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Old 08-25-2010, 03:53 PM
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4.7 L v8 with starting issues?

I've got a 2000 jeep grand cherokee with a 4.7L v8 and i'm having a problem with this starting. Here are my symptoms: In morning when you go to start it, it seems to have a slow crank then it starts runs for 5 sec then shuts down if i dont use gas pedal to keep it running. But sometimes it starts fine after that and sometimes it has an extended cranking where i have to give it gas to start. Every now and then when your idling at a light the idle drops down like it going to stall but then comes back up to normal. The jeep has 141k miles on it with maintainence done every 30k. i've had it since 48k miles. The battery and alternator is charging fine at 13.7v. Battery voltage is 12.9v by itself. Checked connections at battery and starter and they are fine. Cleaned throttle body also. Could it be a starter, tps sensor, fuel pump?Anyone have any ideas? Anything is appreciated. Thanks.
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Old 08-25-2010, 04:08 PM
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Re: 4.7 L v8 with starting issues?

let's hope someone chimes in with help but I would suggest alternator
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Old 08-25-2010, 04:53 PM
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Re: 4.7 L v8 with starting issues?

When you cleaned the throttle body, did you pay special attention to the idle air control passage and did you remove the idle air control stepper motor? This is normally the point where a lot of oil and dirt collects and the air passage gets blocked.
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Old 08-25-2010, 05:12 PM
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Re: 4.7 L v8 with starting issues?

No didnt physically take throttle body off car just cleaned at the point where the blade closes to make sure it was fully closing. Should i take idle air control motor off of t.b.?If it was the alternator the battery light would come on in dash plus i wouldnt get 13.7v it would be much lower i think?
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Old 08-25-2010, 05:47 PM
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Re: 4.7 L v8 with starting issues?

The idle rpm is controlled by the idle air control stepper motor. This one regulates the air passage around the throttle blade for idle control. Most of the time oil and dirt starts blocking the passage, especially where the stepper motor plunger actuates. Remove negative battery lead and remove the stepper motor and use a throttle body cleaner to clean thorougly the air passage and the plunger from the stepper motor. Try not to spill any cleaning fluid into the stepper motor. After cleaning and installing the stepper motor, connect the battry lead again. When you do this, the stepper motor is going from full open to full close, for the PCM to remember those positions (steps). Now the PCM will put the stepper motor in a certain open position for the engine to start.This should normally solve your idle problems.
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Old 08-25-2010, 06:23 PM
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Re: 4.7 L v8 with starting issues?

Just cleaned idle motor and still slow crank then it started up. Then tried to restart it and got strong extended cranking then started. Any more thoughts? Thanks!
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Old 08-25-2010, 06:27 PM
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Re: 4.7 L v8 with starting issues?

Is there an access panel for the fuel pump or do i have to drop the gas tank and is there an inline fuel filter or is it built into fuel pump?
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Old 08-25-2010, 07:15 PM
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Re: 4.7 L v8 with starting issues?

You cleaned the idle air control stepper motor, but also the idle air passage, didn't you? You have to remove the air filter resonator housing to get good access to the idle air passage, which is just under the throttle blade.
To get access to the fuel pump, you have to lower the tank. I have done it myself, and it takes quite some time to do it. Best is to first change the fuel filter/pressure regulator, which is mounted just in front of the fuel tank.
Your check engine light is not on?
Did you check for any DTC fault codes? (ignition on/off 3 times and let it in on the last time. When no faults stored, DONE will be shown)
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Old 08-26-2010, 02:01 PM
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Re: 4.7 L v8 with starting issues?

Yes cleaned motor and passage way thoroughly. There are no codes because i checked with my snap on tester. I dont think i ever changed fuel filter, how often should it be changed? Does this vehicle have same problem with oring going bad on the fuel filter assembly?
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Old 08-26-2010, 05:10 PM
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Re: 4.7 L v8 with starting issues?

According the jeep manual there is no service interval for changing the filter/pressure regulator. You only have to change it when trouble shooting points it out as the problem.
I have indeed heard about an O-ring on the fuel pump which can become bad and cause low fuel pressure. So first check the fuel pressure and if not ok i should first change the fuel filter/regulator before dropping the tank.
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Old 08-27-2010, 10:19 AM
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Re: 4.7 L v8 with starting issues?

Figured out problem last night. The battery had a dead cell causing it to crank slow at first then crank normally after that. While i was diagnosing went ahead a changed spark plugs and now it starts up and runs great. Hope this helps out others down the road. Thanks again for all the members who helped.
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Old 08-27-2010, 10:46 AM
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Re: 4.7 L v8 with starting issues?

glad to know everything worked out for you
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