Low gas milage, rough start.

[Fox4744]

Hey guys,
I've got yet another newbie question for you. My jeep is a 99 with 150k miles and all the sudden the gas milage is in the toilet. It was running like a champ and then I had a weird jump in rpms a few seconds after starting it about 2 weeks ago. It didn't happen again so I wrote it off as bad gas. Now I've started noticing that I'm getting terrible gas milage (10 miles to the gallon and it's still stock) and I'm having to turn the key for longer than usual to get it to start. It seems like it's stumbling a bit too. One time it just didn't start on the first try and then it shut down after starting it another time. It sounds like the fuel pump or the cps but I'm not sure and I've heard 5 different stories on cps failure symptoms. If someone could point me in the right direction I'd really appreciate it.

[Mudderoy]

Hey guys,
I've got yet another newbie question for you. My jeep is a 99 with 150k miles and all the sudden the gas milage is in the toilet. It was running like a champ and then I had a weird jump in rpms a few seconds after starting it about 2 weeks ago. It didn't happen again so I wrote it off as bad gas. Now I've started noticing that I'm getting terrible gas milage (10 miles to the gallon and it's still stock) and I'm having to turn the key for longer than usual to get it to start. It seems like it's stumbling a bit too. One time it just didn't start on the first try and then it shut down after starting it another time. It sounds like the fuel pump or the cps but I'm not sure and I've heard 5 different stories on cps failure symptoms. If someone could point me in the right direction I'd really appreciate it.

Do you have a CEL on the dash?

That would be the best way to pin point the issue.

Has the oxygen sensors ever been replaced?

I believe the flexplate has to make 3 revolutions for the ECM to read the CPS values before starting. Slow cranking might take longer for it to start, or not receiving good clean signals from the CPS. There are tests you can perform on the CPS to check to see if it's good/bad.

You want to replace it before it goes out completely (if that's the problem) otherwise you'll be stranded.

[Fox4744]

The check engine light hasn't come on yet. Honestly not sure if the thing works at this point. I've only had the jeep for a year so I don't know if the O2 sensor has been replaced, unfortunately

[Mudderoy]

The check engine light hasn't come on yet. Honestly not sure if the thing works at this point. I've only had the jeep for a year so I don't know if the O2 sensor has been replaced, unfortunately

I believe you can test them as well. The high idle could be the TPS or IAC. You can test, or you can start throwing parts at it.

For part throwing I'd change out the downstream O2 sensor, that's the one closest to the engine.

I bet someone will jump in here in the next hour or so and give you some better advise. :D

[Fox4744]

It only did the high idle thing once but I'll check the TPS and IAC just in case. Thanks for the help! If that doesn't work hopefully you're right and somebody on here can tell me how to get this thing to behave 😁

[nickyg]

you can test the throttle position sensor here's a vid.https://www.youtube.com/watch?v=URNYaGXM_uQ

[Fox4744]

I'll check that out when I get the chance. I also noticed yesterday when I filled up (again) that the gas gauge took an abnormally long time to get a correct reading so I'm leaning more towards the fuel pump at this stage. Fun fun...

[4.3LXJ]

If your gas gauge is not working very well, check your grounding on the tank. The gauge and pump rely on that ground

[Fox4744]

Ah, didn't think of that! Thanks!

[Mudderoy]

I'll check that out when I get the chance. I also noticed yesterday when I filled up (again) that the gas gauge took an abnormally long time to get a correct reading so I'm leaning more towards the fuel pump at this stage. Fun fun...

It's not too bad to replace the fuel pump assembly, but a float problem doesn't mean you have a whole assembly problem. You can get a fuel pressure gauge and check the pressure at the fuel rail.

Please take a few moments and fill out your Jeep information. It helps members just click a button and know what year your Jeep is, etc... gets you answers quicker instead of having to read back, or post to ask your the basics of your Jeep.

Just go to User CP > Edit Your Details

[Fox4744]

Hey, sorry it took so long for me to get back to this. I work out in the boonies during the summer and Internet isn't really a thing.
I figured out that a lot of the problem was actually water in my gas. I live in texas and we were having some severe flooding at the time. My mom's car was having similar problems. We get gas at the same places. I put two and two together, dumped some heet into the tank and everything was golden again. No stalling, no rough idle, and we're back to normal levels of gas consumption.
Except now I've still occasionally got a long crank time. Alternator, starter and battery all checked out good and it starts up fine after the first start of the day most of the time. But the first start after it sits for a bit can be a tad cranky. Starts on the first try every time so far though (knock on wood). Granted, it's hotter than Satan's buttcrack down here and that may be my whole problem.

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[Fox4744]

Still figuring out the jeep details thing. I'm not great with the technology

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[nickyg]

How long is long? 3 seconds? My jeep takes a a second longer then anything else in the drive way.

weird and funky crank time was 1 of the symptoms my Crank position sensor gave me. as well as a lil backfire when cranking from time to time

If you don't know how old yours is I'd plan on changing it in the future. With a mopar, not one from the box stores.
Just my suggestion.

[Fox4744]

Not really sure how long exactly, just longer than its usual startup

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[Fox4744]

I'm planning on getting a CPS to keep in the jeep just in case though

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[nickyg]

I did do my cable replacement with 4 gauge wire as per Josh's suggestion. (he has a good write up on it) and noticed snapper starter response.

[Fox4744]

I'm probably going to sound stupid here (I apologize for that) but which cables did you replace?

[Mudderoy]

Hey, sorry it took so long for me to get back to this. I work out in the boonies during the summer and Internet isn't really a thing.
I figured out that a lot of the problem was actually water in my gas. I live in texas and we were having some severe flooding at the time. My mom's car was having similar problems. We get gas at the same places. I put two and two together, dumped some heet into the tank and everything was golden again. No stalling, no rough idle, and we're back to normal levels of gas consumption.
Except now I've still occasionally got a long crank time. Alternator, starter and battery all checked out good and it starts up fine after the first start of the day most of the time. But the first start after it sits for a bit can be a tad cranky. Starts on the first try every time so far though (knock on wood). Granted, it's hotter than Satan's buttcrack down here and that may be my whole problem.

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If you have a fuel pressure gauge check it on the rail. Should be 45 -50 psi and should hold that psi after the engine is shut off. Mine would drop to 3 psi about 5 seconds after power off.

The other thing you can do it turn the the key to run then off three times and then see if it starts normally.

[Fox4744]

I don't have a fuel pressure gauge but I know a few people who might. A lot of the time it starts right up normally so the pressure gauge may be the only way to do it and get a sure fire result. If I can figure out when it consistently starts funky I'll try the 3 turn method though.

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[Fox4744]

Oh, I forgot to mention. There's no check engine light but I took it to O'Reilly's and had them check for codes and "low charging voltage" or something to that tune popped up. The battery is only a year old. Keep forgetting to check the thing for corrosion. The voltage gauge on the dash hangs out just below 14, so nothing weird there.

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[nickyg]

I'm probably going to sound stupid here (I apologize for that) but which cables did you replace?

All of them. 5 in total I think. 1pos going to the starter. 1 pos going o the power distribution box and the 2 grounds. plus i replaced the copper strap on the fire wall.
I don't think it will help it start up faster, but it did seem like the starter spun a lil faster when it was done.

[nickyg]

link to Josh's build that covered battery cable swap.

http://www.xjtalk.com/showthread.php?t=11347&page=7

[Fox4744]

So I tried the turning the key to run 3 times thing and it doesn't crank as long before turning over when I do that but it seems like there's a bit more stumbling with that method. It's seemed to start best when I turned the key to run once and then started it but it's so unpredictable I'm not sure if what I'm doing is changing things or the jeep is just being more cooperative. Started right up without any fancy key maneuvers a few times too. I'm gonna get one of my friends who has all the fancy gauges and gadgets to come help me figure it out. Hopefully we'll get somewhere with a fuel pressure gauge and whatnot

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[nickyg]

I'm no mechanic by a long shot. but it sounds like it might be a fuel problem.
Turning the key to ON runs the fuel pump for a few seconds to build pressure. You can usually hear a WRRRR sound from the rear of the jeep. Maybe your jeep is losing fuel pressure when it sits,

What other symptoms you have?

[nickyg]

Just read that Tony gave you some good advice on fuel pressure. Sorry I'm late to the party again.

[Fox4744]

The rough start is actually the only problem since I put the heet in strangely enough

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[Fox4744]

It's all good. I'd rather have too much advice than not enough

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[nickyg]

The rough start is actually the only problem since I put the heet in strangely enough

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Try a full tank of premium since it might be bad gas.

[Fox4744]

Wouldn't it just figure that I just filled up[emoji29]. Guess I've got a lot of driving to do. Or heck, maybe it'll just behave itself now if that's the case. It DID start up perfectly right after I got gas.

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[Fox4744]

Update on brat jeep: After making a 200 mile trip in the jeep I thought I was fine and it was just bad gas. But it then proceeded to go back to its old ways of starting rough and idling like crap culminating in a very annoying stall out in bumper to bumper traffic. Got it started again, took it to mechanic. They said they couldn't get it to stall but the distributor cap, rotor and spark plugs were shot (so much for the previous owners insistence that it JUST got a tune up). $300 later, still starts rough and runs like crap, though the mechanic seems to think it runs like a gazelle. I will say it goes a lot faster now though. So I tested the fuel pressure and I'm getting 30 psi with the key in the on position and about 45 with it running. It's not erratic at all. I did notice that my gauges aren't coming on with the key in the on position and my rpms drop a bit and get slightly erratic when I turn the ac off so I'm gonna check out the cps tomorrow.

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[4.3LXJ]

Jade, the gauges not coming on with the key is a common problem caused by a poor connection in the back of the gauge cluster. Short term fix is to pretend you are a pissed off guy and smack the dash with your hand, not fist. That usually does it. Not sure if I told you to do this, but if the O2 sensor hasn't been changed, like when that last tune up was supposed to have happened, putting one in is a good thing and may help smooth it out

[Fox4744]

Cant say Id be opposed to giving it a good smack at this point. Shouldnt even have to pretend on the pissed off part. Not sure if they put a new O2 sensor in with the tune up but I didn't see it on the receipt so most likely not. It just passed an inspection so I just wrote that off (probably not my best idea). This is probably a stupid question but is there any way to test the sensor to see if it's still good or do you just have to bite the bullet and hope a new one fixes it?

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[4.3LXJ]

Not a stupid question. Yes you can, but it takes equipment I don't have. My rule of thumb is change it every 50K. And while you are at it, the crank position sensor and cam position sensor every 100K. Those two will leave you stranded when they quit. Basically what happens is that the O2 sensor generates its own electrical current. Eventually it starts running out of electrons it can get rid of so it starts generating less current and causes the engine computer to assume the mixture is lean and so it squirts more fuel into the cylinders. Short story is that they wear out just like solar panels

[Fox4744]

That would make sense. I think I'm back at 20 mpg highway again but my exhaust does smell pretty rich. And I'd bet money that none of those 3 have been replaced in eons. The jeep is a reformed mommy mobile and I'm learning pretty quickly that she ran it hard, put it up wet, and decided maintenance was for suckers.

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[4.3LXJ]

That could be. Mommies like to feel acceleration too. 20 mpg is good though. Those of us with lifted Jeeps get less

[Fox4744]

And letting Reese's cups hang under the back seat until petrified apparently. But yeah, thought it would be a bit of a waste to lift a 2wd. Just trying to get it running decent before I sell it next summer. And keeping it running to get me to classes and work in the meantime.

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[4.3LXJ]

It will be a good rig for that. You might even decide to keep it. You could call a paleontologist in to see if there is any evolutionary value to old vs new cups :D

[Fox4744]

Ah, darn. Already partially removed the thing. Coulda been rich!

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[4.3LXJ]

Not to mention a whole new field of GMO vs non GMO peanuts :D

[Fox4744]

There's something genetically modified about that thing, that's for sure 😂

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[4.3LXJ]

I am sure. Or perhaps you can smuggle them into Egypt and sell them to a tourist saying they were just excavated from a pyramid :D

[Fox4744]

Or that guy from ancient aliens. I only have one so gotta make it count 😁

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[4.3LXJ]

That is right, chance favors the prepared mind. If it is alien, maybe it is paranormal

[Fox4744]

Bender the jeep and it's haunted petrified Reese's cup. That's a whole episode right there

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[4.3LXJ]

You could start your own blog with that right there

[Fox4744]

If I get bored enough, I just might.

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[4.3LXJ]

Blogging is the thing to do nowadays. But, boring to me though. Probably a generational thing

[Fox4744]

Eh, I'm still in college and I'm not a big fan. I'd have to be pretty bored

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[4.3LXJ]

Extremely bored. College is when I really started having fun, even though I had a lot of fun in high school. But college was real freedom

[Fox4744]

Yeah, definitely plenty to do. Can't say I'll be sad to graduate though.

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[4.3LXJ]

I wasn't either, but I could be a perpetual student.

[Fox4744]

So I decided to fiddle around with the jeep a bit. Tested the CPS with a voltmeter and it tested good. Checked the spark plugs and as I was pushing on them a bit the last one made a click sound. Now the jeep only idles rough right after starting. At stoplights and in traffic jams it's super smooth. Problem is, it's still starting rough and the engine cut off after I started it this morning (the radio stayed on). The CEL came on while it was being a brat but turned off again when I restarted. Is it possible that the CPS is bad even if it tested as ok? Or is it probably something else? I'd replace everything at once but I'm on the college budget. Trying to find the thing that's the problem and replace it first then replace the other stuff as soon as I can afford it.

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[prerunner1982]

The click sound was the spark plug boot making positive contact with the spark plug (if I understand what you were saying). They should all do that.

[Fox4744]

It was a snapping into place kind of click if that helps any. Almost like the thing wasn't all the way in. Thought I broke it at first

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[prerunner1982]

I would also suggest getting the code checked. Even though it went away it may/should be saved.

[Fox4744]

Yeah, planning on doing that as soon as I'm free. Pretty sure the guys at O'Reilly's start hauling out the diagnostic equipment every time they hear my jeep anymore.

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[prerunner1982]

A bluetooth OBDII dongle and Torque app may be a good investment. I have one (as well as a few other members) and I can say that thing sure is handy. Sure saves trips to the parts stores to have the codes scanned and you can leave it plugged in while you drive and get real time data. Don't forget to go to www.jeeptalkshow.com/amazon before making any purchases.

[Fox4744]

I'll check that out. Tried that link and it doesn't work but that may just be my phone

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[Fox4744]

Looking at it on Amazon. That is super cool

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[prerunner1982]

Try the link now... If you aren't aware of the XJTalk Amazon deal, the forum gets a percentage of the price of the items you buy. You don't pay any extra, but Amazon gives "us" a little of their profit. Also some of the items are discussed on the Jeep Talk Show in the Amazon You Bought What segment. They can't see who bought the items, so it makes it kind of fun.

[Fox4744]

Well that's pretty cool. I'll do that then

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[Fox4744]

I took the jeep to O'Reilly's. They couldn't get any codes to come up so no dice there. I ordered the OBDII thing and it should be here tomorrow. Hopefully that'll get me some answers. I tried hitting the dash to get the gauges to work and the clear plastic had a bit more give than I would have liked so I hit it pretty hard just above the plastic and the only thing that moved was the speedometer. The gauges seem to work fine when the engine is on though.

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[4.3LXJ]

You just forgot the pissed off part :D You say they work when the engine is on? Oil pressure will not work unless it is on. How about gas gauge and temp gauge?

[Fox4744]

Gas gauge and temp aren't budging until the engine is on. Not sure why the speedometer moved. It was parked

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[4.3LXJ]

Not sure what to tell you then

[Fox4744]

Maybe I need to whack it harder

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[Fox4744]

I finally got to use the OBDII. The only thing that's showing up as weird is my vacuum is varying between 4 and 20. I'm going to clean the throttle body today since it looks so gunked up its getting stuck open a little and see if there's any improvment. Not sure if that effects the vacuum pressure at all but it couldn't hurt.

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[Fox4744]

So I hit a pretty big snag. Upon noticing that the inside of the IAC housing was full on caked with crud, I decided to remove it. Then proceeded to break one of the screws. Tried a screw extractor and that snapped too. I can get the other screws back in but I'm worried that won't seal properly without a screw. We're considering using JB weld but it's looking like I'll need a new throttle body. If anybody has any ideas I'm all ears

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[4.3LXJ]

A new used throttle body is probably the easiest and cheapest solution

[Fox4744]

Yeah... Everything short of voodoo magic has failed so far. Pretty sure the thing was shot anyways (at least that's what I'm telling myself). I guess I get to visit the junkyard tomorrow. Whee

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[GoneWithTheWind]

Is there a chance that your intake or exhaust manifold could be a little loose?

[Fox4744]

It's highly possible. Everything around where the exhaust manifold attaches to the engine is terrifyingly rusty. I'm praying that all of that is somehow holding together

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[Fox4744]

I think I found my problem. When I got the new part at the junkyard, I noticed that there were 3 cables attached to the throttle body pulling the lever, not just 2. I only have 2. The middle one is missing. Does anyone know where the other end of that plugs in so I can see if it's still attached somewhere? The diagrams I'm finding aren't proving too helpful

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[Fox4744]

Aaaand I just found this:8266

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[drakan1908]

One should be trans. kickdown, one should be cruise and one should be throttle. Just a guess.

sent from a van down by the river

[Fox4744]

Ah, I don't have cruise control and the diagrams had that one labeled "speed control" so that's probably it. They probably just used the same brackets for Jeeps with and without cruise I guess

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[XJ Wheeler]

Aaaand I just found this:8266

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The tube? A/c drain tube.

Sent via messenger pigeon. I talk, he types.