Bad TPS?

Comatose · 01-05-2002, 05:51 PM

86GT, HO 5.0EFI 5spd. Bone Stock except Hypertech Power Chip.

The idle is inconsistent, and cruising about 25mph, 2k RPM 2nd gear, the car has a mild surging motion. It seems to do this upon acceleration as well. If I accelerate hard from one stoplight, when I stop at the next the car idles at 1200 rpm for a short while, whereas it will usually idle between 500-800rpm.

The Cap, Rotor, Plugs, Plug Wires, Air Filter was all changed 6k miles ago.

Any help would be appreciated.

Thanks,

Jeremiah

exgmguy · 01-05-2002, 06:28 PM

You can check your tps voltage with a digital voltmeter. It should be around .95v at idle, and go to around 4.5v at WOT.

Your problem sounds kinda like a bad O2 sensor.

Comatose · 01-05-2002, 09:59 PM

This may sound silly.....how do I check the TPS voltage? Does the car have to be running to check it? If the the voltage is off, is it adjustable or do I have to replace it? Where are the O2 sensors and how hard are they to replace?
Sorry for all the questions.

Thanks for the help, I am investing in a Repair Manual next week.

Jeremiah

Brad · 01-06-2002, 02:30 PM

I have the same car and the tps went bad after I got it wet. If you have a buddy with a stang just try his tps, it only takes a minute and a screw driver you will know in 5 min. if thats the problem.. Or if your local parts store as a good return policy you can do the same.. Good Luck.

By the way, what do you think of your Hypertech Chip????

Coupe5oh · 01-06-2002, 03:28 PM

Thats what this place is for

, your 02's would probaly have your check engine light on if bad, check the tps voltage bye putting some pins in the wires....dam forgot which ones, green and black? hopefully someone will correct me, im gonna go reset timing on my car so i will look at mine brb.

Comatose · 01-06-2002, 06:16 PM

Do I check the TPS voltage when the car is running? Also, I don't think my 86 has a check engine light, if it does, I guess my o2 sensors are fine.

I bought the car less than 3mos ago and it had the Chip in it when I got it so I don't know the difference, my car is the only 5.0 I've driven. Seems to run pretty good.

Later,

Jeremiah

Coupe5oh · 01-06-2002, 06:23 PM

I remember just turning the key on, but leave motor off. black and green wires i think, i forgot to lookk, and i just got out from under my car.

Rebel79 · 01-07-2002, 11:37 AM

Take a needle and pierce the green wire. Use that as the positive and use your throttle body as your ground. The voltage should read between .950-.999. Different people will tell you different settings for the TPS. Having a blown car I have found no difference between .950 and .995. To adjust, loosen the two screws holding the TPS and rotate slightly.

01-05-2002, 05:51 PM	#1
Comatose Registered Member Join Date: Oct 2001 Location: Goldendale, WA, USA Posts: 84	Bad TPS? 86GT, HO 5.0EFI 5spd. Bone Stock except Hypertech Power Chip. The idle is inconsistent, and cruising about 25mph, 2k RPM 2nd gear, the car has a mild surging motion. It seems to do this upon acceleration as well. If I accelerate hard from one stoplight, when I stop at the next the car idles at 1200 rpm for a short while, whereas it will usually idle between 500-800rpm. The Cap, Rotor, Plugs, Plug Wires, Air Filter was all changed 6k miles ago. Any help would be appreciated. Thanks, Jeremiah __________________ Jeremiah 1986 Mustang GT K&N Filter, Removed Air Silencer, Black Magic Fan, 65mm Explorer TB, 110lph BBK Fuel Pump, F/M Force II Cat -Back, O/R h-pipe, U/D's Timing@14* 1986 Mustang LX SSP--new project car AOD, 3.27's, Dumps, 238k miles

01-05-2002, 09:59 PM	#3
Comatose Registered Member Join Date: Oct 2001 Location: Goldendale, WA, USA Posts: 84	This may sound silly.....how do I check the TPS voltage? Does the car have to be running to check it? If the the voltage is off, is it adjustable or do I have to replace it? Where are the O2 sensors and how hard are they to replace? Sorry for all the questions. Thanks for the help, I am investing in a Repair Manual next week. Jeremiah __________________ Jeremiah 1986 Mustang GT K&N Filter, Removed Air Silencer, Black Magic Fan, 65mm Explorer TB, 110lph BBK Fuel Pump, F/M Force II Cat -Back, O/R h-pipe, U/D's Timing@14* 1986 Mustang LX SSP--new project car AOD, 3.27's, Dumps, 238k miles

01-06-2002, 02:30 PM	#4
Brad Registered Member Join Date: Mar 1999 Location: Auburn,NY Posts: 7	I have the same car and the tps went bad after I got it wet. If you have a buddy with a stang just try his tps, it only takes a minute and a screw driver you will know in 5 min. if thats the problem.. Or if your local parts store as a good return policy you can do the same.. Good Luck. By the way, what do you think of your Hypertech Chip???? __________________ 88GT red,t-tops,pony wheels,underdrive pullys,Dynomax cat-back, K&N, 125,000 miles...

01-06-2002, 03:28 PM	#5
Coupe5oh Registered Member Join Date: Nov 2001 Location: SanAntonio, Tx Posts: 734	Thats what this place is for, your 02's would probaly have your check engine light on if bad, check the tps voltage bye putting some pins in the wires....dam forgot which ones, green and black? hopefully someone will correct me, im gonna go reset timing on my car so i will look at mine brb. __________________ Police package 5spd 90 Lx, Stock original motor, 3.27grs, BM fan, fms 10.5 clutch, D&D quadrant, and adjuster, ADS chip, 180 stat, mac cai, mac h-pipe, mac subframe connectors, ASP crank pulley, ripper shifter, 26x10.5 M/T sport pros welds. 246 hp according to analyzer Race weight: 3,120 E.t-13.57 with 26x10.50's e.t. streets. 1.88 60' mph- 99.92 mph

01-06-2002, 06:16 PM	#6
Comatose Registered Member Join Date: Oct 2001 Location: Goldendale, WA, USA Posts: 84	Do I check the TPS voltage when the car is running? Also, I don't think my 86 has a check engine light, if it does, I guess my o2 sensors are fine. I bought the car less than 3mos ago and it had the Chip in it when I got it so I don't know the difference, my car is the only 5.0 I've driven. Seems to run pretty good. Later, Jeremiah __________________ Jeremiah 1986 Mustang GT K&N Filter, Removed Air Silencer, Black Magic Fan, 65mm Explorer TB, 110lph BBK Fuel Pump, F/M Force II Cat -Back, O/R h-pipe, U/D's Timing@14* 1986 Mustang LX SSP--new project car AOD, 3.27's, Dumps, 238k miles

01-05-2002, 06:28 PM	#2
exgmguy Registered Member Join Date: Feb 1999 Location: Utica, Michigan Posts: 2,631	You can check your tps voltage with a digital voltmeter. It should be around .95v at idle, and go to around 4.5v at WOT. Your problem sounds kinda like a bad O2 sensor.

01-06-2002, 06:23 PM	#7
Coupe5oh Registered Member Join Date: Nov 2001 Location: SanAntonio, Tx Posts: 734	I remember just turning the key on, but leave motor off. black and green wires i think, i forgot to lookk, and i just got out from under my car.

01-07-2002, 11:37 AM	#8
Rebel79 News Editor Join Date: Apr 1999 Location: Concord, CA Posts: 2,101	Take a needle and pierce the green wire. Use that as the positive and use your throttle body as your ground. The voltage should read between .950-.999. Different people will tell you different settings for the TPS. Having a blown car I have found no difference between .950 and .995. To adjust, loosen the two screws holding the TPS and rotate slightly. __________________ Scott Halihan, News Editor The MustangWorks Magazine 1994 Supercharged Mustang Cobra Rebel Racing. Home of Bay Area Mustangs