Ok on my 85 GSL-SE I'm having a problem with my idle, can anyone tell me how to fix it.

when I start my car it idles ok, about 800-850 rpms. When I drive it, it also drives ok. However, when I let off the gas the rpms drop almost down to 0 and sometimes dies. If it doesn't die, after two or three seconds it recovers back to 800-850.

Any answers to this problem?

 

could be spark, possibly a weak alternator. Whats your Volt meter register. And how's your fuel pump? Get your fuel lines pressure tested.

 

Still not idling correctly, My alternator is strong. I can't figure out why its running like crap at idle. I think I'm going to take it to a local Mazda dealer.

 

BEWARE THE DEALER!

Dealers are going to tell you that your engine is shot and you need a new core - $2500, plus labor. Dealers don't know dick about our cars because they aren't called to work on them with any frequency, whatsoever.

That said - my first guess is that your 'Dashpot' isn't working correctly. The DP is mounted to the left side of the Throttle Body (TB) when viewed from the passenger side of the car. It's function is to retard the fast 'drop' of throttle rods and butterfly valves to better control airflow going into the engine on deceleration. Very easy test to check for proper function is to 1) locate it (duh), 2) rotate the TB rod so that the DP plastic rod that contacts a flat spot on the main Throttle Body rod comes OUT, and 3) verify that it's hard to push IN by hand. If you notice resistance pushing it IN, then it's working correctly.

If it's not working correctly, i.e., the plastic rod moves in and out freely without any resistance, there's your problem.

Start there and then report back with your findings. That's the easy fix, and from there, we move on to much more complicated troubleshooting measures (search will give you a headstart). HTH,

 

possible causes based on my experience

-dirty throttle body (causing it to stick)
-bad solenoid

could be something else, but mine had a crappy idle with similar symptoms until these things were fixed.

 

dashpot seems to be working correctly.I even tried ajusting its location some to see if that made a difference, but the engine would still fall below where it was supposed to idle and almost die out.

 

Could be also that your BACV isn't responding quickly enough to the return to idle. This is the Bypass Air Control Valve and is located on the left side of the Dynamic Effect Intake (DEI) chamber at the top of the engine.

Remove the BACV with 2x10mm bolts and the wiring harness and be careful with the gasket under there - if you are careful, it can be reused. Spray carb cleaner into the air passages to clean out any carbon and then reintall and see if that's helping things.

When you mentioned that it idles at 800rpm just fine, that seems to indicate that it's working okay during idle, just the return to idle is causing problems. Manntis has a good suggestion also, to remove the air inlet pipe and spray down the inside of your TB butterfly rods with WD-40 or some other lubricant.

Occasionally, these can cause the TB rods to get stuck and then your engine has a hard time getting back to idle condition because there's too much air coming in, TPS says 'idle', and the BACV is doing it's best to 'help-out'. Reply back when you get a chance to try this,

 

just having no luck, took off the bacv and sprayed it good with carb cleaner and still no dice. Do you think it could be a vac leak somewhere? It still stumbles after you rev it, after it stumbles for awhile it goes up to 800. I even adjusted my throttle body, while it helped a bucking problem I was having it didn't fix the idle problem.

 

Did you look for intake system leaks between the AFM and the TB? There is a metal fitting on the intake air pipe right by the TB which uses a rubber hose that goes to the DEI chamber and over to the BACV. If this has a leak, it could screw up both functions of intake and BACV.

Have a look at it, and pull out the metal 90 degree fitting. Coat it with some silicone and then reinstall, allow to dry, and retest.

 

checked it, no leaks from where i could see

 

I did retried to adjust the throttle position sensor again. I noticed when I got one light to light and switched to the Ohms I would get it adjusted to 1.00 , however when i put the lights back on it both lights would be on again. After the adjusting the lights and putting it back on Ohms it would read 1.22-1.32 at idle and about 5.50 at WOT

Is my throttle position sensor bad? Could this be my problem?

 

seems to me my old engine did this. although i dont have a fix for you, i would just hold my foot on the gas when i came to a stop to prevent it from dying.

Sorry i cant be more of a help. My car also had that wonky idle problem as well (Fluctuating) that never seemed to want to go away. It acted on its own accord, not mine.

 

still can't find a reason for the idle problem, I don't know what else to do. Guess i will have to take it to a shop after all.