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Problem that has Me and My Mechanic Stumped...

E

EASportsRacer13

NAXJA Forum User
Location
Phoenix, AZ
Alright, its a stock XJ which recently (6 months or less) had the radiator, waterpump, and thermostat changed.

Here's the propblem...Every other day or so the Jeep loses A LOT of power from the engine. I mean A LOT. Normally if you floor it and go "pedal to the metal", an XJ hauls, I can almost break the tires free. But sometimes I have no acceleration at all. It will literally take 10 seconds to get to 25mph...and that is when I have the accelerator floored.

Now heres where it gets weird. When the car runs normal...the temperatur stays at about 180-200 F but when I am having this engine drain it over heats very quickly. With the heater running I am driving right at the red line of temp.

I took it to my mechanic and he could not recreate the problem, but it happens intermitently but now more frequently. It is full of coolant and had an oil change 3000 miles ago. The emergency brake is not on...
 
I'd suggest you check the catalytic converter to insure it is not damaged internally.
Sometimes, hitting the bottom with your fist will result in a rattle; that could indicate internal deterioration.
I had a similar problem with my '88 many years ago. The symptoms included no power after the engine came up to temp. I could barely get to 60mph, and climbing a steep hill took "pedal to the metal" just to maintain 50!
Turned out to be the cat. It appears the honey cone interior would "warp" when warm, causing the cat to "clog".
Gutted the cat and all was well.
 
poorboy_616 said:
You may have a catylitic converter that is breaking up and plugging off the exhaust flow.

Our van did about 2 years ago. Just replace the cat....
Click to expand...

I forgot to say that the CAT was replaced 6 months ago to the day...my reg. just expired
 
Are any of your other gauges reading weird? Any codes?
Im thinking maybe a bad ground thats messing with your injectors and temp sensor.
I dont know what year it is but could be a clogged fuel filter causing a lean condition, which may cause overheating.
 
Check the muffler for a loose baffle. It's an old school symptom of a bad exhaust component from the days before stainless. Mufflers did that a lot when they were cheap carbon steel.

A potato shoved in the exhaust simulates it well. Worst case, it won't even start. It's a very old practical joke. Dinosaurs didn't like it all, but men were men back then.
 
Um, is the voltage reading low at the same time?

Sounds to me like the serpentine belt might be slipping. Check that the belt is tight and none of the bearings in any of the pulleys are siezing/loose.

Does it coincide wih the AC being on?

Bearings in AC compressor could be going bad causing drag on the serp. belt and causing it to slip.
 
It sounds like a exhaust restriction of some kind. Good Luck
 
Could be a blown head gasket too. I know you said the coolant is full, but sometimes instead of coolant leaking into the combustion chamber, the explosion leaks out into the coolant. It might not exactly burn or evaportate the coolant and the extra pressure would just squirt into the overflow tank.

Your throttlebody or injectors are over loading.
Click to expand...

Is this a joke?
 
Has to be a bad cat. If the engine is running rich for any reason, like a bad O2 sensor, or other defective sensor leaving it in open loop the cat sees to much fule, overheats and the honeycomb breaks loose or melts. When it gets loose it will bounce around and periodically flow normaly and then turn 90 degrees blocking the exhaust. A loose bafle in a muffler, or delaminated exhaust pipe flutering in the wrong direction can also intermittently block the exhaust flow.

Has it been running rich, and has gas mileage got real bad? If yes, I'd bet on a bad sensor making it run rich and burned up cat as a result. Been there done that. Had a bad pipe do it 25 years ago, a bad muffler do it 30 years ago, and a bad cat do it do it 3 years ago.
 
igotanxj said:
Could be a blown head gasket too. I know you said the coolant is full, but sometimes instead of coolant leaking into the combustion chamber, the explosion leaks out into the coolant. It might not exactly burn or evaportate the coolant and the extra pressure would just squirt into the overflow tank.

Is this a joke? injectors overloading
Click to expand...
i
i meant to say it sounds like its getting to much fuel and not enough air air
 
We need to know the year and type of engine, without this we're just shooting in the dark.
 
Hate to say it, but I'm with the CAT crowd. Get under there and shake the thing (when it's cool). Does it sound like a box o' rocks?

Universal CATs are pretty cheap, and are a great temporary (or even permanent) fix. At least look at it, seems like the symptoms point in that direction.
 
poorboy_616 said:
You may have a catylitic converter that is breaking up and plugging off the exhaust flow.

Our van did about 2 years ago. Just replace the cat....
Click to expand...
this happen to me as well and wasnt constant, happen like you said every other day or so. Took it to the shop and the exhaust guy told me i had pieces of my cat actually moving foreward and not backwards so it was really clogging my heep. Once i got a new cat i was able to spin the 35's no problem, you might want to look into that.
 
I found pieces of the cat both forward of the cat, and in the muffler.

I ended up replacing the muffler due to the pieces lodging inside and not be removable.

The van (94 Chrysler Town & Country 3.8L V6) now has a Dynomax Turbo muffler. Sounds good, even if it is just the grocery getter.....
 
Some exhaust shops should be easily able to determine if the cat is bad by drilling a small hole in the exhaust before the cat and then after and then reading the pressure difference between the holes. Then just welding the holes shut with a small bead.
 
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