I got the idle problem diagnosed

TomEboi · 03-01-2001, 09:01 PM

Well, I took my 2000 GT to the dealer today and wanted to run this by you all. They say the reason my idle is hunting is that I have a bad fuel pump. Does this make sense to anyone? This kind of surprised me as I was not having any problems with acceleration. My problem occurred at idle with the idle hunting. The guy also said that when it was idling it should not have been so rough. What do you people think? Thanks

91LX2Bfast · 03-01-2001, 09:57 PM

I think it sounds like a perfect time to upgrade the fuel pump, lol. Well, if the dealer is doing warranty work, let them replace it and if its not fixed, the can always try again. But I have never owned a new car, so i may not be the one to talk about work under warranty.

------------------
1997 Thunderbird 4.6L: 2001 Mustang GT intake tube, SVT Lightning 80mm MAF, 7" Auto-physics powerstack filter, ram air, B&M 24,000GVW trans cooler, Custom chip, FMS 9mm wires, Dynomax exhaust, many more to come...

No Longer own: 91 LX 5.0L 5 spd Red w/ black interior
2 chamber flowmasters, Bassani off-road X-pipe, MAC cold air induction, Kirban short throw, Heavy duty 3 core radiator, FMS 3:73's, Timing bump to 14 degrees, SRP billet racing pedals, Kenwood sound system

thebean311 · 03-02-2001, 12:42 AM

Tom,

i had the same problem with my 2000 mustang GT. Turned out to be a loose hose. Check out http://www.users.qwest.net/~bpsilva/loosehose.jpg

to see which hose it was. It is the one circled in yellow. once i reconnected it, no more problems. It was weird because the hose seemed rather loose, and there was no hose clamp there or anything. It must have just been bumped out of place. Let me know of you have any other questions. thebean311@hotmail.com

95GTS · 03-02-2001, 07:07 PM

Whatever. Did they do a computer scan on it? How does your car run on the road? Does it miss out any, such as at a particular rpm range, or missing or "bucking around" during acceleration or so? If it does it could possibly be the fuel pump but I doubt it.

If it's the idle it's more like the TPS (Throttle Position Sensor) or IAC (Idle Air Control) or even a spark plug but more likely one of the other two. Take it back to them and have another mechanic work on it. They should run a computer scan which should tell them what's wrong with it. They can also hook up an oscilloscope machine and it can tell such things as spark plugs and wires and more engine detailed stuff. Have them do that first before they go screwing around and replacing a fuel pump that isn't bad.

I may be wrong but I highly doubt that it's the fuel pump. If they think it is then they can hook up a fuel pressure gauge and check it.

------------------
1996 Mustang GTS

[This message has been edited by 96GTS (edited 03-02-2001).]

95GTS · 03-02-2001, 07:19 PM

I just re-read your post again. I didn't notice that you said you were only having problems with idle and none while acceleration or driving.

It's not the fuel pump. No way. Take it back and have the computer scanned. It's not a spark plug because it would be running rough while driving. It's a computer/sensor problem.

------------------
1996 Mustang GTS

95GTS · 03-02-2001, 07:40 PM

thebean311: that tube is a crankcase ventilation tube which allows crankcase gases to be vented back into the air inlet tube to be sucked back into the engine to be burned up. All that is doing is relieving pressure. You could have the tube pointing straight up in the air and it shouldn't effect anything. It shouldn't make any difference on idle but if it did, oh well. Mine looks just like your pic, by the way. It sticks out a bit. It's not supposed to have a clamp or anything in it. It just slips in the hole.

------------------
1996 Mustang GTS

thebean311 · 03-03-2001, 02:05 AM

96GTS, you are right. In the pic, the hose is in the correct position. Before I slipped it back in, it was hanging off to one side. My car was constantly hunting while at idle. It would range between 400 adn 1k rpm. Once I slipped that hose back in (actually my buddy with a 5.0 noticed it), the idle hunting stopped completely.

Rocket 99GT · 03-05-2001, 01:16 PM

I had the same problem with my 99gt, they change the air sensor which helped a lot but I still have some "shaking".
I will check that hose in the engine.

MajorTwit · 03-07-2001, 03:06 PM

Thanks for the pic, thebean. My idle is a little rough, I'll look there first.

[QUOTE]Originally posted by thebean311:
[B]Tom,

i had the same problem with my 2000 mustang GT. Turned out to be a loose hose. Check out http://www.users.qwest.net/~bpsilva/loosehose.jpg

------------------
2000 GT 4.6 Stock

Y2KGT · 03-08-2001, 01:08 AM

I had the exact same problem with the hose being loose that bean was describing in his picture. All of the computer scans in the world will not tell you if the hose is loose.

I do agree with 96GTS in that it doesn't sound like a bad fuel pump. It sounds to me like your MAF doesn't know what to do and is trying to vary the voltage to the fuel pump at idle. If there is an air leak in between the MAF and the throttle body, your MAF will go nuts.

Sometimes the dealership mechanics miss the obvious. Besides, it will only take you about 2 minutes to verify if a hose is loose anyway.

------------------
2000 GT -- Black, 5sp, Mach460, Bassani CatBack & X-Pipe, MAC Cold Air, 70mm Tbody, Hurst Shifter
1966 Mustang Coupe -- Tahoe Turquoise, Pony Int, A-Code, C4 Auto
------------------
scott@pearland.com

03-01-2001, 09:01 PM	#1
TomEboi Registered Member Join Date: Feb 2001 Location: Altamonte Springs, Fl USA Posts: 12	I got the idle problem diagnosed Well, I took my 2000 GT to the dealer today and wanted to run this by you all. They say the reason my idle is hunting is that I have a bad fuel pump. Does this make sense to anyone? This kind of surprised me as I was not having any problems with acceleration. My problem occurred at idle with the idle hunting. The guy also said that when it was idling it should not have been so rough. What do you people think? Thanks

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03-01-2001, 09:57 PM	#2
91LX2Bfast Registered Member Join Date: Dec 1999 Location: Warrington, PA Posts: 694	I think it sounds like a perfect time to upgrade the fuel pump, lol. Well, if the dealer is doing warranty work, let them replace it and if its not fixed, the can always try again. But I have never owned a new car, so i may not be the one to talk about work under warranty. ------------------ 1997 Thunderbird 4.6L: 2001 Mustang GT intake tube, SVT Lightning 80mm MAF, 7" Auto-physics powerstack filter, ram air, B&M 24,000GVW trans cooler, Custom chip, FMS 9mm wires, Dynomax exhaust, many more to come... No Longer own: 91 LX 5.0L 5 spd Red w/ black interior 2 chamber flowmasters, Bassani off-road X-pipe, MAC cold air induction, Kirban short throw, Heavy duty 3 core radiator, FMS 3:73's, Timing bump to 14 degrees, SRP billet racing pedals, Kenwood sound system

03-02-2001, 12:42 AM	#3
thebean311 Registered Member Join Date: May 2000 Location: Phoenix, AZ Posts: 18	Tom, i had the same problem with my 2000 mustang GT. Turned out to be a loose hose. Check out http://www.users.qwest.net/~bpsilva/loosehose.jpg to see which hose it was. It is the one circled in yellow. once i reconnected it, no more problems. It was weird because the hose seemed rather loose, and there was no hose clamp there or anything. It must have just been bumped out of place. Let me know of you have any other questions. thebean311@hotmail.com

03-02-2001, 07:07 PM	#4
95GTS Git jiggy Join Date: Oct 1999 Location: MO USA Posts: 865	Whatever. Did they do a computer scan on it? How does your car run on the road? Does it miss out any, such as at a particular rpm range, or missing or "bucking around" during acceleration or so? If it does it could possibly be the fuel pump but I doubt it. If it's the idle it's more like the TPS (Throttle Position Sensor) or IAC (Idle Air Control) or even a spark plug but more likely one of the other two. Take it back to them and have another mechanic work on it. They should run a computer scan which should tell them what's wrong with it. They can also hook up an oscilloscope machine and it can tell such things as spark plugs and wires and more engine detailed stuff. Have them do that first before they go screwing around and replacing a fuel pump that isn't bad. I may be wrong but I highly doubt that it's the fuel pump. If they think it is then they can hook up a fuel pressure gauge and check it. ------------------ 1996 Mustang GTS [This message has been edited by 96GTS (edited 03-02-2001).]

03-02-2001, 07:19 PM	#5
95GTS Git jiggy Join Date: Oct 1999 Location: MO USA Posts: 865	I just re-read your post again. I didn't notice that you said you were only having problems with idle and none while acceleration or driving. It's not the fuel pump. No way. Take it back and have the computer scanned. It's not a spark plug because it would be running rough while driving. It's a computer/sensor problem. ------------------ 1996 Mustang GTS

03-02-2001, 07:40 PM	#6
95GTS Git jiggy Join Date: Oct 1999 Location: MO USA Posts: 865	thebean311: that tube is a crankcase ventilation tube which allows crankcase gases to be vented back into the air inlet tube to be sucked back into the engine to be burned up. All that is doing is relieving pressure. You could have the tube pointing straight up in the air and it shouldn't effect anything. It shouldn't make any difference on idle but if it did, oh well. Mine looks just like your pic, by the way. It sticks out a bit. It's not supposed to have a clamp or anything in it. It just slips in the hole. ------------------ 1996 Mustang GTS

03-03-2001, 02:05 AM	#7
thebean311 Registered Member Join Date: May 2000 Location: Phoenix, AZ Posts: 18	96GTS, you are right. In the pic, the hose is in the correct position. Before I slipped it back in, it was hanging off to one side. My car was constantly hunting while at idle. It would range between 400 adn 1k rpm. Once I slipped that hose back in (actually my buddy with a 5.0 noticed it), the idle hunting stopped completely.

03-05-2001, 01:16 PM	#8
Rocket 99GT Registered Member Join Date: Jan 2001 Location: gaithersburg md, 20879 usa Posts: 120	I had the same problem with my 99gt, they change the air sensor which helped a lot but I still have some "shaking". I will check that hose in the engine.

03-07-2001, 03:06 PM	#9
MajorTwit Registered Member Join Date: Jun 1999 Posts: 70	Thanks for the pic, thebean. My idle is a little rough, I'll look there first. [QUOTE]Originally posted by thebean311: [B]Tom, i had the same problem with my 2000 mustang GT. Turned out to be a loose hose. Check out http://www.users.qwest.net/~bpsilva/loosehose.jpg ------------------ 2000 GT 4.6 Stock

03-08-2001, 01:08 AM	#10
Y2KGT Registered Member Join Date: Feb 2001 Location: Pearland, TX Posts: 21	I had the exact same problem with the hose being loose that bean was describing in his picture. All of the computer scans in the world will not tell you if the hose is loose. I do agree with 96GTS in that it doesn't sound like a bad fuel pump. It sounds to me like your MAF doesn't know what to do and is trying to vary the voltage to the fuel pump at idle. If there is an air leak in between the MAF and the throttle body, your MAF will go nuts. Sometimes the dealership mechanics miss the obvious. Besides, it will only take you about 2 minutes to verify if a hose is loose anyway. ------------------ 2000 GT -- Black, 5sp, Mach460, Bassani CatBack & X-Pipe, MAC Cold Air, 70mm Tbody, Hurst Shifter 1966 Mustang Coupe -- Tahoe Turquoise, Pony Int, A-Code, C4 Auto ------------------ scott@pearland.com