So i have a 97 civic, about 280k miles, D16Y8, 5spd, cold air intake, 4-2-1 header and pretty much stock otherwise. I've had a problem with the car off and on now for some time. It started out where in certain throttle positions, the car would loose power, like i had taken my foot off the gas, but hadn't. Tested the throttle position sensor with a volt meter and found that it was intermittent in certain positions. Replaced it and the problem went away. Now some months later I'm having a similar issue, where the power falls off like i took my foot off the gas, but haven't, and then without moving my foot, power comes back. If i push in the clutch when it does this fall out thing, the engine drops to idle, but doesn't die.

Seems to be worse in colder weather than in warm. Over time it has gotten worse. At first it would only do this when the car was cold, but then after it was fully warmed up it was fine. Now it does it warm or cold, but at random and unpredictable times. Still does it more when the weather is cold than warm.

I have been probing the wires going into the engine computer, hoping to see some correlation to sensor inputs and failure, but thus far i have yet to have a meter connected when it did this.

One time while sitting still in the driveway and trying to get the car to act up, i was holding the gas part way down, car in neutral, holding about 3krpms, and the engine rpms started to bounce from 3k to idle and back again.

i have also noticed that at times, the idle seems to hang up and be higher than normal, irs fine, for a couple lights, and then the next light the car idles at 1200-1500, tap the gas pedal and it will sometimes drop down to the normal 500-750 neighborhood, sometimes it wont... does this more often when the car is colder than when warm.

the most recent driving failure was on a cold night, about 35f and i was going about 65mph, steady speed, not moving the gas at all, and the car pulsed and jerked like i was going from full throttle to idle, very hard on the drive line... it did it long enough that i tried constantly moving the gas peddle up and down very slightly, and this greatly reduced the jerking of the engine. it seemed to me that by having the tps moving and not sitting in just one place i was able to control the issue. i got the car home, but am afraid to drive it now.

I have also recently put one of those elcheapo volt meters in the cig lighter to watch voltage, and have noticed that at times the voltage drops from the normal running and charging voltage of 14.1 to 12.5. seems to do this more often when in gear but foot off the gas, where the engine is doing the breaking.

I tried to drive the car around the block a few times last week to see what it would do, but it was 70f outside and the car drove perfectly. it did however throw a code(the CHECK ENGINE LIGHT came on) and when i pulled the code it was throttle position sensor. I checked the input and output voltages and all were correct. good ground, good 5v in, and a steady and smooth output voltage all the way through its travel.

I've checked the map sensor, the tps, the coolant sensors, and everything i know how, and i just cant find anything... Being that it is an intermittent problem, i know that i have a challenging road ahead of me, but if anyone has had this problem, or has some input on what it could be, i'd love to hear it... i need my little car. driving my big truck to work every day is eating me out of house and home on gas.

 

NO CELs?? Is the 97 an OBDII system? If so you need to see if there are any codes stored. My other thought was a possible fuel pump giving up, or a plugged fuel filter.

 

yes it did have a code, it threw an 07? (not sure on the number now), but i definitely remember that it was, according to the hanes book i have, throttle position sensor. I remember this so specifically because of having changed it before and re-checking its ground, 5v in and output voltages as soon as i pulled the codes...

the other thing that i didn't mention in the first post was that i have noticed that occasionally the idle is lower than normal as well as sometimes higher, this makes me think about the idle air control valve, and as i have never touched it, wondering if it could be a culprit in the problem, but I'm having a hard time imagining a scenario where it would cause the steady 3k rpm driving fluctuation issue..

no the 97 is obd1.

I'm not gonna say that it cant be fuel delivery, ie a fuel pump or filter, but i have driven the car long and hard, and at high rpm's and under those conditions(maximum fuel usage) there is never a failure... the most common issue is under a steady load, holding basically a steady speed, around 65-70 mph, turning around 3k rpm's. if it were fuel delivery, i would think that the issue would be more pronounced under hard acceleration, and at long high rpm's(when its using more fuel.) if i run the car out to redline in second or third gear, foot hard to the floor, it never shudders, but when i'm just easing down the highway, holding a steady speed it acts up.

 

Test TPS again carefully with a voltmeter, it sounds like it is bad. Also check the TPS plug for corrosion, etc.

The 97 has OBDII though it also supports OBD1 style blink codes. An OBDII scanner could provide more detailed information.

 

i have tested the tps a couple times now with a good meter, and i have not found anything that makes me think that its bad, i understand that its just a potentiometer, (variable resistor) and is used as a voltage divider, and in that, if there was anything wrong with it, it would show up in the output voltage...

as for the connector, now that's something that i didn't spend much time looking at... and could explain the problem... except that i cant see the connector or wires being part of this problem in this one respect, when it acted up the most recent time, moving the gas pedal seemed to control the issue, and if it were the connector it shouldn't... that one fact makes me think its the tps and not connections...

it is obd II, 96 and newer are all obd II right? i dont know why I said it was obd I before... brain fart i guess...

Ive only ever used the blink method of pulling codes...

would this unit be a good enough?
CAN OBDII Code Reader with Multilingual Menu

or should i spend a little more and get
OBD II / EOBD Code Scanner - Save Big on this Code Scanner

or maybe i should go big for the one that does live read and data recording?
CAN OBD II Code Reader / EOBD Scanner

I know so very little about code readers, i understand that i may be able to get more information from one than i have been getting from the light blink method, i just don't wanna go spending money if its not gonna get me closer to a fix....

 

Anyone?

 

It was recently suggested to me that with the way the car acts, and having checked the TPS, that it could be the ECU. I was thinking about finding a junkyard car, and getting the ecu and swapping them out. i believe that one would be available for around $40...
but thats just swapping parts hoping for a fix, and i want to know for sure...

 

ever figure this one out? i am having what seems to be very similar issues:

car starts and drives fine around town. zero slips/studders/hesitions. HOWEVER, at highway speeds, 65-75 holding a steady throttle, the car will do the above. give it more gas or release the gas pedal and issue goes away. it seems MUCH more prevalent when under a load such as going up small (or large) inclines on the highway but not letting it downshift. HELP!