offroader1580

I have a 98 jeep grand cherokee I6 stock exhaust and the cat and muffler glow red when you are going and the temp gauge reads 1/4 of the way. at that point the engine also starts to missfire and tries to stall. However if you let it idle it will run just fine all the way to temp. What could my problem be???? I have tried new cat, new muffler, new 02 sensors, new spark plugs, and new crank positioning sensor.

OverlandZJ

Wonder if something broke inside the cat or muffler and is now lodged in the tailpipe.

Usually this is a typical clogged cat symptom.

OrvisKrawler

x2, sounds like you have blockage somewhere in the exhaust, since youve replaced the cat and muffler its gotta be something to do with the tail pipe

xxlcherokee

Are you dumping gas? Sounds like a vehicle that I had that had bad distributor caps and was dumping gas, killed the cats and fouled my O2 sensor our.

Bustedback

Your cat converter is in melt down and clogging the exhaust, which causes the engine to run hotter while under load.

jeep-e

I had the same problem & symptoms recently. 96' gc I6. After a new cat, muffler & o2 sensor I traced it to a fouled out plug (#1) All 6 were new, but done before exaust repair. Its a cheap, easy check & or fix. Also cheap & easy is to make sure your firing order is correct & check your factory trouble codes. Autozone will check them for free if your check engine light is on & be able to pinpoint it alittle more. Good luck & keep us posted.

jnicewan

x2 for misfires, a leaking injector can do it too. The thing is a rich condition doesn't cause the heat, but excessive fuel will destroy and then restrict a cat which then could cause the heat. A excessive lean condition will cause cause very high combustion temps and an exhaust system to glow but you should see it glowing the from manifold (possibly particular cylinder ports) and maybe some length of the tailpipe behind the manifold). If the exhaust was restricted to the point of causing the system to glow, you should also notice a loss of power on the top end, I have seen convertors restricted so bad the engine would barely run and even idle, even had a couple where it wouldn't even start (fouled plugs)

CRoading

One of my wheeling mate had the same problem like this one... Hope someone has the solution so I can share it to him...

freegdr

def sounds like raw unburned fuel is getting into the exhaust and heating every thing up ,is the exhaust tail pipe have a lot of black soot in it

dave1123

Sounds to me you've got a furnace in your cat! For whatever reason, raw gas is maintaining a flame in the convertor and will eventually melt the matrix and cause it to plug. Also, as the matrix fails, it will plug your muffler as well. Check out the source of you "over-rich" exhaust QUICKLY before it sets you vehicle on fire!

poorstang

It also could be moisture in the distributer cap

offroader1580

Got a new cap and rotor and still glowing red, however it is not not glowing as red as it used to and its taking longer to glow red. This problem started when my brother got gas and sat in the meijer parking lot and then it started acting funny....the rpms were fluctuating a lot and then it would stall. We have run the jeep without the muffler back and the cat still glowed red. Thanks for the tips though, I really appreciate them!

2Evil4U

It would be interesting to know what the ignition timing is running at when it's doing this. (A scan tool should be able to tell you this.) I know it's not adjustable and is controlled by a computer, but I can make the headers on a small block chevy glow nicely by retarding the timing significantly. The fuel burns out the exhaust rather than in the combustion chamber.

offroader1580

That never crossed my mind till u said something that my timing might be off. Is there a way to regulate fuel pressure on a 98 gc? One of my buddies wants to do a fuel pressure test.......

jnicewan

Fuel pressure is tested at the injector rail, you will see a pressure tap port thats looks much like a tire valve and its between #2 & #3 injectors. You should note running pressure and leakdown specs.

running pressure should be 49 PSI +/-5 PSI
leakdown pressure should not drop approx 10 PSI in 5 min

With your jeeps condition, if you have leakdown I would suspect an injector. Its pretty easy to remove the injector and rail assembly from the intake. I think you will only need to remove the cables at the throttle body and the cable bracket. You shouldn't even need to remove the fuel supply line, just swing/pivot the rail up on the fuel line connection. What I would do with the injector rail up and out is, turn the key to run and inspect the injector tips for leakage/spray.