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05/30/10, 05:32 PM
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Join Date: May 2010
Posts: 113
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any auto mechanics out there?
any auto mechanics out there? i have a 1990 jeep that is giving me fits. it loses power when i accelerate, go up hills, or pull a trailer. i have to just about floor it to get it accelerate and then it'll roar to life and then lose power again a few seconds later. when i first jump in it in the morning, it runs fine for about 8 minutes, until it is all warmed up, then it starts to fail and get worse. i have replaced all the plugs, the cap, and the rotor as well as the fuel filter. could it be an O2 sensor? any ideas? my wife tells me its time for a new truck but im not ready to give up on it quite yet. thanks for any ideas!
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05/30/10, 08:27 PM
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Rockin In The Free World
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Join Date: Feb 2007
Posts: 1,058
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A bad coil will do that. Also, if the vehicle has a cat converter, you may want to make sure its not plugged. I'm not a mechanic, just a backyard hack.
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05/30/10, 09:57 PM
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Join Date: Dec 2002
Location: East TN
Posts: 6,977
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I'm out there.
A jeep what with what engine? Can you check fuel pressure? Is the check engine light on? Any stored codes?
__________________
"Education is the ability to listen to almost anything without losing your temper or your self confidence"
Robert Frost
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05/30/10, 11:25 PM
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Join Date: May 2010
Posts: 113
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the check engine light is not on. i shouldn't admit this but i cut the cat convertor out with a torch because the muffler rusted off of it and i couldnt afford to replace it. i just ran flex pipe out of the muffler. im not sure how to check fuel pressure except for that little button there on the fuel rail. if i push that with a screw driver a high pressure spray of gasoline shoots out. i thought that it might be the fuel pump but usually they completely fail all at once dont they? how do i check if the coil is bad? thanks a lot for the help.
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05/31/10, 12:22 AM
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Join Date: May 2004
Location: Minnesota
Posts: 17,225
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Does it have a carb or a fuel injector?
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Flaming Xtian
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Libertarindependent
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05/31/10, 02:38 AM
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Join Date: Oct 2006
Location: Upstate NY
Posts: 479
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I'm thinking like OnterioMan. Coils have a way of acting like just about anything but a coil when they get tired. Mike
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05/31/10, 07:46 AM
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Join Date: Feb 2005
Location: Wisconsin
Posts: 110
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I would be watching fuel pressure. Install a gauge with a hose you can wedge under the wiper blade or something and take a drive. I had one of these Jeeps with the 4.0L. The fuel pressure regulator on these can cause this type of symptom. The gauge we had installed on the schrader valve on the fuel rail and had about 4' of rubber hose on it. I don't remember what the pressure was but it should remain fairly constant. Just my opinion based on some of my own experiences.
Good Luck
Theront
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05/31/10, 08:09 AM
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Join Date: Dec 2002
Location: MO
Posts: 935
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hi
if your not getting any engine code, the first thing I would check is the fuel filter. A partially plugged filter has those same symptoms, runs ok on level ground and down hill but nearly quits going up hill or with a load.
Its pretty easy to get bad gas today, if you fill up while a tanker truck is filling the bulk tank your getting fuel out of, you can pick up all kinds of dirt and garbage that can plug a filter real quick. If thats it be sure to check your tank for water in the bottom too, it will burn but can cause problems in certain systems. most any other problem should send a code to your check engine light, best wishes, ray
P. S. as Ontario man suggested a plugged catalytic converter can do the same type thing, if its not the fuel filter see how much exhaust you have coming out when it nearly stops running, the plugged converter is like sealing the exhaust, an not allowing any exhaust to leave the engine and builds up a back pressure until the engine just can't run because there is more back pressure in the engine than it can handle. kinda like putting a potato in someones tailpipe, it just kills the engine or dogs it down till it can't run.
make sure nothing is plugging the air filter after these steps.
An engine only has fuel, air, and spark, to run, these newer computer controlled engines are harder to troubleshoot without a code, but there are only a few places to look. its got to have enough gas and air at the right time in the piston, then the spark has to be hot enough to fire. if it keeps running all the time but is loosing power it sounds like the timing might be off. you lose power when the piston is firing at the wrong time. if it gets too far out of time they can actually backfire, either through the carburetor, or air breather, or the other way it can backfire through the exhaust.
there is also a fuel mix chip on some engines that read the MAP or "manifold absolute pressure" oxygen sensor, etc. and adjust the amount of gas to send to the injectors or fuel sys. it kinda learns what fuel you use, and adjusts itself for optimum efficiency, if you change fuel types drastically. like you use 87 octane for a year then switch to high test all the sudden the chip has to learn the most efficient air fuel ratio all over again, and starts changing air fuel amounts, so with these systems its best to stay with one type fuel all the time.
As you see there are a few different things you can look at, just decide which it sounds like the most and start there, best wishes, ray
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Ray
Last edited by Ray; 05/31/10 at 08:41 AM.
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05/31/10, 12:43 PM
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Join Date: Jan 2005
Location: NC
Posts: 622
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Another question for you...when it loses power, are there any other symptoms? Bucking, backfiring, coughing back through the carb, clackety noises, pingy noises?
My first guess is that it is a clogged fuel filter. It only fails when you're demanding lots of gas.
Replace the gas filter, shake the fuel backwards out of the old one to see what all is in there, then just drive it. If it's not fixed, you could take the fuel line off the carb/fuel rail/throttle body and put it in a jar and turn the key to turn on the fuel pump and see how much fuel it is capable of delivering. If it's too low, suspect the fuel filter in the tank.
Diagnose by blowing backwards thru the fuel line to dislodge all the stuff and retry the volume test. If it passes, the fuel filter in the tank is clogged.
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06/01/10, 08:03 AM
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de oppresso liber
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Join Date: Sep 2006
Posts: 13,900
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Change the fuel filter and see if that fixes it. It sounds like that's the problem.
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Remember, when seconds count. . .
the police are just MINUTES away!
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06/01/10, 06:28 PM
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Rockin In The Free World
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Join Date: Feb 2007
Posts: 1,058
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From the original post, it appears that the fuel filter has already been changed and the problem continues.
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06/02/10, 06:36 AM
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Join Date: Dec 2003
Posts: 3,693
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It would help if you'd specify Wrangler or Cherokee, and if it's the fuel injected 4 cylinder, the carburetor equipped straight 6. But since the straight 6 was the most popular, I'll suspect that, with a carburetor and mechanical fuel pump.
Fuel pump is quite suspect. They do go bad and produce inadequate flow. If you're unfortunate, it produces just enough flow to keep the carburetor bowl full under light loads, but not enough for heavier loads. This causes weak knees under load, with the resulting bogging and surging and such. Disconnect the fuel line from the carburetor and check flow while cranking the engine on the starter motor.
Dirty or maladjusted carburetor is also suspect. Especially if someone has been monkeying with it.
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06/02/10, 08:17 AM
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Registered User
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Join Date: Feb 2010
Posts: 18
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Almost 99% certain this is the fuel filter, seen it a hundred times on vehicles I have fixed and driven, runs fine flat or downhill but dead going up and sometimes simply after warmup as that clog catches again once you get going. BUT since you changed that already I dont know what else it could be but a coil problem.
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06/02/10, 09:02 AM
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Join Date: Nov 2008
Location: Southern Indiana
Posts: 730
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Sounds something like a head gasket, but you didn't mention any oil in the water or milky color in the oil or smoke out the pipe, did you?
It is not overheating is it?
Some jeep models are kind of bad about this...
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06/02/10, 09:58 AM
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de oppresso liber
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Join Date: Sep 2006
Posts: 13,900
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Still sounds like a fuel flow problem. Since the fuel filter has been changed I'd check the fuel flow. Could be the fuel pump or a clogged fuel line.
__________________
Remember, when seconds count. . .
the police are just MINUTES away!
Congress has no power to appropriate this money as an act of charity. Every member upon this floor knows it. . .Davy Crockett
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06/02/10, 02:30 PM
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Join Date: Nov 2008
Location: Southern Indiana
Posts: 730
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Could have two filters, an inline under the hood and a larger steel one back by the tank?
Did we decide if it was carb or EFI?
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06/06/10, 12:44 PM
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Join Date: Apr 2010
Posts: 168
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fuel injected inline 6 is my vote since he mentioned having a fuel rail.
I'm leaning towards the coil being bad. Runs good for few minutes then not. Sounds like the coil has a short in it that opens up as it warms up. my 2 cents
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06/17/10, 11:14 AM
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Join Date: Feb 2009
Location: WV
Posts: 3,268
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Replace the accelerator pump.
or the regulator on the end of the fuel rail.
Best regards,
Dave
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06/20/10, 04:57 PM
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"Slick"
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Join Date: Apr 2009
Location: Moving from NM to TX, & back to NM.
Posts: 2,329
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I have the same problem, except mine is a 1990 Mazda MPV 3.0.
__________________
We will meet in the golden city, called the New Jerusalem,
All our pain and all our tears will be no more.....
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06/20/10, 05:51 PM
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Join Date: May 2008
Location: Stockton, Ca
Posts: 44
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Since it is a 1990 the Engine light will only come on when it detects an open or short. Does it smell like fuel when the problems start? The reason I ask is because the cat converter is used to measure how much fuel is being dumped into the combustion chamber. Your O2 sensor sends the signal back to the computer telling it to add more fuel, or scale it back.. Like others have said you are going to have to put a fuel pressure gauge on the valve at your fuel rail, and tape the gauge to the windshield so you can see what the pressure is doing as you are driving. Good luck and let us know how this test turns out.
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