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ECM and sensors


 
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Titan4u2c
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Joined: 03 Dec 2005
Location: Clayton, NC

PostPosted: Thu Apr 13, 2006 4:59 pm    Post subject: ECM and sensors Reply with quote

Hey guys, anyone know what kinda sensor the XJ came with in '91? I am hearing all 3.... a map a maf and a mat sensor? It's a manual 4.0L sport 4wd and was wondering what this sensor whichever one it is, does exactly. Also anybody know up to what year I can swap out ECM's? Nothing really wrong with mine I don't think but was curious if a newer one say up to a '96 or so would fit. Thanks. Neutral
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scorpio_vette
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Joined: 02 Nov 2005
Location: milwaukee WI

PostPosted: Thu Apr 13, 2006 7:38 pm    Post subject: Reply with quote

you can only swap up to 95. in 96 they started OBD-II.

i could be wrong on this, but i don't believe that they came with MAP or MAF sensors.
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Last edited by scorpio_vette on Wed Feb 02, 2011 5:09 pm; edited 1 time in total
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Titan4u2c
Member


Joined: 03 Dec 2005
Location: Clayton, NC

PostPosted: Fri Apr 14, 2006 7:15 am    Post subject: Reply with quote

thanks scorp, so did they come with a mat sensor then? It is on the driverside up on the firewall and has a 2 prong plug and a vacuum line attached to it. so if it's not a map or maf then must be a mat maybe? still trying ot figure out why she wont run right after installing a high-flow cat and exhaust. replaced tps, iac and tb so left with a air/fuel issue I think somewhere. I can get it to catch if I choke off the air to the intake and when I floor it it bogs down or cuts off and I think it's runnin really rich cuz the cat and exhaust get real hot and change colors and smell of fuel. I was hoping that this sensor was the culprit. Thanks again.
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scorpio_vette
Member


Joined: 02 Nov 2005
Location: milwaukee WI

PostPosted: Fri Apr 14, 2006 7:58 am    Post subject: Reply with quote

you know what. ignore my last post. i don't know where my head was sorry.

the MAP sensor on a 91 should be:
UNDER HOOD, CENTER, REAR ENGINE AREA, MOUNTED ON UPPER FIREWALL

it does not come with a MAF and i believe it does not come with a MAT.

again sorry for my last post, not sure what i was thinking.

ok. now you really need to figure out what your problem is before you keep running/driving your jeep. excess fuel will kill a cat.

a highflow cat and exhaust shouldn't really cause any problems since it's just allowing the exhaust to flow smoother. did you replace the exhaust manifold too??? if you did, did you replace the O2 sensor???

i'm having a little bit of a brain fart about why it's getting excess fuel right now. usually when it dumps excess fuel is because the computer thinks the engine isn't warmed up yet, so it'll add a little extra till it warms up. so you could have a bad temp sensor too.

on my jeep the O2 sensor went bad and was constantly reading lean. so my computer kept compensating by adding more fuel. once i replaced the O2 sensor everything was fine.

go check out www.naxja.org it's a cherokee only site, and you should be able to find some more help about that problem there.
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Last edited by scorpio_vette on Wed Feb 02, 2011 5:09 pm; edited 1 time in total
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Titan4u2c
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Joined: 03 Dec 2005
Location: Clayton, NC

PostPosted: Fri Apr 14, 2006 10:36 am    Post subject: Reply with quote

Yeah I thought that's what I had but didn't want to disagree with you as I wasn't sure haha. Yes I replaced the O2 sensor as well and wires, plugs, dist, and cap as well as fuel fitler. It was funny I posted it up here and got all kinda possiblities but still not a fix. And no I'm not running it I just try to start it every other week. Here's the deal, originally it ran like a top but after the muffler shop lowered it from the lift, she wouldn't start. I finally got it to catch and had to feather the throttle and keep it tweeb 1500 and say 3000 rpm. If it goes under it would cut-off or over and it would bog down and studder. So I got it home and thought there was a backpressure issue or somethign to do with the new exhaust. But no there's plenty air flowing out back and the plugs aren't fouled so my mech said could have just been time for something to go, just dunno wtf it is ... haha Anyway after installing numerous new stuff a bigger bore TB and a tps and an IAC motor and leaving the batt off for awhile I thought this might work. Now liek I said if I choke off the intake and allow only a little air in and hold the pedal to the floor it catches after alot of coaxing and revs up and settles back down. So I know the new IAC worked but dunno if the TPS did. So I was thinking either it seemed with the boggin down if I floor it problem that maybe it was a fuel issue so was gonna throw in new injectors but a few ppl say may not be the case and I'm holding off on that $150 HA. Anyway I noticed this sensor on the firewall and if it has anything to do with air/fuel regulation, then this sensor is next to try. I asked about the newer ECM unit because if I cannot get this thing to run right I was wondering if I found a newer one for a manual XJ that I might swap out and hopefully sorta clear out all old stuff and hope to start from scratch and maybe my old one has faulty inputs so ....worth a thought. But as for holding the pedal to the floor and pumping it as she coughs and sputters made me think fuel flow, as well as the bogging down when I floor it. Does that MAF sensor not stand for Mass Air Flow??? This HAS to be my problem. I hope haha thanks again.
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Titan4u2c
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Joined: 03 Dec 2005
Location: Clayton, NC

PostPosted: Fri Apr 14, 2006 10:38 am    Post subject: Reply with quote

Yeah I thought that's what I had but didn't want to disagree with you as I wasn't sure haha. Yes I replaced the O2 sensor as well and wires, plugs, dist, and cap as well as fuel fitler. It was funny I posted it up here and got all kinda possiblities but still not a fix. And no I'm not running it I just try to start it every other week. Here's the deal, originally it ran like a top but after the muffler shop lowered it from the lift, she wouldn't start. ( had a high-flow cat and 40 series flowmaster installed). I finally got it to catch and had to feather the throttle and keep it tween 1500 and say 3000 rpm. If it goes under it would cut-off or over and it would bog down and studder. So I got it home and thought there was a backpressure issue or somethign to do with the new exhaust. But no there's plenty air flowing out back and the plugs aren't fouled so my mech said could have just been time for something to go, just dunno wtf it is ... haha Anyway after installing numerous new stuff a bigger bore TB and a tps and an IAC motor and leaving the batt off for awhile I thought this might work. Now liek I said if I choke off the intake and allow only a little air in and hold the pedal to the floor it catches after alot of coaxing and revs up and settles back down. So I know the new IAC worked but dunno if the TPS did. So I was thinking either it seemed with the boggin down if I floor it problem that maybe it was a fuel issue so was gonna throw in new injectors but a few ppl say may not be the case and I'm holding off on that $150 HA. Anyway I noticed this sensor on the firewall and if it has anything to do with air/fuel regulation, then this sensor is next to try. I asked about the newer ECM unit because if I cannot get this thing to run right I was wondering if I found a newer one for a manual XJ that I might swap out and hopefully sorta clear out all old stuff and hope to start from scratch and maybe my old one has faulty inputs so ....worth a thought. But as for holding the pedal to the floor and pumping it as she coughs and sputters made me think fuel flow, as well as the bogging down when I floor it. Does that MAF sensor not stand for Mass Air Flow??? This HAS to be my problem. I hope haha thanks again.
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scorpio_vette
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Joined: 02 Nov 2005
Location: milwaukee WI

PostPosted: Fri Apr 14, 2006 11:31 am    Post subject: Reply with quote

you are correct that MAF means mass air flow. but usually it's right after the air filter and that's where it get's it's reading. i honestly don't believe that it has that. i looked at my cherokee just incase and it doesn't.

i really wouldn't recommend replacing every part in the fuel system, specially the injectors. that can all start adding up and get expensive.

it would be alot easier to diagnose it if i had the vehicle here so i could hook my scanner up to it and get the reading from all the different sensors and see which one is acting up.

did you already check out the link i posted above??? www.naxja.org

if you didn't, go check it out and post what you wrote here on that board. it's cherokee only and i'm sure that the guys there would be able to give you alot more specific pointers. i know i could fix it if i was working on it at my shop, but right now just trying to think about all the possibilities i'm just drawing a blank.
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Last edited by scorpio_vette on Thu Mar 10, 2011 6:26 am; edited 1 time in total
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Titan4u2c
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Joined: 03 Dec 2005
Location: Clayton, NC

PostPosted: Fri Apr 14, 2006 1:39 pm    Post subject: Reply with quote

Yeah it's got a green plug that goes from the sensor into a wad of wiring conduit and who knows where it runs from there either to the ecm or to a plug in on the manifold and the vacuum line goes from the sensor onto the manifold so maybe my issue is a vac leak although I hear none. Yeah gonna check on that nax site now, thanks. Yeah if I still lived up there in wis I could tow it over to milwaukee and play with it. By the way do you know the website for codes on these? I saw it on here before from Phantum I think but cannot find it now. Maybe if I checked to see what code it's throwing it might help.
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gtouimet
Member


Joined: 07 Feb 2006
Location: San Diego, Ca.

PostPosted: Sun Apr 16, 2006 2:58 pm    Post subject: Reply with quote

That sounds like a problem I had a while ago. It ended up being my header gasket. It was blown and was leaking on two cylinders. Also if you have made the mod that you say to the intake and exhaust, you might think about getting an adjustable map sensor or a modifier. If you have modified the way your engine runs with performance enhancers, you need this to get your fuel curve back in line and help gain up to 5-8HP by running the proper fuel curve again. Also increases fuel economy by avoiding running too rich. You can pick one up on ebay for $80 or xj-armor.com has them for $10 more. These are the cheapest I have seen them. I hope something here help. Good luck!
_________________
'91 XJ, 8" lift, 35x12.5x15 BFGs, 8.8, 4.56
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Titan4u2c
Member


Joined: 03 Dec 2005
Location: Clayton, NC

PostPosted: Mon Apr 17, 2006 4:15 am    Post subject: Reply with quote

Hey thanks GT I hope I am getting close how exactly do those attach? Same as normal place for map sensor or will I need to do any mods with wiring or what have you? Also found some articles on the possibility of it being a volt issue and I need to check the A and B prongs of that sensor for ohm load I heard. As well as maybe the cap in the rotor not doing what it's supposed to and this may be throwing something out of wack in the ignition/running loop. Someone also said that I may have a vacuum leak at the line where it attaches to the sensor or even at the manifold, how I test this with basic tools, I dunno. haha. SO would you say I should go with the adj. sensor instead of a stocker if I replace it? OE around $38 vs. what u said. If they are the same trouble to attach I'm gonna try the adj. one. I don't wanna go there on the head gasket, this to me, would be an eaiser swap. Thanks.
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gtouimet
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Joined: 07 Feb 2006
Location: San Diego, Ca.

PostPosted: Mon Apr 17, 2006 7:31 pm    Post subject: Reply with quote

Well, I am not sure how much an adjustable one costs. The modifier that I quoted is just a harness that attaches to the map sensor ( one in working condition). The way it works is, you would attach it to your sensor and it allows the sensor to be adjusted with a screwdriver and a voltmeter. I had suggested it not meaning that your map sensor is bad, just that it needs to be adjusted and this is the way to do it. Also, depending on your jeep's year and what company the modifier is made by, it either connects straight to the map or it requires minimal splicing.
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'91 XJ, 8" lift, 35x12.5x15 BFGs, 8.8, 4.56
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