'95 XJ has some issues...

[the_mechanic]

I have a '95 XJ that has been giving me some issues. I doubt all are related but going to list them all here in case I am wrong and I can tie some of them together. I recently put in a rebuilt motor because the old one was burning 4 quarts between changes and started losing lifters...it was time. When I did that, I also did all tune-up parts, all new sensors, new exhaust, new cowl intake, and new injectors. These are some of the issues I've been having:

1. Pretty soon after I put in the new engine, I developed a backfiring issue. If I step on the gas too hard, too quickly, it will backfire through the exhaust repeatedly.

2. Even before the rebuild, I would have a slight misfire at idle. Injector changes, tune-ups, etc. made no difference but it was so minimal that I never really thought much of it and had just been living with it. The rebuilt engine does the same exact thing (leads me to think potential ECM issue?)

3. Recently I have been getting an intermittent CEL. Codes are
a. 12 (Battery disconnected in last 50 cycles): Not worried about that one.
b. 17 (Engine too cold too long): I have a 180 tstat in it right now because I had trouble getting a 195 to open when I did the rebuild and it kept wanting to overheat my new engine. I could swap in a 195 but it already sits at 210 (on the gauge) at lights which makes me nervous enough.
c. 23 (IAT issue): Sensor is basically new but considering swapping a new one in for S&G.
d. 27 (Injector control circuit issue): Injectors are new and I didn't see any obvious wiring issues when I had the motor out.

4. When I get above ~40 mph, I can hear and feel (through the body, not really through the steering) a vibration that seems to be in the front end. If I put a little right rudder in, the vibration goes away completely. All my ball joints, tie rod ends, u-joints, etc. look and feel tight and right. Took it into a shop and they couldn't find anything either.

When it comes to EFI, I am well out of my element for diagnosis other than the basic fuel, air, and spark. Any help is appreciated!

 

[Woodswanderer]

Most of it sounds like fuel delivery or timing issues (1,2,3c-d). Very well could be related to ECU, but take my word on that with a grain of salt. The backfiring would indicate timing/too rich or lean, vacuum/airflow readings incorrect...Start with the easy stuff...injector condition (clean, no cracks, good wiring), fuel pressure readings at the rail and at the pump, double and triple check grounds and wiring, coolant temp sensor, map/iac/tps connections and condition, throttle body clean/no blocked ports/all vac lines hooked up, crank sensor condition, distributor condition, vacuum elbows and lines all connected and in good condition, etc.

3b i wouldnt worry about too much...210 is normal temp for the 4.0. Fwiw, even with my overkill beefed up cooling system i sit right below 210 at full temp (high flow everything, 3 row rad, 195 tstat). Best thing to do if you havent already done it is backflush the hell out of the system and run good clean coolant. If you are really concerned, replace the water pump with a hesco or a high flow pump and install hood vents for more airflow *. Keep in mind, thermostat ratings are where it opens into the block and do not reflect max temp of engine.


codename 99 problems: Daily driver/tow rig build thread

 

[SleeperXJ]

My wife's TJ had issue with the catalytic converter, it was causing backfire and loss of power. I diagnosed by checking temps before the cat and behind the cat, temps should be pretty close.
I'm not sure when catalytic converters went into the XJ so this may be pretty far off base.

 

[Woodswanderer]

My wife's TJ had issue with the catalytic converter, it was causing backfire and loss of power. I diagnosed by checking temps before the cat and behind the cat, temps should be pretty close.
I'm not sure when catalytic converters went into the XJ so this may be pretty far off base.

Cats have been standard since late 70s on all vehicles...

But you bring up a valid point. Clogged cat or faulty o2 sensors would be something to look at. Upstream o2 sensor (pre cat) is more important than downstream. Cant say for certain with the jeeps, but downstream on most vehicles isnt as important (acts as a reference sensor)


codename 99 problems: Daily driver/tow rig build thread

 

[lawsoncl]

I'd start by cleaning and checking the ground at the dipstick. I would open up the lwire loom and inspect the wiring harness across the injectors and to the firewall for damage as all of the sensors giving codes run through there. Bad engine mounts can cause lots of flexing and wiring issues there.

Test the resistance of the coolant temp and the IAT sensors before you decide to replace them. Check that the black wire at their connectors has a good ground too. https://www.fixjeeps.com/coolant-temperature-sensor.html

 

[SleeperXJ]

Cats have been standard since late 70s on all vehicles...

But you bring up a valid point. Clogged cat or faulty o2 sensors would be something to look at. Upstream o2 sensor (pre cat) is more important than downstream. Cant say for certain with the jeeps, but downstream on most vehicles isn't as important (acts as a reference sensor)


codename 99 problems: Daily driver/tow rig build thread

Thanks Woods,
I went through the route of replacing O2 sensors before taking temp readings.
I should have gone through a more detailed check of the sensors but... lazy:gee: