MX-3.com

I had some work done on my mx3, it is a 92 GS, stock with a recent (2004) j-spec engine.
Prior to work done, idle is steady.
After:
seems to be a vacuum issue
Car idle is not steady the way it used to be. Bouncing a bit.
When cold idle is 2000rpm.
After about 5 minutes, idle drops to 700-1500 rpm and holds.
The tach shows some play, but is very slight.
When going from neutral to any gear first shift, foot on clutch, tach bounces down to 700 rpm, then slowly climbs up to 1500 rpm. And drops to drops to 750 again. It cycles like this. I can drive, need to keep rpm above1500 when in gear, otherwise I get a dip in power then a surge of power - and while in a low gear, -that's a bad driving experience. So I go back to neutral, to make it stop revving, but then the car idles at 1500 rpm.

Work done.

New plugs
Air filter
Transmission fluid
Oil flush and swapped to synthetic
PCV Valve replaced.

Since then I noticed that my distributer cap was cracked, and I replaced that,along with a rotor.

I think that the air filter may not have been installed correctly, I removed it, and reinserted it. Tightened some screws, seems to have made a difference, yet, it has only improved the issue, and has not solved the issue.

if you spray something flamable on your vacuum lines while you flex them with the car idling it will help to find leaks. when the rpm raise youve found your faulty hose.

does your idle always bounce or run high when in neutral? high/bouncing idle could also be caused by it being set too high. try playing with the idle screw and see if it helps at all.

Thanks dude, let's try it and see.

I literally just solved a very similar issue. Try putting on a short ram intake, ditching the box. Mine wasn't sealing properly, and it did almost exactly what you're experiencing. Good luck!

Only post-airflow meter leaks matter... The box won't affect it at all. I run my DE mx with an open AFM just to get it around the yard all the time.

The flammable spary works decent sometimes, but won't diagnose the smaller cracks or bad intake manifold gaskets.

Keep in mind the entire vac system is suspect, not just the intake rubber. The vac chambers are prone to getting old, losing nipples, or detached hoses on the back of the manifold, or some doofus hooking them up wrong...

I've used propane, and I've used a flammable throttle body cleaner.

So far I've found about 5 things.
Yesterday I had this thing working awesome! Just roasting that old K8 reving to 4500/5000 with a consistent power.

I am going to post pictures or a you tube video.

Spete, does this problem go away after warming up, after being driven for 10 or so mins?

spete701 wrote:I've used propane, and I've used a flammable throttle body cleaner.

So far I've found about 5 things.
Yesterday I had this thing working awesome! Just roasting that old K8 reving to 4500/5000 with a consistent power.

sounds like hes solved the, or the majority of his problems...

Yes I think the problem has been solved. -
Sort of hacked through it.

I replaced some of the vacuum lines.

One going to a from a sensor to what I think is a charcoal filter. No more hiss from that part of the engine bay.
Charcoal to the purge solenoid valve.

VRIS Shutter valve actuators, one of the lines was not connected at all.
From the 2nd VRIS shutter valve to a port on the back of the intake.


A line running from a VRIS component. (I'm not sure if it was a solenoid or not.

Another line which I think was going from the stock air intake was not connected at all. (I don't even know what it does.) Seemingly nothing.

is it a skinny line thats on the front left of the filter box? if so that connects to your egr solenoids on the right side of the throttlebody. if you dont have emissions testing in your area i wouldnt worry too much about it. if you do need to get it tested soon itd be worth checking over the entire egr system before you do...

Grrr. Problem persists. Hew I smell coolant when I run the heater.

Talking with a "car guy" who says swap the tps. Just 2 Boltzmann, easy!

I go to picknpull, and I buy two of the blasted things. He does not mention I need a good volt meter and feeler gauges to get it back on, aligned the way it is supposed to be.

We could tab the top of the TB with a wrench and the idle would change.

Check the wiring on your neutral switch on the trans. If it gets frayed or broken it will produce a bouncing idle when in neutral. I agree in checking for vaccum leaks first, but the neutral switch would be my second guess.
You can set the TPS without the feeler guages and volt meter. I am a pretty good electrician and still prefer the collant fan method for setting the TPS (and have better results that way too). However, I doubt that is your issue.