brent clement

I have an '86 gx and it won't idle after it's warmed up. First the rpm's keep going up and down then it eventually starts stalling. I've shortened the air intake and added an open air filter. I've also got 2.5 inch exhaust.(not that i think the ex has anything to do with it) Just wondering if the air flow meter would be affected by heat from the ex seeing as how it's closer to it now.

Amur_

Doubt it. Sounds like a big vacuum leak.

brent clement

Thanks, I think you're right. I just warmed the car up and I hadn't noticed but it idles fine until I hit the brake pedal than it starts to idle up and down. I looked at all the lines but so far I don't see anything. Is there anything specific I might check?

Amur_

Looking won't tell you anything. With the motor running, grab a garden hose, turn it on so there's a small but steady stream, and work your way around your motor, holding the hose so that the water runs over hoses and joints. Let it run over one item at a time for at least ten seconds each. When the motor starts bogging you've found a leak.

There is a vac line going from the motor to the brake booster - get the hose on it as well...

gergrx7

check the tps

brent clement

I already swapped the tps. No change. Thanks for the tip on the hose.

brent clement

Tried water on the vacuum lines but nothing happened. It doesn't seem to happen until I drive the car for a bit at normal operating temp. When I hit the brake pedal this time the rpms dropped to about 500 for a second but went right back to normal. I don't know much about fuel inj. and the electronics that go with it. Any help is much appreciated.

NZConvertible

That won't help unless it was faulty. The TPS has to be correctly adjusted or it will cause all sorts of strange idle problems. Search for a how-to.

Also, read this article on troubleshooting idle problems. It's for Turbos, but the NA idle control system is practially identical.

brent clement

How would the tps end up needing adjustment? I never touched it until now. Anyway thanks for the tip, I'll give it a shot. I've got the Mazda mecanics manual.

HAILERS

Got the FSM! Yeah! Now go to the FUEL section, set the timing, then the idle using the initial set coupler, then set the tps. Don't do any of the above unless the engine is fully hot. See the section in Fuel section dealing with the fast idle cam/screw for the meaning of the last sentence.

walterh

could be your BAC

brent clement

I ripped the motor out a week ago to rebuild and port and polish it and found a huge tear through a vaccum line under the tb. No wonder I could'nt find the damn leak. LOL. Appreciate the help. I'm learning a lot from this site. Next I'm building a header(304 stainless) and was wondering if anyone had any simple solution for opening the secondaries. Butterflys? I hear the euro models come with them? How much? Where do I get them? Or how could I go about doing it myself? Way to many ?'s. The list just goes on and on.LOL.

Thanx for the help.

Cosmo Donk

Opening the secondaries? What do you mean? The throttle plates? Most people just do the TB mod so there are only the 3 primary plates in there.

brent clement

I'm talking about the tubes that open at 3500 rpm. I want to remove them to get better flow and replace them with something more reliable. I guess secondaries is the wrong term. The 5th and 6th port. I read somewhere that the euro models uses butterflies. Don't know if its true. But since you mention it, is removing the throttle plates worthwhile? What are the pros and cons.

Amur_

5th/6th ports

http://home.rmci.net/panther/6PortSolution.htm

brent clement

Thanks for the tip Amur.