Erinyes

I just bought a 1989 Cherokee. 169,000 miles, 4.0L, AT, everything in nice shape, several new sensors, but 12mpg on the highway.

Replaced the O2 sensor (resistance was above specs), tuneup parts (typical plugs, cap, rotor, wires, filter), and checked out the injectors.

Turns out a PO had upgraded the injectors to a 4-hole Bosch, part #0280150943. It appears to be a 19# injector, with 14.7-14.8 ohms resistance (checked all six). It is recommended for 1995-2000 GM vehicles, everything from 3.8L Buicks to 7.4L Suburbans.

My question is, is it a suitable injector for a stock 1989 Cherokee? I'm going to clean them and put them back in with new o-rings, but I'm giving this rig to my son in a week or so to use in various wildlife research jobs, so I don't have time to do the "testing over time" routine. Could they be causing poor mileage, or should they function as normal (although hopefully with better atomization characteristics, due to four nozzles instead of one)?

Thanks for any help.

freegdr

Newer style injectors have a finer mist spray than old single hole oems resulting in better atomization and smoother idle and better throttle response not sure of the bosh number you running is recommended for 89.

freegdr

What temps it run in daily driving ?

Erinyes

I've only driven it for a day - about 80° outside, a little in-town driving, 140 miles on the interstate at 70-75 mph. Gauge never showed anything remarkable, somewhere under 210° for certain.

I did let it sit and idle for 20 minutes to heat it up to test a few sensors, and it never got above say 200°, probably closer to 180°. That was on a 95° day. The electric auxiliary fan never kicked on, except when I turned on the AC to make sure the fan worked.

freegdr

I asked because a lot of guys remocve thermostat wich kills mpg what your getting is perfect id aalso recommend testing o2 circuit and coolant temp sensor.12s not bad but 15 would be better.

freegdr

https://www.cherokeeforum.com/f2/how...-renix-155971/

freegdr

https://www.cherokeeforum.com/f51/cr...x-tips-153657/

freegdr

http://www.lunghd.com/Tech_Articles/...iagnostics.htm

fallenknight308

http://www.witchhunter.com/flowdatapix/b0280150943.jpg
Those look about right, just a little on the lean side.
But alot of ppl report no trouble with 19's and RENIX Jeeps.
I'm running 19's and have not noticed abnormal temps.

fallenknight308

As to poor mileage it could be a few things.
Leaking injector.
Leaking Fuel Pressure Regulator.
Bad o2.
TPS.
Vac lines.
Sounds like you're on the right track though.
Read up on the links Freegdr provided.
Good luck.

Erinyes

Excellent news, just what I hoped.

I also found the TPS was out of adjustment just a trifle, and adjusted it.

The jeep is currently apart in the driveway, waiting for parts to arrive tomorrow. All new o-rings on the injectors and fuel rail, tightened the manifold bolts (found four that were loose), will have new plugs, cap, rotor, plug wires, will recheck the TPS after everything is back together, and see what I've got.

At the very least, I'm hoping the surging idle will be better; ideally, it will also pick up a few mpg.

I'm getting kind of attached to this rig - too bad I have to give it away so soon.

freegdr

Im currently running bosch 746s from Volvo better idle and noticible mpg increase instantly .

fallenknight308

Yeah, same:
http://www.witchhunter.com/flowdatapix/b0280155746.jpg
They are a might lean, but I haven't noticed any trouble.
OP: you can stick with what you have, as long as they aren't leaking
or sticky they should be fine.