Poor fuel economy, any guesses? - TCCoA Forums
 
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post #1 of 25 (permalink) Old 09-26-2005, 10:42 AM Thread Starter
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Poor fuel economy, any guesses?

Ok, well thanks to everyone from before i finally got my TC up and running, only thing is, i get awful fuel economy, when i mean awful i mean 9-10 mpg. I still have one code that is constant, its a code 64, which is a vam code for low voltage reading. I already replaced the vam twice, possible that a wire could be grounded somewhere? Im dumping fuel like crazy, and i need to get better gas mileage with the cost of gas the way it is.
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post #2 of 25 (permalink) Old 09-27-2005, 02:43 PM
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Grounded, pinched? I would drive it too much if it dumpping that kinda fuel.

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post #3 of 25 (permalink) Old 09-27-2005, 03:03 PM Thread Starter
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yeah thats what im leaning towards, looks like im doing some wire fishing, by chance does anyone know the resistance or voltage on those lines?
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post #4 of 25 (permalink) Old 09-27-2005, 03:08 PM
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I don't know the resistence right of hand. Did you have your first one tested, or just swapped it? Where are you testing it, at the sensor, plug?

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post #5 of 25 (permalink) Old 09-27-2005, 10:04 PM Thread Starter
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Well theres no real way to test how they're running unless you have an oscilliscope, because mafs use square waves they're not the same type as normal electrical sensors. But i swapped it and its the same code, and i also swapped the ecm. Theres actually a lot i swapped, but that was for other reasons. But the code is the one thing that has been constant. And the only thing i can think is that there is a ground or a short in one of the wires. So i figured i'd test resistance on all the wires, unless anyone else has had a problem with one of these mafs before?
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post #6 of 25 (permalink) Old 09-27-2005, 10:46 PM
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Not trying to pawn you off or anything. I just dont remember how i fixed it on mine.

1988 Lincoln Mark VII
Paxton Novi 1000 6psi kit, 30lb injectors 73mm C&L, MAF converted A3M, gt-40's, Felpro headgaskets, 1.7 Cobra RR's, typhoon intake,1 5/8 shorty headers, off road x-pipe, and full mandrel catback, electric fan, 3.73's, TKO 500, pro 5.0 shifter

372.4hp / 394.6tq 5psi

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post #7 of 25 (permalink) Old 09-28-2005, 06:00 PM Thread Starter
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Could it possibly be a Air Charge Temp sensor? Or as ford calls it the VAT, because in my little handbook its either a vaf or a vat low voltage code. So could it possibly be a VAT?
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post #8 of 25 (permalink) Old 09-28-2005, 06:44 PM
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that could be it but also check the ECT, when it gose bad it defaults the ecu to like -40
and will dump fuel like a mad man and at times wont set a code

they are less than 20 bux (motorcraft is 35 bux) and make sure you get a brass body one and not a plastic body one
should be like part# wt386 for borg or parts pro from O'reilly auto parts
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post #9 of 25 (permalink) Old 09-28-2005, 09:30 PM
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yeah the VAT is the upper ??? sensor on the lower intake manifold on the back side. well one of them is the knock sensor i know that Unplug that thing the 2.3L makes enough noise to trip it when it's running good. If you have the switch set to premium just run premium it shouldnt detonate if everything is good.

1988 Lincoln Mark VII
Paxton Novi 1000 6psi kit, 30lb injectors 73mm C&L, MAF converted A3M, gt-40's, Felpro headgaskets, 1.7 Cobra RR's, typhoon intake,1 5/8 shorty headers, off road x-pipe, and full mandrel catback, electric fan, 3.73's, TKO 500, pro 5.0 shifter

372.4hp / 394.6tq 5psi

Rest in Peace Joel R. Bender.
July 30, 1979 - March 26, 2006
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post #10 of 25 (permalink) Old 09-29-2005, 07:49 AM Thread Starter
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Yeah the vat is one of the only things i haven't switched out yet, things i've changed so far:
Fuel filter
Air filter
Oil filter(of course)
PCV
plugs, wires, cap, rotor, coil, module, dist. (only cuz i had one lyin around)
Maf sensor(VAF)
Map sensor
ECT sensor
IAC
TPS
O2
probably a few other things but i can't remember at the moment.
The only two sensors i haven't replaced are the knock and ACT, so im assuming that the ACT is my problem. Oh yeah i've also replaced the ECM as well. My timing is set at 10btc and fuel pressure is 39 with vaccum off and 35 with it on. My compression is exactly 130 on all 4 cylinders. If you can figure it out, to me you are god.
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post #11 of 25 (permalink) Old 09-29-2005, 10:41 AM
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did ya use a brass body or plastic body ECT? I repalced mine with a plastic body one ia it went bad in less than 30 min. You have to use the brass body one

from chilton repair manual #26760 pg. 4-13
engine coolent/air charge temp sensor values

F Volts Restance
248 .27 1.18
230 .35 1.55
212 .46 2.07
194 .60 2.80
176 .78 3.84
158 1.02 5.37
140 1.33 7.70
122 1.70 10.97
104 2.13 16.15
86 2.60 24.27
68 3.07 37.30
50 3.51 58.75


Hope this helps noe go grab you DVOM and check the 2 sensors
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post #12 of 25 (permalink) Old 09-29-2005, 10:46 AM Thread Starter
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yeah i replaced it with a bass body one, plastic + aluminum = BFP's. I can't decypher which resistance value and voltages are for which wires by your diagram. Colors would be more helpful, because i don't have a chiltons.
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post #13 of 25 (permalink) Old 09-29-2005, 11:44 AM
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at the sensor ,un plugged, ohom it cold then after warm up

If ya want give me a call
(850)485-2300
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post #14 of 25 (permalink) Old 09-29-2005, 12:13 PM Thread Starter
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Ok i got ya the F is farenheit gotcha. I'll go play around with it today, i don't think that is the problem though, but i'll give it a shot.
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post #15 of 25 (permalink) Old 09-30-2005, 02:31 PM
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Exclamation Check the FP regulator!

I think you guys are chasing down the wrong trail. I had the same problem. I was getting black smoke, poor low-end performance, poor fuel economy. I was also getting a trouble code pointing to a bad VAM. When I replaced it and that didn't help, I dug a little further.
I'll bet you that you don't have an electrical or sensor problem; it's a mechanical problem.
Check the vacuum hose that connnects to the fuel pressure regulator on the fuel rail (feeds fuel to the fuel injectors.) The FP regulator is held on with three Torx or allen-head screws (can't remember which) and is easily replaceable. The hose should be dry. If there is gas inside the vacuum hose, the diaphragm has ruptured and that's your problem. Before I checked the hose, I put a fuel pressure gauge on the Schrader valve fitting and found 80PSI. It should be more like 35-40. That's why you're getting poor fuel economy. The regulator was about $35 10 years ago and was in stock at O'Reilly's. It's a common part.

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post #16 of 25 (permalink) Old 09-30-2005, 02:36 PM
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Hmmm---didn't see in your previous msg. that you already checked fuel pressure. What about a leaky fuel injector? Have you done an injector pressure drop test? Does it hold fuel pressure after you shut it down?

I think that code is because it's running so rich, though.
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post #17 of 25 (permalink) Old 09-30-2005, 09:24 PM Thread Starter
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i know, its because its running rich, thats why my fuel economy is poor, well i first tested it when it was off because that way no fire and no vaccum, and it was 39 so im good there, vaccum is at 18hg. and spark timing is dead on, the only thing wrong with it mechanically is that i have to switch the followers and lifters cuz one was real worn cuz a lifter blew out on me so im doing it as a just in case kinda thing, other than that nothin mechanically is wrong, besides a mechanical fault wouldn't make it dump fuel, thats all computer controlled. Just about everything in the car has been changed so i have no idea what would be causing it to run rich. btw cam timing is also dead on
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post #18 of 25 (permalink) Old 09-30-2005, 11:13 PM
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If you are using the stock rubber acordian hose from the VAM to the turbo check that for cuts. It may look good at first but check it real good. I had one do the same thing before. I wrapped it in black electrical tape for a quick fix..
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post #19 of 25 (permalink) Old 10-01-2005, 11:00 AM Thread Starter
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nah i already ran a boost leak tester on it so i doubt that i have any holes in the hoses, my vaccum is pretty good actually.
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post #20 of 25 (permalink) Old 10-01-2005, 11:17 AM
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ok , Is your TPS out of range? should be .85-.98 vdc at idle and (if I remember)4.6-5.0 at WOT

If its set wrong the ECU will think the engine needs more than it does.

How did the othe sensors ohm out?
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post #21 of 25 (permalink) Old 10-02-2005, 08:14 PM Thread Starter
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The other sensor is good, and the tps is set at .90.
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post #22 of 25 (permalink) Old 10-10-2005, 01:38 PM Thread Starter
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well it turned out that it was the vat, no more code, now to blast it around and see what my mileage is. No more tap either... woohoo
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post #23 of 25 (permalink) Old 10-24-2005, 02:59 PM Thread Starter
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Ok i killed the code, but my mileage has only jump up about a mile or 2 per gallon. So i know i should be gettin close to 20 im only gettin between 11-12, so im stumped. I've tried just about everything and anything. So anyone have suggestions im open to ideas.
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post #24 of 25 (permalink) Old 10-24-2005, 03:05 PM
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With so much fuel running through it is possible you may of damaged the catylitic converter. If you still have them in place. Do you know what kinda shape the turbo is in?

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post #25 of 25 (permalink) Old 10-25-2005, 03:26 PM Thread Starter
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That really doesn't solve my problem though, and yes the turbo had a rebuild about 30k ago. I need to know why its running rich, not the effect of the running rich to my exhaust, believe me everything will probably have to go eventually.
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