Chillichinchilla

Ok, so I replaced all of the vacuum lines, adjusted the idle stop screw, thermowax, tps, idle speed screw and I am getting a rough idle. it idles at 900 and the exhaust pops a lot and decreases from 900 down to 800 really quick and then goes back to 900. (The popping happens on sudden rpm drops). THEN when I turn on the headlight and a/c. I have a VERY stable exhaust at 1000 rpm. As smooth as it can get, no popping, sounds beautiful. I am getting a 14.45-14.46 volts from alt without load and 14.6 volts with load (a/c and headlights)! Setting the throttle stop screw so the engine idles at 1K rpm without a load makes no difference. Fresh engine.

Rotaryterror

iTrader: (3)

Whats up dude?,

* What is your Setup consist of? Do you have BAC?
* Is your setup turbo or non turbo?
* Do you have a wideband?

Does this situation still apply when the motor is at full operating temperature or only when cold?

Chillichinchilla

1990 rx7 n/a. My setup is as stock as it can get, only aftermarket thing is R.A Apex seals. and no I do not have a wideband, stock as it can get. When I first start the car (AWS disabled) it goes to 1500 RPM and idles fairly smooth, but I can hear a few pops from exhaust every now and then. When warm, she idles at 900 with quick drop to 800 and popping exhaust. Idle stabilizes and stops popping with headlights and a/c on. A/c doesn't even have to be on, just the fan will do.

archaphil

iTrader: (1)

define popping? Like little exhaust queefs? Little farts? or like... Bang?

Chillichinchilla

Rpm quick drop: https://youtu.be/Jrzl8a3kNYgt's like a queef I guess. Again its very silent even my camera doesn't register the noise. I will however try to describe it best as I can, here goes nothing. spell the letter p, it's like that, but more muffled. You know when you or someone puts on chap stick and then they roll their lips to get the chapstick to the very edge of the lip, now if you were to do that and blow air out at 1 or 2 quick bursts, that's what it sounds like. Like I said, it only pops like that during the rpm drop from from 900 to 800, but with a/c and a/c on it does NOT do that, and idles smooth as butter. Here is a video. My camera could not hear the noise but it picked up something when i pointed it into the exhaust. Exhaust pop:
https://youtu.be/q26ghSDLzh8
.Rpm quick drop:
https://youtu.be/Jrzl8a3kNYg

Also as extra information that i noticed only now... checked alternator and at one point it was at 15.9 volts and then at 15 volts also my dashlights are flickering a lot. But could an alternator that is starting to go bad cause this idle issue?

Rotaryterror

iTrader: (3)

Have you checked your tps is in calibration?

I am also curious about the alternator ,the description you gave about the popping/back fire noise is what my car is doing also, and the volt guage reads 16 volts and is very warm.

the only time i can get this to not happen ( regarding the popping noise) is after i have adjusted my tps verifying it is at 1 volt on the G/R wire. the idle will be very smooth around 1000 to 1500. its possible the throttle body might have a sticky part causing reading to not stay accurate.

But it seems once the motor gets to operating temperature the car wants to HIgh rev and backfire

Rotaryterror

iTrader: (3)

Im cleaning the throttle body now while at work and will install once i get back home, When i find a solution i will let you know the out come and hope it can help you also

Chillichinchilla

Thank you RotaryTerror, I have myself cleaned out the butterflies when the whole engine was dissassembled. And yes I have set it to 1 volt also tried .9 and .8 It It doesnt make THAT MUCH difference but best idle so far was at 1 volt.

Update: I remembered I broke off power steering sensor and the wire was actually touching metal when I took a look at it, so I used electrical tape and secured the sensor wire out of the way, and that stopped my exhaust from popping when completely warm! Still pops when cold. Now the idle is pretty stable, but it still wanders a little bit. I would like to get a perfect idle, any other input appreciated. Will/can provide pics/videos if asked.

Edit: Responding to your question abnout tps setting. I actually just checked right now and after warmup, the car was at 1.2 volts... odd, but anyway, set it down to 1, then I let her run for a little longer, took her out on a drive down the block, came back, it was at .56... ok so I set it back to 1 again, took it for a drive and it went up to 2.2 volts. I checked all the wires and according to FSM numbers, my tps is well in spec... I just wish someone had an s5 tps I could borrow close to me instead of shelling out 500$.

Rotaryterror

iTrader: (3)

Hey Chillichinchilla, Ive been working on the Fc and so far my idle still bounces but i went ahead and took for a drive, everything is find except the idle, i was told due to not having my Auxiliary port sleeves installed what is happening is there is a pressure wave from auxilery port that is getting backfed from the motor back up into the Intake manifold causing this bouncing idle.

Do you know if the Sleeves are still installed or functioning correctly?

RotaryEvolution

iTrader: (30)

just drive the car and see if it goes away in time. many issues are associated with giving things time to settle in after a rebuild.

if it doesn't then i would recommend checking compression with an accurate test gauge so you can see if any rotor faces are significantly lower than the others, which would cause backfiring.

driftxsequence

iTrader: (8)

I would agree. I had an idle issue where it would die when cold after I rebuilt it. I put around 1000 miles on it and figured it was "broken in". Lots of short cycles back and forth to work. We went on a 4 hour cruise to the beach, each way, and I noticed a week after that it would start and idle on its own instead of requiring a pump of the gas pedal to hold an idle. However if your TPS is that erratic, it may be an issue...unless the temperature is swinging a lot and the thermowax is moving.

MickeytFC

iTrader: (1)

To piggy back on these issues: When would you start to try correcting idle issues after a rebuild? Is 1000 miles a typical number?

sir revalot

Any more than 14.4v from the alternator is too much..

Sort this out first before you fry something..

Sounds to me like you don't have a voltage reference signal to the alternator or the voltage regulator in the alternator is bad.

driftxsequence

iTrader: (8)

Having known mine idled BEFORE tear down, and not removing any of the stock parts I knew when it went back together it should have acted the same. I guess in my car it was about 3k miles before it would hold its own idle without any interjection. This might explain why my highly modified FC with 2500 miles still has issues....

I would also add that I use a LOT of premix, so maybe my break-in was slowed by so much lubrication? I do 14-16 oz of premix on TOP of the stock OMP on the stock NA, and 16-24oz of premix on the highly modified car.

MickeytFC

iTrader: (1)

That makes it tough to get things right. Seeing as most things are adjusted at idle spec, I don't know when I can get the thing running right and start tuning the thing.

jesseluck

iTrader: (2)

I had the little popping too. Set timing back and smoothed out.

Chillichinchilla

What do you mean set the timing back..? Advance it i suppose? By how much? Or did you just move the cas and hope for the best haha. Btw guys, car is stock as i said anything and everything that is stock is there.

RotaryEvolution

iTrader: (30)

no, advanced timing will cause a lumpy idle(but not backfiring unless you start adding stupid amounts)
retarding the timing will smooth out the idle but it will also cause the RPMs to drop.


so if the timing isn't set properly and it is advanced then retarding it may help some.