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I have had a pulsing idle('89 S5 NA) since it has gotten colder that consistently pulses from 1500-1300. It used to only happen on cold days and didn't happen on warm days, but lately it has happened every time. On warmer days it only start to happen after I hit the gas for the first time and then it will start to pulse. After a good 10 or so minutes of constant driving the pulsing goes away and it idles beautifully. I suspected TPS due to it being after I hit the gas for the first time and the fact that no vacuum leaks were present, so I bought a known good used TPS and threw it on. It went on smoothly and after I started it up and hit the gas a few times I had no more pulsing and it idled good, but I did have a check engine light at idle but when I touched the gas the CEL would go away(never had a CEL with the old TPS). After I let it warm up a bit I drove it up and down my driveway and on the way down it started to pulse again. I unplugged the TPS and the pulsing went away but I know that this TPS work from 1-5 volts as it should. So I'm wondering if there's a adjustment procedure or anything that I'm doing incorrectly with this new one or if it is something completely different?
With the known good TPS the narrow range ohms(1.157) are within spec yet the full range isn’t(0.141). when i’m checking the narrow when I start to move the throttle at all it looses all ohms and with the full range I can lightly touch the throttle and it starts to go up but after a little farther it also looses continuity. With the green wire voltage set to 1.0 V while running(top right pin of connected if looking at the pin side of the TPS side of the connector) it still pulses and throws a CEL at idle and again goes away after the throttle is touched but comes back once the throttle is released. Am I doing something wrong or need to check other things or something?
What is your idle normally? As far as adjusting TPS, what procedure did you use to set it? follow procedure in FSM and it should work fine
If I remember correctly when it's warmed up and not pulsing it idles ~800 or so. I adjusted the volts to 1.0 but still had pulsing problems. I explain more in the above reply, I didn't see this reply until after I posted the one I just sorry.
If the pulsing is only when cold, fast idle cam not engaged, the tps will be slightly above normal idle position so having discontinuities right above idle sounds like a probable culprit. The tps should sweep smoothly through the range 0k ~ 5k, according to this thread: https://www.rx7club.com/2nd-generati...stment-322241/, if not that means tps is internally messed up. You can try spraying electrical connection cleaner, trying to get it into the plunger, while actuating the tps to try and restore electrical continuity.
Also it sounds like you do not need to adjust the upper tps, only need to set the lower one to ~ 1kOhms
once you get the TPS right, the other thing that can cause trouble is the idle speed. the S5 uses timing to make quick corrections, and if the idle is too high or too low it can cause surging
If the pulsing is only when cold, fast idle cam not engaged, the tps will be slightly above normal idle position so having discontinuities right above idle sounds like a probable culprit. The tps should sweep smoothly through the range 0k ~ 5k, according to this thread: https://www.rx7club.com/2nd-generati...stment-322241/, if not that means tps is internally messed up. You can try spraying electrical connection cleaner, trying to get it into the plunger, while actuating the tps to try and restore electrical continuity.
Also it sounds like you do not need to adjust the upper tps, only need to set the lower one to ~ 1kOhms
correction: first sentence should not say “not”, i.e. fast idle cam will be engaged when coolant is not at operating temp
correction: first sentence should not say “not”, i.e. fast idle cam will be engaged when coolant is not at operating temp
excuse my handwriting but basically have had little to no changes in the actual results of what the car is doing(i.e. whether it pulses or not). However the "known good" TPS I had bought that I referenced before I took off and bench tested the continuity of the wires and they were present when closed and wide open throttle, so I put it back on and the results above are what came from it after I put it on. As you can see the narrow is within spec yet the full isn't in spec when the throttle is closed. I know there's that adjustment screw with the little spring on it that you can turn and it'll adjust the TPS, but it was just adjusting the narrow range while the full range only changed by ~0.03. Is there a way to just adjust the narrow without changing the full or are will they both be evenly changed while adjusting? Also I got a volt reading which seemed to be within spec, I know the closed was good at the 1.01 V but the wide open was at 4.81 V should it be at 5 V or is 4.81 close enough?
**little update. I messed with a few things and I now have no CEL at idle or while revving. The pulsing doesn't happen until it is basically fully warm(it's about 65 F here so it's hard to get a cold weather start lol). When the motor is cold and I start the car it will start to idle at ~1300 or so maybe a little lower and slowly as it gets warmer it will rev a little higher and once it's fully warm it goes to 1500 rpms and will then subsequently start to pulse. While it is warming up though I can hit the throttle as many times as I want and it won't start to pulse, but it's only when it hits that 1500 mark it will start to pulse. I tried turning down the idle screw on the top of the throttle body to no avail so not sure where to go from here. The readings still aren't completely correct for the TPS to be in spec so I'm not sure if it still points to that or something else. The reading were roughly the same as they were in the recorded data I had from before.
once you get the TPS right, the other thing that can cause trouble is the idle speed. the S5 uses timing to make quick corrections, and if the idle is too high or too low it can cause surging
Obviously the TPS isn't correct yet, but I did try to adjust the main idle screw(the one on the very top of the throttle body) just for ***** and giggles and all it did was change the frequency of the pulses. The tighter the idle screw the slower the pule frequency, and vise versa. Also thought I would mention that again there were no pulses with the TPS unplugged which I don't know if that gives any information or if the ECU's just default if there's no signal from the TPS.
**little update. I messed with a few things and I now have no CEL at idle or while revving. The pulsing doesn't happen until it is basically fully warm(it's about 65 F here so it's hard to get a cold weather start lol). When the motor is cold and I start the car it will start to idle at ~1300 or so maybe a little lower and slowly as it gets warmer it will rev a little higher and once it's fully warm it goes to 1500 rpms and will then subsequently start to pulse. While it is warming up though I can hit the throttle as many times as I want and it won't start to pulse, but it's only when it hits that 1500 mark it will start to pulse. I tried turning down the idle screw on the top of the throttle body to no avail so not sure where to go from here. The readings still aren't completely correct for the TPS to be in spec so I'm not sure if it still points to that or something else. The reading were roughly the same as they were in the recorded data I had from before.
if it surges while its warming up, that can be kind of tricky. the ecu has target idle speeds for the coolant temp, and if you are too far out it surges. you might try adjusting the thermowax. the screw that actually touches the wax pellet, you should give it like a half turn one way and see what it does. actually it might be a good idea to pop a hose off and make sure its not plugged and it has coolant up there. it sits up high in the system and its pretty easy to be air bound or plugged with junk
the thermowax is a PITA to adjust, so keep it simple.
According to the fsm you do not need to mess with the upper tps, there is a control module that adjusts its readings accordingly. 4.81 is within spec.
The idle should not rise while warming up and it should be nowhere near 1500 so something is quite messed up.
Check that nothing it holding the throttle open.
1. Fast idle cam: this should only be engaged while warming up. When at operating temp, make sure the cam is not touching the throttle.
2. Cables: make sure both the throttle and cruise control cables are not holding the throttle open.
After checking and adjusting, set the lower tps to 1kOhm or 1 V and see where idle is. When adjusting idle using the idle adjust screw you must jumper the initial set coupler to take the BAC out of the control loop.
03-15-22, 06:20 PM
