Jeff 98XJ WI
NAXJA Forum User
- Location
- Butternut, WI
First, I did do some searching, but didn't find anything leading me to the cause of my problem so far, so here is my story:
Hey guys, I am looking for advice as to why my '98 is running poorly.
First some background:
'98 4.0HO, auto, air, 100000+ miles
It will start ok, idle ok usually, and run ok at part throttle. I can
get it to rev to redline if the throttle is operated slowly. However,
if the throttle is snapped open and or if there is a load like while
driving down the road, it will blubber, sputter, and cough usually above
3000rpm.
First, I cleaned the air cleaner. Then I checked for a fuel filter only
to find that it is in the tank. I suspected the fuel pump or regulator
originally, so I did some tests. Fuel pressure is fine. Leak down is
fine, volume is fine. I changed cap and rotor this morning and pulled
one plug. It was a Bosch Platinum +4 and looked to be in really clean,
good condition. They must have been installed by the previous owner. I
checked the Throttle Position sensor with an ohm meter and it seemed to
be fine and not have any rough spots or anything. I can't find any
vacuum leaks or anything obvious under the hood. The catalytic convertor probably has over 200,000mi on it since I took it off my '92 and put it on this '98 along with the rest of the exhaust including a Borla header and cat back about a year ago. However, I am not getting a check engine light indicating that the Cat. is not doing it's job. That's about where I am at now.
I tried getting any codes in the computer by cycling the key, but it
doesn't seem to work in the '98. The manual just talks about using a
DRB II tool. Oh yeah, I have NOT gotten a Check Engine light...until
this evening when I unplugged the sensors connected to the throttle
body with the engine running. Is there a way to check the O2 sensors with a volt meter? Could they be causing this problem? Also, when revving the engine while under the hood doing a visual and having the engine run poorly, I did notice that the Borla header actually glowed cherry red! I'm not sure that is normal or not, but it made me think of a rich fuel mixture. I did get it to run ok while revving for a bit and the exhaust manifold got red then too. Also, the check engine light did go out this morning after a number of restarts. Thanks for any inf. Jeff
Hey guys, I am looking for advice as to why my '98 is running poorly.
First some background:
'98 4.0HO, auto, air, 100000+ miles
It will start ok, idle ok usually, and run ok at part throttle. I can
get it to rev to redline if the throttle is operated slowly. However,
if the throttle is snapped open and or if there is a load like while
driving down the road, it will blubber, sputter, and cough usually above
3000rpm.
First, I cleaned the air cleaner. Then I checked for a fuel filter only
to find that it is in the tank. I suspected the fuel pump or regulator
originally, so I did some tests. Fuel pressure is fine. Leak down is
fine, volume is fine. I changed cap and rotor this morning and pulled
one plug. It was a Bosch Platinum +4 and looked to be in really clean,
good condition. They must have been installed by the previous owner. I
checked the Throttle Position sensor with an ohm meter and it seemed to
be fine and not have any rough spots or anything. I can't find any
vacuum leaks or anything obvious under the hood. The catalytic convertor probably has over 200,000mi on it since I took it off my '92 and put it on this '98 along with the rest of the exhaust including a Borla header and cat back about a year ago. However, I am not getting a check engine light indicating that the Cat. is not doing it's job. That's about where I am at now.
I tried getting any codes in the computer by cycling the key, but it
doesn't seem to work in the '98. The manual just talks about using a
DRB II tool. Oh yeah, I have NOT gotten a Check Engine light...until
this evening when I unplugged the sensors connected to the throttle
body with the engine running. Is there a way to check the O2 sensors with a volt meter? Could they be causing this problem? Also, when revving the engine while under the hood doing a visual and having the engine run poorly, I did notice that the Borla header actually glowed cherry red! I'm not sure that is normal or not, but it made me think of a rich fuel mixture. I did get it to run ok while revving for a bit and the exhaust manifold got red then too. Also, the check engine light did go out this morning after a number of restarts. Thanks for any inf. Jeff