Low bouncy Idle problem help!!
 

I hope I posted in the right place but I can't take this and I've been dealing with this for weeks and im out of ideas on what could be wrong and causing this annoying idle problem so here's my long story. I checked for vacuum leaks everywhere but nothing everything's been replaced with new everything so I don't know why I would have one but I just double checked anyways. I used compress air through the intake system and soap and water everywhere but no vacuum leaks. I went through 3 tps sensors and checked all of them and got one good one with both ranges in spec. My cars a 1988 vert na rebuilt with only 6k miles with intake and exhaust no cats but has a power pulse silencer (for the 6 ports) and a mild port with s5 rotors and all emissions deleted like rotary resurrection site (acv, bac, egr, rats nest). The only vacume lines I have are the primary injector atomizer to the dynamic chamber and pressure sensor the rest are capped. I set my tps but my idle bounces from 0-1000 rpms. I disconnect the tps idles fine plug it in bouncing idle . I can't get it to idle lower then around 1200 when the tps is in spec. It'll bounce so low the shift light will come on and go back up too 1000 rpm. I messed with the tps and adjusted it by ear till it idle around 850- 900rpm drove it around and drives horrible I engine brake and bucks like crazy, back fires and just absolutly horrible. So I set idle with tps disconnected around 850-900 rpms and tps in spec again -__- and disconnected the battery over night thinking the ecu need to be reset from messing with it so much, but nothing still bouncing idle. So I came across this thread after reading every idle problem thread that wasn't close to my problem and read what he said about removing a vacuum line so I did so I unplugged the vacuum hose that goes to the primary injector atomizer on the lower intake to the dynamic chamber and bam no more bouncing idle. Would this mean the car is too rich ? If so how would I go about adjusting it ? Or is their something I'm doing wrong or does anyone ever had a problem with this? I know the bac just control the idle when stress is put on the engine to raise the idle but I don't see how that would cause the car to not idle below 1000rpm.

How did you do this. The hose feeds all of the injectors and not just the primary injectors. And the G/R wire of the TPS is to be set to 1 volt w/key to on and the engine as hot as it can get (20 minute drive). And what year is your car?

It's an 88 s4 na vert tps is set and nothing still bouncing idle I forgot to mention I premix so the OMP is removed and the oil injectors have bolts with crush washers . But I'm completely lost on what to do or is causing this. The one thing I haven't touched is the idle mixture screw that has lean or rich written on it. But I don't know why messing with it would help

Well, you might be in luck.... I went through the same ordeal.
Hours upon hours of research in the web yielded nothing. Here's the story, read it as it will help.
I bought a 1989 Rx7, $750 bucks, beautiful car except for the dam idle surge, idle bounce, erratic idle etc.
I wasn't too worried about the idle since it ran great above idle. It was always high and my only concern was passing emissions. Not doable with high and surging idle.

First off I read through the forums and my fsm over and over and over.... It was a starting point but mainly useless. Several smoke tests found small vacuum leaks her and there, but once fixed no change in idle the TPS was probably adjusted a million times but never replaced.

I gave up and striped down everything, the whole intake manifold was cleaned, the throttle body mod was done, all vacuum lines replaced, the hard lines tested for leaks (positive leak in a hard line, crack) injector seals replaced... every thing was changed.

The dam thing was still present, this demon, that feeds of the suffering souls of rx7 owners every where.

I was about to give up, until it dawned on me...when I had the manifold out and was doing the mod I checked the clearance on the throttle plates..I adjusted them through the locking nut and boom rock solid idle, no surge and passed emissions with flying colors.

The only way I could adjust the idle was through the top throttle plates that move the two throttle plate. When you set throttle plate into spec was it the single bottom throttle plate or the double throttle plate? And do you know the clearance spec for both bottom single and top double plates? I have the fsm but it's a little confusing to me on which one their talking about

Good question, theres different specs pending where your reading. The only one I have found so far in searching is for the primary plate, but it talks about bending a tab, nothing to do with the throttle stop screw.

In for the correct answer, my info was on 4B of the fuel and emissions section of the FSM

I figured it out but it was in spec and still I don't know what's causing this I checked my afm and it's in spec. Im getting frustrated so I messed with the idle mixture screw and it helped a little it moves around between 800and 900 now but it's almost close to full lean . Is that bad ? And the guy who build my motor says to put 91 only . And if I install the bac back on would it make a difference and help ? Or would it just be a waste of time putting it back on ?

The BAC is not an emissions item but an idling item.

Would that be a problem of why it's hard to idle below 1000rpm?

Could be.