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Cody
06-02-2005, 01:16 PM
I have 2 little engine bugs that are beginning to piss me off and I want to know what you guys think the most likely cause is....

1.

The engine starts fine, but when I"m running and I give it gas, once it drops back to idle it dies, or almost dies. Usually it dies. Kinda like it's not getting fuel.

2.

what happens is that when I give it gas, it will die as if it's not getting anything, but when I let off it idles just fine. I have to shut it off, let it sit for a minute or two, and restart. The bitch of it is that it only does it maybe 1 trip every 6 months, then it goes away.

So, now that I look at it, it seems at times my engine is doing opposite things, sometimes when it drops to idle it dies, but when I give it gas it's fine, and other times when I give it gas it dies, and when it drops to idle it's cool. So, would this be an IAC issue? TPS? I plan on putting in new fuel filters this week, but I was going to pick up a sensor and put it in if need be.

Any thoughts?

Cody

OverkillZJ
06-02-2005, 01:27 PM
When mine was doing that, it was definately IAC, but my problem wasn't intermittent like yours seems to be.

I bet it's working better now that it's running on 8 cylinders though :partyman:

Cody
06-02-2005, 01:40 PM
Dude, it totally was. There was noticably more power. But late in the day on the pre-run is when it started dieing on idle. I think some of you may remember that. I would inch up to an obstacle, and when I let off the gas it would die. It was really irritating last weekend.

The other problem is really a bitch, but it's only done it a couple times. How hard is the IAC to do? Can't you 'adjust' or 'clean' the TPS or one of those sensors that is in the throttle body?

Cody

Jim311
06-02-2005, 02:07 PM
IAC is two small screws on the front of the throttle body, and one little tiny ass hose if I recall correctly. Very easy repair.

nathaniel
06-02-2005, 02:08 PM
IAC can be removed and cleaned. Also look at pcm connections. Have known of a few jeeps that when the connections get wet from coolant usually idle goes wacky. Try some conductive grease on the connections.

TrojanMan
06-02-2005, 02:41 PM
Could be something fuel related too.. maybe when you press on the gas pedal not enough gas is flowing through, but air is.. causing a bad mixture which would cause your engine to do funny things, I know alot of ZJ fuel pumps die. Maybe yours is on the way out. Changing fuel filters would be a good idea too.

Cody
06-02-2005, 03:38 PM
My fuel pump is external for a full size ford van. I guess it could be going out....maybe I'll try re-wiring it this weekend. I think it has a life time warrenty from vato-zone. I'll clean up the TPS and change the IAC this weekend and hopefully that will fix it. If not, I'll be surrounded by 75 grand cherokee heads next week so I'll make them figure it out ;)

Cody

FinlayZJ
06-02-2005, 04:06 PM
Completely not Jeep related, but my girlfriends Camry did that exact thing, and it was her O2 sensors.

Cody
06-02-2005, 04:41 PM
someone else said 02 sensor too. how hard are they to get too on the v8 zj's?

Cody

jdoom
06-02-2005, 04:46 PM
o2 sensors are very easy to get too. just look underneath, one is in the cat and one is in the piping right after the two downtubes connect, before the subframe. I replaced both of mine when doing my exhaust, piece of cake, but not super cheap.

Cody
06-02-2005, 05:40 PM
I don't have a cat, so I guess I only have 1. I'll go out and looksie in a bit and see how hard it would be...

Cody

dasVettemeister
06-02-2005, 06:57 PM
First problem sounds like IAC. Clean the IAC plunger AND throttle body thoroughly with throttle body/carbureator cleaner.

Second problem sounds like it could be TPS. The only way to test the TPS in lieu of replacing it is to scope it and make sure you have a linear (sine) curve with no dropoffs.

If you come down to the issue being the O2 sensor (which it could be, but I would doubt it) then procure one at www.bosch4less.com. That place is the absolute cheapest for a genuine Bosch O2 sesor. I think I paid $42.00 for mine several weeks ago AND they had free shipping! It's not one of the universal ones either that requires splicing, it's plug and play!

Cody
06-02-2005, 10:46 PM
Well, I swapped out both fuel filters, the pvc valve, and cleaned my muddy-ass air filter. I have the IAC coming in tomorrow. I'll clean up the TB this weekend and hopefully that will do it. The shitty thing is, I won't know if it helped until I get out onto the trail and see what it does.

Thanks for the help dudes. Whats the best process for cleaning the TB? the stuff I have says I have to run the motor until it reaches normal operating temperatures--is this true?

Cody

dasVettemeister
06-02-2005, 10:58 PM
Be sure to use a spray that is "sensor safe" or designed for fuel injected vehicles. Make sure the motor is warmed up and douche the sucker good! Don't let it stall, yet don't rev the snot outta the thing.

chadjans
06-04-2005, 12:56 AM
Fuel pump.....