My xj runs horribly :beatdeadhorse:

My question: I have 2 XJ's...a renix 89 and a 97 HO

I have a renix cherokee and there is a site listing all the resistances/test procedures for the renix sensors. It's a wonderful resource.

Is there any such resource for my new to me 97? It ran wonderfully when I got it a few days ago, but it's recently developed an extremely rough idle. It's dumping fuel like it's nobody's business. When i take it out it will clear up after a few minutes and smooths right out. Pull it back into the garage thinking I'm a master mechanic and it starts to get rough again after a moment. There's also a distinct noticeable increase in air flow in the air box during all this.

I changed plugs/wires/cap/rotor after it started to bog out a little at light throttle. It seems to have gotten progressively worse. I cleaned the IAC, and there's no change in idle at all when I un plug it when it's running rough.

I was really hoping to start swapping some of the lift parts around tonight, but it looks like I'll be racking my brain trying to get this diagnosed instead.


I don't have a scanner at my disposal at this very moment and I'd like to check things before I start throwing parts at it.

Assuming no check engine light? If so, pull codes for guidance. Even if one isn't on now, there can sometimes be stored codes which can yield clues. An actual scan tool can not only read codes but can be very valuable for checking data real time on your 4.0

As for specs/testing procedures for your 97, I'd recommend purchasing a manual. If you're going to be doing ANY work on your vehicle yourself, this will pay for itself very quickly. The Factory Service Manual (FSM) is the best. Here is a link to a licensed, legal site to obtain them. They can also be found once in a while on ebay.
Haynes/Chiltons are just OK, they are generic and cover many years/engines, not as comprehensive, and contain some errors.

https://techauthority.gltghosting.c...Home?storeId=10051&langId=-1&catalogId=10051'

Don't throw parts at it. Start the testing process as troubleshooting is a "process of elimination". Fuel pressure with a gauge (looking for 49.2 psi plus or minus 5 psi), coolant temp sensor, map sensor, throttle position sensor can easily be tested for starters. How many miles on this 97?

Just off the top of my head, rough idle and dumping fuel sounds like a leaking or sticking injector. If it loads up at idle, it will clear after you run it out, but not actually cure it. Your best bet for this is to get a fuel pressure tester and an injector tester to fire the injectors (or have it done). This will tell you in pretty short order if you have a fuel pressure problem, or an injector that's not snapping shut properly.

It's a good idea to get a code reading even if you get no codes, because even that can steer you in the right direction. Most electronic issues will set a code, even if they don't light the light, but there is no diagnostic system on board that will pick up mechanical problems such as clogged injectors or excessive fuel pressure. If you have problems but no codes, you should start looking at the kind of problems that OBDII cannot spot.

hghgrad said:

.....there is a site listing all the resistances/test procedures for the renix sensors. It's a wonderful resource.......

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Sidetrack: where might this site be? I've never heard of it, but I did know this info existed somewhere.

Care to share? Thank you!

Here it is:
http://www.lunghd.com/On_Site_Tech.htmhttp://www.lunghd.com/Off_Site_Tech.htm

I know that I have seen this posted on here... I believe that I may have posted a link to the site before as well. Also the renix test procedures are in the renix manual if you should want or need that hit me up.

Oh, I've seen that. I thought that you were talking about testing the yellow plugs where the "OBD" is read. ( I know the renix system is not OBDI or II).

Thank you anyhow.

you need a special piece of gear for the connector to read the renix I know there are a few on here with one. you can take some of your measurements from there too without having to back probe. Its a shame you cannot do the TPS there.

Renix is easy enough with a meter...I prefer that method to the scanner method.

I got to autozone today and had the codes pulled on the 97.

A bunch of transmission codes, but the trans shifts fine...so that's of little concern to me.

The 2 that really made some sense were the short/ground for INJ1 and the CTS code. Got the CTS while I was there, only to find out that it doesn't fit the harness. The motor was installed by a chrysler dealer some time back...and it appears to have a 00/01 cts plug. So, I'll get that traded out and do the swap while I'm at work later on. I figured the #1 injector went bad, but it tests out fine. I had a heck of a time getting the connector off, and it appears that was the issue. Connector goes on and off smooth now and my idle and low end misfire have cleared up completely.

I was also missing all of the left marker lights, which appears to be caused by a missing fuse. Looks like I'm going to have a little more cleaning up to do than I thought.

Thanks for the encouragement, I've been building cars for quite some time and switching to Jeeps is like re-learning everything. I'm definitely going to have to get the FSM. I have a couple from my other vehicles, just haven't gotten around to this one yet.

Glad you seem to have found the trouble. Keep an eye on that injector, though, because although I've not heard of this on later models, some earlier ones had some harness issues in the injector wiring, which can be very hard to track down. My stepson's 93 had a bad splice that killed one injector when it heated up, but because the injector tester gives a "go" reading at something like 8 volts, and the injector stops firing at something around 9, I missed it for quite a while.

Well, the harness wasn't the issue as it started acting up again after I posted. I changed the cts out and noticed that the manifold was wet at the number 1. Seeems that the injector was locking up. Tossed some gas in with a can of seafoam and it appears to have cleared up so far. I'm going to start looking for some injectors tonight as I don't trust these any longer.

hghgrad said:

Well, the harness wasn't the issue as it started acting up again after I posted. I changed the cts out and noticed that the manifold was wet at the number 1. Seeems that the injector was locking up. Tossed some gas in with a can of seafoam and it appears to have cleared up so far. I'm going to start looking for some injectors tonight as I don't trust these any longer.

Click to expand...

True, a harness problem is unlikely to make it hang open. Much more likely not to open at all. Maybe you'll get lucky, and find it was just a little crud in the injector. good luck.

Couple days later and all is well. Going to start hitting the junkyards soon since it's supposed to warm up this week.

get some ford orange/yellow tops. rated at 19lbs... should be plentiful.

I need a set for my renix and the ho. My renix is getting around 12mpg and i've put all new sensors in Along with a full tune up.

I'm getting a stumble with the 97 on occasion at light throttle, I'm thinking that I've got a leaky injector still on that one.

Too many jeeps, not enough time to fix them both

just make sure to keep one running and driving at a time! gotta make it to work, the junkyard, and the beer store...