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  #1  
Old 12-14-2015, 09:45 PM
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2001 Jeep Grand Cherokee rough start but then runs fine

Trying to diagnose what's wrong with my Jeep. Very slow and tough to start. Once it fires it runs great however MPG's are awful! The plugs have been replaced. Any ideas? Fuel pump? Sensor of some sort?

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  #2  
Old 12-14-2015, 11:27 PM
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Re: 2001 Jeep Grand Cherokee rough start but then runs fine

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Originally Posted by matt337 View Post
Trying to diagnose what's wrong with my Jeep. Very slow and tough to start. Once it fires it runs great however MPG's are awful! The plugs have been replaced. Any ideas? Fuel pump? Sensor of some sort?
Welcome to the garage.
If you have a fuel pressure gauge, you could check the fuel pressure first, or just change the filter/pressure regulator. If this unit allows the fuel to return to the tank after shutdown, then it will take several seconds before the engine will start. Also a bad regulator can cause a too low fuel pressure. The spray pattern at the nozzles will not be good, which will negatively influence the mpg.
It can eventually be the fuel pump, but i would start with the cheapest part first.
The filter/regulator sits just in front of the fuel tank, on the left hand side. Can be a pain to get the "quick disconnects" loose after many years of dirt, water and salt did their thing. I recommend to spray the three connections with WD40 or some other type of lubricant a day before trying to loosen them, it will make live much easier. Just changed mine (and the fuel pump module) few weeks ago and the lines came of without too much struggle.
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Old 12-15-2015, 03:12 PM
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Re: 2001 Jeep Grand Cherokee rough start but then runs fine

Thank you! Gives me some place to start. I will update when I figure it out for future folks who have same issue.
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Old 12-27-2015, 06:44 PM
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Re: 2001 Jeep Grand Cherokee rough start but then runs fine

Matt I'm having the same problem with my 01 GC Ltd. only 71k it runs fine at cruising speeds but tough to crank then stumbles a little and has even stalled. I've replaced the TPS and IAS but didn't help much if any. Did you find out what was causing your problems? I'd greatly appreciate any help. I have just bought this thing it's in amazing shape for its age, this just started yesterday. Thanks to anyone that may be able to help.
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Old 12-27-2015, 06:45 PM
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Re: 2001 Jeep Grand Cherokee rough start but then runs fine

[QUOTE=Hogslayer45;1249470]Matt I'm having the same problem with my 01 GC Ltd. only 71k it runs fine at cruising speeds but tough to crank then stumbles a little and has even stalled. I've replaced the TPS and IAS but didn't help much if any. Did you find out what was causing your problems? I'd greatly appreciate any help. I have just bought this thing it's in amazing shape for its age, this just started yesterday. Thanks to anyone that may be able to help.
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Old 12-27-2015, 08:31 PM
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Re: 2001 Jeep Grand Cherokee rough start but then runs fine

Yes, It ended up being fuel pump. We replaced the pump and filter assembly and it now fires up at start, idles smooth and runs smooth. Seems to have fixed the issue.
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Old 12-28-2015, 07:10 AM
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Re: 2001 Jeep Grand Cherokee rough start but then runs fine

[QUOTE=Hogslayer45;1249471]
Quote:
Originally Posted by Hogslayer45 View Post
Matt I'm having the same problem with my 01 GC Ltd. only 71k it runs fine at cruising speeds but tough to crank then stumbles a little and has even stalled. I've replaced the TPS and IAS but didn't help much if any. Did you find out what was causing your problems? I'd greatly appreciate any help. I have just bought this thing it's in amazing shape for its age, this just started yesterday. Thanks to anyone that may be able to help.
I would start changing the fuel filter/regulator. Besides its cheap, its also outside of the tank and not too difficult to change and many times its the problem. Eventhough the pressure will bleed away after shutdown (will take some time), the filter/regulator should keep the fuel lines full of fuel and should prevent it from flowing back to the tank. Hard starting is many times caused by air in the fuel lines due to drain back. Eventually a bad O´ring in the fuel pump module can be the problem as well. If it even runs bad after warming up, it could be a bad fuel pump, delivering a too low pressure, Had this happening on my jeep and got a check engine light due to a too lean mixture. You will see the LTFT (long term fuel trim) figures maxing out at around +32% when you put it on a scanner with live data.
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Old 01-04-2016, 07:47 AM
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Re: 2001 Jeep Grand Cherokee rough start but then runs fine

wy my jeep grand cherokee have o/d off active i dont need and i can't desactive and dont go more thant 60km

---------- Post added at 12:47 PM ---------- Previous post was at 12:44 PM ----------

pleas i need some answer my mecanic have change the drive box and i have the same probleme
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Old 01-04-2016, 08:48 AM
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Re: 2001 Jeep Grand Cherokee rough start but then runs fine

Welcome to the garage.
Which engine/transmission?
Depending on which engine/transmission, the switch signal goes to the TCM (transmission control module) for the 4.7L, or to the PCM (powertrain control module) for the 4.0L. First the switch function must be checked, if ok then the wiring be measured for continuity between the switch and the TCM/PCM.
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Old 01-04-2016, 09:02 AM
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Re: 2001 Jeep Grand Cherokee rough start but then runs fine

thanks and why warming causes massive box automativo change the engine 2001 jeep cherokee 3: 100 and not going 80km / h
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  #11  
Old 01-04-2016, 09:33 AM
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Re: 2001 Jeep Grand Cherokee rough start but then runs fine

Does your jeep have the 3.1L diesel engine? Any idea which transmission it has?
What happens after warming up?
Is the check engine light on? Was the jeep already put on a scanner to check for any fault codes?
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