88 grand marquis 5.0 bucking bad at light acceleration 55mph

Ohsplat · July 6th, 2011, 05:20 PM

So I replaced, Plugs, Wires, Cap, Rotor. Still bucked. Replaced Module. still bucks. It happens when Im in 4th gear in a AOD and slightly step on gas. Will also happen when I reach 70 mph. If I WOT from start to 70, no problem. Could this be a fuel problem?

Ruffellbaker · July 6th, 2011, 11:39 PM

When is the last time you changed your fuel filter or used a fuel injector cleaner? Also I would check your TPS sensor.

Ohsplat · July 7th, 2011, 09:10 PM

Just changed fuel filter today. Never used injector cleaner. TPS sits at .9 volts and idle. Slowly raises to 4.35 at WOT. Fuel pressure sits a 32#, and stays at 32 when revving. You can hear popping in the exhaust but its not a backfire. Coil tested .9 on the primary coil and 9k on the secondary... all within specs... im lost.

Ohsplat · July 7th, 2011, 09:14 PM

The bucking is real bad. Feels like im running out of gas...To make sure a injector is working, cant you hook a lead up to the pos bat term and touch it to the pos on the injector to listen for the click.

Ruffellbaker · July 8th, 2011, 01:47 AM

Just checking the voltage of the TPS doesnt usually work. Ud need to use a scan tool to see a graph. They normally only go bad at a certain rpm and are fine everywhere else, so they can be tricky to find. Also if you want to check for injector function you would need a noid light. One injector going bad wouldnt really make it buck horribly tho. Just a misfire. Have any CEL codes?

Ohsplat · July 8th, 2011, 01:56 PM

engine off codes.
11
12

engine on codes.
12
33
45
74

I do know the egr vacuum is unhooked and blocked off because it broke, but that was after this all started.

Ohsplat · July 8th, 2011, 03:27 PM

Fuel pump is bad. Used a set of snap on gauges instead of autozone rentals and it showed 28# at idle. When i floored it with the snap ons hooked up, it dropped like a brick.

What have I learned from this.. the mechanic is only as good as his tools lol.. dont buy cheap shit.

July 6th, 2011, 05:20 PM	#1
Ohsplat Enthusiast 1983GT No motor or trans Join Date: Nov 2010 Location: Middle River MD Posts: 540 iTrader: 0 reviews	88 grand marquis 5.0 bucking bad at light acceleration 55mph So I replaced, Plugs, Wires, Cap, Rotor. Still bucked. Replaced Module. still bucks. It happens when Im in 4th gear in a AOD and slightly step on gas. Will also happen when I reach 70 mph. If I WOT from start to 70, no problem. Could this be a fuel problem?

July 6th, 2011, 11:39 PM	#2
Ruffellbaker Regular 1997 Mustang GT Join Date: May 2010 Location: Hagerstown, MD Posts: 264 iTrader: 0 reviews	When is the last time you changed your fuel filter or used a fuel injector cleaner? Also I would check your TPS sensor. __________________ PI Cam Swap, MAC C/A intake, BBK 70mm TB, C&L Plenum, Ford 24lb injectors, March UD, 160 T Stat, MSD ignition, 3.73 gears, Stage 2 Clutch, Steeda Short Shifter, O/R X, Flow 40s, SCT Race Tune.

July 8th, 2011, 01:47 AM	#5
Ruffellbaker Regular 1997 Mustang GT Join Date: May 2010 Location: Hagerstown, MD Posts: 264 iTrader: 0 reviews	Just checking the voltage of the TPS doesnt usually work. Ud need to use a scan tool to see a graph. They normally only go bad at a certain rpm and are fine everywhere else, so they can be tricky to find. Also if you want to check for injector function you would need a noid light. One injector going bad wouldnt really make it buck horribly tho. Just a misfire. Have any CEL codes? __________________ PI Cam Swap, MAC C/A intake, BBK 70mm TB, C&L Plenum, Ford 24lb injectors, March UD, 160 T Stat, MSD ignition, 3.73 gears, Stage 2 Clutch, Steeda Short Shifter, O/R X, Flow 40s, SCT Race Tune.

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July 7th, 2011, 09:10 PM	#3
Ohsplat Enthusiast 1983GT No motor or trans Join Date: Nov 2010 Location: Middle River MD Posts: 540 iTrader: 0 reviews	Just changed fuel filter today. Never used injector cleaner. TPS sits at .9 volts and idle. Slowly raises to 4.35 at WOT. Fuel pressure sits a 32#, and stays at 32 when revving. You can hear popping in the exhaust but its not a backfire. Coil tested .9 on the primary coil and 9k on the secondary... all within specs... im lost.

July 7th, 2011, 09:14 PM	#4
Ohsplat Enthusiast 1983GT No motor or trans Join Date: Nov 2010 Location: Middle River MD Posts: 540 iTrader: 0 reviews	The bucking is real bad. Feels like im running out of gas...To make sure a injector is working, cant you hook a lead up to the pos bat term and touch it to the pos on the injector to listen for the click.

July 8th, 2011, 01:56 PM	#6
Ohsplat Enthusiast 1983GT No motor or trans Join Date: Nov 2010 Location: Middle River MD Posts: 540 iTrader: 0 reviews	engine off codes. 11 12 engine on codes. 12 33 45 74 I do know the egr vacuum is unhooked and blocked off because it broke, but that was after this all started.

July 8th, 2011, 03:27 PM	#7
Ohsplat Enthusiast 1983GT No motor or trans Join Date: Nov 2010 Location: Middle River MD Posts: 540 iTrader: 0 reviews	Fuel pump is bad. Used a set of snap on gauges instead of autozone rentals and it showed 28# at idle. When i floored it with the snap ons hooked up, it dropped like a brick. What have I learned from this.. the mechanic is only as good as his tools lol.. dont buy cheap shit.

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