" HAD MORE FUN WITH MY JEEPS THAN HE EVER DID WITH HIS FORDS

PICS ARE MY 1ST (EARLY 1983), 2ND (LATE 1983, #1 T-BONED BY A SEMI AT 45 MPH), OLE WILLY IS #7, MY LATEST DEER STAND SHOT, HE LOOKS LIKE A TOY).I SORTA USED A SIMILAR PAINT SCHEME WHEN I PAINTED #6 CJ5 LIKE THAT OF #1

LET ME KNOW IF YOU NEED MORE ASSISTANCE. AND TELL MOM AND DAD THAT CJ MEDEVAC SAYS HEY. AND NOT TO BE SO HARD ON YOU!

THE MEDIC

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Monday, April 30th, 2012 AT 4:03 AM
Tiny
CJ MEDEVAC
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. AND?

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Wednesday, May 2nd, 2012 AT 12:14 AM
Tiny
GRIZZLY93
  • MEMBER

Well parts are ordered, just waiting on them to get here than ill be able to confirm or deny whether the wheel bearings are the culprit. So itll be a few days. In the mean time im pickin up some leaf springs for it on sunday. The ones on there now are shot to hell. Still the factory ones, and they hit the bumbstops everytime I hit even the slightest bump in the road.

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Thursday, May 3rd, 2012 AT 1:46 AM
Tiny
BENJAMINSELINGER
  • MEMBER

Hate to sideline a good theory, but I had exactly the same issue with my 92 xj a few years ago. Spent weeks troubleshooting driveline stuff until I gave up on repairs and went back to data collection.
I discovered that the bucking only occurred in forward gears and not in reverse so I checked the engine torque direction in forward, grabbed the wire harness above the injectors and gave them a twist the same direction till I found it was a single strand of wire poking out of my MAP sensor 5V lead to ground. Was causing the computer to short and reset every time the engine torqued hard.
Exact same issues as you. Bucking under acceleration, gets worse when it's wet, gets worse when it warms up. I figured the wet just increased the conductivity of an already bad short and the warm let my engine mounts stretch further thus the motor would pull on the harness more.

I'd check if you can reproduce while doing a breakstand in both forward and reverse. If you only get it in one or the other, it's probably a bad sensor wire shorting out.

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Thursday, October 11th, 2012 AT 5:07 AM

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