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hot 'bogging' issue

in4aride

in4aride

NAXJA Forum User
Location
Montrose
1996 4.0 aw4 196k rebuilt with about 70k on it lifted dual lockers 35's cone air filter stock exhaust


before jumpin down my throat to search, ive read and read and replaced suggested things
tps ahs been replaced, NSS replaced, plugs and wires replaced. fluid levels are good and clean and jeep runs average 220*



after a lond day of driving (driving to trail, running trail, drive home) the jeep begins to have a serious fall on its face issue...
jeep idles perfectly fine and smooth but holding steady speed or accellerating makes the jeep feel like its running out of gas or misfiring.

again ive replaced TPS, NSS, plugs and wires...still happens....
any suggestions?

jeep does not throw any codes
 
Hahahaha. Don't make fun of me. I do suspension and steering not motor stuff lol.
So check it while driving when it's hot and acting up?


Wouldn't O2 sensor throw codes?
 
O2 sensor- maybe, maybe not. That's the great thing about the internet. You always get the guys saying 'I had the exact same thing happen, it was a bad turn signal.' Ignore all that, diagnose the problem. If the fuel pressure drops out it's gonna run like crap since engines don't run on air very well. If that checks out then move on to the next thing.
 
Ya that's been what I'm trying to do is go from one thing to the next but nothing is helping lol.
I'll check fuel pressure (with fuel pressure guage :doh: ) hopefully tomorrow but definitely this week. I've had jeep on obdII scanner and checked live datastream as I drove around and nothing popped out as out of the norm, after I fixed the tps, so I just don't know.

I'm leaning to a fuel problem or a sensor of some sort due to heat.

Here's crazy thing. Jeep drove PERFECt prior to droppin into Indy. I had smashed my crossmember hard andpushed it uplike 1/2-1". That day was the first time I experienced these symptoms :dunno:

looked and haven't seen any split wires or anything. So I dunno
 
I just had to replace the fuel pump on my heap. My symptoms were almost identical to yours. It would start and idle just fine but fall on its face if I tried to accelerate. A fuel pressure guage showed good pressure at idle but at rev it started to fall off and under heavy load it really fell off.
You really need to see what the pressure is under rev and load to make sure.

If that's not the problem you might want to look into a plugged cat or lean/rich condition usually driven by bad sensors (MAP, TPS, Temp, O2)
 
in4aride said:
Ya that's been what I'm trying to do is go from one thing to the next but nothing is helping lol.
I'll check fuel pressure (with fuel pressure guage :doh: ) hopefully tomorrow but definitely this week. I've had jeep on obdII scanner and checked live datastream as I drove around and nothing popped out as out of the norm, after I fixed the tps, so I just don't know.

I'm leaning to a fuel problem or a sensor of some sort due to heat.

Here's crazy thing. Jeep drove PERFECt prior to droppin into Indy. I had smashed my crossmember hard andpushed it uplike 1/2-1". That day was the first time I experienced these symptoms :dunno:

looked and haven't seen any split wires or anything. So I dunno
Click to expand...

Have you had it checked for exhaust leaks with a gas sniffer? Bending the crossmember lifts up the transmission and tilts the engine, while the exhaust piping can't move. It has to bend, which puts stress on the seals, which could make leaks, which would affect the O2 sensors (along with possibly exposing you to toxic fumes)
 
Fuel gauge? Yep, good idea.

Exhaust damage/o2 sensor? Yep, two good ideas, in particular damage to the CAT.

Runs at 220 degrees NORMALLY? Why is it running so hot? 205-210 would be more normal.
 
every jeep ive ever had here in CO has run about this hot...so i dont see it as TOO out of the norm...
but back to the o2 sensor thing, wouldnt that throw a code?..

still havent checked fuel press
 
in4aride said:
every jeep ive ever had here in CO has run about this hot...so i dont see it as TOO out of the norm...
but back to the o2 sensor thing, wouldnt that throw a code?..

still havent checked fuel press
Click to expand...

Unfortunately, o2 sensors tend to be WAY PAST bad before/if a code ever appears. I change mine at 60k miles, although 80k is doable on quality sensors.

Looked at your location--might be an altitude/air density thing.
 
Well whatever it is, is now getting worse. Before it took at least hour of driving to feel effects, today it took a few miles and maybe ten minutes.

I had swapped relays as my fuel pump relay went bad a few weeks back and I'm wondering if that's the case again this time. If the relay could be 'going out'?
Or if fuel pump could be going bad?
It was also suggested that an output speed sensor, on side of transmission under t-case linkage plate, could be going bad. That possibility?
Will fuel pressure guage be usable as I'm driving the jeep?
Sorry guys for all the repeat stuff this is just makin me crazy and I need jeep running in lil over a week for a trail run. Thanks
 
Only one place had it. $35. Just check while driving? Or do the tests at idle? If doing while driving am I just lookinfor drop in pressure when it bogs?
 
Well here's where I'm at. Had the guage on the jeep for two days now, because of the guage not being long enough I had to remove the hood to b able to see the guage. The operating temperature of the jeep has stayed the same, it's been running just as hot.
But, I have not been able to get the jeep to Bog down. From fuel pump priming to turning it off jeep is keeping right around 50psi. (if the guage is accurate)

today I did catch the guage dipping to approx 25-30psi. But the jeep did not bog down. It ran the same. The drop in fuel pressure was fast and quickly rebounded. It dropped about 3-4 times before maintaning 50psi again.


Thoughts?....
Sucks not being able to get jeep to bog now, took it for a long drive around town and all
 
There is your problem, you are losing fuel pressure intermittently. Now, you need to determine why. Failing pump, failing relay, bad harness, crap in the tank/fuel filter. You now know what is wrong, you just need to find the source.

Good luck.
 
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