getting 8MPG. ...

[Adaa60]

So my 93 ZJ is seriously getting 8MPG highway and worse city...

I know it's running rich I can smell the waisted fuel when I stand 4ft from her. So I'm going to give a tune up. I have no CEL light on that I can see. So I was going to do another shotgun repair on her. My list is as follows.
new O2 sensors
Double platinum plugs
cap & rotor
plug wires
ignition coil
PCV valve
fuel & air filter's & Lucas fuel system treatment
Quakerstate oil change w/ Fram filter and Lucas oil stabilizer.
And a Computer Reset

Anyone good with the OBD1-318 think I'm missing anything?
Also Is there a way to install the better fuel injectors from the Neon like in the 4.0?

[The StRanger]

Check base timing and in tank injection flush.
O2 sensors are a good idea but unless you have a CEL there doing what they need to do.

[Adaa60]

I have no idea how to check the base timing or do a in tank injection flush.

[Adaa60]

I'm worried that the aftermarket hypertech computer could be part of my issue as well & not showing a CEL

[94ToyBear]

is the Cats working properly ?

[Adaa60]

I'm not sure on the cats, but I figured when I bought it I was going to have to have it replaced with an aftermarket. You think the cat would be giving me bad MPG?

[Rick]

You think the cat would be giving me bad MPG?yep...on my white ram it was going bad and was killing my already terrible mileage(12 down to 6) now with a new one on Im getting 16

[Adaa60]

OK. If tuneup do sent solve I'll replace the cat next.

[The StRanger]

I have no idea how to check the base timing or do a in tank injection flush.
A can of Injector flush, Just pour it in the tank when you fill up.
If you dont have a timing light, Dont worry about the timing.

[The StRanger]

is the Cats working properly ?
If it had cat or O2 issues it would flash a P0420 ?

[The StRanger]

A can of Injector flush, Just pour it in the tank when you fill up.
If you dont have a timing light, Dont worry about the timing.

And never mind the timing. It has to be set with a diag scanner.

[Rick]

If it had cat or O2 issues it would flash a P0420 ?Mine didn't throw a code..Did fail emissions test though and that was the issue

[gm4x4lover]

It would also have a loss of power issue. Can you unplug the hypertec thing?

[Adaa60]

No its a complete ecu replacement. And I just turned the key to test and the CEL light does in fact light up and then turn off after starting. I only have ano Abs and airbag light.

[gm4x4lover]

With it being obd1 that doesn't surprise me. It has a very limited range of self diagnostics it can perform. I think a tune up isn't a bad idea but swapping anything else is just a gamble. You need to scan it and see what it says. Coolant temp sensor could make it run supper rich. Does it have any other drive ability issues? High idle, studder, surging, etc?

[The StRanger]

Oh Shoot. OBD 1 didnt register with me.
I was thinkin OBD II

[Adaa60]

It's just running game rich. Under 1000rpm idle. Stalling sometimes when coming to a stop or changing from drive to reverse

[redneck23ms]

try this.
https://sites.google.com/site/thezjpage/zj-diagnostic-trouble-codes-dtc-s

[Adaa60]

Wow thanks redneck!

[Adaa60]

So sure enough! Thanks to Alex's post I found she is getting a bad O2 sensor code, abnormally lean signal from O2 sensor.

Nice to know however, it had 3 codes , pcm power disconnect within last 50 key starts, speed sensor no input, and O2 sensor.

I disconnected the battery the other day, and Mike helped me connect my speedometer sensor the day we repaired the ABS system. So looks like if I replace my O2 sensor she should be a happy jeep.

[Adaa60]

How do I reset the OBD1 computer codes back to zero?

[redneck23ms]

Disconnect the battery for 15 mins. Or so

[xaza]

Glad you got it found, didn't know the key trick worked on the older older ZJ's, good info.

[Adaa60]

Glad you got it found, didn't know the key trick worked on the older older ZJ's, good info.

I know right!!!

Just left LKQ, found a lot of my truck, but only 3 with aftermarket o2 sensors. I got them all. One is anot almost new bosh so I'm on my way home to install that bad boy. How long will it take to a just my fuel trim? Other than unplugging the battery while I swap to reset is there anything else I should do?

[Adaa60]

Jeep is running a LOT better. Went from totally nasty fumes standing 4 ft from it to no fumes laying 12" from under the tip! Also sat down with the tape mesure and stretched out & evened up the long arms in the front. I also noticed a serious issue, my shocks up front areally 30" fully extended however are 2" from being maxed out. I'm going to make some custom extensions for them so I can get more wheel travel in a few days I guess.