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'88 XJ engine problem

R

red94yj

NAXJA Forum User
Location
Blue Ridge Ga
Hey, I got one and need help fast.... XJ 4.0L runs fine at idle and when your on it hard,but at cruise speed ( no matter if your at 35 or 70 if your tring to hold a set speed) it spits and sputters????? TPS/coil/distributer/computer all changed and it looks like the timing is at about 9 degrees before top dead.
any and all help greatly appreciated. I've stump yellowxj(Travis) but he's in Florida and I'm in north Ga (Blue Ridge to be exact)

Phone # 7066325715

Thanks
Brian Peay
94 YJ 4banger 35" 4.88 spooled XJ D44
88 XJ
98 ZJ
always looking(she wants another TJ)
4banger4ever
 
Sorry - no help - but I have the exact same problem with my 88!

I've have asked about it a couple of time before, but still haven't found an answer yet.

Chris
 
The 2 things I would check are fuel rail pressure and vacuum lines. Almost sounds like a fuel pump going out Hope it helps.
Keith
 
Keith:

That's a possibility, but wouldn't fuel pressure affect the Jeep more at WOT then when cruising?

Another thing to add:
I recently found that the vacumm line to my EGR motor (right on the intake) was disconnected. When I connected the line, the Jeep would die right away. I replaced the EGR solenoid on the driver's side fenderwell, now the Jeep does not buck or sputter at all - but now it stalls when coming to a stop.

Somehow the two are related, but I don't know how.

Chris
 
The pump can do some strange things. I had a 944 that did the sputter thing and it turned out to be the pump. Couldn't maintain constant fuel pressure. But if it's not doing that now thr pump is probably not the problem. Noticed you changed the dist. That takes care of the cam sensor. Have you checked or changed the crank sensor? The crank sensor and plug are known problems on the 4.0. It's located on the back of the block, just above the bellhousing. They're cheap and fairly easy to change. When my 87 did the stalling at light thing it was a combination of the MAP and cam sensors. I say condination because I change them together. The MAP sensor is located on the firewall about center on the motor. It's also easy to change and cheap.
Just a couple things to check. Don't know how to check them without swapping them.
Keith
 
This sounds to me like an EGR issue. I have had the exact symptoms on my 88. I have not had a chance to put on a new egr yet, so I just disconnected the vacuum line and plugged it. It runs perfectly disconnected with no stumble. I do believe I will be able to pass emissions also. They don't check for Nox in Wa.
 
The stalling at idle could very well be the EGR valve sticking. It's supposed to be closed at idle and WOT; and open at part throttle. A test for it is simply to remove and plug the vacuum hose. If idle troubles dissappear, then the EGR is bad or sticking.

The bucking at cruise/part throttle might be the MAP sensor. Remove the vacuum hose and see if the sensor diaphram will hold vacuum. If not, it's bad. Another test is to put a timing light on the engine, blip the throttle, and see if the timing advances and retards. If not, then suspect a bad MAP......
 
red94yj said:
Hey, I got one and need help fast.... XJ 4.0L runs fine at idle and when your on it hard,but at cruise speed ( no matter if your at 35 or 70 if your tring to hold a set speed) it spits and sputters????? TPS/coil/distributer/computer all changed and it looks like the timing is at about 9 degrees before top dead.
any and all help greatly appreciated. I've stump yellowxj(Travis) but he's in Florida and I'm in north Ga (Blue Ridge to be exact)

Phone # 7066325715

Thanks
Brian Peay
94 YJ 4banger 35" 4.88 spooled XJ D44
88 XJ
98 ZJ
always looking(she wants another TJ)
4banger4ever
Click to expand...
 
LEAVE THE EGR VALVE CONNECTED , START VEHICLE PUT YOUR FINGERS UNDER THE EGR VALVE & PUSH THE VALVE UP THE VEHICLE SHOULD STALL OUT IF IT STALLS THE VALVE IS BAD. DALE [email protected]
THIS CAN ALSO BE DONE WITH A VACUUM PUMP< BE CAREFUL THE VALVE IS HOT
 
The EGR is the metal piece under the throttle body, correct? Which way is it supposed to move in response to engine revving? I do not see it move at all. Also, what is the part to the left of it the connects by a vacuum tube? My gas mileage is crap (8-10mpg), and I think this may be the problem. Thanks.
 
I second the map idea.

check that hard vacum line from throttle body to map sensor... make sure it isn't cracked or broken at the base where it goes into the throttle body.
 
TNSlaytanic said:
The EGR is the metal piece under the throttle body, correct? Which way is it supposed to move in response to engine revving? I do not see it move at all. Also, what is the part to the left of it the connects by a vacuum tube? My gas mileage is crap (8-10mpg), and I think this may be the problem. Thanks.
Click to expand...
THE EGR VALVE IS MOUNTED JUST UNDER THE THROTTLE BODY THE DIAPHRAGM INSIDE MOVES UP & DOWN I HAD ONE THAT HUNG UP ON THE SHAFT IT KEPT CATCHING & HANGING UP,.THE THING THAT IS ON THE LEFT & HAS A HOSE GOING TO IT IS A CTO, COOLANT TEMPERATURE OVERRIDE SWITCH. IT HOLDS THE EGR VALVE FROM OPENING BELOW 100 DEGREES,CHECK BY OPERATING THE ENGINE AT 1,500RPM VACUUM SHOULD BE PRESENT IF NOT REPLACE THE CTO SWITCH HOPE THIS HELPS. QUESTIONS EMAIL AT [email protected] DALE
 
TNSlaytanic said:
The EGR is the metal piece under the throttle body, correct? Which way is it supposed to move in response to engine revving? I do not see it move at all. Also, what is the part to the left of it the connects by a vacuum tube? My gas mileage is crap (8-10mpg), and I think this may be the problem. Thanks.
Click to expand...
IF YOU PUT A HOSE DIRECTLY TO THE EGR VALVE & USE A VACUUM PUMP THE ENGINE SHOULD STUMBLE BADLY OR STALL ALL TOGETHER IF YOU HAVE HOOKED UP & THE ENGINE RUNNINGYOU CAN REACH IN BETWEEN THAT DIAPHGRAM HOUSING & PUSHUP ON THE DIAPHGRAM & IT SHOULD STALL IF notchecked for blocked passageway under Egr valve IF YOU PUT YOUR FINGER UP AGAINST THE DIAPHGRAM & REV THE ENGINE YOU SHOULD FEEL MOVEMENTIF NOT IT ISN'T WORKING [email protected] USE GLOVE IT'S HOT
 
badge714 said:
IF YOU PUT A HOSE DIRECTLY TO THE EGR VALVE & USE A VACUUM PUMP THE ENGINE SHOULD STUMBLE BADLY OR STALL ALL TOGETHER IF YOU HAVE HOOKED UP & THE ENGINE RUNNINGYOU CAN REACH IN BETWEEN THAT DIAPHGRAM HOUSING & PUSHUP ON THE DIAPHGRAM & IT SHOULD STALL IF notchecked for blocked passageway under Egr valve IF YOU PUT YOUR FINGER UP AGAINST THE DIAPHGRAM & REV THE ENGINE YOU SHOULD FEEL MOVEMENTIF NOT IT ISN'T WORKING [email protected] USE GLOVE IT'S HOT
Click to expand...

One thing I must add is that if you have the older 1-piece EGR with a built-in back-pressure valve in the diaphragm (my 87 had this), putting vacuum to it may NOT be a valid test. It will fail even if it's good, unless exhaust back pressure is present to close the valve. If you just test the diaphragm with a vacuum pump it will ALWAYS fail.

On the later version, there's a tendency when it wears, to hang up intermittently in the open position, causing unpredictable stalling.
 
Last edited:
red94yj said:
Hey, I got one and need help fast.... XJ 4.0L runs fine at idle and when your on it hard,but at cruise speed ( no matter if your at 35 or 70 if your tring to hold a set speed) it spits and sputters????? TPS/coil/distributer/computer all changed and it looks like the timing is at about 9 degrees before top dead.
any and all help greatly appreciated. I've stump yellowxj(Travis) but he's in Florida and I'm in north Ga (Blue Ridge to be exact)

Phone # 7066325715

Thanks
Brian Peay
94 YJ 4banger 35" 4.88 spooled XJ D44
88 XJ
98 ZJ
always looking(she wants another TJ)
4banger4ever
Click to expand...
 
I have an 88 as well, this problem happened to me about a year ago...

brought it to a jeep tech --- and he changed the throttle positioning system sensor

i think it was a 25 dollar fix
 
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