TPS volts 4.0... how to change to 4.7?

[hockey10588]

my mechanic said that my TPS volts were 4.0 and factory should be 4.7 to 4.8 volts at wide open throttle. he said he would change it to 4.7 volts but for $50! so I just told him I would do it because I have a multimeter and everything.

so how do I go about doing this? I think it's different than setting your input/output 83% thing right?

[XgeekstarX]

wait.. what year?

[hockey10588]

wait.. what year?
O ya sorry guys
1990 Cherokee
automatic

[philip_g]

here we go again.

[XgeekstarX]

just do a search. i don't have a renix so i don't have to worry about adjusting the tps so i don't know the procedure offhand.

[hockey10588]

ok guys I'm going out right now to buy a whole new TPS unit from Napa so once I put that in I'll let you know how things are going.

Do you think a faulty TPS and a faulty EGR valve could give the same symptoms? I've read sometimes a bad EGR shows the same symptoms my Jeep is going through but I know my TPS is out of whack now, but could it be both?

[lawsoncl]

Check all of your grounds first. It another post you mention that it won't even start?

[5-90]

Um - are we talking about INPUT voltage, or OUTPUT voltage?

Output voltage can be adjusted by loosening the two mounting screws and slipping the TPS about, but INPUT voltage is a reference signal from the ECU and can't be altered without changing the ECU. Since the TPS is used as a voltage divider, and the output signal is read as a percentage of the input voltage (rather than as an absolute voltage signal,) having a low input voltage should not be a significant problem. FSM adjustment procedure even lists idle output voltage as a percentage of input (I think 17%, but I'd have to check,) so you have to see what your input voltage is before you can properly adjust it anyhow.

5-90

[hockey10588]

alrighty well I didnt buy a new TPS because I think I finally adjusted mine correctly.

input- 4.71 v
so I adjusted my output to 3.91 v which is ~83%

It'll start now but the idle jumps really high (2000rpm) and back down after a couple seconds and I can give it all the gas I want and it'll be fine for about 20 seconds and then all the problems start coming back (choking, extremely low idle, some intake backfiring, and if I give it alot of gas it boogs down and stalls completely).
I also unplugged my vac line to the EGR valve and plugged it with my finger to see if it was a bad EGR valve and problems are still there.

can anyone give me anymore advice before I have to take it in?

[5-90]

Check your EGR vacuum line and make sure it's blocked off without leaks.

Check the rest of the vacuum harness and make sure it's no lines are cracked. RENIX vacuum lines are available in the aftermarket - search for the part numbers here, and get them from NAPA. It's a set of three numbers, and should cost about $50 all up.

Also, think about replacing the IAC on the throttle body - I'm having problems with "roaming idle," and I've tracked it down to the IAC (it's the only thing I haven't tested yet - and I've replaced the TPS due to a "flat spot" around cruise.)

5-90

[maxen24]

my tps caused the same probs i hooked it up to a snap on reader and it would show crazy readings when it should be closed or wide open so i just replaced it instead of looking forever but only cost me 25 bucks for the new tps sensor..