North American Turbocoupe Organization



IAC/TPS adjustment
Michael Jordan Offline
Senior Member
#1
I've reviewed the revised Tech Article on this process and my throttle body and TPS harness don't look like the ones in the photos.

First, the adjustment screw on the throttle body actually faces down toward the valve cover on my TB ruling out any use of a screwdriver for this one. A 10mm wrench is the only way to get to this. Second, the TPS harness is attached to the TB facing backward instead of to the right side of the card as the photo shows, thus not allowing access to back probe from the harness. Can back probing be done from the plug that attaches to the harness? I tried yesterday but could not get my meter's pins in through the holes at the appropriate wires. I tried the pin through the insulation technique but could not get good contact. I have ground the pins on my meter down to needle points to see if that will allow them to reach through the holes to the contacts in the plug. I will try this later today. Do the green and black wires going to this plug correspond to the ones in the harness?

Has anyone seen this configuration or have any other thoughts on this matter?

Thanks.

MJ
1986 TC stock with full option package. K&N, DIY boost valve at 14 psi, Walbro 255.
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Ryan H Offline
Posting Freak
#2
Can you take any pics? I haven't heard of this before but then again I've never owned a pre '87-'88.
'88 TC Smile Walbro 255HP, Stinger FMIC, PIT BOV, Pro 5.0, Kirban, RR cam, FRPP strut tower brace, T3
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Michael Jordan Offline
Senior Member
#3
I'll take some tonite and try to get them on the site tomorrow.

MJ
1986 TC stock with full option package. K&N, DIY boost valve at 14 psi, Walbro 255.
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Keith Nubel Offline
Posting Freak
#4
Some of the idle adjustment screws face downward towards the valve cover and others face outward to the side. They both work the same. Back probe the wires with some sharp needles and pierce the wire for the TPS.
1985 TC
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Michael Jordan Offline
Senior Member
#5
So far I've had no success getting this adjustment right. The TPS harness is impossible to back probe so I've got to try to back probe the connector that plugs into the TPS. I think my meter is screwed up too. I can't seem to get a consistent reading which could be because of the accessibility (the probes may not be making contact inside the connector). I've tried the pins through the insulation and can't get a reading that way either. My meter just wanders around. I checked the meter with some batteries and it seems to work with them. I may try the pins again by either soldering them to the probes or using alligator clips. I took pictures of the whole mess and will try to get them on a post later.

Now my troubles don't stop here. I took the IAC off and separated it from the solenoid to clean the valve with some carb cleaner. That all seemed to go pretty well, but my adjustment is off more than when I started and the car won't start now without giving it a little help with the gas pedal. The idle seemed to stabilize at about 1000 to 1100 RPM last night but this morning it was stuck up at 1500. Twice when it sat running for a few minutes this morning it dropped down to about 800. But after getting back in and driving it was right back up to 1500 untile I pulled into work when it dropped down again.

I guess I won't be able to get this straightened out until I figure my meter situation out. Any pointers would be greatly appreciated. Thanks.

MJ
1986 TC stock with full option package. K&N, DIY boost valve at 14 psi, Walbro 255.
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Kev Offline
Posting Freak
#6
I couldn't get the pics to upload so I created a page at my cardomain site to try and help you out with this TPS situation. I hope it helps.

http://www.cardomain.com/ride/451092/5
Kev
1988 TC 5spd
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Keith Nubel Offline
Posting Freak
#7
Kev, from your photo it looks like your reading the reference voltage. The 5.0 is normal. Don't pay any attention to the changes of several tenths on the meter. You need to move one of your probes to the other wire on the tps. Your voltage should be around 1.0. I don't think your to far off. If necessary carefully strip off some insulation so you can get to the wire. One of my pictures shows what I did. I used 2 butt splice connectors, crimped the wire into 1 end and use the other end to stick my probe into.
1985 TC
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Pete D Offline
Administrator
#8
Michael,
I seen wandering voltage on a tps and it was bad. Make sure you got good connections before you decide it's bad. It is much easier to probe the harness connector to the TPS than to probe the TPS side of the connector
Pete Dunham


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Kev Offline
Posting Freak
#9
Quote:Originally posted by Keith Nubel:
Kev, from your photo it looks like your reading the reference voltage. The 5.0 is normal. Don't pay any attention to the changes of several tenths on the meter. You need to move one of your probes to the other wire on the tps. Your voltage should be around 1.0. I don't think your to far off. If necessary carefully strip off some insulation so you can get to the wire. One of my pictures shows what I did. I used 2 butt splice connectors, crimped the wire into 1 end and use the other end to stick my probe into.
Directly from the tech articles....
Back probe the back of the TPS connector to connect the meter... The + (positive) side of the meter connects to the green wire. The – (negative) side connects to the black wire (SIGNAL RETURN). NOTE: you must connect the negative side of the meter to the black wire (SIGNAL RETURN). Do not just ground it to the chassis; it’s not the same thing. Back probing means sticking pins down the back side of the harness side of the connector for the appropriate wires. It can be tricky but is better than sticking pins through the wire insulation. The connector is left attached to the TPS.
Using the small Phillips screwdriver to loosen the two hold down screws slightly, then rotate the TPS to change the voltage setting. Adjust the TPS output voltage to just under 1.0 volt. Most turbo tuners find that setting TPS voltage to around .90 - .95 volts works best. I set mine around .94 volts. When set, tighten the screws and recheck the reading.******

This is how I've set my TPS for years. I'm not sure what you mean by reading the wrong wire for the voltage. I'm using the green wire for positive and the black wire for negative. Can you elaborate on this further. I'd hate to try and help the guy only to mess him up further.
Kev
1988 TC 5spd
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trashline Offline
Posting Freak
#10
I made up a connector for my tps. I cut the line and soldered in connections so I can insert my meter probes. And made rubber caps for them to seal them air tight. Its easier then tearing up the wires time and time again and possibly messing something up.
Brian

www.BCPCustom.com

06 Cobalt SS
66 mustang 289 C4 handfully modded

Stingers IC install and tbird photos
http://community.webshots.com/user/trashline
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