always something. I cannot keep this car running.

[hottscennessey]

It seems that with this car it has been one thing after another. I love it, but i'm getting aggrivated and need some help with this problem.

I was about a mile from work cruising at a steady 14% throttle when i see my tach randomly drop 700 rpms (i mean 1/4 second quick, stock flywheel). This problem is common and will happen once randomly about every third time i drive the car. The car will keep driving fine like nothing happened. Just a little jolt and back to normal. Anyways, this time was different. The car does it once, i think its gone, but no. The car jolts and the tach bounces again. and again. I'm headed downhill and just pray for the car ahead of me to speed up. so i can possibly make it back up the next hill. no such luck. I decide to keep going considering there is nowhere at all to park it. I give it some more throttle and the car jolts and backfires up the hill. The problem comes and goes but is getting increasingly worse. I arrive at my destination. I check codes (i get 14). I jiggle the CPS wire. No worky. i check coils, plugs. Everything accesable. I check my maft wires and for vacume leaks. none. I re-set my ecu. No change. The car idles fine, i guess perfect? Its hard to judge how well it idles when your looking for something to be wrong. It pulls 21 vac.

what i think...
I'm gonna go check it out tomorrow with some tools. It sounds eletrical. My wiring harness is like a rats nest with a zeitronix, SAFC, and MAFT. I think my RPM wire could possibly be grounding out. Now dont flame on me because i dont know what the effects of this would be. It seems to make a little sence since the ECU reads RPM and the tach was going crazy. This does not explain ignition, unless the igniton map (or whatever) is screwed up because its confused by the RPM

 

[PIONEER]

If I was a betting man, I'd check the pink and orange wires on the SAFC. If you have a loose connection there the car would do what you are saying.

 

[hottscennessey]

good idea, i'll definately check. I soldered but Its bound to be something i did to the car.

 

[PIONEER]

its some kinda loose electrical connection. I would say take the glove box out, start the car and gently move the wires under the dash and see if the car acts up.

 

[hottscennessey]

lol, ok no problem. I havnt had a glove box for months.

 

[PIONEER]

is your ECU mounted or hanging by the wires? that could be another problem if your ECU is not secure.

 

[hottscennessey]

nah, its secure, i didnt mess with any wires when i was trying to fix it, but i did make sure everythign was plugged in securely.

 

[hottscennessey]

I just dont know. I cannot find the problem. I jiggled the ECU wires i think that might have helped. I took some logs. You can easily see where i'm holding a consistant throtle possition but the RPM signal is jumping around. It doesnt make sense to me.

 

[hottscennessey]

:1zhelp:

 

[hottscennessey]

Where does the RPM signal come from? Is it the CPS?

 

[hottscennessey]

Has anyone ever heard of the RPM signal dipping and spiking like this? HELP!

 

[SupraMario]

Man i wish i could help you but know nothing about SAFC and MAFT all that turbo stuff i will soon, but the only thing i can think of is stupid and simple.

 

[mk3troubles]

i had the same problem with my car... i took out the safc, traced all the wires and made sure everythign on the cars harness was fine, no cutes anywhere to where it would ground out... then i respliced the safc harness one by one, soldered the bad boys back together and heat shrunk everything... never had the problem again... yorus is a little tricky though... all that splicing under there would piss me off too... i hope you figure it out man, im betting is your safc wiring...

 

[rakkasan]

I had symptoms that were very, very similar. Check you vacuum lines again and pay close attention for any cracks. The bad thing about checking for vacuum leaks while the car isn't moving is that they can 'heal' themselves. When a car is moving, vacuum lines endure the same movement, therefor a crack can open itself up.

 

[hottscennessey]

I ordered a new igniter, I'm hoping this will take care of code 14? who knows. We'll see what happens.

 

[malloynx]

i would also check all the wiring, make sure it's nice and good

 

[siman]

I had that happen about 4 months back.

The car would misfire always around 3-4K rpm. Steady driving...then lean into the throttle and it would misfire and STUTTERRRRRRR.....then back to normal.

Sometimes it would not even start!

come to find out it was corroted CPS wires ( where the male and female CPS harness connectors are)....the clutch fan was litterally BLOWING the wires around and grounding them out!

Needless to say me and the brother got some connecoters and did surgery on the tiny wires...

its been 4 months and NO HICKUPS. NO THROTTLE BLIPS, NO MISFIRES.

Check your CPS wires. I am willing to bet the heat has baked the coating and they are not connecting the signal like they should.

-Jonathan

 

[hottscennessey]

I checked it up and down, looked good. Looks are misleading.

 

[hottscennessey]

I had that happen about 4 months back.

The car would misfire always around 3-4K rpm. Steady driving...then lean into the throttle and it would misfire and STUTTERRRRRRR.....then back to normal.

Sometimes it would not even start!

come to find out it was corroted CPS wires ( where the male and female CPS harness connectors are)....the clutch fan was litterally BLOWING the wires around and grounding them out!

Needless to say me and the brother got some connecoters and did surgery on the tiny wires...

its been 4 months and NO HICKUPS. NO THROTTLE BLIPS, NO MISFIRES.

Check your CPS wires. I am willing to bet the heat has baked the coating and they are not connecting the signal like they should.

-Jonathan

Kick ass, thats exactly what i'm looking for. So Jonathan, did you get code 14 at all? That sounds similar to my problem, but did you have the RPM signal spike and surge?

 

[siman]

Kick ass, thats exactly what i'm looking for. So Jonathan, did you get code 14 at all? That sounds similar to my problem, but did you have the RPM signal spike and surge?

Yep.

The Tachometer just JUMPED around like crazy....it was SOO funny how i figured the whole situation out.

1. I was watching a best motoring video with the Bee-Racing R32/34 drift car...as you well may know Bee-R makes the "rev limiter" that allows to hit rev cut at a set RPM and shoot flames yada yada...

2. When Orido (drifter and JGTC driver) was drifting ( driving) the car around the track he would hit the rev cut with the rev limiter device...the tachometer would JUMP just like my car was doing....NO JOKE..I studied the way the car sounded when it hit the "cut"....and watched the tach.

3. EXACTLY the same. I did run a code though, cannot remember since my car routinely runs codes like Neo from "The Matrix":biglaugh:

4. All of it made sense the way the rev limiter worked and how my car was misfiring....the rev limiter cuts the signal to the ignition...basically dumping fuel inside the motor then re-igniting it and shooting a fireball......

Our supra's problems ( with the CPS wiring) was that the CPS was not sending the "firing" signal to the ECU...it was MISFIRING....so it would stutter...essentially hitting a "rev cut"...then the signal would reach the ECU and so the ignition would be again revived...

Get me?

Its all in the wiring.

1. CPS wires dont connect>No firing signal to ECU>No spark> Rev Cut> Seen as weird tachometer jumps and stuttering of the car under load

That should sum it up....I told you it was funny how I figured it out....I like using context clues:icon_razz

-Jonathan