Idle Issue

[Raider9864]

Hey guys whats going on? My 93 lx has been having some idle issues for about a month now and since its getting warmer, i want to get it taken care of. Cold start is 1500 like its supposed to be, but when it warms up it doesnt go below ~1200 rpms. When i first bought the car it would go down to 800-900 like normal but since I've been driving it, it hasnt gone back down. I disconnected the IAC valve and the idle went up, so that means the IAC is good, correct? I did notice a bolt missing on the back section of the intake manifold but i dont think theres a vac leak there. I took some fuel injection cleaner and sprayed around the manifold and the air filter housing and came up with nothing. I can hear air around the filter housing but im not coming up with anything! The air horn has been replaced so i know thats not the issue. I do have a coolant temp sensor sitting at the shop, so i was gonna throw that in since it was only an $18 part but i dont just wanna throw money at the car and not fix the issue. I cant find the damn Mazda connector so im S.O.L. on using our scan tool to pull some data outta this puppy.

The issue occurs during warm and cold conditions. I also noticed that if i tap the gas a little it may jump up to 2k rpms and stay there for a few seconds then gradually drop back down to 1200. I can get a new TPS for roughly $65 and this was my first assumption but i want your opinions. One more thing, when shutting the car off, it gets somewhat rough and i can hear air escaping from somewhere. I think i might just smoke-test it to clear any vaccum leaks out of the way but im just really stumped!

I'll take any and all suggestions, just dont tell me to throw a bunch of parts at the car because im not looking to do that. PLEASE HELP!

[jibou74]

i haven't any suggestions , but i have the exact same problem.

[Raider9864]

Bump!?

[1Mazda323Fan]

Could be your throttle plate is sticking open slightly. Or your throttle cable is adjusted too tightly and is pulling the plate open. Check the cruise control cable as well, if so equipped. That's where I'd start, since checking things is free. Speaking of, check EVERYTHING for a vac leak, not just one or two things. Although, a vac leak usually presents as a hunting idle, not a steady high one.

[Raider9864]

Anyone else have any suggestions?

Jibou- have you fixed the problem yet?

[Escort92man]

ok take a look at your throttle body, there should be a black rubber plug that covers a screw, turn that screw all the way IN and see if that solves the problem, that's the idle air bypass screw, it's supposed to be all the way in then the IAC controls idle on it's own, sounds like that screw coulda worked it's way out some maybe? idk I'd check that out though!

[jibou74]

haven't solved the problem yet , 'cause she's in a complete inspection, i'm checking the whole induction system and doing some cranck maintenance.

anyway i have cleaned the throttle body and it hasn't solved the problem.

my iddle is high ~-1200-1400t/m and sometimes return to 750-800 when hot. i suspect a sticky IAC.....

ps : excuse me for the poor english , i'm french.

[Raider9864]

Escort- Thanks, ill look into that! Where on the T/B is the screw located? I dont recall a rubber plug covering anything.

[Escort92man]

it's on the throttle cable side of the TB, it's at a funky angle too it's just a flat head screw down in a hole, if you find that turn it all the way in and see if that helps, also yea it could be a sticky IAC jibou74, you can just shoot that IAC with some carb cleaner.

I'd try that air bypass screw first see what happens, and no problemo, I did the 4 wire TPS upgrade and my car idled at 1200ish all the time, 2k when cold, and I went to that air bypass screw right away, turned it in and haven't had any idle issues since!

[Raider9864]

Good ****! Thanks a lot man, ill see if that helps.

[bcowie]

If I turn that screw all the way in my car stalls, I have to have it open a lot what could be the issue?

[Raider9864]

The issue is thread-jacking.

Sounds like it could be your IAC valve.

[bcowie]

The issue is thread-jacking.

Sounds like it could be your IAC valve.

Your right
My apologies

For your issue how is it if you d/c the tps?

[Raider9864]

I've never disconnected the tps, ill have to try that too. When i d/c the iac the idle went up a few hundred rpms.

[Raider9864]

The problem is pretty much solved now. The screw on the T/B was screwed out a lot, so with a little patience i got it perfect! Sometimes it will still stop at 1200 rpms for a few seconds then drop all the way down to 800-900 rpms.