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Fuel Economy - 1990 Renix XJ

BulletMaker

NAXJA Forum User
Location
Cascades, WA
I don't know exactly what it is, but when you baby a jeep, you're asking for trouble... A few weeks ago I did a massive fluid replacement on the heep, trans, oil, tc, front and rear axles, coolant, etc.

I also did new plugs (autolite, IIRC), new cap, rotor and wires.

Since then however, it's been somewhat moody at me, cleaning the throttle body, IAC, and the IAT (the temp sensor on the manifold), hasn't really done much, adding a few oz of MMO to the fuel hasn't really seemed to do much to clear up the rather obnoxious idle (it seems to be rattling something, not sure what). However one of the most pronounced issues has been a rather persistent fuel odor coming from the back, and highway economy dropping from the usual ~20mpg to a less than steller ~12-15.

While racking my brain trying to come up with some ideas to work through this issue, I'm thinking O2 sensor (perhaps fuel map is defaulting to open), fuel injectors are clogged, having other issues, and with 260K on the clock, it seems spending a few hundred on new injectors wouldn't be imprudent.

I also need to take a drive down to southern cal in the next few weeks, and at present, the mileage recovery from the injectors would more than make up for $$ spent on it.

So, the principle questions are:

1) Is it worth replacing the injectors, and if so which provide the best ! for the $. The best info I've found on this is some terse references to dodge neon injectors *703. Is this dealer only, or will napa have it?
2) Obviously O2 sensor testing is in order, any idea if this could be contributing to the problem?
3) In a previous post, I was having a low idle/rough idle/intermittent that was frequently causing cut-outs, it ended up being the IAT mentioned earlier being dirty and requiring cleaning. Is it too clean?
4) Is there something I'm forgetting? Is it worth going to a different spark plug, or any other upgrade I could make here that would deliver better economy?
 
I did this on my '90 Renix and it made a huge difference. The injectors tend to get clogged over time and the fuel moves from a mist to a stream which results in a less efficient burn. Also, the rubber washers that seal the injectors to the fuel rail and the intake manifold tend to get hard and can develop cracks which further screws up the fuel mixture.

I ended up buying a used set of Ford injectors from eBay:

http://www.ebay.com/itm/GENUINE-BOS...es&fits=Make:Jeep&hash=item2330d67bf9&vxp=mtr

This gives you a 4 hole (4 streams) instead of 1 which vaporizes the fuel more efficiently.

They work great and not only did I pass emissions with flying colors, my gas mileage improved as well.

btw, a bad O2 sensor will result in a rich condition so it is definitely worth replacing as well.

HTH
Todd
 
Are you sure you put the plug wires back the same way?
 
Persistent fuel odor from rear

Could be a fuel leak at the fuel filter - the two little hose pieces that connect the metal lines were leaking on my XJ...couldn't tell until the thing was running and I looked under there.

Could also be hose detached off of one or both of the rollover valves on the tank...or the hoses from the tank to the EVAP canister.

X2 on the ebay injectors...I put a set on my MJ for $109 and liked them so much I put another set on the XJ. Could not be happier with the Bosch injectors.

Vaccum lines: Make sure you didn't knock off any vac lines while working on it. Some vac lines will be immediate indicators, but some will be insipid little ****'s and rob your MPG without you even knowing it...only showing up as minor little idle or running issues.
 
Are you sure you put the plug wires back the same way?

Yes, first thing I checked and re-checked, checked again, and had someone else double check. I typically write the numbers on the top of the new cap before I even disconnect the old ones, making sure clock position and all the other stuff is right. One time I reversed two wires on another vehicle, I felt so dopey I wanted to make sure I never did it again.

Persistent fuel odor from rear

Could be a fuel leak at the fuel filter - the two little hose pieces that connect the metal lines were leaking on my XJ...couldn't tell until the thing was running and I looked under there.

Could also be hose detached off of one or both of the rollover valves on the tank...or the hoses from the tank to the EVAP canister.

X2 on the ebay injectors...I put a set on my MJ for $109 and liked them so much I put another set on the XJ. Could not be happier with the Bosch injectors.

Vaccum lines: Make sure you didn't knock off any vac lines while working on it. Some vac lines will be immediate indicators, but some will be insipid little ****'s and rob your MPG without you even knowing it...only showing up as minor little idle or running issues.

I did have the leak at the fuel filter... some time ago, I had to drop the tank 2 years ago to get the vehicle to pass california emissions evap test, and apparently I didn't have the line quite tight enough. I'm about to put on a new fuel filter anyways just to make sure I didn't get some crap stuck in it from one of my gas cans (I noticed the liner wasn't doing so hot in one of the tanks, only after dumping it in)

Since I need to get down to CA anyways, I'll see if I can throw a fresh O2 sensor on there (vehicle is CA emissions) and see if that clears up any of the issues, I think it's a likely culprit.

Also, I've noticed this issue getting more annoying as the weather has gotten a lot cooler. Even though I'm back down in the valleys on the coastal side, temps are usually in the 40's and 50's. I'm going to refresh the warm air intake and see if that makes any difference.

I also noticed that I've got a pin-hole leak in the radiator, I'm trying to decide if it's time to replace or repair. Since I have an all-copper radiator I could just sweat on some solder to plug it up (horay for copper!) but I'm wondering if this radiator is just getting too long in the tooth for that.
 
I did this on my '90 Renix and it made a huge difference. The injectors tend to get clogged over time and the fuel moves from a mist to a stream which results in a less efficient burn. Also, the rubber washers that seal the injectors to the fuel rail and the intake manifold tend to get hard and can develop cracks which further screws up the fuel mixture.

I ended up buying a used set of Ford injectors from eBay:

http://www.ebay.com/itm/GENUINE-BOS...es&fits=Make:Jeep&hash=item2330d67bf9&vxp=mtr

This gives you a 4 hole (4 streams) instead of 1 which vaporizes the fuel more efficiently.

They work great and not only did I pass emissions with flying colors, my gas mileage improved as well.

btw, a bad O2 sensor will result in a rich condition so it is definitely worth replacing as well.

HTH
Todd

That's exactly what I was looking for, somehow doing the google search of the board returned lots of results that included everything but the part numbers I needed. Thanks!

Also, what's your opinion on buying them off ebay? I don't mind spending the coin on new injectors, but the way most autopart stores operate these days getting what you want often requires circumnavigating their ordering system.
 
That's exactly what I was looking for, somehow doing the google search of the board returned lots of results that included everything but the part numbers I needed. Thanks!

Also, what's your opinion on buying them off ebay? I don't mind spending the coin on new injectors, but the way most autopart stores operate these days getting what you want often requires circumnavigating their ordering system.

I've had pretty good luck on eBay when I am careful. I find a lot of good companies (even Summit Racing) posting their wares here but the key is to read through the reviews for the seller. You have to be aware that eBay has setup a "false positive" system for reviews which means that the seller can post their review of you AFTER you post your review of them so even people who had a negative experience will often post positive reviews to keep from getting a bad review on their account but many of these people will call the vendor out in their comments section for the review. If someone had a really bad experience it will show up as a bad review so I start with these to see how the company handled it. Next, I scan the last 50 or so positive (or neutral) reviews to see if anyone called the seller out in the text (the bigger sellers don't read the text, only the "stars"). If all is good, I bid/buy.

As an example of this, one of the big vendors for rebuilt heads on eBay is notorious for this. If you search for a Jeep cylinder head and then read the reviews for the sellers you will spot this guy since he responds to all negative reviews by insulting the reviewer rather than addressing the problem. With this guy, I found that while people would give him a positive review to ensure he didn't trash their own rating, they would call him out in the comments section with comments like "I would never buy from this axxhole again....".

HTH
Todd
 
BulletMaker:

While you're poking around under the hood, you might want to eliminate some wiring/grounding/connection issues that are known culprits causing faulty sensor readings to the ECU
http://www.cherokeeforum.com/f51/cruiser54s-mostly-renix-tips-153657/
.

Click on the link below and read posts 1, 3, and 4.

Cruiser, you need to keep a list of all the people you dispense this to, I've seen it and done it. I thank you for your persistence on this issue though.

Also, before I go completely apoplectic regarding the abject failure that is the world of online autoparts, and launch into a rant about how much I hate ebay (I signed up for an acct to buy those injectors, and next thing you know they wanted my bank account info, no thanks!)

I'm going to go put the airbox back in (put in a new pre-heater hose and refreshed a bunch of vacuum lines) and drive over to the shooting range and unleash a few mags full of tracers on a propane cylinder. Yes, I believe that will make me feel better.

As a footnote: I did some testing with the multi-meter, and yea it looks like the O2 sensor is likely the culprit at this point. I think I have a working unit I pulled before my last smog check that I replaced "just in case" I'll throw that in and see if anything improves.

To help anyone else out who may be looking to do the same thing, I did some searching based off that e-bay link, and found this site:

http://www.injectors4u.com/injector_prices.htm
do a search for PN: 0280-155-700 and he has rebuilt injectors listed for $23 each. As a matter of completeness, motorman (website above) also has the MOPAR part for the same price... HMMMM I WONDER!

Also, if you're looking for an OEM injector it's mopar 53003956

The tech specs are 19lb/hr injector @39PSI I don't know if there is much variation in package size between injectors (I would imagine there is) but I havn't found much info on that as yet.
 
EcoMike did some posts about his fuel regulator seeping raw fuel into the intake. I've taken to doing a periodic sniff test, I pull the vacuum line off the regulator and sniff the vacuum opening into the regulator for a fuel smell. I've only had one go bad over twenty years ago, but keep an eye on the regulator anyway. My regulator has got to be way old, the diaphragms don't last forever.

Most times when my fuel mileage goes down it turns out to be a vacuum leak. I usually test for a vacuum leak at the injectors with a propane torch (no flame just the propane). For the rest of the system I plug off all of the vacuum openings in the intake, except the regulator and the MAP and see if there is any noticeable (the IAC/ECU adjusts) difference in my idle. A small vacuum leak may be hardly noticeable, but many of the vacuum lines enter the intake off center. These off center vacuum leaks tend to lean out a couple of cylinders, the O2 sensor richens the mixture to compensate and you have a rich mixture on a few cylinders and a little lean on others, it seems to screw up motor management pretty good. The vacuum lines going to the center of the intake don't seem to screw with things much, though any vacuum leak can make your motor hunt for idle. Hunt for idle means the idle may rhythmically change (cycle) from normal to low or even a little high to normal, as the motor management system tries to adjust. I once watched a guy burn his engine up testing for vacuum leaks with Ether, flammable liquids aren't my first choice. :).

The engine temp sensor (lower left of the block) and the MAT sensor are worth a test. Either can richen the mixture if they are putting out faulty info.

You said something about rattling, if your CAT starts coming apart the dust and particles can clog the screen inside the CAT and constipate your motor.

Like cruiser said, check the grounds.

15-16 MPG is all I've ever really had on my Renix, I've never done much better than that, with a combination of city/highway driving (mostly city).

The dealer O2 sensor is really expensive around here, I can buy two "Standard" (manufacturers name) O2 sensors for the price of one OEM O2 sensor and they seem to work well.

I bagged a Chicken killing Fox this morning, 250 yards, right through the ten ring.
 
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All of the fuel smell is coming from the tailpipe, not anywhere else. I'll check the regulator (can't hurt right?)

I'm finishing up my vacuum maintenance (replace vacuum line from back of airbox to warm air intake valve). I checked the cat the other day with the IR heat gun, it is in fact doing it's job (getting hot) but it could still be coming apart inside. I think what the rattle is, is the exhaust pipe rattling against where it's mounted to the transmission (there's a bracket there).

For S&G I am also going to put in a fresh T-stat, and top off the coolant (just in case this issue is leak related).

The MAT sensor was cleaned fairly recently, which fixed a nagging low-idle and die issue.

I keep pretty good stats on my fuel consumption, and highway I average about 19.9 mpg, this is even including the time I spend idling (running the heater while I take a nap).

However this:

Hunt for idle means the idle may rhythmically change (cycle) from normal to low or even a little high to normal, as the motor management system tries to adjust.

May prove to be quite productive, as it was doing this when I got over here last night in a big (and annoying) way.

Also good job on the fox, I hear they make lovely hats (I am going to try for a cougar tag next year)
 
8mud,

Congrats, you get the cookie of sorts. While poking around looking spraying propane everywhere I kept hearing a leak somewhere, but couldn't really pinpoint it, then I noticed that stupid vacuum tree on the front of the engine was sitting up, I pushed it down, noise went away, engine idled normally. Oh look there's your problem $.05 of rubber hose.

So, at the very least, this likely is the source of my intermittent idling issues. Now lets see if I can get that fuel economy up with some of these other fixes.

renix%20vacuum%20leak.jpg
 
8mud,

Go buy a lottery ticket.

While replacing the hose shown above, I removed the hose from the regulator... guess what spilled out? You got it, gasoline!
 
Thank EcoMike, he is the one who got me to looking at the regulator, it used to be mostly ignored and last on my list of things to check. It is now a regular part of my inspection routine (since he has had two go out on him).

I was really jazzed about that Fox, I've got cataracts and was worried my skills were totally gone. Operation this monday and the other eye a week later. That .308 pretty much exploded him, hit a rib, early in the winter for good pelts anyway. The farmer is going to be happy though, that darned Fox killed a dozen Chickens and only ate one.
 
Also, I just heard back from Injectors4u, another one of those times where it really pays to have someone with a metric f-ton of expertise answer your questions.

[FONT=Times New Roman, Times, serif]the best injectors to use are Bosch 0280150556 or 0280150943 both injectors are the same but have different casting numbers. these injectors are a bosch EV1 design and have a 4 hole nozzle. these injectors will be a direct fit in place of the OE 53003956 injectors. you will be able to use your original clip to hold the injector in the fuel rail.
I reccomend the 943/556 over the 700/710 because the 943/556 can be secured to the rail with the clip in the same manner as the OE injector, not allowing the fuel pressure to push it down out of the fuel rail. The 700/710 cannot be secured with the clip and must bottom out on the intake in order to not push out of the rail. this is a fire hazard. the reason these injectors work in the Fords without a clip is because the ford intake is machined to fit the bottom bevel of the 700/710 injector.

you can click the link below to purchase the injectors, I can ship Thursday or Friday. we use USPS Priority Mail. 2-3 day delivery, tracking info is emailed after shipment. we accept paypal and credit cards.

http://www.fuelinjector.citymaker.com/catalog/item/4511825/4532416.htm
[/FONT]

Seriously, this is absolutely THE BEST information I've found regarding fuel injectors.

I have a few more questions (namely warranty, shipping, etc) that I just e-mailed him with, once I get a response, order the injectors, I'll try to actually do a full write-up on this if it pans out.
 
Thank EcoMike, he is the one who got me to looking at the regulator, it used to be mostly ignored and last on my list of things to check. It is now a regular part of my inspection routine (since he has had two go out on him).

I was really jazzed about that Fox, I've got cataracts and was worried my skills were totally gone. Operation this monday and the other eye a week later. That .308 pretty much exploded him, hit a rib, early in the winter for good pelts anyway. The farmer is going to be happy though, that darned Fox killed a dozen Chickens and only ate one.

I've been having a huge impact on the coyote population at the family ranch over the last year (giving the deer a chance to drop fawns without a lot of hassle) with a Mk12Mod1 clone I built (AR-15) with the barnes MPG .223 bullets. I've been using it as a testbed for a SS monocore suppressor design I've been working on, you can just about hear that bullet hit at 200 yards, and all the kills are quick and clean.

I've got some stuff in the works on some new frangible .30 cal rounds that are in development, so far the .223 variant is working out well that it's going to be expanding into other calibers. I'll have to see what the legality is on export and send you some (do you reload?).
 
I've been having a huge impact on the coyote population at the family ranch over the last year (giving the deer a chance to drop fawns without a lot of hassle) with a Mk12Mod1 clone I built (AR-15) with the barnes MPG .223 bullets. I've been using it as a testbed for a SS monocore suppressor design I've been working on, you can just about hear that bullet hit at 200 yards, and all the kills are quick and clean.

I've got some stuff in the works on some new frangible .30 cal rounds that are in development, so far the .223 variant is working out well that it's going to be expanding into other calibers. I'll have to see what the legality is on export and send you some (do you reload?).

We get the same thing here in the spring, the Foxes kill the fawns. We have a Fox plague at present, they reproduce in multi year cycles of feast and famine, they seem to be in an up phase right now. I've shot twenty this year and haven't made much of a dent in the population. I like bird hunting (and other small game), if I reduce the Foxes I see a lot more pheasants, Rabbits and Ducks.

I reload for my .308, nothing exotic, just for consistency. I have an old SSG that is a for sure tack driver. My .222 is pretty much shot out, at one time it was a straight shooter. I've never had much good to say about the .223, I guess I never had a good enough rifle to explore it's potential. My Ruger mini in .223 makes a better shotgun than a rifle. :)

I have enough reloading supplies and ammo to last for a decade or more.

If we had a few more Yotes (Jackals) or Lynx here we'd likely have fewer Foxes. The only real population control they have here is hunters, cars, disease and starvation.
 
How is this OEM Tech?

It's not, but it's fun.

Anyways:

New fuel regulator - man getting that connector back on is a PITA

New injectors ordered - will update more once these show up.

Fixed obtuse vacuum leaks

Radiator has gone from "soon" to "today" in terms of a pin-hole leak that just keeps getting worse and is probably going to blow very soon.

Looking at this as a one-and-done (all aluminum radiator, no plastic BS):
http://www.championradiators.com/Jeep/Cherokee/radiator-3-row-1984-1990

Results:

So 8mud is 2 for 2 on my issue, the fuel regulator diaphram had ruptured, dumping excess fuel into the intake manifold, I bought the napa unit $63 with AAA discount. Installation was a little goofy as you need a torx wrench, and a tiny open end wrench to get those nuts tight.

Between this and fixing the leaks, the jeep is back up and running to most of it's former glory, I filled up the gas tank and it's ready to roll, going to put a mileage test on it this weekend. (I expect it to be improved)

I will update once injectors show up.
 
Sorry about the off topic, but XJ's aren't my only passion. :) In my experience you'll rarely go wrong following Cruisers write ups. If one of his write ups isn't exactly the solution to your problem, it in all likelihood needed to be done anyway. He has taken years of posts and knowledge and compiled them into concise, step by step, easy to follow lists that are much better organized and articulate than I'm able to convey.

I learned my lesson the hard way about those pin hole leaks. They often spew a fine mist all over the engine compartment that is almost invisible. Enough coolant in the wrong spot can short out an alternator, empty your battery or cause multiple voltage leaks that add up to charging system overload. If coolant seeps into your sensor connectors, there is no telling what is going to happen. And the worst part about coolant is, it is a lot like Coca Cola, electronic spray or brake cleaner doesn't really dissolve it much if any. The only thing that seems to dissolve it reliably is very hot water, suds, rinse and air dry.
 
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