Ok, I've changed spark plugs, pcv value, oxygen sensor, oil, oil filter, fixed one vacuum hose, air cleaner, cleaned pulleys/replaced all belts, replaced battery, and tested the alternator.
I have used the idle adjustment screw to adjust the idle before. Here is what it is currently doing:
In park, when cold, it runs perfect at around 900 rpm. Go from that to drive and it goes to 750 rpm. This is ideal and if it would stay this way, I'd be happy.
But, once the engine warms up, idle in park or neutral goes to around 1250.
Does the fact that it is normal when the engine is cold and higher when it is warm suggest anything?
I still have not checked all the rest of the vacuum hoses looking for leaks. The guy at the auto parts store suggested I spray some carb cleaner near the hoses and wait to see if the rpm increases and that this might help me find a hose with cracks in it.
Would a hose "heat up" and then start sucking air through cracks?
At that age I would check every hose, (and there are a lot of little hoses)right where they connect, bend them and you will see the cracks and don't forget to look underneath where you normally can't see. Sometimes you can just trim a bit of the hose off and re-attach, getting rid of the bad part.
It might be the idle-up solenoid valve. It looks like that valve is in the right proximity of where an IAC would be. At first, I thought the idle-up valve was the throttle position sensor, but on the throttle chamber pic, it looks like the TPS is attached to the throttle body (where it should be). Just a guess. Anyone?
I found the idle-up solenoid valve. Does anyone have the 86 stanza service manual with how to test it?
It looks like the large side of the solenoid is hooked to the air regulator.
So, my theory might be that this valve is stuck shut or is not getting any electricity to open. In the closed position, the engine never gets extra air when the engine is cold. Because of this the idle screw is turned up too much (so that it gets enough to idle when cold), but once the engine warms up and no longer needs the air the valve would have provided, it runs too fast because (again because the idle screw is turned up too much). What do you think?
Should I hear it CLICK if I apply 12V to it? On a cold engine, does the computer ECCS tell it to open up and then after a certain engine warm point it turns it off?
I'm not familiar with the ISV, however on Ford IACs, you can take it apart and clean it with choke cleaner because the internal components (i.e. a spring) get gunked up with carbon which is what causes it to quit working properly. The one on my Stanza is similar to the Ford's, but it has a coolant line running through it. I took it off and cleaned it as well. Worst thing that can happen is that you have to get a new gasket.
1. I ohmed the connector and it came up at 28 ohms which seems pretty good.
2. I turned the ignition on without starting the engine and plugged and unplugged the connector. I can hear it actuating, but I didn't take it off enough to see if it is plugged or not.
3. At first, when I ran the engine and unplugged and plugged the connector, I noticed no rpm change, but after playing around with it for awhile, I did notice a rpm change when I plugged and unplugged it.
4. Their are two wires going to it. One is red and one is black. When I check the connector on the wiring harness it is really odd. At first neither one showed any connector to ground, but eventually the wire I didn't expect to be a ground, did show no resistance to ground. Here is the odd thing, when I measure DC voltage between it and ground, it shows 11.7 volts! Switch to resistance, shows 0 ohms, switch to voltage shows 11.7 volts. Is this some sort of phantom voltage that would become zero if I actually put a load between it and ground? The other conductor showed something like 0.2 volts. It makes no sense to me.
I can see the 11.7 wire looks like it has a odd bend in it and I wonder if it has a weak connection. At the end of my testing, engine still not warmed up, I noticed that unplugging and plugging causes the rpm to change.
What do you guys think? Should I cut the connector off and put some QD crimp on connectors on there? Should I take it off and look at it? I'll call tomorrow to find out what they cost...
Some other suggestions:
Have you cleaned the MAF or checked its resistance?
Have you replaced the throttle position sensor?
Have you replaced the coolant temperature sensor?
I replaced the thermostat today and that went surprisingly easy.
I did try spraying some carb cleaner around some of the vacuum hoses today to see if the RPM would increase if they were sucking air in, but I detected no RPM increase so maybe it isn't a vacuum leak issue.
What is the MAF ???
I haven't looked at the TPS or the coolant temp sensor, but thanks for the tips, I will.
The MAF is the mass air flow sensor located in the intake air box/air flow meter. These can become corroded over time and need cleaning. Also, they are easy to check function with a multimeter. Not sure if your car has one.
A bad coolant temp sensor can cause the car to run rich or lean and have erratic idle because the ECM receives erroneous information. The TPS can cause an erratic idle.
And on a simpler note, have you adjusted the timing? After a tune-up, I would suggest hitting it with a timing light or just move it by hand to see if the idle changes at operating temperature. And I don't know if your distributor has a crank angle sensor, but blasting it with a good contact cleaner can help.
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