1986 f150 Map sensor issues?
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Cross-Country
Joined: Jan 2025
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1986 f150 Map sensor issues?
my 1986 f150 has a severe high idle problem when I plug the map sensor into vacuum supply. It will rev to two grand off of startup and go to 2500 if I tap the throttle. Now it does this with a new map sensor and the old map sensor. also it runs very rich without the map plugged in and it sounds like it has a stage 2 cam and has all of the power its supposed to put out. when I have the map sensor vacuum supply plugged in it backfires and sputters when I give it beans.
I have tried unplugging these things
computer bypass (without truck running and then starting truck)
tps
Iac
and I recently replaced upper intake and throttle body gaskets
also o2 sensor is new
please help! It runs about 3-5 mpg without map and I dont want the truck to carbon up.
I will try spraying carb cleaner around seals.
I also have to note that I have shorty headers, no cats, no muffler. so I am wondering if truck needs more obstruction for o2 sensor to read properly?
thanks!
video attached is what it does when I plug map sensor in
btw, video is missing question mark on caption, I wasn't being confidently wrong
I have tried unplugging these things
computer bypass (without truck running and then starting truck)
tps
Iac
and I recently replaced upper intake and throttle body gaskets
also o2 sensor is new
please help! It runs about 3-5 mpg without map and I dont want the truck to carbon up.
I will try spraying carb cleaner around seals.
I also have to note that I have shorty headers, no cats, no muffler. so I am wondering if truck needs more obstruction for o2 sensor to read properly?
thanks!
video attached is what it does when I plug map sensor in
btw, video is missing question mark on caption, I wasn't being confidently wrong
Thread Starter
|
Cross-Country
Joined: Jan 2025
Posts: 57
Likes: 6
Update! I sprayed all the flanges with ether and I didn't find any leaks and also I ordered a fancy 25 dollar digital scan tool. So I let the engine warm up, shut the motor off and hooked the scan tool up, she only gave codes when I made something wrong like unplugging the egr and it threw codes but when I plugged the egr back in I didn’t get any codes so I did my koer test and nothing came up but my rpms idled high again but after 30 seconds it came down to 1200 and I believe that issue is from the TPS being off a little and once I set it that it will work. But I have a battery disconnect and I know that the computer resets after 15 minutes of no batterY and it relearns the fuel table. I started it this morning and didn’t disconnect the battery and it ran at 2500 for 39 seconds and then fell back down to 1200 again, I believe it’s my tps because I’m stunned and took it off when cleaning throttle body
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