Problem: TPS or other?

so my car started doing this a couple days ago, i think the TPS is the problem, one of my friends believes it is the MAF. i’ll do my best to describe what it is doing.

the first 40% or so of the throttle gives me the same slow acceleration but if i hit a certain point it is like a switch flips and i suddenly am accelerating like the car normally would. this is very noticeable in first gear, it is almost as sudden as if i suddenly went WOT from nothing.

in addition to this it also isn’t idling properly, it will idle at 800 RPM like the car normally will, then it will start fluctuating up and down, while decreasing to about 500 RPM, then it will rev itself back up to 800 RPM and repeat, the cycle takes about 15 seconds.

i drove to my shop and the car was running/driving perfectly but the radio stopped working on the way, i wasn’t too concerned about it as nothing else stopped working at the same time, car wasn’t having this problem yet. parked my car and worked on some other projects, didn’t touch my car at all until i was about to leave for home. pulled out the panel around the deck and found my accessory wire had shorted out because some tape fell off of it because i did a rush job installing the deck, taped it up properly, put in a new fuse and the deck worked again. when i started it up to drive home this new problem started happening. car is a '92 240, stock except an air intake, deck and some gauges.

i have a feeling its a TPS because i sold my spare one 2 days before figuring that i wouldn’t need it, haha.

any suggestions would be great, thanks.

I don’t have a sure fire answer for you but I would guess TPS as well. I would also bet against it being the MAFS since this happens according to the throttle which is not directly associated with the amount of air being taken in.

so after having to drive the car around a bit tonight its gotten worse and i pretty much have two speeds, idle and almost full throttle.

tps for sure.

Hook a multimeter up to the wires coming off the TPS. If you read 0v with the throttle closed and 4.5V at 100% throttle then the TPS is fine.

i think its a dead spot in the tps though so it will say 0V at idle, maybe 1V at 20% then 0V at 30-60% throttle, then 4.5V at WOT, i’m going to my shop tonight so i was going to try that, this is what i’m expecting to see it read.

if this is the case, does anyone have an S13 kade tps for sale? the one that only has one plug as some of them have two.

so its not the TPS, MAF or ECU as i swapped all of those today from my buddy’s running car and it still acted the same.

next thing i’m thinking is the O2 sensor, bogging down in closed loop and then acting proper in open loop, make sense? i’m going to give that a shot tomorrow.

I’m having the same problem with you but. When my cars idling at a red light the rpm flickers up and down. Im going to try my TPS as well. Make sure all of your vacuum hoses are attatched and snug.

Try and disconnect the tps first. If it does the same thing then theres your problem, if the cars idel changes more then rule it out. Let me know how it goes.

already ruled out the tps.

changed the O2 today, its not that either.

i had a similar problem with mine and same as you tried everything couldnt figure it out so i tryed Coolent temp sensor and car runs great now

well that makes no sense at all… but neither does this car so i guess i’ll try it tomorrow, haha.

thanks.

so my car started doing this a couple days ago, i think the TPS is the problem, one of my friends believes it is the MAF. i’ll do my best to describe what it is doing.

the first 40% or so of the throttle gives me the same slow acceleration but if i hit a certain point it is like a switch flips and i suddenly am accelerating like the car normally would. this is very noticeable in first gear, it is almost as sudden as if i suddenly went WOT from nothing.

in addition to this it also isn’t idling properly, it will idle at 800 RPM like the car normally will, then it will start fluctuating up and down, while decreasing to about 500 RPM, then it will rev itself back up to 800 RPM and repeat, the cycle takes about 15 seconds.

i drove to my shop and the car was running/driving perfectly but the radio stopped working on the way, i wasn’t too concerned about it as nothing else stopped working at the same time, car wasn’t having this problem yet. parked my car and worked on some other projects, didn’t touch my car at all until i was about to leave for home. pulled out the panel around the deck and found my accessory wire had shorted out because some tape fell off of it because i did a rush job installing the deck, taped it up properly, put in a new fuse and the deck worked again. when i started it up to drive home this new problem started happening. car is a '92 240, stock except an air intake, deck and some gauges.

i have a feeling its a TPS because i sold my spare one 2 days before figuring that i wouldn’t need it, haha.

any suggestions would be great, thanks.

I don’t have a sure fire answer for you but I would guess TPS as well. I would also bet against it being the MAFS since this happens according to the throttle which is not directly associated with the amount of air being taken in.

so after having to drive the car around a bit tonight its gotten worse and i pretty much have two speeds, idle and almost full throttle.

tps for sure.

Hook a multimeter up to the wires coming off the TPS. If you read 0v with the throttle closed and 4.5V at 100% throttle then the TPS is fine.

i think its a dead spot in the tps though so it will say 0V at idle, maybe 1V at 20% then 0V at 30-60% throttle, then 4.5V at WOT, i’m going to my shop tonight so i was going to try that, this is what i’m expecting to see it read.

if this is the case, does anyone have an S13 kade tps for sale? the one that only has one plug as some of them have two.

so its not the TPS, MAF or ECU as i swapped all of those today from my buddy’s running car and it still acted the same.

next thing i’m thinking is the O2 sensor, bogging down in closed loop and then acting proper in open loop, make sense? i’m going to give that a shot tomorrow.

I’m having the same problem with you but. When my cars idling at a red light the rpm flickers up and down. Im going to try my TPS as well. Make sure all of your vacuum hoses are attatched and snug.

Try and disconnect the tps first. If it does the same thing then theres your problem, if the cars idel changes more then rule it out. Let me know how it goes.

already ruled out the tps.

changed the O2 today, its not that either.