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Hypocrisy_Central's avatar

Gutless low power Jeep Cherokee Sport with fuel injected straight 6 what is up with that?

Asked by Hypocrisy_Central (26798points) August 11th, 2010

What I want to know is what is the possible cause of why my Jeep Cherokee Sport ’97 lacks power and umph when it gets to regular operating temperature? I will try to be brief with the details but here is the particulars.

My next door neighbor had the Jeep, he use to drive it to work about 26 miles away. It started to over heat, the tappets would get noisy and then the thing would putter to a stop. He was always adding fluid so he thought he blew a head. He offered it to me for a mere $150 I wish it were the heads because it would be a straight forward problem. It turned out to be more sticking thermostat and failing water pump was the problem. So, I replaced them, over heating problem solved. However, when it was overheating it had power, I could go ripping down the freeway and keep up just not very far because the Jeep would overheat. Now that it doesn’t overheat it runs too rich I know, I seen the signs when I replaced the plugs, cap and rotor. Since the lack of power was not the cap, rotor, and plugs which were indeed bad and replaced or a bad fuel filter I am thinking it maybe the fuel pressure regulator because it is running too rich as oppose to starving of fuel. With your mechanic brain what do you think? Vehicles with a 6 cyl. (straight), fuel injection that loses power can most likely be what? And I have put better octane fuel in it, and injector cleaner and performance still has not improved after the engine warms up, same old sputtering and stalling. What do you got, I am kinda stumped?

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10 Answers

Tropical_Willie's avatar

You need to take it to a garage with diagnostic equipment.
It may the the black box for the fuel system, it may be the O2 sensor, it may be the timing….... You can throw many dollars at it without fixing it.
Find what is wrong/broken and replace it. Get it to a garage.

tedd's avatar

There’s a list of things that could be wrong. To me it sounds like something is up with your fuel injection system. Assuming that its not just completely stalling out once it reaches running temp, it could just be that theres some added draw to your engine from the new water pump (a stretch but who knows?).

As stated @Tropical_Willie get it to somewhere with diagnostic stuff and see what it says. You could also try finding a jeep enthusiast website, maybe someone there has faced this problem before.

IchtheosaurusRex's avatar

Since this is an OBD II vehicle, I would start by tapping into the computer and find out what it’s doing. I have this. Since you can use it with any vehicle built since 1996, it’s worth having as a diagnostic aid.

Sputtering and stalling can be any number of things. EGR valve, faulty position sensors, ignition timing off – really no way to tell without more information.

ApolloX64's avatar

A clogged catalytic converter will cause this problem 85% of the time. As soon as you said “lacks power and umph when it gets to regular operating temperature” that flagged it. Definitely get your exhaust system checked, have a diagnostic run on it. A Cat won’t always set off the engine light and may trigger a bad O2 sensor reading. The overheating issue the vehicle had before probably caused the catalyst to melt and form a blockage.
Easy way to tell is to take it for a drive in the evening for about an hour then go home and as soon as you park it look underneath at your catalytic converter, if it’s bright red hot then you know for sure it’s clogged, I speak from personal experience on this one.
The AMC straight 6 is one hell of a workhorse engine designed to go through a lot of shit, it takes a long time to destroy one even if you don’t maintain it.

tedd's avatar

It sounds like @ApolloX64 knows what he’s talking about, that makes perfect sense to me. For the record though, no part of your car should ever be glowing bright red hot, :)

IchtheosaurusRex's avatar

@Hypocrisy_Central , just to ask a stupid question, but isn’t your Check Engine light on right now? If it isn’t, it’s either burned out or somebody pulled the wires. @ApolloX64 has good advice, but a toasted cat will throw multiple codes every time. Get them read, and all will be revealed. If you don’t want to spend the money on a scanner, you can get the codes read at AutoZone for free.

Hypocrisy_Central's avatar

@IchtheosaurusRex If I owned a laptop I would sure invest in that software. The “check engine” l,ight was on until I changed the plugs, cap, and rotor, but has not seen it on since. I think I will try the Autozone option make my being in their rewards program worth something at least.

@ApolloX64 I would love to get that beast to run (and be drivable) for 60 minutes. About 2 miles down the road from a cool, dead stop the sputtering and loss of power crap happens. I know it has to be fuel, and somehow connected to heat, but why the heat effects flow etc, I can’t figure.

IchtheosaurusRex's avatar

@Hypocrisy_Central , did you by any chance disconnect the battery when you changed out the ignition components? That will reset the CEL but it won’t clear the trouble codes, which is actually good news since they can tell you more about what’s wrong.

Hypocrisy_Central's avatar

@IchtheosaurusRex Atcually I did, the repair book suggested it because the fans are eletric and can operate independently of the engine running so to minimumize the risk if getting whacked by the fan starting for any reason to disconnect the ground terminal. Good thing the codes are still stored I was wondering about that.

kritiper's avatar

The piston rings have lost their tension due to the overheating. You need a ring job or a new/different engine. See your mechanic and have him perform a compression check with the engine at operating temp. If it checks as good, follow the advice of ApolloX64 above.

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