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hesitation driving me NUTS!

S

southernrebel20

NAXJA Forum User
Location
Georgia
Since I got my 99 XJ it hesitats (like starving for fuel) and losses power/rpm when I start it up after letting it sit over night or for a few hours. It starts and idles fine but when I put it in gear and drive 20 feet or so it starts the hesitating, I will feather the throttle and it will return to normal and will run perfectly fine all day long. Fuel pump starting to go out?? The ignition from the cap and rotor on is all new. What could be the problem. P.S. sorry for the long thread.
 
check your inline fuel filter going to the tank, and if you have the fuel gage, test teh pressure at the rail, i think its supposed to be about 34 PSi, not totally sure o nthat.
 
i have same prob.... but ive also replaced the tps, trans filter, and flushed trans.... good luck... let me know if ya fix it....
 
jk333 said:
check your inline fuel filter going to the tank, and if you have the fuel gage, test teh pressure at the rail, i think its supposed to be about 34 PSi, not totally sure o nthat.
Click to expand...

If his is same as mine, the filter is in tank, no in-line.... and my pressure is about 40-60 when running....at the rail...

Austin
 
I have the EXACT same problem with my 99. I figure it's probably a combination of the filter in the tank being clogged and the fuel pump weakened after 100k miles. A side question for you two with the 99s, do you have the popping noise from the gas tank for a couple hours after you shut it off like I do?
 
the "popping" noise you hear (if its the same one im thinking of...) is a normal condition that happens with most vehicles... as for the plugged filter and pump, I've scoped my pump while its running at school, and its running perfectly..... One of my buddies has been leading me towards a bad Torque Converter... which almost makes sense..... but still investigating.....

Austin
 
I will try checking my grounds, but as far as 02 sensors go, wouldn't it throw a code if it wasn't working/sending the correct voltage? My in-tank fuel screen could be the culprit but I would think it would run crappy all the time if it was clogged. It will only do it for a minute until i feather the throttle, then it will run perfect all day long. I'm thinkin my fuel pump might be acting up on cold starts. Links to a write up on this for the newer XJ's??
 
I'm in the same boat as well with my 98. I'm throwing a code for an 02 sensor but 2 new Bosch sensors have not cured it. I haven't lost any gas milelage or anything like that. It only happens after it has been sitting and happens once and never again for the rest of the day at least. I do have a crack in my header at the "Y" it could have something to do with it as well.
 
I have not lost any MPG either. Still getting 18 or better around town. I also have recently replaced my cracked exhaust manifold with an edelbrock piece. I don't know what the deal is. This sucks!!
 
check your crank sensor. thats how mine behaved when it first started going out.
 
My 99 did the same thing would turn on after being off for a while and then would sputter and act all weird and then shoot back into life and be fine for the rest of the trip. As it turns out the number 3 injector was getting heat soaked. and i had to take heater hose insulator and wrap it.
 
My 99 has the same problem. Sometimes it's worse than others. I was under the impression that it is the TPS, got one, haven't put it in yet. I also throw an O2 code. Lately it's been really bad in 4lo. I don't mind the hickup on the road, but in 4lo, hickuping sux!! I also have an aftermarket header.

If the TPS doesn't fix it, I'm going for CPS next....
 
Check fuel pump pressure at the rail on the schrader valve. Compare to spec. You need to start the process of elimination.

As for sensors, the TPS is one that comes to mind as a possibility. I believe there is a test procedure for it but it sounds like you have a new TPS to install already. Let us know if this fixes your problem.
 
Will do. I find it strange that it seems like so many people with 97-99 XJs are having the exact same problem, and no one has pinned it down yet!!!


there is another thread on this that talks about initial errors in sensors doing it that sounds like it may be something to look into further. Maybe I'll get a dealer O2 sensor? Also, seemed like everyone who had the problem had aftermarket headers...
 
what does an injector getting heat soaked mean? I've never heard of this. I want to try the tps and cps first before dropping the tank for the pump. Let me know how replacing your TPS helps out.
 
I've had this problem before as well on a few XJ's and each and everytime it turned out as either a bad TPS or one that was out of adjustment. It's worth looking into if it were me.
 
does it idle ok, or idle high? If the IAS/AICV is bad, it can get goofy like that. Mine was idling real high after startup, and would have bad hesitation if I gave it light throttle. full throttle was ok, but light/medium throttle would be rough until it warmed up.

TPS is usually more of switching between gears for no reason, or locking you out of OD or 3rd. (sudden drop to 2nd gear at 65mph is NOT fun)
 
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