95cherokee89

My stock injectors were shot, one was stuck open, and one was stuck closed. Needless to say, it didn't run very well, I put some refurbished 703 Injectors in last fall and it runs pretty smooth now

redindian

That's your problem (703's). The Renix era 4.0 will go into open loop due to too much fuel with these injectors.

I had them in my '89 and with a Snap on scanner hooked up, I could see the fuel trim rise out of it's limits and go into open loop.

I have the 746's in now and all trims check out good when scanned.

DFlintstone

I disagree. 703's are just a tad rich in "open loop", (running on the ECU's default pulse width). Running at temp Renix can "trim" the 703'3 higher flow rate.

With a little nudge from Programbo, I'm the one who brought out the 746's.

They might worsen flooding if that was the issue though!

EDIT>>I've never uses a scanner, but being over rich is new to me as a reason to go to open loop.

'90Cherokee

Any amount of visible exhaust is an issue. Black is way rich, grey could be a combination of rich and oil burn.

95cherokee89

I don't really think the 703s are the problem, They were more of a recent mod. I was actually getting worse mileage with the stock injectors probably because they were clogged up.

A friend of mine put 5.0 Mustang injectors in his renix Cherokee and said the mileage didnt noticeably decrease so I doubt mine are the problem.

95cherokee89

Bit of an update.

I suspected the problem lay with the map sensor, I tested the resistance at the map ground wire, and it had over 130 ohms of resistance. I added a wire to the firewall and managed to bring the resistance down to about 1-1.5 ohms. When I started it up, I immediately noticed a difference in the tone of the engine, it sounded a bit quieter, and smoother, driving around the block, it also felt like it had a bit more power, and the exhaust smelt more or less normal. The sensor was reading about 1.3-2.4v at idle, and would go up to about 3.6 if I hit the throttle. I think that's about what it should be

I really hope this fixes the problem as gas here is over 1.24 a litre

DFlintstone

Supper! Hope you nailed it!

cruiser54

Post 4 had the answer for you had you done the sensor ground test I included. just sayin'.

redindian

Map values<br/>

Glad you found the problem.

95cherokee89

I tested every ground I could find, all were good, I just somehow missed testing the map ground at the sensor, its a bit too soon to tell if the problem is fixed, however, it does seem to be better.

still has reduced poweron the highway and wont really go past 140, I suspect that the fuel filter may be clogged, I'll replace that tomorrow,

cruiser54

That Tip, again posted below, specifically addressed the "sensor grounds". It's a known issue. I've added the "fix" below that. Tip 6 in my list of Tips with photos.

Cruiser’s Renix Sensor Ground Test


This sensor ground circuit affects the CTS, TPS, IAT, MAP, ECU and diagnostic connector grounds. It’s very important and not something to overlook in diagnosing your Renix Jeep as it is common for the harnesses to have poor crimps causing poor grounds. If any or all of the sensors do not have a good ground, the signal the ECU receives from these sensors is inaccurate.

Set your meter to measure Ohms. Be sure the key is in the OFF position. Using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS . The letters are embossed on the connector itself.
Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it runs parallel to the valve cover and also near the MAP sensor mounted on the firewall. If you have an 87 or 88 with the C101 connector mounted on the firewall above the brake booster, wiggle it, too.

You want to see as close to 0 ohms of resistance as possible. And when wiggling the harnesses/connectors the resistance value should stay low. If there is a variance in the values when wiggling the wires, you have a poor crimp/connection in the wiring harness or a poor ground at the engine dipstick tube stud.

Refreshing of the dipstick tube connection is covered in Tip #1, and the sensor ground upgrade is covered in Tip #6.

On 87 and 88 models, you could have a poor connection at the C101 connector as well. See Tip #2 and Tip # 27.

Revised 11/01/2014


Find your Intake Air Temp sensor. It's the sensor just to the rear of the throttle body, has 2 wires, and screws into the intake manifold.
Where it's connector plugs into the harness you will see that one of the wires on the harness side is brown with a white stripe. Follow the brown with white stripe wire back into the harness. You'll have to open up the split-loom plastic sheathing to follow it. It will come to a splice with 2 other brown with white wires with duct tape over them. They're from the TPS and the CTS. The 3 wires will be spliced to a single wire headed toward the C101 connector if you have an 87 or 88. If you have an 89 or 90, you do not have the C101 bulkhead connector.

Now go to the MAP sensor. Follow the brown with white wire into the harness from there. You will find a splice with 2 more brown with white wires with duct tape over them. At the splice you will find the 3 wires connected to a single brown with white wire going toward the C101, or just along the firewall towards the engine if you have an 89 or 90. On an 89 or 90 you will find 4 wires going to 1 wire. Along with the MAP sensor that you traced, they are the ECU sensor ground port and the diagnostic connector on the passenger inner fender.

You now have 2 sets of 3 brown with white wires, one near the firewall and one near the engine. If it’s an 89 or 90, you have 4 wires going to 1 wire.

Cut the splices out of each set of wires eliminating not only the crappy factory splices, but also the single wire between them. Bring both sets of 3 wires together. Solder the 2 sets of wires together and insulate them properly with tape or shrink tubing.

Zip-tie up your new sensor loom to allow for engine movement. I prefer to cover it with some new split-loom or wrap it neatly with electrical tape when done.



Revised 05-03-2015

'90Cherokee

Gas in California is about the same, the rest of the country is enjoying the cheap stuff. 1-1.5 resistance still seems too high, especially with an added ground wire, the engine to chassis ground strap may be faulty--assuming you checked the resistance between the MAP connector and the battery neg. 1.3-2.4v at idle seems like a really big range, it should be pretty steady. Eng. off should be just under 5v. If it was running really rich the catalytic converter may have been damaged and may plug up leading to more running problems, at first you'll find a loss of power and it'll just keep getting worse.

I just added a second chassis ground, first thing I noticed was that my window motors run faster then noticed that the voltmeter drops less when running the A/C. I'm now motivated to actually remove & clean the original ground rather than rely on the fact that it looks ok and is tight. Then on to the rest of Cruiser's tips before a problem arrises. I too have neglected to verify sensor ground resistance tests because it runs well, but they could be marginal and just be working OK enough to seem right.

cruiser54

Excellent plan. Use this:

http://www.gardnerbender.com/en/ox-100b

'90Cherokee

Thanks, I use dielectric grease on almost all my connections. I put it in crimp terminals, battery terminals, etc. and have never had one corrode at all even in marine environments. That stuff may be a bit better. I've also used CorrosionX on some stuff where I want something that'll flow and penetrate and it's shown to be pretty good too, the film stays even after being submerged in water.

The general description of the ox-guard sounds similar to anti seize; is it similar in appearance and adhesion?

cruiser54

Not like anti-seize at all.

It improves the connection and seals it from oxidation.