PDA

View Full Version : No power 4.0



nate
08-30-2004, 02:29 AM
Well I brought my 98 4.0 ZJ in to get some help.. haha. (to 5 Star if your wondering Brentt).

Well the problem is that it really lacks power. Kurt (owner of 5 Star) said they had a TJ come in that was the same and never did figure it out. We put it on the Snap On scanner the first time I brought it over and everything checked ok. I'm leaving it with them to figure it out, as I'll be gone to Korea for a while.

Anyway...

170psi compression
cat isn't plugged
new TPS
bored Throttle body
had MotorVac done (pro injector cleaner).
Fuel pressure is at 49psi.
33s with 4.56 gears.

If I want to hold 60-65 on a hill, even a small one, it kicks right down into 4th gear, gains speed, back into O/D, looses speed, back into 4th, back into O/D... you get the idea. The whole time I'm running it at 3/4 to full throttle, otherwise, I'll be doing 40 up the hill.
The engine temp will run up to 215-225* while doing this, otherwise stays right around 210* on the flats.

Kraqa
09-02-2004, 03:20 PM
check your clutch on your fan mine went and was robbing my engione of alot of power on the hills and mine would also over heat.

nate
09-17-2004, 08:30 AM
I wish it was that easy.
I have an e-fan from a WJ I swapped in.

I have it down at the shop since I'm in Korea for a while. (Yeah 5 Star Brentt... where else?)

Anyway, so far what has been established is when it's in open loop it's fine. Once it goes into closed loop, it turns gutless. No codes being throw... weird stuff.

K2
09-18-2004, 04:17 PM
Maybe it is not the engine but the tranny not applying the engine power?

Just a thought.

K2

nate
10-13-2004, 06:32 AM
Well it's still down at 5 Star. Been there since the last week of Aug... no luck so far. I'm in Korea for 4 months or so, so they have time, but I didn't expect to take this long.

I guess it seems to be something electronic. It's fine in open loop and gutless in closed loop. I'm thinking maybe the PCM

I'm pretty much discouraged with moving on with the ZJ though. I've put way too much time, money, blood, sweat and tears into the thing. Anyone want a ZJ? :D

Mtn WJ
10-13-2004, 06:05 PM
Not sure this is your problem but my brother had an F150 with the 4.9 six that had the same problem on the highway. It turned out to be the cat converter was plugged up so bad that under load on the highway he had no power. Otherwise it ran fine because their was nothing wrong with the engine. Just a thought if the shop did not think of it.

nate
10-19-2004, 07:06 AM
I hollowed out the cat thinking maybe it was plugged and that didn't make a difference.
Honestly I wish it was that simple. Thanks for the ideas though.

nate
11-02-2004, 01:36 PM
I've been in touch with the guys at 5 Star (where I dropped the Jeep off) and they aren't finding any real problems with it. It seems to be a heat related thing, so now that it's 20*, I'm sure it's a bit harder to replicate.

Well I've been doing some web surfing and found a few posts on boards with the same problem. Alot of references to the MAP sensor, or bad ECU. Both aren't too expensive, so I may just replace them.

I've been thinking maybe a vac leak somewhere. Thing is when I disco a vac line and purposely create a leak, the motor sputters a bit and comes back to idling just the way it was before. That sound right?

OverkillZJ
11-02-2004, 02:10 PM
Nate - get a scan tool...

and test for vacume leaks with a gauge, they're cheapo :)

nate
11-02-2004, 02:25 PM
Snap On scan tool is showing everything to be OK, so I doubt anything I'd buy would show different.

Yup about the vac guage.

OverkillZJ
11-02-2004, 02:38 PM
Snap On scan tool is showing everything to be OK, so I doubt anything I'd buy would show different.

Yup about the vac guage.

I'm not saying check for codes, but get out your FSM and check sensor ranges, like where the MAP should be reading at a certain altitude, all that fun stuff. Make sure WOT on the TPS actually measures 100%, stuff like that :)

nate
11-04-2004, 03:38 PM
Yeah I know what you mean. The Snap On scanner checks the sensors and makes sure what they are reading makes sense.

What the shop established is the problem is heat related. It's now 10* in Alaska, so gonna have to wait to summer to figure it out.