Smoothing Out Idle

Heard the Click

Thanks, Greg.

I got my ear down and gently rocked the TPS after loosening the two screws. It was faint, but I heard the clicking sound you and Hussein referred to. Anyway, I made a minor adjustment to the throttle cable linkage, opened the idle screw a little, set the TPS right where I heard the click, and tightened every thing down. The car is very happy. It's idling cold around 1000. It's amazing how much a few minor tweaks can make such a big difference.

Here is a picture of a nut and screw, adjacent to the throttle - what is it for?

throttle.jpg


Thanks again,

Don
 
That's the real idle speed setting screw.

EDIT---well it is for my circumstances because I had my whole plenum and throttle assy apart. The entire process is on page 10-104 of the FSM.
 
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Thanks, Dan

Thanks, Dan.

I saved the links to my Bertone folder.

Last year when I was rebuilding the motor for my X, I could have used this information. In restoring old tractors, it is amazing just how many manuals and forums there are out there.

I have the Haynes book on X-1/9's but have never found it to be of much use - especially with the FI cars. So, it's nice to be collecting such good reference material. I don't feel like I'm alone on an island, anymore.

Don
 
Idle screws

The small one by the throttle is just to keep the throttle plate from totally closing and potentially sticking, it should BARELY affect idle when properly set. The one on the plenum is the real adjustment.

If I recall, setting idle involves: [ignore the following ramblings of a seriously confused individual :)]

1) Disconnect TPS connector
2) Back off small adjustment screw
3) Set idle to about 800 with big screw
4) Raise idle slightly (850 or so) with small screw
5) Re-attach TPS connector (you can turn off car)
6) Adjust TPS to click reliably just as throttle moves

Oh yes, make sure your throttle cable isn't so tight that it affects the idle adjustment...
 
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Thanks, Steve.

I've printed out your instructions for setting the idle. I think I'm pretty close, now. I put around 50 miles on the car in a variety of driving situations (also in the morning when it's cold, and in the afternoon, when it's hot). So far, so good. After the next tankful of gas, I'm going to look at things again.

One thing I do notice is the difference in idle speeds once the car gets warm. When it's cold, it idles around 1,000 - when hot, around 1,500. Is that normal?

Thanks again.

Don
 
it's the other way around..

.... you set the base idle with the throttle plate adjuster (700-800rpm)

then set the idle with the large screw to 850-900rpm

This is done with a WARM engine.

Don, the Aux air valve allows air to bypass the throttle when cold/cool, raising the idle, until the temperature of the head (where the air valve is bolted) reaches the level that causes the air valve to close (don't know the values).

Warm idle should be under 1000rpm, for stock setup.
 
Idle speed...

You want to warm it up until it's running hot, then set the (max) idle to around 1K. Later, see if it will idle when cold at this setting. Sometimes you have to set your idle to work as best as possible in both conditions.

Mine can sometimes take a while to settle down to a proper warm idle. If yours doesn't eventually settle down when warm, check the Aux Air Valve for proper operation. It opens when cold to allow more air into the intake to increase idle speed when the engine is cold. It closes down (but not completely) as it warms up; it is heated with 12v as well as block heat. It's down low on the block on the forward driver's side of the engine. The hoses go to and from the main air hose; one on each side of the throttle.

Also, sometimes an engine will briefly idle high after a cruise, this is likely due to oil or blowby gases contributing to the combustion mix. Often after a few minutes the idle will settle down.

Another function to check is the idle speed when warm with the A/C on, if so fitted. There is an electrovalve on the AFM that is supposed to increase the idle slightly when the A/C is on... so if you use your A/C you want to set the idle so that it is high enough with this system engaged.
 
Don... Great advice given here for Idle Speed...

BUT...

If you have an imbalance in cylinder pressure it is all for NAUGHT!

That is why you should always test your compression FIRST!

1. Pull all the plugs and disconnect the coil wire just for giggles.
2. Best to use a screw in type compression tester and an assistant.
3. Crank the engine over with the throttle WIDE OPEN and observe the compression needle rise as that particular cylinder cycles at least FOUR times. Record.
4. Repeat for other three cylinders. This is a DRY test.
5. Now squirt about a teaspoon's worth of clean engine oil into the cylinders and retest and record. This is a WET test.

Comments...

1. You should have about 145 pounds minimum and even across all cylinders, within 10 pounds difference, preferably.
2. The pressure should not rise more than about 10 pounds with the oil installed on a wet test. If it does, then it indicates possible ring sealing issues.
3. If the cylinder pressures are LOW, 10 - 90 pounds and they do not change significantly when WET, then you probably have bad valves.
4. If the cylinder pressures change drastically when WET, then you possibly have bad rings.
5. In either case... reinstalling the plugs and running the engine at 3000 rpm while dumping about 1/3 quart of ATF (automatic transmission fluid - cheap red GM type...) into the intake CAN and DOES restore many different compression problems. A squirt can works well for FI cars, just pouring down the carb works for carbed cars...

THIS MAKES LOTS OF SMOKE... and takes about 10 minutes... use caution or warn neighbors...

I've seen many cars repaired this way over the last 50 years!

Restest compression when done and record! Let us know how ya do... and then install the NEW plugs.

Good luck!
 
Oops, you're right

Must be getting old and senile.. :nuts: :) Sorry for leading you astray Don, I'd better check mine, I probably adjusted it wrong.

Found the correct method in the manual:

Connect tachometer. Run engine until it reaches normal operating temperature.

Turn idle speed adjustment screw (big one) in all the way. Adjust stop screw (little one) to obtain 700 to 800 RPM. Hold stop screw and tighten locknut.

Adjust idle speed adjustment screw (big one) to obtain 800 to 900 RPM. Hold adjustment screw and tighten locknut.

Check the throttle plate switch and adjust as needed.
 
Great Tutorial

Thanks for the "how to," Tony. I'll have to wait till I have another person available to do the cranking - but really want to find out what the compression values are.

'Course, I'll have to get my car back. Now that it's running, my wife would rather drive it than my '78 Chevy 1-ton pickup. Don't know why!

My little toy has become indespensable pretty fast. Our '97 Dodge Minivan is in need of it's 4th transmission. We've been lucky with the van, though. For the most part, we've gotten 75K miles out of a transmission. This third time, we only got 35K. I was blown away when a couple of mechanics told me how fortunate we were to get such great performance. Hope Fiat doesn't screw up the stellar Chrysler brand.

Thanks again. I'll post my compression results as soon as I can do the test.

Don
 
OK... and then again... there is a tool called...

... a remote starter switch!

HA!

Hey... sorry about Chrysler's poor performance in their Vans!

I didn't, and still don't carry rental car insurance on my car policy as we've always had more cars than drivers... but a few years back I lost two cars in two weeks to uninsured motorists and my wife and I were stuck driving he FIAT everyday! HAHAHA!

Looks like yur gonna haveta get another X for yourself. BE HAPPY she APPRECIATES that car... mos don't!
 
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