I just installed a new exhaust mani and my muffler glows red now any ideas? - Jeep Wrangler Forum
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Old 11-02-2008, 02:30 PM   #1
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I just installed a new exhaust mani and my muffler glows red now any ideas?

i just recently put a new exhaust manifold on. there was one plug that i could find where it goes so i left it unplugged and it starts just fine without it but is this the reason that my muffler was glowing red. i drove it 2 houses down n pulled it back in my driveway and the muffler was glowing red. the other thing that was different when put the new exhaust manifold on was that the egr tube would not come of the intake manifold so i just cut it and closed the end off. you think that it could be a bad cat or muffler it didnt do it before i drove n everything fine with the old cracked manifold just ran a lil rough. if anyone has any ideas please let me know

this is the plug that is unplugged can someone tell me what it is and where it goes thank you











jeep 1990 4cycl fuel injec. 2.5L

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Old 11-02-2008, 02:42 PM   #2
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i would say it might have something to do with taking that hose and cutting and plugging it.

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Old 11-02-2008, 03:10 PM   #3
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I'm thinking an utra rich air-fuel mixture. How's the 02 sensor near your exhaust header? The 02 sensor nearest the engine directly controls the air-fuel mixture so if it's not working properly, it could screw up the air fuel ratio. No idea on the plug, that's out of an older model than I am familiar with. It is electrical so it could have something to do with why your air-fuel mixture may be ultra-rich (if indeed it is).
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Old 11-02-2008, 04:59 PM   #4
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bump bump please any hellp would be great thanks for everyone that responded so far
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Old 11-02-2008, 08:15 PM   #5
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I think it is for a heater plate that were on some models.Check to see if you have a thick base plate under the carb???If so it should plug in on it somewere.
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Old 11-02-2008, 08:58 PM   #6
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by any chance you know exactly where it would be to me it doesnt look like there is a plate under the carb. do you think that having this plug unplugged could cause the muffler to get like that and glow red. i will try to post pics of the whole engine bay so maybe someone can point it out for me sorry im new to jeeps. all my other cars have been hondas thanks for all the help. its greatly appreciated!!!
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Old 11-02-2008, 09:29 PM   #7
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here is a new picture of the wire that is unplugged may be a clear picture since it is a wider view. if anyone knows where this goes it would really help thanks alot


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Old 11-02-2008, 10:19 PM   #8
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If part of your exhaust system is glowing red you are running way too rich, I also think you are mistaking the cat for the muffler. The cat has materials in it that are *supposed* to burn any unburned hydrocarbons through chemical reaction. If It's cherry red you have unburned fuel being dumped directly into the exhaust. I am not familiar with the 90 4 cylinder though I *think* it was the first of the wranglers to get fuel injection. If I am wrong and it has a carter carb on it that plug you are showing may plug into the back of the carb on the side nearest the firewall. It was part of the first basic computer controlled carb. I had an 89 4.2 that had this. Do not drive it like this, you will do one of two things, probably both in short order, either you will cause the cat to melt down or if you park over any leaves you WILL start a fire under it. You need to find out what you failed to hook up and what you replaced might have had missing. As for closing off that port, not a good idea, you really need to get this stuff hooked up and working correctly.

I would find another one of your year and compare the two, see whats missing and go from there.
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Old 11-02-2008, 10:54 PM   #9
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I checked many places and it did not have the base plate heater so I am not sure what that plug is but I agree with rich and jerry it is running way too rich and if the cat is getting hot enough to glow it may already be to late to save it because the catalyst honey comb inside will withstand extreme heat but not that extreme.It will start to melt together and clog.If it is in fact the muffler then not only are you running rich but the muffler has a restriction in it in order to build that kind of heat.BTW what happened to the other manifold???Just curious to see if it may have cracked from getting too hot which would tell you the jeep was running rich before the change.
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Old 11-03-2008, 12:23 AM   #10
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the old exhaust manifold was cracked when i got the jeep. so you think the plug goes into the back of the carb? i really think this is the reason it is running like this because it was running fine before just a little rough due to the crack in the exhaust manifold. and trust me i wont be driving it again until i figure out where this plugs goes. thanks alot
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Old 11-03-2008, 09:20 AM   #11
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Bump if anyone can help it would be greatly appreciated
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Old 11-03-2008, 11:00 AM   #12
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According to what I can find about the 1990YJ you have fuel injection. My guess is you are missing some parts, either not put back on by you or removed from it by the person you got it from. You really need to find another 89 or 90 2.5 and give it a look see, I'd also take some detailed pictures, best bet would be to pull up or get someone with one to pull up next to you and start comparing. I'm basing the fuel injection by quadratec listing FI parts for your year.
Jeep CJ, YJ Wrangler and TJ Wrangler, Cherokee XJ, Grand Cherokee ZJ and WJ, and Liberty Series OEM Style Fuel Replacement Parts - Fuel Injector and Related Parts - Quadratec
The ideal thing would be to get a factory service manual or <shudder> a Haynes or chiltons manual.
This is what a carter bbl looks like, that plug is the computer control for the carb. This probably does not apply to you
Original Replacement Parts 2-904 - Carter BBD Remanufactured 2BBL Carburator w/ Electric FeedBack Motor for 1982-1990 Jeep CJ & Wrangler YJ w/ 258 Inline Six Cylinder Engine - Quadratec

You might also get a much better response by posting this in the correct forum, you have a YJ not a TJ.
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Old 11-03-2008, 11:05 AM   #13
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thanks for the information i really think that this plug controls the amount of fuel, and like you said before i think that it is running rich and dumping gas into the exhaust system that caused the muffler to glow. i think if i find where this plug goes exactly it should fix the problem. everything else is back on there right.
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Old 11-03-2008, 12:34 PM   #14
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please if anyone knows exactly where this clip goes please let me know or anyone that knows alot about the 89 90 4cycl fuel injected 2.5l model
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Old 11-03-2008, 12:52 PM   #15
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ur 90 will be TBI. im not sure on that plug, i will look on mine when i get home tonight.

a couple of things come to mind.
1. if its ur cat that is glowing, i would suspect a clogged cat. the reason it didnt glow or cause a prob before was that your manifold was leaking enough to vent the excess pressure. usually, a clogged cat will rob horsepower on the top end. i know thats hard to tell on our 4 bangers but does it get worse when you give it some throttle?

2nd theory would be that its a result of you blocking off the EGR. i never have done this so im not sure. which end is connected and which end is closed off? my egr was stuck closed and didnt cause this problem, so im not sure. if you left it dosconnected on the intake manifold side and didnt plug the hole, that would def cause a problem, but i dont know that itd even run?
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Old 11-03-2008, 01:35 PM   #16
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the egr tube is still connected to the egr valve on the intake manifold i just cut it because it was frozen solid on the exhaust manifold i even to use heat to get it off. it wasnt moving at all. yea if you could let me know what you think that plug is and try and take a picture of where yours is plugged in that would really help, and you think that it could have been the pressure that was being released that didnt cause the cat to glow before and now that there is no crack for the pressure to escape u think thats whats causing it. you dont think that this plug could possibly regulate the amount of fuel, and possibly that it is dumping fuel into the exhaust system, and causing the cat to heat up from the unburned fuel in the exhaust. thanks alot for all the help.
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Old 11-03-2008, 01:49 PM   #17
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the egr tube is still connected to the egr valve on the intake manifold i just cut it because it was frozen solid on the exhaust manifold i even to use heat to get it off. it wasnt moving at all. yea if you could let me know what you think that plug is and try and take a picture of where yours is plugged in that would really help, and you think that it could have been the pressure that was being released that didnt cause the cat to glow before and now that there is no crack for the pressure to escape u think thats whats causing it. you dont think that this plug could possibly regulate the amount of fuel, and possibly that it is dumping fuel into the exhaust system, and causing the cat to heat up from the unburned fuel in the exhaust. thanks alot for all the help.
Oh boy, a 'solution' to a non working part is not to cut it off and ignore it, they don't go away, not when the emissions and fuel system is concerned.
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Old 11-03-2008, 02:38 PM   #18
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i called a local mechanic and he said that cutting the tube would not have anything to do with it running rich or dumping fuel into the exhaust system i really think that it is the pressure that is not being released because of the new manifold not leaking any pressure and there possibly be a clogged cat or it is the plug. the mechanic did not think that it had anything to do with the tube. so its either the cat is clogged and the pressure that is not being released or the plug may have something to do with regulating the amount of fuel being used. ( fuel control) thanks if anyone knows anything let me know.
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Old 11-03-2008, 05:00 PM   #19
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bump bump anyone know where this plug could go
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Old 11-03-2008, 06:56 PM   #20
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it goes to the power steering high pressure hose
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Old 11-03-2008, 08:01 PM   #21
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theres a pressure sensor/switch thing on the hp steering hose. i think its sposed to bump up the throttle a little bit when your on the steering. it wouldnt affect the issue you're having. id start looking hard at the cat imo.
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Old 11-03-2008, 08:52 PM   #22
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it doesnt have power steering i traced the wire back and the 2 wires go to the carb. one is red one is black. i pretty sure it is like a fuel regulator. ill try and get pictures up tomorrow of where in the carb the 2 wires go to
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Old 11-03-2008, 08:54 PM   #23
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Now that you know were the plug goes,,,now focus,,,, the cat needs to come off for inspection.If it is clogged they can reach temps 400 degrees and above.Cut it out and see if you can see light through it while holding toward a light or the sun or what ever just see if you can see through it.If you look down in it and it looks melted then you are and have been running way rich for a while.I it is just all broke loose inside causing the blockage that is normal for one its age to do this but it is not usable.If you have either one of these then replace the cat if you have to pass testing,,, if you show signs of melting get that rich problem fixed before the cat is replaced.If it is open then you have problems someplace else and can reuse the cat.
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Old 11-03-2008, 08:57 PM   #24
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Oh boy!!!back to square one.
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Old 11-03-2008, 09:00 PM   #25
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Lay the hood all the way back on the windshield and climb up on the tire and look it over real good to see if you can find the terminals that it plugs into.
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Old 11-03-2008, 09:01 PM   #26
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it doesnt have power steering i traced the wire back and the 2 wires go to the carb. one is red one is black. i pretty sure it is like a fuel regulator. ill try and get pictures up tomorrow of where in the carb the 2 wires go to
thats probably why its not connected

the fuel pressure regulator is just a diaphragm built into the throttle body, theres no wires involved.
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Old 11-03-2008, 09:13 PM   #27
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Old 11-03-2008, 09:14 PM   #28
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totally possible mine is in the wrong place (previous owner did some weird chit) but, all the same, mines not glowing red
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Old 11-03-2008, 10:11 PM   #29
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thanks alot for taking those pictures man, but the pics are a little dark could you tell me where exactly the plug plugs in. sorry was just a little hard to tell i was out there for awhile looking for where exactly it plugged in.
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Old 11-03-2008, 10:13 PM   #30
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if you follow the high pressure ps hose, right where it transitions from rubber to metal line, there is a plug built into the hose, just above the ps pump.

sorry for the crappy pics. i used my cell phone and a flashlight LOL

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