94 Cobra prob.

94gt5.0 · September 13th, 2007, 03:23 PM

My buddy's 94 Cobra has a problem. When he pulls away from a light or even sometimes just cruising in traffic, the car will hesitate and then buck. I mean hard. I've ridden in it several times since this problem started and every single time it just about slams my head into the windshield and then into the seat. The MAF is new, he just got a new plug and harness for it, and it shows that the MAF is getting too much voltage (that's the code it's throwing). Does anyone have any clue? We're about at our wits end with this thing.

Bullitt95 · September 13th, 2007, 07:40 PM

I was thinking this could be a fuel delivery problem. Perhaps the fuel pump itself or its relay.

94gt5.0 · September 17th, 2007, 12:51 AM

Fuel pump recently went out on the car, and it just got replaced with a new Walbro 190lph pump I believe. So no, it's not the pump.

Bullitt95 · September 17th, 2007, 02:00 PM

That degree of bucking is rarely caused by an ignition or electrical problem. There could be a problem with the fuel pump relay but I doubt it 'cause when they do go, they go completely.
If the symptoms are the same as what your friend's Cobra was producing before he replaced the fuel pump, it's just possible that the new pump's a dud. Sometimes even new parts can be bad but we always take it for granted that they'll not cause a problem. One way to find out is to hook up a fuel pressure gauge to the Schrader valve on the fuel rail. If the fuel pressure drops when the engine bucks, you've found the problem.

94gt5.0 · September 17th, 2007, 11:46 PM

My question is then... why is it throwing the too much voltage to MAF code?

Bullitt95 · September 18th, 2007, 04:22 AM

That's a good question and I've been thinking about the answer. His engine will have 24lb injectors, so I doubt that the MAF voltage would peg even with several mods unless something else is going on.
Was this problem already there before your friend installed the new MAF? Is it getting the correct 5v reference voltage? Is it properly grounded?

94gt5.0 · September 18th, 2007, 02:29 PM

Yea, he does have 24 lb. injectors, and it's a Cobra MAF tuned for 24 lbers. The problem didn't happen for awhile after he installed the new MAF and suddenly just started happening 3 or so months after. As far as I know everything else is wired in correctly... it was installed by the "Mustang Expert" in town so I don't see how anything would have been wrong.

Bullitt95 · September 19th, 2007, 10:08 AM

Is the air filter shielded from the underhood compartment? If it's exposed, fan "wash" when the electric fan operates can cause erratic MAF voltages.
Check the other things that I mentioned earlier.

94gt5.0 · September 19th, 2007, 11:55 PM

We currently have reason to believe that it's the TPS that is making this thing go crazy... will keep updated.

September 13th, 2007, 03:23 PM	#1
94gt5.0 Newbie Join Date: Sep 2007 Posts: 11 iTrader: 0 reviews	94 Cobra prob. My buddy's 94 Cobra has a problem. When he pulls away from a light or even sometimes just cruising in traffic, the car will hesitate and then buck. I mean hard. I've ridden in it several times since this problem started and every single time it just about slams my head into the windshield and then into the seat. The MAF is new, he just got a new plug and harness for it, and it shows that the MAF is getting too much voltage (that's the code it's throwing). Does anyone have any clue? We're about at our wits end with this thing.

September 13th, 2007, 07:40 PM	#2
Bullitt95 Hardcore Enthusiast 1995 Mustang GT auto 13.36 @ 105.0 Join Date: Apr 2007 Location: Al Ain, UAE Posts: 1,391 iTrader: 0 reviews	I was thinking this could be a fuel delivery problem. Perhaps the fuel pump itself or its relay. __________________ 244whp/284wtq Mod list in My Garage

September 17th, 2007, 02:00 PM	#4
Bullitt95 Hardcore Enthusiast 1995 Mustang GT auto 13.36 @ 105.0 Join Date: Apr 2007 Location: Al Ain, UAE Posts: 1,391 iTrader: 0 reviews	That degree of bucking is rarely caused by an ignition or electrical problem. There could be a problem with the fuel pump relay but I doubt it 'cause when they do go, they go completely. If the symptoms are the same as what your friend's Cobra was producing before he replaced the fuel pump, it's just possible that the new pump's a dud. Sometimes even new parts can be bad but we always take it for granted that they'll not cause a problem. One way to find out is to hook up a fuel pressure gauge to the Schrader valve on the fuel rail. If the fuel pressure drops when the engine bucks, you've found the problem. __________________ 244whp/284wtq Mod list in My Garage

September 18th, 2007, 04:22 AM	#6
Bullitt95 Hardcore Enthusiast 1995 Mustang GT auto 13.36 @ 105.0 Join Date: Apr 2007 Location: Al Ain, UAE Posts: 1,391 iTrader: 0 reviews	That's a good question and I've been thinking about the answer. His engine will have 24lb injectors, so I doubt that the MAF voltage would peg even with several mods unless something else is going on. Was this problem already there before your friend installed the new MAF? Is it getting the correct 5v reference voltage? Is it properly grounded? __________________ 244whp/284wtq Mod list in My Garage

September 19th, 2007, 10:08 AM	#8
Bullitt95 Hardcore Enthusiast 1995 Mustang GT auto 13.36 @ 105.0 Join Date: Apr 2007 Location: Al Ain, UAE Posts: 1,391 iTrader: 0 reviews	Is the air filter shielded from the underhood compartment? If it's exposed, fan "wash" when the electric fan operates can cause erratic MAF voltages. Check the other things that I mentioned earlier. __________________ 244whp/284wtq Mod list in My Garage

September 17th, 2007, 12:51 AM	#3
94gt5.0 Newbie Join Date: Sep 2007 Posts: 11 iTrader: 0 reviews	Fuel pump recently went out on the car, and it just got replaced with a new Walbro 190lph pump I believe. So no, it's not the pump.

September 17th, 2007, 11:46 PM	#5
94gt5.0 Newbie Join Date: Sep 2007 Posts: 11 iTrader: 0 reviews	My question is then... why is it throwing the too much voltage to MAF code?

September 18th, 2007, 02:29 PM	#7
94gt5.0 Newbie Join Date: Sep 2007 Posts: 11 iTrader: 0 reviews	Yea, he does have 24 lb. injectors, and it's a Cobra MAF tuned for 24 lbers. The problem didn't happen for awhile after he installed the new MAF and suddenly just started happening 3 or so months after. As far as I know everything else is wired in correctly... it was installed by the "Mustang Expert" in town so I don't see how anything would have been wrong.

September 19th, 2007, 11:55 PM	#9
94gt5.0 Newbie Join Date: Sep 2007 Posts: 11 iTrader: 0 reviews	We currently have reason to believe that it's the TPS that is making this thing go crazy... will keep updated.

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