l-man Posted January 26, 2012 Share Posted January 26, 2012 Have 88 MJ, did new engine swap, changed all sensors except manifold air temperature sensor. can't find mat sensor anywhere for this year. Starts up great,idles great, but back fires and sputters when gas it. This sensor is the only thing left I can think of that might be cause. Where can I find this sensor? Tried local parts stores and dealerships and some online sites, getting frustrated. Thanks for any help. Link to comment Share on other sites More sharing options...
maddzz1 Posted January 26, 2012 Share Posted January 26, 2012 Have 88 MJ, did new engine swap, changed all sensors except manifold air temperature sensor. can't find mat sensor anywhere for this year. Starts up great,idles great, but back fires and sputters when gas it. This sensor is the only thing left I can think of that might be cause. Where can I find this sensor? Tried local parts stores and dealerships and some online sites, getting frustrated. Thanks for any help. I think they call it an air charge sensor or something like that. Link to comment Share on other sites More sharing options...
cruiser54 Posted January 26, 2012 Share Posted January 26, 2012 IAT, Intake Air Temp sensor. Did you swap distributors? Link to comment Share on other sites More sharing options...
l-man Posted January 26, 2012 Author Share Posted January 26, 2012 put reman distributor in, yes. IAT gives me ambient air, MAT - no luck (online) Link to comment Share on other sites More sharing options...
Jeep Driver Posted January 26, 2012 Share Posted January 26, 2012 viewtopic.php?f=2&t=33023 Link to comment Share on other sites More sharing options...
l-man Posted January 26, 2012 Author Share Posted January 26, 2012 guess i should have mentioned i have a 4.0L. Looking for same deal that will work for 6cyl. not sure this link will but thanks for trying Link to comment Share on other sites More sharing options...
Jeep Driver Posted January 26, 2012 Share Posted January 26, 2012 I don't 'try', I do. http://www.teamcherokee.com/Emissions/index.html #18 down the page. 2.5 or 4.0 is the same, the pigtail is different. The one I posted in my link will work also, you will need a pigtail. If you buy new the pigtail is about $24 IIRC so I point you to the JY for a Chrysler tail. Link to comment Share on other sites More sharing options...
Jeep Driver Posted January 27, 2012 Share Posted January 27, 2012 BTW as you are finding out or will find out.........new parts for autos more than 20 years old are being phased out. I don't know if it's a matter of the market or a matter of it being purposeful by the PTB, maybe a little of both. We will have to work around this. Link to comment Share on other sites More sharing options...
shawn Posted January 27, 2012 Share Posted January 27, 2012 I don't 'try', I do. http://www.teamcherokee.com/Emissions/index.html #18 down the page. 2.5 or 4.0 is the same, the pigtail is different. The one I posted in my link will work also, you will need a pigtail. If you buy new the pigtail is about $24 IIRC so I point you to the JY for a Chrysler tail. :hijack: - i spent a lot of time looking for one of those for an '86 2.5, - but never did have any luck, although the one for the '87 seems to do it. (pigtails needed changing). Link to comment Share on other sites More sharing options...
skidoo_j Posted January 27, 2012 Share Posted January 27, 2012 The sensor values from 88-90 vs 91-93 are off quite a bit. wouldn't that cause some issues. It's over 60 degrees difference that the computer would be reading. So our renix system would think the air coming in is 60 degrees colder then it actually is. Colder air denser air more fuel? so it would run too rich from this sensor input then the o2 would cut it back except o2 is only read at cruise in a renix system... Anybody have a different MAT sensor replacement or is this as close as it gets? Link to comment Share on other sites More sharing options...
cruiser54 Posted January 27, 2012 Share Posted January 27, 2012 The sensor values from 88-90 vs 91-93 are off quite a bit. wouldn't that cause some issues. It's over 60 degrees difference that the computer would be reading. So our renix system would think the air coming in is 60 degrees colder then it actually is. Colder air denser air more fuel? so it would run too rich from this sensor input then the o2 would cut it back except o2 is only read at cruise in a renix system... Anybody have a different MAT sensor replacement or is this as close as it gets? I've moved the IAT sensor on 3 Renix Jeeps over to the air intake boot/air cleaner. You can bet the air coming in there is more than 60* cooler than in the intake manifold. No mileage loss. Something that concerns me more is how many Renix Jeeps I've found with bad sensor ground circuit connections causing the MAP, IAT, CTS and TPS to send erroneous signals to the ECU. Cruiser’s Renix Jeep Sensor Ground Test 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. If you see more than 1 ohm of resistance a modification/upgrade to the sensor ground harness will be necessary. This project will require soldering skills. Link to comment Share on other sites More sharing options...
skidoo_j Posted January 27, 2012 Share Posted January 27, 2012 I've moved the IAT sensor on 3 Renix Jeeps over to the air intake boot/air cleaner. You can bet the air coming in there is more than 60* cooler than in the intake manifold. No mileage loss. I plotted the data from the fsm and generated log functions. so if the intake temp was 100 degrees and using 91-93 sensor the ecu would think it's 38. if 75 would think 25 if 45 would link 1 degree 150 would think 85... So what your saying is if the sensor is in the stock location and is bad replacing it with 91-93 sensor is equivalent to the relocation of a stock sensor... and relocating the 91-93 sensor would cause the effect to be doubled ... I've done the tps sensor ground loop test before Link to comment Share on other sites More sharing options...
Exxon Valdez Jeep Posted January 27, 2012 Share Posted January 27, 2012 did you calibrate the new TPS when you installed it? Link to comment Share on other sites More sharing options...
cruiser54 Posted January 27, 2012 Share Posted January 27, 2012 I've moved the IAT sensor on 3 Renix Jeeps over to the air intake boot/air cleaner. You can bet the air coming in there is more than 60* cooler than in the intake manifold. No mileage loss. I plotted the data from the fsm and generated log functions. so if the intake temp was 100 degrees and using 91-93 sensor the ecu would think it's 38. if 75 would think 25 if 45 would link 1 degree 150 would think 85... So what your saying is if the sensor is in the stock location and is bad replacing it with 91-93 sensor is equivalent to the relocation of a stock sensor... and relocating the 91-93 sensor would cause the effect to be doubled ... I've done the tps sensor ground loop test before Sounds about right. You're the mathematician!! In other words, I'm thinking that using the later model sensor in the original location would be no worse than relocating the stock sensor to the intake boot. Link to comment Share on other sites More sharing options...
skidoo_j Posted January 28, 2012 Share Posted January 28, 2012 correct sensors for our renix system that will not cause rich idle. correct info, but have to order $30 worth of parts from them plus shipping http://www.injector.com/cart/pc/Air-Cha ... -12p65.htm The following two appear to be 3/8" pipe (verify prior to purchase) and have the correct ohm thermistor so the computer reads correctly, you will need to get the pig tail out of late 80's era chevy or buy it. Took quite awhile to find the charts for the readings. Napa Part : ECH TS5100 Schucks part : WT382 Link to comment Share on other sites More sharing options...
cruiser54 Posted January 28, 2012 Share Posted January 28, 2012 Rich idle is affected the most by the folowing parts, in order of effect, biggest to smallest: MAP, CTS, IAT, O2 Sensor Link to comment Share on other sites More sharing options...
l-man Posted January 28, 2012 Author Share Posted January 28, 2012 i appreciate all the input. found and changed all sensors now. still have the same problem. idle is good, high rpm good, but back fires when i let off. seems to stumble from 1500 to 3500 rpms. i am stumped, i know on my dirt bikes back fire means to lean. could i have a short to ground somewhere? anybody have a DRBII for sale cheap? oh ya, did do the 17% with TPS. thanks Link to comment Share on other sites More sharing options...
mvusse Posted January 28, 2012 Share Posted January 28, 2012 Sounds to me like a timing issue. I'm guessing the distributor was installed a tooth (or more) out. Link to comment Share on other sites More sharing options...
l-man Posted January 28, 2012 Author Share Posted January 28, 2012 ok, i'll check that out. Link to comment Share on other sites More sharing options...
cruiser54 Posted January 28, 2012 Share Posted January 28, 2012 Sounds to me like a timing issue. I'm guessing the distributor was installed a tooth (or more) out. Ignition timing on a Renix is done by the ECU. Have you ever done a fuel pressure test? Link to comment Share on other sites More sharing options...
l-man Posted January 28, 2012 Author Share Posted January 28, 2012 no, i have not. i do have pressure at the schrader valve, but don't know how much. Link to comment Share on other sites More sharing options...
skidoo_j Posted March 22, 2012 Share Posted March 22, 2012 no, i have not. i do have pressure at the schrader valve, but don't know how much. I-man did you ever chase out the cause??? Link to comment Share on other sites More sharing options...
Dirteatr717 Posted March 23, 2012 Share Posted March 23, 2012 What are you using for exhaust, do you have an exhaust leak and do you have a cat, muffler and tailpipe ? My friends XJ back fired like crazy when he ripped the exhaust off from the cat back by accident when we were offroading one night. Link to comment Share on other sites More sharing options...
mvusse Posted March 23, 2012 Share Posted March 23, 2012 My trail rig is running a stock front pipe going into a glass pack and that's it. No problem with backfiring. Link to comment Share on other sites More sharing options...
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