Valkyrie

Man... this is getting really old.

I've elminated any possible vacuum leaks from what I can tell, but my car just refuses to idle well when it's fully warm.

Strangely enough, whenever I give it a bit of throttle the timing will advance and it'll idle, although a little high (because the idle is adjusted a little high at the moment). If I leave it alone (parked), the idle won't go back down...but whenever I try to drie it like this the timing goes back to normal and it starts to idle like crap again.

I'm pretty sure it's normal for the timing to advance when you increase the revs, but I'm having a hell of a time just getting it to idle well without highly advanced timing (even if I DO advance the base timing, it still doesn't idle *that* well).

On the other hand, it idles relatively well when the car is cold, and warm, but not when it's full warm (hot).

anewconvert

iTrader: (1)

what does the idle do? Bounce, stall, miss?

Is the TPS adjusted correctly?

I know there is probably another thread out there that you have made about this, but im too lazy to go find it.

BC

Valkyrie

It bounces but it's also very low.

I swear it seems like it acts like the timing is severely retarded when it's fully hot... since I have to advance the timing much more before it'll idle well than when it's just warm.

NCross

iTrader: (18)

is the thermp wax over extending or something?

NZConvertible

The thermowax linkage seperates from the throttle linkage once the engine's warm, so it can't have any effect.

What speed is this crappy idle at? Does increasing the idle speed with the throttle stop screw make it less crappy?

Valkyrie

It would, but that would that make my idle too high when it's warm. And it still tends to bounce a bit.

It hangs around 500 but it sometimes goes as low as 250.

IMO it basically acts like either there's a vacuum leak that only happens at full temp, or perhaps the compression drops whenever it's fully hot.

micah

+1. Had this same problem... it affected me at all temps, just was only REALLY noticable at high temps. KILLED my idle.. expecially when it was hot outside. When the air-temps were cooler it didn't bother me as much.

Replaced my intake gaskets and the problem went away.

Could be something different for you though I suppose.

RockLobster

iTrader: (7)

Sounds like either a small vac leak or your BAC valve idle screw needs adjustment.

If messing with the BAC screw makes no difference then you need to adjust the hard throttle set screw.

NCross

iTrader: (18)

if its bouncing up ad down that means the TPS is out of adjustment. mine did this. it would start up and idle fine at about 800 RPM and when you took off down the road at about 40-50 MPH it would bounce up and down between 1500-3000 RPM.

Valkyrie

The TPS is adjusted... it's bouncy but it's not hunting like a maladjusted TPS would cause.

IMO it's probably bouncing because it dropped too low and the BAC is the only thing keeping it running.

Turning the fan on, or putting my foot on the brake tends to make it worse.

The question being, what changes when the engine goes from warm to hot?

When I set my timing to stock when it's hot, the problem gets even worse, although my light has the annoying advance dial, and I don't know whether it's really accurately showing my timing when I set it to 0 advance.

OTOH the car will idle relatively well if I open the idle so high that it makes the timing advance (idles at 1100 ish).

Valkyrie

I noticed one thing, which is that my throttle cable didn't have any free play... so I adjusted that a bit.

Well, either way, I've found a reasonable setting that'll either keep it at 1100 when it's weak, or 750 when it's strong...

What confuses me is why when I turn the idle down, it goes from idling healthy at 900 and then a second later it drops to 500 and starts bouncing around.

Valkyrie

It seemed to get a bit better when I opened the secondary throttle plates up a bit (apparently it IS supposed to be adjusted to open a bit...otherwise they wouldn't put a screw on it at all)...

NZConvertible

There is no need for the secondary throttles to be open at idle, and nor should they be. Opening them would have the same effect as opening the primary throttle further, which is what you should be doing instead.

Suiicidalpenguin

I'm with micaheli on this one as an engine gets hotter the gaskets and hoses become more maluabe and any cracks or holes will leak easier than when it cools and shrinks the hole

Rx7TyreBurna

iTrader: (1)

Mine is doing this too.

But, I am just waiting for my S5 manifolds to come in and then I am replacing all hoses and gaskets. Also getting fuel injectors cleaned and tested.

Well, hopefully you figure it out.

Things I noticed about mine:

Only when warm. I can idle just fine at 750-800 until the car warms up to 1/4 on the temp gauge. As soon as it hits there. It will start to bounce. Though, I have found that if I just barely touch the throttle the car will stop bouncing, and start holding idle again. After a bit, the idle starts bouncing again. TPS set to .95K OHMS, and tested full range of TPS using analog MM.

I think my problem is showing in other ways too. Like when I start to press the throttle at low RPM going down the road, there is a lag between press and power. I just think of it as my turbo lag.... LoL... But anywho.

Good luck! Check all those hoses and maybe replace the intake gaskets. Sounds like vacuum leak.

4RAZOR

whats TPS thanks

micah

Its when you don't wear a condom... You get "The TPS".

Search dude. It stands for Throttle Position Sensor.

Valkyrie

The problem with that is the fact that you have to take the throttle body off in order to adjust the primary throttle, so you can't adjust it while the car is running... but obviously the secondaries SHOULD be a little bit open (I just felt like using them to adjut the idle just a little bit) because otherwise they wouldn't bother putting an adjustment screw on the secondaries (I work under the several guys who were in the company at the same time they were still making the FC throttle bodies...he said the throttle plates should be open a little bit....they have 30,000-dollar machines that do nothing but adjust throttle screws all day, so it's obviously important to get it set right).



That's a very interesting theory. I hadn't thought of it before.

OTOH I sprayed a bit of starting fluid on the hoses and I didn't see any changes.

The only vacuum hose that looks really IFFY is the brake vacuum hose that connects straight to the booster...but seeing as how that hose costs 35 dollars to replace (due to the check valve)...I'll probably need to surgically remove the check valve and transplant it into a new heater/emissions hose.

NZConvertible

Ah, so this is an NA. You didn't mention that. So what about the idle screw on top of the TB? That's how you're supposed to adjust idle speed on NA's. Did you jumper the initial set coupler?

Can you think of one good reason why the secondaries would need to be open in order to have a good idle? Remember there's also air entering through the primary throttle, the air bleeds for the injector and oil nozzles and the idle bypass screw. My secondaries have always been closed at idle and my idle's just fine.

The best way to find vac leaks is to pressurise the intake system with compressed air, like this:

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/water-sensors-water-pump-diff-models-583211/ (Scroll down to posts #11 and #16)

Valkyrie

I typically set it slightly higher than 750 (the closer I get to 750 the worse my luck seems to be getting it to idle steady), so I don't think it matters much.

Because the primaries aren't getting enough air?

This was partially a matter of me just seeing what would happen, and partially because I didn't feel like taking the throttle body off. It seemed to work last night, either way.

The issue with the idle screw being that I had it all the way out (highest), but even so it still refused to idle sometimes (but then the idle would shoot to 1200 as soon as the timing advanced on itself).


What confuses me at this point is why the timing will stay advanced basically forever if the car is idling, after I give it some throttle, and leave it alone. The second I start trying to drive it, it goes back into pansy *** idle mode.

Valkyrie

I still have this issue...

I think it must be a heat-sensitive vacuum leak, because if it was simply something like the ignition/electric system not working to it's full potential, I'd have performance issues, and the same thing goes for lowered compression due to heat. I also don't imagine it's an issue with something like the thermowax not letting the throttle close until it's much hotter than it needs to be, since if that was the case, the car wouldn't need the extra ignition advance to keep it running (that is a trait of vacuum leaks).

It's also possible that the injectors decide to put too much fuel into the car when it's hot, requiring more timing to keep it running... or perhaps the IAT sensor gets heat-soaked...or something.

Valkyrie

I've noticed that hitting the A/C switch when the fan is on raises the idle to like 1400, compared to the weak 700-500 bounce.

Perhaps I accidentally set the idle screw and primary throttle screw with the switch on...