I'm still experiencing the bouncing/ surging idle from 1,000 to 1,500 rpms, and I can't seem to even adjust the idle?

I'm turning the screw on the side of the BAC valve and it makes no difference, do i need to jump that initial set coupler or something? I also didn't notice a difference when i unplugged the bac valve, how can i check my timing if i can't get it to idle below 1,000rpms. I even rewired the bac valve w a new connector and redid all of the hoses to and from w/ clamps.

I've tried to set the TPS but it doesn't seem to work...I'll try again.

I'm really tired of this crappy idle, i wish i had the loot to just have a mechanic "fix it"....

heres a video:

 

Its your TPS. If you are having problems adjusting it.... it might not be in-spec and you may need to replace it. Check the write-ups section of my site (in my sig)

 

Yeah I had the same problem on my S4, adjusted the TPS like 6 times, never could get it right. Got another one off an NA car, installed it and set it, smoothed right out, no more idle bounce.

 

Also check the accelerated warmup device (vacuum solenoid on top of intake manifold). Use a pair of pliers to pinch the vacuum hose closed while it's idling. If the idle stabilizes, I suggest removing it entirely. Another thing:....Watch the throttle lever closely with a small mirror to see if it moves (very slightly) while it's idling. I noticed your engine temp is low, perhaps from a weak thermostat. This can affect the thermowax unit on the throttle body. Trapped air in the coolant hose to the thermowax can also cause a fluctuating idle. Run the engine slightly above idle for a few mins with the rad. cap off to clear out trapped air. Pinch off all vacuum hoses one at a time and look for changes in idle.

 

ok, so i had the palm pilot hooked to the Rtek the other day and was logging this idle condition, and noticed a couple things..

the TPS was shown at 16 the whole time never treally changed at all.

the coolant temp was shown to be close to 200* after like 15 minutes of idling.

I'm gonna try to set the tps again right after running the car, i don't thnk i actaully got to set it before when it was hot. Maybe that would help.

Also as far as that screw on the BAC valve, what would be a good position for to have that set at? ie how many turns from all the way to the right??

 

From what I heard in the video, it is much more likely a thermowax issue than a tps. The rpms change very little, but rhythmically. The tps reading on your palm pilot may not see the small changes in throttle position due to it's relatively slow baud rate. It might be helpful to place your hand right on the throttle lever to feel if it's moving, or use a mirror and a good light source. Don't forget to pinch off vacuum hoses like I said in my last post, and check for trapped air. Looks like your coolant gauge is inaccurate, not surprising for an fc.

EDIT: Unplug the BAC connector. If the idle still fluctuates, worry about it's screw adjustment later.

 

ok, so this sunday afternoon I'll go through prcess of :

1) checking the throttle linkage to see if it is moving at all during the pulsation
2)Pinch off various vacuum hoses and see what happens
3)Runniing engine slightly above idle for a couple minutes with rad cap off to bleed collant system ( maybe tell me more about this part)

I had mentioned before, a long time ago, that this all started all of a suddent when cruisin down my road. It didn't used to pulsate like this, but one day just cruisin, I was going into 4th from 3rd at like 3,250 rpms and when I let off of the gas and pushed in the clutch the rpms dropped but then bounced back up again before i let the clutch out, then it started to kinda buck/surge with the clutch in or out until i pulled it down my driveway and shut it off.

The next time i went to start it, it shot to 3,000 rpms ans stayed there until i shut it off after a couple secs like that, it did that a couple times in a row but finally stopped sticking and now it just pulsates.

I have replaced fuel injectors, ECU, fuel filter, spark plugs, various hoses clamps, connectors...

Juast thought i would add those details, something must have happened ( let loose, came undone, cracked, slipped off, broke) to make it start surging like that when it didn't before.

Thank you for all of your help, I really appreciate it.

 

hah thermowax???? why would that make idle surge? set the TPS with lights and check resistance. NEVER rule out a vacuum leak. hook an air compressor up to the intake like has been shown on this forum in previous posts, listen for a leak. id bet on vacuum leak.

 

Yeah, I'm hoping for a loose hose, thats kinda what I pictured happening when it just starting doing it, I'll hook up the compressor and pressure test the intake system. Do you have a link to this procedure, or i can just search later, thanks again though for your input..

 

Bullshit. IF the TPS is reading 16 with a FULLY H0T engine, then just screw the TPS screw til it reads 20 percent, where it belongs. Low baud rate my royal ***.

Pull the plug off the BAC for now and leave it off. At this point it's not clear what the rpms are when you do that. You said the rpms went down. IF the rpms are below 1100 on the PALM (not on the cars tach), then get a timing light out and set the timing. You can jumper the intitial set coupler if you want, but it has NO effect on timing,. It's to put the BAC at a set duty cycle and the BAC plug is off. Mute point.

I'm inclined to agree that this is a water thermowax problem. It's cam probably isn't seperating from the pin and that causes the throttle plate to stay open a minute amount. Enough to cause a fast idle.

By the way, the screw on the side of the BAC isn't going to have any effect if the rpms are over approx 750rpm. It's just a small air bleed screw.

In a *sense* it's a tps problem but only because the fast idle cam isn't coming off the roll pin.

By the way, IF it turns out to be the water thermowax and fast idle cam...........after you have seperated/adjusted them, the TPS will have to be set again ....BECAUSE the throttle shaft has moved when you adjusted the fast idle cam.

From now on forget the BS on setting the TPS using X, y, and Z method. The thing when the engine is fully hot should read the 20 percent you read on the PALM. EXCEPT when the engine is cold and then it will read higher......because the thermowax is doing it's job and opening the throttle plates when the engine is cold so you will have a fast idle. Idle of approx 1000-1300 rpm.

For adjusting the thermowax it's suggested to put the intercooler on the shelf in the garage. In it's place put some PVC tubing b/t the turbo outlet hose to the intercooler to the throttle body 90* inlet hose. I'll try to attach a NZ jpg of what I mean....later.

 

Here's a jpg of NZ's PVC pipe in lieu of the intercooler arrangement. Removal of the intercooler gives you access to the adjustment screws while the engine is running.

I'm making a lot of assumptions. I'm assuming there is no air leak. Like around a ACV blockoff plate etc. Big assumption.

In the second thermowax pictue................turn that screw all the way clockwise. That should seperate the fast idle cam from the fixed pin, especially if the engine is full hot.

There is no clear picture of the throttle stop screw. It is about where I suggested in the jpg. IT is a small screw with a 8mm jamnut on it. When the engine is full hot there should be no light b/t the screw end and the throttle shaft stop. IF you see air, most likely the thermowax is holding the shaft open a touch.

Or before you start doing anything, stare at the throttle stop screw and the air gap and lift up on the screw that I have an arrow going to saying *TURN CW*, That act should lift the fast idle cam off the roll pin making the throttle plates close completly.

I'm assuming there is a touch of slack in the throttle cable also. Just a tash slack.

 

Turning that screw all the way cw is NOT the proper way to set a thermowax. That was just to confirm that is the thing causing the problem of a high idle. Later you can set it right per the FSM. You can fudge on the FSM to work in YOUR favor though.

 

All *HAIL* his royal ***!

 

One thing to keep in the BACK of your mind. The ECU will automatically advance the timing when it reaches around 1100 rpm. On a regular car that idles fine at 759 rpm, if you slowly rev it up in the driveway, as you reach around 1100 rpm, the rpms will suddenly advance to around 1300 or so rpm. It's the ECU that is doing that and you can't stop it with the pedal because it advances so fast.

So you need to confirm with the Palm/RTEK2.0 that you have, that the rpms are safely under 1000 rpms. The stock tach CAN be off on some cars by as much as 100rpm. Not all cars, some cars.

I'm just making you aware of this *trait* of the ECU so it does not confuse you. Just anything under the 1000 rpm should be good for setting the timing using a timing light. I've yet to see the install of the initial set coupler make a bit of difference setting the timing.. Effects the BAC duty cycle, but that's about it.

Like I mentioned above, a lot of things are *** u MED (as in make a *** out of you and me by not mentioning some siqnificant thing).

Even a BAC that is malfunctioning can cause a high idle. Just inserting some gasket paper b/t the bac and the manifold to act as a blockoff can determine if that is a problem ....or not.

A misplaced vacuum line can cause problems. Like the line for the fuel injector bleeds going to a source of vacuum instead of where it's supposed to go. Or a line or two off the oil injectors will cause air leaks. Or not using soft fuel injector grommets at the base of the injectors will cause an erratic idle/high idle. There's other stuff out there also.

But go for the thermowax mal adjustment first along with the idle stop screw.

For grins if you don't have much time today, just get the engine hot and then turn the variable resistor in the rich direction and then back to the lean direction. Listen to hear/see if the idle changes in one direction or the other. It could give you a clue.

No need to bow to my Royal ****. Most times the problem turns out to be *another thing all together* and this will have been an exercise wasted.

I really, really don't wanna go to work today, but........

 

Hailer : I have the same problem also on my 90. Can i use the same procedure for the fast idle cam ?

Dumarjo

 

ok i just got in so i'm gonna have to read through this but it looks like alot of good advice, thanks...i'll post in a lil lit.
THANK YOU

 

It's worth looking at. On a n/a its a little harder to look at since the throttle body is turned upside down and on the right side.

Just remember, this is just a lot of guessing about things that MIGHT be the problem.

 

hailers. the original question was about a surging problem. how can a thermowax have anything to do with surging? high idle yes, why surging? (geniune question, cause you know more about it than me). i always attributed surging to tps or vac leak. i didnt think anything on the throttle body would move in a surging motion.

if high idle is the problem. shouldnt the surging be taken care of first?

 

I'll concede your probably right on the vacuum leak somewhere after the throttle plates.

The up/down and the rpms mentioned reminded me a lot of how if the engine goes above 1100 rpm, the ECU will then advance the timing and thru the advanced timing , the rpms to approx 1300 rpm plus.

On my n/a car I had the two small vacuum lines on the front of the dynamic chamber swapped. Doing that put a vacuum source on the fuel injector air bleed nipple b/t the oil injectors and put a source of air to a vacuum nipple. That caused a hunting idle/crummy idle.

To prove it's not a TPS issue he can just disconnec the TPS when it's doing its up/down.

 

disconnecting the tps should not change anything for the idle ? (if the tps is not the problem of course).

dumarjo

 

If you guys would listen to the audio portion of his video you would notice that the idle isn't a "rolling rough idle" which would be more indicative of a vacuum leak. This is a distinct, consistent "on-off" idle with the same amount of rpm change every time. I have worked on countless Hondas with the exact same cyclic idle and every time it was due to trapped air in the cooling system. They use a thermal wax-driven unit similar to our rx7s. They also have a bleeder screw, much like a brake bleeder, to release this trapped air, and when the trapped air is gone and is replaced by a steady flow of coolant, the thermal unit stops cycling. This is why I have pushed the idea 3 times here in this thread. I have yet to see a response from the original poster if he has confirmed his thermowax or not. I also suggested pinching off vac lines, if there is a leak at one end of the rat's nest such as a split vac hose, you would see a change when pinched.

 

^ Regaurdless if there is trapped air or not, the TPS reading should corrospond with the thermowax adjustment. So say if the thermowax is holding the engine at 1500rpm, the TPS should be giving the correct reading to the ECU for that amount of throttle given. So if there was air in the coolent system and the thermowax was not allowing the engine to come down to idle, you still wouldn't have a problem since the TPS would be telling the ECU what the throttle opening is.

This has happend to me a few times, it was due to the incorrect setting of the TPS, and the dash pot threading its self in and holding the throttle open a bit more. Hi idle is one thing, but a surging hi idle is a combination of things such as the thermowax and TPS. I don't know if you can reach the Thermowax adjustment screw that sits at the bottom of the piston, but if you, push the screw AWAY from the piston and see if the idle drops down. Also make sure there is NOTHING holding the throttle open.

Like I said, TPS and something holding the throttle open such as thermowax or long shot, dash pot(very long shot but happend to me).

I would say even if you fix the HI IDLE portion, you will still have a bouncy cold idle around 1300-1500, where it is now if the TPS is not adjusted correctly. When you are adjust thing the TPS, are you trying to adjust it to 1v while the rpms are where there are? If so, this will only aggravate the issue, fix the hi idle problem and then adjust the TPS.

 

I agree with Rotaman on one basic point....the bottom line is that the throttle lever needs to be against the throttle stop screw, and that the throttle stop screw is adjusted correctly before any tps adjustments/ diagnostics are made. Under most circumstances the stop screw should never need to be adjusted, it is locked with a nut from the factory. As I listen to his video again, it is even more clear that either the throttle lever is moving very slightly away from the stop screw, or the control unit is seeing an inappropriate reading from the tps at that particular position and possibly sending a different pulse signal to the BAC, I asked in an earlier post for him to disconnect the BAC and watch for change.

 

As Hailers said, disconnecting the tps should eliminate it's contribution to the bouncing idle, I also re-read this guy's first post where it said that he unplugged the BAC with no change. This still leaves the possibility of the throttle leever moving via the thermowax. I watched the video AGAIN, and the idle speed is only changing +/- 150 rpms. You likely won't see that much movement if you stared at the throttle, but you might feel it with your fingers. It would be easier to bypass the intercooler as Hailers said earlier so you can get a better look at the throttle movements/ adjustments.

 

I admit I didn't listen to that before or view it. I had to go to WORK to view/hear it.

That's what is called "Cool". Rummmmpf, Rummmpf, Rummmph, Rummmmpf as it revs fairly quick b/t 1500rpm and what? 1700? Up down, up down. Pulsing idle at a set cycle. Always the same up/down/up/down.

I think I'll try to duplicat that tomorrow on my day off. I'd still disconnect the TPS and see what happens. It's almost like when you go to a car that idle just fine, but then reach in there and with your finger push the tps screw in all the way for a Moment then let go. The rev's should change when you do that in/out with the tps plunger. Can't do that on a Turbo car with the intercooler on.

I've seen/heard that pulsing before. I'd almost swear it was when I put the fuel injector air bleed hose on a vacuum nipple on the back of the manifold instead of on one of the *air* nipples.

It's be pretty hard to find a vacuum leak with starter fluid on that high an *idle*.

Be sure to tell us what fixes it. LIke I say, I'll try to dup it tomorrow.

I'm backing off the water thermowax idea since I heard the *Video*. Still worth looking at though. Two pieces of PCV pipe and an elbow inbetween gets the intercooler out of the way.