Bucking and stalling in drive
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Mountain Pass
Joined: Oct 2002
Posts: 205
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From: Jaqcksonville
Bucking and stalling in drive
97 Aerostar. After 5 mins driving at stop lights ac on engine starts to hunt then stall. Ac clutch cycles. No issues with ac off. Checked freon level all ok, ac clutch ok pulled plug on press switch releases clutch as it should, replaced wot relay under hood . This started to happen recently. No issues driving just happens when stopped at a light. In neutral no issues. Any ideas.
Lead Driver
Joined: Sep 2003
Posts: 7,015
Likes: 208
From: SoCal
Usually, the compressor should not put so much load on the engine that it stalls, unless the compressor is jamming up. Does your AC cool properly?
Other possibility is that the EEC is not kicking up the engine speed when it engages the compressor. Try this: pull the connector to the AC clutch, then turn on the AC (or defrost), and check to see if the engine speeds up.
Other possibility is that the EEC is not kicking up the engine speed when it engages the compressor. Try this: pull the connector to the AC clutch, then turn on the AC (or defrost), and check to see if the engine speeds up.
Postmaster
Joined: Apr 2001
Posts: 3,818
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Idle adjust control (IAC) needs cleaned or replaced. Its job is to kick up the idle when a load is placed on the engine - such as the AC compressor. Do a forum search for IAC cleaning. Sometimes this will help for a while but eventually, the IAC unit must be replaced. Rather pricey little affairs but easy to repair/replace. If replacing, ask if the gasket is included.
Postmaster
Joined: Oct 2009
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Also the IAC is one of the items where OE versus aftermarket matters. I have had aftermarket ones cause idle surging right out of the box. The OEM lasts for many years in service. If you go aftermarket make sure you choose a reputable brand.
Laughing Gas
Joined: Jun 2004
Posts: 1,240
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From: Dallas, Texas
I pull mine off once a year and clean it real good, Then use RXP Fuel treatment does the rest.
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Mountain Pass
Joined: Oct 2002
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From: Jaqcksonville
Update. Did all what was suggested pulling ac plug cleaned air bypass and everything appears ok. Engine idled up when i pulled ac plug with ac on and bypass works ok. Cleaned maf too. I had replaced the sparkplug wires and plugs not long ago so ruled that out. Decided to power brake engine under load ac on in the dark and i see small missfire flashes from the base of the coil tower. Very faint but there. Looks like i need a coil pack. So the problem only shows up under certain rpm and sounds like a faint injector tick. Ill replace the coil tomorrow and follow up. Thanks again for suggestions. Ive turned 372k on the engine last week.
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Vic93
1987 - 1996 F150 & Larger F-Series Trucks
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Sep 8, 2013 09:38 AM
