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Discussion Starter · #1 ·
I have a '97 Jeep TJ with the 2.5l and 5-speed; it has 101k on it right now. A while back I had a problem with it dying on me going down the road, taking off from idle, sometimes even while idling, and it idled rough. Since then I have replaced the entire exhaust (the manifold had a crack and the catalytic converter was breaking up), the throttle body, all 4 injectors, the TPS, the MAP sensor, both O2 sensors, the distributor, cap, rotor, spark plugs, spark plug wires, coil, thermostat, air filter assembly (went with a Rock-It Parts system), the battery, and went over the vaccume lines. Now; it stumbles at idle; and it backfires and stumbles between shifts; especially once you accelerate in the next gear. While it is idling you can hear it "hiss" each time it sends fuel to the injector's fuel rail and I don't know if this is normal or not. It never causes the "Check Engine" light to come on when it stumbles and backfires, either. I hope sopmeone can give me some fresh ideas; I feel as though I am just throwing money at it.
 

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Discussion Starter · #3 ·
I actually have considered that; in fact, shortly after I submitted this post I got to thinking; when the problem started I had a leaking valve cover; the cover was loose in the back so I had a stream of engine oil running down the driver's side of the engine; the same side as the CPS. Could engine oil cause it to misread the signal?
 

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I was gonna say check your timing but that would make more sense. Oil can mess up your cps yes. Good luck /ubbthreads/images/graemlins/smile.gif
 

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And it's about the only thing you haven't replaced...
 

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Discussion Starter · #6 ·
I will remove my CPS and look it over; I had just thought it was one of those things that either worked or it didn't; and since the Jeep would start and run I thought maybe it was allright. But as I mentioned yesterday; I didn't think about the oil leaking on it until after I submitted my original post; I am sure that it can mess it up just enough to cause it to run like it does.
 

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Even without oil they can be very nasty causing hard starts and rough idling...
 

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Have a look at the connector to it - seems to be a problem area too.
Disconnect the connector, clean it, put back together.
 

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What happens when your timing chain goes in an OBDII engine /ubbthreads/images/graemlins/confused.gif That is, ...just stretched or jumped a tooth?? Would it mistime the spark and fuel squirt (spark is from the crank sensor ..fuel is from the cam sensor).

what happens??
 

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Discussion Starter · #11 ·
That was another problem I was hoping it did not have; I really don't feel like replacing the timing chain/gear assembly.
 

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Discussion Starter · #12 ·
By the way; if you want to get factory Jeep parts at a discounted price, shop www.jeepoemparts.com; it is a dealership in south Texas that I get most of my parts through. For example; Autozone wanted $104.99 for my CPS; I ordered the oem CPS for $79.79 from these guys.
 

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[ QUOTE ]
That was another problem I was hoping it did not have; I really don't feel like replacing the timing chain/gear assembly.

[/ QUOTE ]

Just rotate the crank while watching the rotor. I think you've done just about everything else.
 

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Should have taken the lower price back to Advance. They will price match. Saves time and shipping fees.
 

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If you are worried about the chain being loose -
Key off!
Rotate the crank by hand in any direction at least 1/4 turn, stop at TDC. While watching the distributor rotor closely, rotate the crank back in the other direction slowly until the rotor just barely moves in the opposite direction.
Mark that spot on the damper. The distance it moves - read it in degrees - a new chain will be about 4-6 degrees, a normally worn chain may be up to 10. Over 12 needs replacement, 15+ means it'll jump soon.
20+ means you are on a lucky streak - time to go to Vegas!
 

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Discussion Starter · #16 ·
I may have to try that; there was a noticeable difference in how it ran after I replaced the CPS, but it still backfires and stumbles between shifts. I also checked the fuel pump assembly (drained the gas, removed the tank, removed pump assembly, looked for debris in tank, checked fuel strainer, and refilled with fresh gasoline). While idling it drops RPM and comes back about every 3-4 seconds, but it does not die. Still no Check Engine light. Just out of curiosity; what kind of problems would a small exhaust leak at the stock exhaust manifold collector flange cause? I don't really notice a leak during idle; but I hit a small bump in the road and heard some exhaust noise come from the front for a split second.
 

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That flange is ahead of the O2 sensor, so a leak there could really affect it.
Try wiggling/shaking the head pipe while it's running - listen.

Another way that MIGHT detect if it's leaking -
At night or a dark garage - shine a strong narrow beam flashlight around the possible leak. The strong light beam against the dark background can show the smoke from it. You can shoot some WD-40 or carb cleaner in the intake to help it smoke more to see it.
 

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I'm also thinking the steppermotor could be too slow. Did you clean the TB with some carb cleaner or remove the steppermotor to give it a thorough cleaning? The idle bypass can clog up really bad. But the backfiring also indicates a leak somewhere...
 

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Discussion Starter · #19 ·
[ QUOTE ]
I'm also thinking the steppermotor could be too slow. Did you clean the TB with some carb cleaner or remove the steppermotor to give it a thorough cleaning? The idle bypass can clog up really bad. But the backfiring also indicates a leak somewhere...

[/ QUOTE ]

By steppermotor I am guessing you mean the Idle Air Controller (IAC)? I have not replaced that; I installed a brand-new throttle body, MAP sensor, and Throttle Position Sensor (TPS) but the new IAC that came with my throttle body was for a later model Jeep. So, I cleaned up the old IAC with some throttle body cleaner before I reinstalled it. I really don't know how to test it to see if it is malfunctioning; I have never had one go bad so I don't know the symptoms, either.
 

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Discussion Starter · #20 ·
Also, I noticed that once I reset the computer (By disconnecting the battery terminals for several minutes) it runs fine for a few minutes until it warms up; then it starts in again with the problems.
 
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