k, my idle isnt being very nice, when its cold it actually idle's where its supposed to ~750 but when its warm it sometimes stays at ~ 1400rpms but if i leave it in gear and bring it down to the right idle rpms it stays there. however after a few seconds it starts to bounce up and down...ive adjusted the tps but i still have no clue why its doing this, the car pulls nice and hard when im driving but it sucks sitting in traffic and having your engine rev up and down. i did the tb mod rencently so thats prolly the cause of some problems, i have that coolant hose that went to the back of the tb rerouted to the bac. but i should be able to get it all correct...or i hope i can. thanks

 

I believe the TPS is still out of spec. Or yu have a vac leak.

 

I agree its either a vacuum leak or the TPS is outta whack.. How did you go about setting the TPS? Did you check the resistance with an ohm meter? Did you set it when the car was fully warmed up?

 

Also it could possibly be a BAC problem clean it out and see if it works ok.

 

Ususally a idle related BAC problem only occurs when the engine is put under load, such as A/C or applying the brakes, etc.. Not saying that it isnt possible, but that wouldnt be my 1st guess.

 

just to make sure though

 

i set up the tps with the led lights taht mazda uses to do it...mazda techs left one on my car once. yes the car was fully warmed up. i suppose it could be a vac leak, were/are any hoses that connect to the tb vac lines?

 

there are many vac lines all over the car. I would say change them all. The ones that cause major problems are the ones on the spider that go to the oil injectors. Get a silicone hose kit and start replacing them one by one as not to forget where they go

 

Ok, if the idle just kind of slowly goes lower till the car dies. Then it's something like a fuel filter or injectors plugged. But if the motor is bouncing up and down. Then its vaccum.

 

vaccum you say. i guess ill have to get some hose soon. i cleaned out the BAC. it seems ok, is there anyway to adjust the bac or does it just work by itself? also could the bouncing idle be an air leak in the intake or would that show up on the engine warning light?

 

uh an air leak is a vaccume leak. lol check all the hoses and intake connections.

 

I have the exact problem as you, have not yet found a solution, but I am replacing all my vac lines soon with silicon so if it fixes idle, ill let ya know.

 

When I went with pre-mix my idle got better.
I attribute it to the removal of the vaccume spider and those lines.

 

hmmm im thinking it much be a vac problem...thats it the tb is coming off now...i think the holes from where the throttle plates i removed must be leaking air so ill get some more jb weld and fix that.

 

I believe all of us mean a hose is loose or not connected or a gasket is not doiing its duty bro. ther have been some bad things happen and JB weld involved in possible engine failures.

 

While were at it, my car idles like ****, sometimes it does idle sometimes it doesnt. Everytime I rev my motor up or come down from high rpms, like after a race, my idle will just drop fast till it dies. Any ideas? I replaced my vacuum lines the other day but I dunno. None of this started till I put that new throttle body on...

 

Hello. Just a word. The hose that are connected to the oil injector spider are NOT vacuum hoses. Check it out for yourself. It's quite impossible for the oil injector hose to cause a problem of your type. The worst scenario is that the hose would crack/fall off, and cause a minor inlet of unfiltered air into the intake.

 

ok well this is all good info, ill post tommarow when i get to work on it more...neighbors dont like the rex running at night...together we can conquer evil idle problems

 

Mine is doing the same thing. Regardless of the temperature it will rev up and down. I adjusted the TPS and the BAC but to no avail. When it does idle ( for a couple of seconds.) It idles perfect. But then it goes back in to the rev cycle. Up and down, up and down, you get the idea. Its pissin me off. Cause with a full 3 inch catless race muffler exhaust its a little hard to be discreet in traffic, hell much less order something in drive thru when your car wont stop reving it self. People ask me why it does that I'm just like "Its breathing"

 

(BDoty311)

You have a fuel-line problem. Change fuel filter. Check fuel pump. Or injectors could use a cleaning. Dont mess with your throttle body until you know for shure.

 

fuel filter was changed 10,000 miles ago and my injectors were cleaned ~5000...and i run injector cleaner every few tanks. i guess it could be the fuel pump...ive always suspected my fuel pump was bad...any way i can check for sure?

 

Thanks man, one of the few people left who are good at diagnosing problems. I check my injectors and replace fuel filter tomorrow.

 

Uh I don't know if you have seen the vaccume lines that connect to the top of the oil injectors but if you have not you need to go look at your car. I don't mean the oil injector lines that carry oil i mean the black vaccume lines that go to the intake.

 

definately a vacuum problem. My '87 n/a did the same thing. Idled fine cold, but when warm would surge to 1400 and then back down constantly. Went the whole TPS and everything else route to no avail. Finally took it to someone who knows these FI systems and he found my water thermo valve and block to be clogged with coolant deposits due to age. That's where the vacuum problem was coming from. FSM has a way to check the valve and the block is just a visual inspection. Replaced both and it happily idles at a steady 750. Just another thing to possibly check, not saying that's definately your problem.

 

i think i fixed it...i had to adjust all those little screws on the TB and i finially got it all idlin' perfect...so far. however im very optimistic b/c i know my car and she doesnt act good for very long haha. anyways ill drive it around today and see what happens. i still think it needs a new fuel pump though