1997 ZJ Engine Question

[newman187]

So I have a 1997 Jeep Grand Cherokee Orvis edition with the 5.2l V8 I purchased about a month ago. Everything fine and dandy, I changed the Spark Plugs with the Bosch Platinum +2 spark plugs, had the oil changed, new oil filter.

2 nights ago I took the Jeep for a drive just around the block after working on the brakes and when I started the Jeep the engine started just fine, but when I put it in reverse the RPM's droped around the 250 range or lower and almsot died, backed up put it in drive same thing. . . fluke I thought, drove it around the block no problems.

My wife drove the jeep to work last night and she calls me to come out when she got home and was like listen to this, she was in park in the drive way, put it in reverse and the same damn thing. I checked all the vacuum hoses that I could find, checked the vacuum diagram and everything seemed to check out, everything was connected. I called my brother in law who is a mechanic and he thought it was a vacuum problem, or a timing issue.

Any one have this problem?

[Jim311]

Bad IAC or TPS possibly.

[Dragonfuel]

If I were a betting man, I'd say you need to clean the throttle body and IAC passage first. Could just be coininsidence. It is poss. there is a vacuum leak, but you would more than likely hear a hissing noise. With the engine running, Spray suspected area's with carb cleaner and if the engine idle changes, you've found your leak.
I also wouldn't use platinum spark plugs becuse of the resistance and strain on your coil. Run copper or Iridinum one's instead. The only benifit platinum gives you is they last longer. They actually hamper performance.

[newman187]

I know what a TPS is, but IAC I dont, do tell.

[OverkillZJ]

Intake Air Control.

It keeps your idle.

[newman187]

What do you guys suggest for plugs, brand, possible part numbers and links. . . yes links are goood. I'm just curious as i'm looking for anything that helps with Gas mileage as this thing gets a whopping 10 MPG average

[newman187]

Apparently Jeep uses Champion plugs and the electrode is copper so bonus there.

As for the IAC, is there a particular way to clean it with out damaging it, I want to clean it up first prior to replacing it to see if that solves the problem. . .

Thoughts?

[OverkillZJ]

The IAC is an enclosed unservicable unit, but you should first just clean up the area it functions in first (throttle body.)

Champion truck plugs are the ones I've had the best luck with in the ZJ, the multi-electrode crap is just BS.

[newman187]

Yea, i'm begining to figure that out, even though they were installed for a week or 2, i'm for sure taking them back to Autozone and getting a refund, its pretty bad when they tell you it will get better gas mileage and then the gas mileage goes down. I'm sure the computer in the jeep that calculates the MPG is gonna be off a bit, but still tis just sad!

Also I bought a new IAC, but I would like to try and fix the problem and see if it is possible that it was the plugs, if not, then i'll start cleaning up the suspected problem areas, and if all else fails, i'll install the $80.00 IAC

[napajeep]

Try the Champion platinums, it's an OE plug for DC. I've had great performance with them in my 98 5.2.

[TrojanMan]

Intake Air Control.

It keeps your idle.

Idle Air Control.

*edit* and yeah, get those bosch plugs out of there. Those are only good in German engines like BMW's. I bet the guy sold them to you because there is a SPIFF (commission) on them.

[newman187]

Yea, i'm probaly gonna take them back and make a big deal about it, its pretty sad the gas mileage went down, when not only autozone as well as Bosch says you'll get better MPG. The worn plugs in there before yielded better MPG and they were pretty worn.

[newman187]

I have changed the plugs, and rechecked all vacuum lines but still have a low idle, any thoughts? I went a purchased a new IAC but i'm told they rarely go bad, and since it cost 80 bucks i'm hesitant to install it because as soon as it is installed I can not return it.

[CurtP]

I *hate* Champion plugs - I've never had any luck with them, including their truck plugs that are supposed to be the same as OEM. I use either AC Delco or NGK copper plugs. I currently have NGK installed in the 'Niner and AC Delco in the '96 4.0 - no problems with either.

Have you tried to clean your existing IAC? Pull it out, take a look at the pintle - it's probably caked with carbon. I'd recommend using throttle body cleaner (NOT carb cleaner) to clean the pintle and the IAC passages. While you're there, you might as well clean the throttle body bore too (open up the butterfly and get all the way down the bores). When you clean the IAC, keep the pintle pointed down; don't let the cleaner run into the stepper motor.

What other maintenance items have you serviced? Air filter, cap and rotor and plug wires all could probably stand to be replaced. My suggestions are to stay away from all fiters made by Fram (I recommend Purolator Pure One oil filters and AC Delco air filters) and I really *love* Magnecor spark plug wires. Magnecor plug wires are a little pricey, but they should be the last spark plug wires you'll ever need to buy (as long as you take care of them).

[Ds4x4]

you can remove the IAC and clean it with carb cleaner/brake cleaner... Refer to JF


http://www.jeepforum.com/forum/showp...3&postcount=22

he has the 4.0 I6 but same deal for the V8 just harder to get it out..

[newman187]

That is a very informative link, when I get home tonight i'll do it and report back, I visually inspected the IAC last week and come to think of it, it was quite dirty. I'll clean it up and let you all know.

As for the plugs, I used Champion Copper plugs I purchased from Jeep directly, they told me they are the same plugs the jeep came with. I have not changed the cap and rotor yet, i'm going to Autozone on my lunch break to return the Piece of SHIT plugs they sold me, i'll get the cap/rotor at that time. I have not replaced the spark plug wires either.