Help please
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New User
Joined: Sep 2002
Posts: 14
Likes: 0
From: Dove Creek US
Help please
ok here is my problem. I have an 87 F-250 with a 302. at startup it idles around 1100 and doesn't come down much. Then sometimes it will idle from 800 to 1300 just going up and down (usually after running for a while). Then when driving I push in the clutch to shift and the RPM's will either stay where they where or they will run up to about 2500. Sometimes when I tap the throttle it will idle back down to 1000 or somewhere around there. I have replaced the IAC, TPS, PCV, cleaned the throttle body, and looked for vacum leaks using Starter Fluid? Iam stumped. I had the engine rebuilt about a year ago and it was doing it at the time, but after the rebuilt it, it stopped until recently. I don't know what to do next. any advice is apreciated. Thanks.
Kyle
Kyle
Lead Driver
Joined: Nov 2002
Posts: 9,557
Likes: 44
From: Concord, NC
Have you tried pulling codes from the computer? Also I would double check the TPS voltage, even though it is new. There might be a little adjustment you can make to get it to idle down. Also try unplugging the IAC and see what the rpm's do. If they still fluctuate, then you know the problem is elsewhere. I would check the MAP sensor as well.
Lead Driver
Joined: Nov 2002
Posts: 9,557
Likes: 44
From: Concord, NC
I think it depends on who you ask as to whether or not the engine should die. What I have read, it should idle at the correct speed with the IAC unplugged and the engine warm. The TPS should only have about .9V at closed throttle, and around 4.8V at full throttle (check with engine off, but key on). This voltage is measured between the green wire and the black wire. Also double check that there is only 5V on the orange wire.
Lead Driver
Joined: Nov 2002
Posts: 9,557
Likes: 44
From: Concord, NC
Alright, the voltage is a little high for closed. It should be right around .9V. You may have to take the throttle body off to do this, but try to adjust it until you get it down to .9V. If you can't get it to turn enough, open up the holes in the tps with a drill until you can get it to turn enough. Idle voltage is more critical than WOT voltage, so once you get the idle voltage down below 1V then that should help a lot.
Thread Starter
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New User
Joined: Sep 2002
Posts: 14
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From: Dove Creek US
ok I didn't know that much would make such a difference. to adjust the TPS I just lossen the screws and turn it right? Iam not sure, I haven't ever done it before. But Thanks for the help.
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Elder User
Joined: Apr 2001
Posts: 772
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From: Glen Burnie Maryland
Some TPS are adjustable from the factory, and some aren't. Just loosen the two screws holding it down and rotate one way or the other until the voltage is .9vdc. It won't take much, more like a twitch. If it won't rotate, take a drill and egg out the screw holes until you can read .9vdc at idle.
The other thing you might do is pull the IAC off and clean the plunger and seat really good, and re-install.
Have fun.
Larry
The other thing you might do is pull the IAC off and clean the plunger and seat really good, and re-install.
Have fun.
Larry
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