Hey cool. Some looks familiar from here>> http://www.jeep4.0performance.4mg.com/tech_specs.html

The WEB is the (potential) problem. It least one guy tested the stock on a "professional " bench and came up with 22#/Hr. Or 21? I forget. I was just hoping to actually verify it as opposed to seeing it posted. A admit I suck at navigating an FSM. Anyway he should pass with stock injectors...MAP, Plugs, compression?

 

The front relay there, of the 4 powers the larger orange or red wire on the 02 heater. Something I might rule put if I didn't pass smog. You can just unplug it and check the Jeep side for 12V. Might as well see that one of the others has about 5 coming from the ECU. The third (ground), should show less than 1 ohm to battery neg.

OH! Engine running for the 12V to the heater, everything OFF for the resistance check. (just ign for the ecu 5V)

 

Firstly, I passed the re-smog. I did all of the following:
Swapped o2 sensor, plugs n wires, went overkill on the IAC tho, and did the Renix grounding project. I passed w subtantially low numbers and ill post late for ref.

So about the injector discussion. Woul someone care to break it down for me? I know nothin about the subject or good or bad about them.

 

Right on, good job.

The injector deal is just the operating pressure being within spec 87-90 used a 19-21lb per hour inj. where the later cherokees used a 21-24lb inj. By using the wrong inj. pressure you can lean or richen your fuel and possibly throw the computer into some sort of shock. Ultimately it won't run right.
The injector that is stock on our cherokees is a big one hole injector which isn't very efficient in atomizing fuel(also has a habit of leaking and causing fires). The injector most here are using to replace it with is the one out of dodge neons and caravans with the 703 number on them. These are a four hole inj that atomizes the fuel better has small power and fuel gains, better emissions? and so on. The 703 matches the stock inj flow rate. Threre is also a few Ford inj. that can be used.
If you keep your cherokee long enough to rebuild it as it gets bored out and the compression gets increased the injector needs to have a higher flow rate to fill the gap.

 

And the Crowd Cheers! ......, Well done!

The stock Renix injectors have one hole, like a squirt gun, and are known to leak where the housing crimps together. The newer 4 hole injectors have 4 holes and are often one piece. Right away you might notice a smoother idle and snappy, smooth throttle response. Since a used set is not too spendy, even a meager mileage improvement will pay off at some point. My.o2 anyway, glad you passed!

 

Thanks for this thread. I was going to post a new thread but can't find that button?
I'm new so may not have it yet. So forgive posting over another.
Good info here.


I have a 1994 4.0L Jeep Cherokee, 2WD Sport.
I have sky high numbers on NOx. At first failed 15mph. Found cracks in the exhaust manifold and sealed that with a very high temp (rated 2400F) ceramic epoxy. Later I will pull it and install a new or weld it closed. So confident no leaks there. Put in a Bosch O2 sensor. learned later that Jeeps do not like Bosch O2.
It failed really sky high. Higher than the original O2 sensor and with the sealed exhaust manifold.
In the 2200ppm range when 500ppm is allowed. Looked like Catalytic converter was bad. No real temp difference between inlet and outlet, approx 40F difference. Should be over 100F difference. I reinstalled old O2 sensor. Put in a New Cat. At retest, brought numbers down to 1000ppm. So good direction this time. But still fail. Am now putting in new spark plugs, NGK, wires. And will put in new Bosch sensor for the retest to see if numbers pass. Then if passes, should I put in the other recommended O2 sensor anyway. Its a NKN or something like that. have to look it up again.

I was told that my jeep has no EGR? Is that right. I looked up at Auto parts sites and they sell the EGR gasket? So must be an egr there?
At Autozone website, they state:
"Under hood, center, upper engine area, driver side of valve cover, mounted on intake manifold"

But I don't see it. I probably don't recognize what I'm looking at. If I can find it, I'll clean it out. I had an older Mazda PU that kept failing smog because it was clogged. Cleaned it every smog time and no issue. Was going to clean the Jeep too but was told no EGR? A few smog techs have told me a problem with my chevy smogging is also the lack of EGR. Because it always runs high numbers, even newer condition. Thinking now, maybe my jeep needs it cleaned out. But can't locate it.
Any help ?

 

EGR ended in 1990. NGK plugs, wires. New cap and rotor with brass terminals?

 

The last year for EGR was 1990. You definitely don't have that.

Have you ever cleaned the throttle body, tested the MAP and coolant temperature sensor?

When you did the spark plugs, what color were the electrodes on the old ones? Can indicate a lean or rich condition. Or have you not done spark plugs yet? (ALWAYS start with the basics!)

Oh, the brand name on your O2 sensor is NTK.

 

Thanks for clarifying the EGR. I thought I did not have one. Then ran across parts line saying it did? Reason I couldn't find it. But why do I find I can buy the EGR gasket online at AutoZone and Napa. Catalog issue I guess.
New Cap and rotor. Yep. Brass terminals I will have to check. Will inspect the plugs when I replace them. Never cleaned the throttle body. How ? Injector cleaner thru tank or carb cleaner type sprays?
How to test MAP sensor and Temp coolant sensor? Jeep stays nice and cool. Never really over midrange on gauge, assuming gauge reading correctly. New radiator as of 3 years ago. I do need to flush the coolant out. Had hose break. And replaced with water and 'some' antifreeze.
I assume the O2 NTK sensor available only thru dealer. NAPA sells Bosch, NGK, and Denso. AutoZone sells Bosch. Haven't checked other stores.

 

Parts catalogs aren't always terribly accurate Curious how that made it in there!

The "proper" throttle body cleaning involved removing the whole thing and cleaning it all with a tooth brush and carb cleaner spray. You want to get the crap out of the IAC, butterfly valve, and all the nooks and crannies. The Throttle Position Sensor is tested with a multimeter, bunch of writeups on here for how to do it. tjwalker posts his frequently so it should be easily found. MAP sensor also has a few writeups on how to verify that it's working right. it's very important to make sure that it has good clean vacuum into the (throttle body? intake manifold? can't remember - it's that box on the firewall above the valve cover though)

The fun part about XJs prior to 1997 is that the engine's coolant temperature sensor, used in fuel mix, is actually a different unit from the one driving the in-dash gauge. It can be checked with a multimeter. Same for the Intake Air Temperature sensor (which you can remove and clean)

NTK is actually manufactured by NGK. No idea why the names are different. Cheapest place for them I've seen is rockauto.com

 

The ceramic epoxy will not hold long enough to deal with any problems, to boot you will have unknown chem fumes added to you exhaust as that stuff burns off(been there dealt with that) messing with your emissions. The epoxy may be rated at 2400F but it will crack and burn off.
If you can as far as the exhaust mani goes get a used one and fix it or fix what you've got proper.
It is a good idea to post your smog #s' and location, Cali has different #s' for different regions, and some of us may be able to read the smog #s'.

 

Thanks for the heads up on the possibility the Ceramic is adding fumes. That may be a real issue. I was planning just to get past smog then salvage a manifold from the yard, weld it up and install it. But AFTER smog. Seems may have to do it now.
As far as smog numbers, first time reading

The following tests showed NOx over 2000ppm with new Bosch O2 Sensor. Sealed the Exhaust manifold.
Put in original old O2 Sensor and a new Catalytic converter. Nox lowered to 1100ppm.

Next trial to put in New O2 Sensor, New plugs, new wires. and re-run pretest.

I will put in new plugs tonight.
Are the Autozone plugwires ok to use? I can get those tonight.

 

No problem. Went through this a few years ago, first time having to smog in @seven years and had my battles.
Have a smog thread I started when it happened, click my stats and threads started and you'll find it, good stuff.

 

I also posted the first smog numbers previous post.
Trying to add what is important and I was screwing up the post.

Riverside County. Approx 30 miles East of Los Angeles.
As far as smog numbers, first time reading

I will put in new plugs tonight.
Are the Autozone plugwires ok to use? I can get those tonight



Nox was high, HC was almost fail.
2nd pretest: (no print out , halted as soon as Nox skyrocketed)
showed NOx over 2000ppm with new Bosch O2 Sensor and the Sealed the Exhaust manifold with ceramic epoxy.
You may be right in the out gassing.

3rd Pretest: Put in original old O2 Sensor and a new Catalytic converter.
NOx lowered to less than 1100ppm.

Next trial to put in the New Bosch O2 Sensor I already have, New plugs, new wires. and re-run pretest. I will ask for full test and print out. Probably Tuesday.

Could there be a possible issue with MAP sensor? Or Throttle Body as I read somewhere?

 

Read your past posts. Good stuff there. What year was yours. Mine is a '94 Jeep Cherokee, 2WD 4.0L Does not have the EGR but all the other things apply.
You relocated the MAT sensor? Relocated to where? Is that MAT or MAP sensor. Don't know what a MAT sensor is. I have a bunch of work to do. The vacuum lines are really suspect. I spliced in a Poly tube to the Gas canister because it was all cracked tubing. Probably need to replace that whole line and some others.
===============

What does the MAT sensor look like?