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If you have 5.0L or 4.9L or a 5.8L, California, 49 States Under 8600 GVW or an 7.5L California.
Then you would have a Mass Air Flow (MAF) Sensor center of engine compartment near safety wall.
If you have a 7.5L, Except California or a 5.8L, 49 States Over 8600 GVW then you would have Manifold Absolute Pressure (MAP) Sensor mounted on safety wall near the AC blower.
Yea, we figured that out, no MAP sensor finally. Been trying to fix the popping when you stomp the pedal. Put an adjustable fuel regulator on it today and bumped the pressure up to 50-60 psi. That didn't fix it. One thing we did find it's retarding the timing when you get into the pedal, which seems odd to me. I'm going to pull the throttle body off next chance I get to work on it and see if the EGR isn't sticking open. And change the throttle position sensor while at it. Might also give it a set of new injectors while at it too.
SDEFI uses MAP sensor to measure manifold vacuum, 96 and later MAF uses "hot-wire" sensor to measure air-flow.
The tungsten element is heated to a reference temperature using a specified amount of current and as air flow through the "sensor" increases or decreases the ECU measures how much current is required to maintain reference temperature and adjusts a/f ratio accordingly when combined with throttle position / coolant temp / manifold vacuum and vehicle speed but coolant temp just dictates closed loop or open loop operation, open loop is a table of premeasured values and closed loop is sensor based..
I think that eliminates fuel and mixture control as the source of the problem then, it has to be ignition related and prime suspects would be the PIP and TFI modules. Are either of these not Motorcraft parts?
I think that eliminates fuel and mixture control as the source of the problem then, it has to be ignition related and prime suspects would be the PIP and TFI modules. Are either of these not Motorcraft parts?
PIP ? As for the TFI, it has none I know of. Nothing on the distributor at least. Not even the pad for when they had them previously. Like I posted before, it retards the timing when accelerating which puzzles me. Down sometimes to 10*BTC according to my unit plugged into the OBD port. Comes back up at cruise. Never does the popping at partial throttle acceleration.
PIP is the pickup inside the distriutor, TFI module is mounted in a heatsink on the fender, firewall, or maybe the rad support somewhere, vans are different than pickups with component locations. And your truck should have a black TFI module not a grey one.
At WOT and high load the timing will back right off to prevent detonation, if it is doing that at partial throttle openings there is an issue.
I looked for a PIP on both Summit and O'Reilly's sites and found nothing. So sounds like I'd have to change the distributor if that's what the problem was. I haven't seen anything in it that looks like that TFI. And we looked all over it yesterday with a flashlight.
This is a PIP module for your vintage truck, installing or removing this involves dismantling the distributor as it is the shaft that positions the module in the distributor body so people often just buy a complete distributor instead.
I think that eliminates fuel and mixture control as the source of the problem then, it has to be ignition related and prime suspects would be the PIP and TFI modules. Are either of these not Motorcraft parts?
Distributor's the same one came with this van. Might have to wait till next weekend to look for the TFI again. Never misfires at partial throttle and cruising. Only when you nail the pedal at low speeds, and only occasionally when nailed at highway speeds. Really sounds like backfiring.
Ok, update time. We changed the TFI module this past weekend. It's hidden in the driver's side fender wall in the corner. Popping still there. Mileage did seem to go up a mile per gallon though with the new TFI. The timing is also not being retarded as much when the gas is nailed. I'm beginning to suspect the TPS though here. At WOT its only showing 90.2% on the TPS on my reader. And the misfiring/popping isn't a constant thing. If you ease into the pedal from a stop, it runs normally. It's only when you suddenly nail it at low speeds and only occasionally at highway speeds when it downshifts into 2nd gear that it occurs. Nail it at 55-60 and it'll downshift into 3rd but runs normally. I'm going to wait till the weather cools before digging into it to change the TPS. Not my daily driver anyway.
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