I'm sorry guys, I know there's a whole lot of idle surge threads here but I've read them all and don't know what to do.

The current symptoms:

Car starts fine when giving it a little gas.

Car revs up to around 3000 with the cold idle.

Car then drops down to 2000 for a few seconds and then starts to bounce anywhere between 1000-2000.

When accelerator is pressed the surging stops and it drives excellently.

If AC is turned on the idle will Rev up to about 1800-2000 and stay there (until accelerator is pressed).

Sometimes during the idle surge there is a isn't rattle from the right side of the motor on the decel (hopefully a motor mount or something).

Things I have done already, somewhat in the order that I have done them:

Removed and tested the BAC per FSM.

Done pretty much everything I can do with the idle screws.

Tested the TPS and replaced it.

Set the new TPS per FSM resistance.

Checker proper voltage at the red/green wire on the TPS.

Adjusted timing (it was off), set it making the L1 lead meet up with the yellow timing mark.

Sprayed carb cleaner eeeeveeerrrywhere. Like 3 cans worth.

I'm sure I'll remember more stuff I've tried and make another post on this thread. It's been doing this since november when I got the car and I have been trying to fix it since.

The car is a 91 S5 vert N/A completely stock except for some snazzy LED headlamps.

Any help will be so very greatly appreciated guys. I'm fed up with this honestly. I have fixed everything that I have wanted to fix on the car except this. Thank you.

 

Remembered something else!

Three of the OMP lines going to the oil injectors broke at the banjo bolts on the OMP so I plugged them with screws. I premix.

 

you say it drives fine? is that at all RPM?

 

Yes. Other than the fact that the secondary air intake ports don't open anymore (they're stuck), the car driver great. It would sputter when overtaking on the freeway before I set the timing. But it's golden now (except for the surging idle).

 

Plugged them? Did you remove the oil injectors?

 

No, I only plugged the lines

 

Well..I'd address that as soon as you can too.
Try holding back a ****..see how you feel.
That oil pump need to put oil somewhere and you plugging the lines can't be any good for a Electrical OMP..
I can see that taking a dump on you soon.

Doesn't matter if you are Premixing to "fix the broken lines" as That OMP needs to be seen by the ECU as Working.(ok for lube..,not OK for ECU)
If not you put the Car into Limp Mode.

 

Okay. I began to order the lines this morning going after reading your post. I have let it go liken this for too long. Do I need new injectors as well? So far I have found the lines and am looking for the UIM and LIM gaskets on mazdatrix.

 

Oh! And I plugged the lines going to the injectors (to try and prevent a vacuum leak). The OMP does not have any back pressure it's free to dump oil all over the floor as it pleases.

 

Update: today I ordered the lines from Mazdatrix and the gaskets from Atkins Rotary. Also, today while I was out with the lady, I decided to get my redline of the day over with. I accelerated from a stop light fairly quickly (right up to the speed limit) and in 2nd gear around 6000 it sputtered once. So maybe it's not perfect at all RPMs. I'm not sure if this is related to the idle though.

 

I was battling with this demon for weeks in my N/A car. I tried it all, the grounds, the TPS, etc. I ended up replacing all the vacuum lines in the engine bay, intake gaskets and the fuel injector grommets. After all this the idle still surged..........I found out I did in fact have several vacuum leaks but I solved it by adjusting the idle screw on the top of the intake manifold. The one for the throttle stop.

 

Rxmiles I have tried that. Just out of curiosity, from the point that it touches the throttle lever, how many turns did you turn it? Because I spent a whole day messing with the damn throttle screws. XD

 

If the oil injector lines are still broken at the injector ends there will certainly be a vac leak.

 

@spikederailed I don't know if the lure broken at the injectors. All I know is their broken at the OMP. I will be getting the lines and intake manifold gaskets in the next two days. I will keep you guys posted.

 

I really don't remember how many turns I screwed it. That being said the idea of adjusting the throttle stop screw came to mind when I would close the throttle by hand, if it doesn't help replace vac lines. The idle surge demon must be fought, as it is a right of passage. Conquering it will give you your rotary wings, being conquered by it will make insane to the point where pistons make sense.

 

If the new lines do not fix your problem........

Try setting the TPS via the test light method.

 

@LunchboxCritter i shall. I have however pulled off my UIM and LIM and found that two lines were also broken at the oil injectors. And the smaller shorter vacuum lines were beginning to Crack. Replacing oil and vacuum lines and hoping for the best. I probably will end up getting a test light though, just so I can troubleshoot using the FSM easier.

 

So I did all these things with the oil lines and vacuum lines under the intake manifold aaaaand it's still surging. And now there's a misfire to accompany it. I will however say that the overall idle speed is lower, and it doesn't throw oil all over the floor. Does a vacuum leak truly cause rhythmatic revving?

 

Yes and no. It depends on weather or not the vacuum leak can seal itself or not. Why not try disconnecting the BAC and see if the idle will stabilize.

 

https://www.rx7club.com/2nd-generati...stment-657023/

https://www.rx7club.com/2nd-gen-arch...oblems-334730/

 

Thank you so much satch. That really helps. I have removed the LIM/UIM and replaced the oil injector lines as well as all of the small vacuum lines underneath them, and the fuel injector o-rings and grommets. I also cleaned off and replaced the gaskets on the manifolds. I Put it all back together and no more leaking. However when I first tried to start it, it fired up and smoked like crazy them died. The few minutes it was on, I saw the check engine light flash on and off. I decided to ground the ISC and get an MIL. The code was for the Water thermosensor, which I know I unplugged to get off those oil lines. I checked and I had indeed plugged it back in. Just for good measure though I reached with a large flat top screw driver between the manifolds and the alternator and put a little pressure on the connector towards the sensor. I cranked it again and it started up after a bit of struggle. No more check engine light. HOWEVER, it is running VERY rich. Only at idle though. Lots of afterburn at idle. When I Rev it up good there is no afterburn on the decel, but when It is idling there is a lot. It is also still surging but I would like to go down that second post that Satch posted and do everything. The rich idle mixture however is new, does the thermosensor only control the mixture at idle? Is it possible that it is bad?

 

The thermosensor affects the mixture pretty much all the time when the engine is running be it idling or driving. The sensor's plug is very delicate and causes problems when one of the two wires in the plug are making a poor connection. The ECU pin for the sensor would tell you if its plugged in and operating properly. W/key to on the pin would read 2 to 3 volts w/the engine cold and it drops to .4 volts completely warmed up.

 

Does this mean I must tear out my carpet to test my ECU pinout?

 

Pin 2E of the ECU. And yes, but it's more like folding it some and pushing it out of the way temporarily.

 

Well, I haven't had time to check the ECU yet, but this morning I started it and it was running rich. All the way up until I got to the gas station. Then I filled up and it leaned out. Perhaps the quart of two cycle I put in before I fixed my oil lines was being mixed with the oil from the OMP? Idk... The mixture seems fine now though.