North American Turbocoupe Organization



Found my Vacuum! now VAM out of spec??
Matt S Offline
Posting Freak
#1
Well, I'm smiling as when I finally got a whole new round of gaskets on the upper I am now getting about 19-20" vacuum. MUCH better.
But it still idles rough and misses a bit under load.
I checked my VAM, and the door closed is showing .2575v and all the way open it's 4.61. I have a digital volt meter, but the best I can tell is the output is smooth.

The papers I have for adjusting the VAM have differing opinions. One says closed should read .5 volts, and 4.5 open. The other says to set the spring at .247 closed; which is almost half the other.
So are my readings ok, and if not, which one should they be??

I don't want to mess with this unless absolutely necessary. I suppose I just pop off the black plastic box on top to get at all this??

[This message has been edited by Matt S (edited 08-03-2003).]
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Matt S Offline
Posting Freak
#2
Can anyone help me on the VAM specs?

Also, I'm thinking of getting new TFI/PIP. Does it matter if I mix brands (motorcraft TFI, NAPA PIP)
But from what I've read, the computer doesn't use those for signal until the car is warm...mine does it cold or otherwise. ALL the time it runs rough and misses under load. I don't want to throw money away, but it appears that I will have to start doing just that.

Again, 88 with auto - new or cleaned out everything that is suggested here, tried 2 different (used) distributors, now getting 19" - 20" vacuum. Still idles/runs bad, and gets HORRIBLE (like 13) mpg. NOthing I've done has changed the way it idles and runs for 2 years now.
Any thoughts or suggestions, no matter how wild, would really help. I don't have any factory manuals, so I'm in the dark here - or should I say - in the Haynes (that's all I got).
Thanks again.
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Pete D Offline
Administrator
#3
Matt, I never messed with a VAM, but I tend to believe the source on the 0.5 to 4.5v

Quote:the computer doesn't use those for signal until the car is warm.

How else is the computer going to know when to fire the plugs and the injectors, hot or cold? If it's running rough cold, it could be the ECT which doesn't always set a code when defective.
Pete Dunham


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Matt S Offline
Posting Freak
#4
Thanks Pete. I'll try to set it for .5v by adjusting the spring. I did find the ECT was out of spec, so there's a new one in there. Also did the IAT, and TPS. It runs like this between the 2 distributors I have tried. Maybe they're both bad?

Also, I just popped the top off the valve cover, and snapped the pictures attached here. Maybe a cam too, huh? I don't have much experience with identifying wear on a cam. Only a few looked this way. I couldn't feel any ridges, but my fingernail could tell the difference between the polished part and oily part on all the lobe tips. If it's a ridge, it's nowhere near a sheet of paper thick.
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Pete D Offline
Administrator
#5
Cam sounds like it's good. I've seen them a lot worse than that and the car ran smooth.
Pete Dunham


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Matt S Offline
Posting Freak
#6
Quote:Originally posted by Pete D:
Cam sounds like it's good. I've seen them a lot worse than that and the car ran smooth.


Thanks Pete. So that'll be the LAST thing I do... [Image: biggrin.gif]
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Jeff K Offline
Administrator
#7
.3V with VAM door fully closed is about right. 4.5 to 4.8 V fully open is just fine.

------------------
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 20 psi, forced air intercooler, water injection, bypass valve, Ranger roller cam, subframes, etc., etc.. // 86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP nitrous, ignition, gears, suspension, etc., etc.... // 91 Escort: Bone stock winter car // 02 Taurus Vulcan(wifes car)
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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Matt S Offline
Posting Freak
#8
Thanks Jeff.
I pushed in the door when it was idleing all warmed up, and it seemed like a bit more tension on the door might help. I don't think my finger held it steady by the readings I saw. I'll try for a little more.

I also picked up an echlin tfi and pip from Napa today, and I need to pick up a puller from Harbor then I'll get on that.
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