Idle Surging and flat (no power) >2000 RPM

[jbaier]

All,
I'm also curious about reliability. I had a 95 Wrangler, 4.0L, with 140K on it when I sold. It was completely reliable. I performed all maintenance. The only things to break was a water pump failed about 110K and I replaced rear main seal and clutch about 120K. When I pulled the oil pan off it was so clean all you got was an oil film if you drug your finger inside.

This XJ has 115K and I'm replacing everything it seems. Is this unusual. Or is it due to the previous owner's lack of maintenance.

Thanks,
Jeff

 

[StaleAle]

Is the antifreeze rust colored and the oil milky. Maybe a blown head gasket.

 

[89xj]

All,
I'm also curious about reliability. I had a 95 Wrangler, 4.0L, with 140K on it when I sold. It was completely reliable. I performed all maintenance. The only things to break was a water pump failed about 110K and I replaced rear main seal and clutch about 120K. When I pulled the oil pan off it was so clean all you got was an oil film if you drug your finger inside.

This XJ has 115K and I'm replacing everything it seems. Is this unusual. Or is it due to the previous owner's lack of maintenance.

Thanks,
Jeff

well, i have have 245k miles on my 89 and have owned it since 1990 and its still my daily driver. ive done all the repairs(brakes, water pumps, rms, clutch and throwout/slave, radiators,...) but the engine still runs very strong.

at 115k, i dont see a radiator being an unuasual repair. i wouldnt be surprised if the waterpump will be next to go. then the nss or cps will give you a no start problem. not to be a downer, but its the small things that usually go after about 120-150k.

 

[winterbeater]

If you over-rev a motor like this don't the valves usually just float? And how does a damaged valvetrain cause cylinder leakdown? Bent valve? Does that ever happen? Not that I've seen.

These are most known for cracked heads. Is the valve cover milkey on the inside?

To put on an older head with a valve job would actually be an upgrade.

 

[jneary]

if you had a bad plug or bent push rod or weak spring, it would show a misfire, on the scan tool and store a code. i tend to think the distributor isnt indexed correctly.

 

[jbaier]

UPDATE
Sorry for the long delay, I've been out of the area.

I ended up replacing the engine due other issues (water in oil, no compression on 2 cylinders, etc). Quess what, it still does it. The replaced items are (with no change in problem):

- Engine
- Trans
- Flywheel & clutch assy
- Cat
- CPS
- TPS
- IAC
- MAP
- Radiator
- Water Pump
- Thermostat & Housing
- All water hoses
- PCM

I've verifed:
- Fuel Press at 48# (49.2 +-5#)
- Disconn Vac lines and plugged
- And all the other stuff in the previous posts

On checking the wiring, I found a jumper (piece of wire) in the plug which I think is for the extended idle (police pack). It made no difference if I removed it or not. Is it supposed to be there?

Is there a difference in flywheels throughout the years? My does have the notches for the CPS. It is the part number called out by the parts store and the same one I used on my 94 wrangler.

Thanks,
Jeff

 

[winterbeater]

There was another thread where someone had changed an engine and had the wrong flexplate in there for his year. But it had the wrong number of notches or something. It wouldn't run on 2 of the 6 cylinders.

 

[winterbeater]

Is the new motor a JY or a reman? Still a 98?

 

[jbaier]

Reman long block

 

[IH392]

I don't know if a bad oxygen could do this, but maybe it got damaged during the trans replacement. Maybe try unplugging it and see if it runs any different. My only other suggestion is maybe you have a cloggged fuel injector. What I have done in the past is pull the injector rail off with the injectors with wiring and fuel line attached, and have someone crank the engine and see if they all spray. Then at least you know they all work. If you do this be careful because it might catch fire like it did with me, so make sure to disconnect the coil wire, and get a rag ready to snuff the flame.

 

[winterbeater]

In your long list, you don't say that you tested the Cam Position Sensor. I don't think the 02 sensor could cause that.

 

[joe_peters]

x2.

 

[Ghost]

Did you just change the TPS once? I have a friend that told me recently that there is a batch of bad TPS for the 4.0. Apparently the local jeep dealership has gotten some. The reving of a 4.0 has always indicated a TPS problem in my experience.

 

[winterbeater]

TPS is relatively easy to check with analog voltmeter!

 

[jbaier]

The cam position sensor was replaced with the distributor.

 

[jbaier]

TPS was replaced once. But, it's kind of odd, when using my scan tool shows throttle position at 18.4% when not touching throttle. It increases linearly when opening the throttle.