zshakespeare

I bought an 84 GSL-SE on wednesday, and it's having idle problems

I've read through previous threads on this article, and followed the standard procedure for idle adjustment, and I can get it to idle at 800 properly when I do that. the problem is when I start the car when it's cold it idles at 600 rpms roughly (and by roughly I mean like: "BUM Bum bum BUM Bum bum") then I drive it for a minute and come to a stop, and it's idling roughly at 800rpms. then the temp guage starts moving to about 1/4 of the way it starts idling smoothly at 1100 rpms, then when the temp guage is pointing straight down, it's idling smoothly at 1500 rpms. Now the smooth idle isn't perfectly smooth like I'd expect, but much better than the loppy rough idle. I can detect a very slight surging at partial throttle too.

Now originally the problem was that it was surgng pretty badly and idling down near 400rpms, and very roughly. I made sure that the air meter was moving properly, as well as the throttle plates. I disconnected the vent and vacuum solenoid valves, and found that if I opened the air adjust screw all the way it would idle at 600 rpms when warm. I noticed that the throttle cable was loose so I tightened it and of course the idle went right up. I readjusted the air adjust screw to bring it down to 800rpms (about half way) and readjusted the TPS for the new settings. to bring it to it's current state.

I've tried removing the BAC so I can check the valve for proper function, the two bolts came off but I was unable to remove it from the block, am I missing something?

No other problems that could possibly be related are that I have a coolant leak from the weep hole in the water pump. I'm picking up and installing my new water pump today, as well as flushing the rad. I also have an exhaust leak before the cat, and my new exhaust system is in the mail, so I'm waiting on that. I want to be sure that I've covered all my bases before I take it to mazda to have it looked at. What say you?

Feds

Step 1: Tune up. Make sure your plugs and wires are good, and your timing is right. Check for vac leaks.

Step 2: make sure your TPS is working right. Not just its electircal function, but the mechanical side as well. Set the TPS, floor the gas, then make sure that only one light comes on again. This one hung me up for a while.

How are you starting the car? From what I've heard, an -se needs to have the fast idle cams set when starting. Put the pedal to the metal, release, then start the car. Works for me anyway.

Also, you need to do the idle setting with the car warm. Also (based on experience) double check that you are disconnecting the right connectors, and re-connecting them when you should.

The BAC can get stuck to the manifold via the gasket. A few swift shots with a rubber mallet will get things moving.

Finally, go through the procedure a few times. Depending on how far out your settings are, it may be a closer-closer-got it kind of thing. And screw around with the idle mixture screw. Start in the middle of travel, and fiddle from there.

zshakespeare

I have a brand new rotor, dist cap, plugs and wires. I'll buy a timing light today. How do I check for vac leaks?

I start the car simply by turning the key, it revs to 2k and then drops to 600

I have been adjusting the idle to 800 while it's warm, and it works fine until I turn it off and let it cool, it seems.

as for the idle mixture, giving the sypmtoms I describe, do you think it should be more rich, or more lean?

Feds

Definitely check your tps for proper return as described in step 2. Also, try the floor-it-release-then-crank starting method.

Ignore what I said earlier. the easiest way to set the idle mixture is:

Mark your starting position, then move the screw to full rich. Try to set the idle. Move the screw 1/4 or 1/8th of the way through the range, and try again. Repeat until it's right. If you can't get it, go back to your original mark.

do a search on vacuum leaks, basically, you spray a little fluid/gas (WD-40 or propane) around the intake manifold and the hoses, and see if the engine suddenly revs up. If it does, you have a general idea of where the leak is.

zshakespeare

I forgot to mention that if I downshift to slow down, I get a popping sound. I'm told that it has to do with my exhaust leak. could that be contributing?

LongDuck

Popping on decel is certainly the exhaust system leak, but the rest of the idle issues are completely unrelated - the exhaust system is not connected to the intake system other than feedback to '6'-port operation, and that's not in effect during idle conditions.

As prior poster stated, the 'Mazda' way to cold-start an SE is to put accelerator to the floor, let it up all the way (no pressure at all), and THEN turn the key to start it. This sets the fast-idle cams on the left side of the TB and resets the cold-start thermopellet device (that green plastic protrusion below the throttles). When this is set correctly, on cold start, the engine will idle at about 1500-2000 rpm for about 2-3 minutes, then drop down to about 1200-1500 rpm for another few minutes. There are not set 'standards' for the rpm or time interval, since it's entirely based on outside air temperature and coolant temperature vs engine temperature. As the engine warms up to normal, the idle should return to the factory default of 800-900 rpm.

Idle fluctuations around electrical load are controlled by the BACV on the driver's side, and this should be removed and cleaned as a primary course of action. From there, move to the idle air adjust screw at the top of the TB, and then to the idle mixture adjustment at the passenger side strut tower. The Idle Mixture is a the 'Variable Rheostat' that Mazda put in there for emissions adjustment, and usually does not need to be adjusted by the driver. This is good for setting idle 'quality' however, once you get all other factors sorted out and the car idling at the correct rpm range.

That your idle speed keeps changing between when you turn it on and off isn't necessary strange - if you let it cool down, you go back to the cold-start mode, which will result in elevated idle speed until warmed up.

Keep at it, you'll get there. Reply back with questions,

zshakespeare

The idle speed increases with engine temp, not the other way around. Now what is wrong if my car doesn't do the warm up procedure? it turns on, revs to 2000 then immediately returns to normal idle speed. it doesn't do any of the 1500-2000 for 2 or three minutes. what would cause that? Also the cold start technique worked great, when the engine is cold I start it up and it idles at 800. once I've been driving it the idle speed increases.

I'm probably gonna take it to mazda tomorrow and have them take a gander.

edit: there shouldn't be much of any electrical load. none of my accessaries work other than the power windows, exterior lights and wipers

GavinJuice

make another edit: MAZDA DOESN'T KNOW JACK They're going to tell you you need a new motor. HAHA Check out this site http://www.nellump.net/peri/epi/firs...gslseIdle.html They have alot of symptoms and procedures to check/fix if something is out of wack. The MAIN contributing factors have been discussed so far on this thread, but it could be something a little more specific.

zshakespeare

That page was where I started. I cleaned out the BAC, and I noticed that if I used my power windows, my idle fell, so I adjusted it a bit so that wouldn't happen. The engine still hunts a bit when starting cold, and is still very loppy. it looks like the idle mixture has been tampered with as the cap for it is gone. I'll play around with that some.

riofrio

Hey zshakespeare... I have a very similar problem... my 84 SE will idle "good" when I start it (regardless of whether or not the engine is warm). But, after driving it for a little while, it will hang high, between 1300 and 1500. It's possible that your butterflies are not closing all the way (mechanical wear). After driving it, when it's idling high, pop the hood open and manually apply torque (slowly) to the throtle rods, and see if your idle goes down that way. If it does noticeably, then it wouldn't hurt to remove the TB and clean the linkages thoroughly (I have yet to do it myself). The other thing that I found is a little screw, near where the air adjust screw is, which seems to set the return position of the throttle linkages. I messed around with it a little and it did help me out (now, I don't think this is the best way to attack this, though). If you don't know which screw I'm talking about, I'll post a pic tonight.
Good luck.