Idle no longer changes?

[H.G.P.]

One month ago my idle used to start low and get higher as when returning from Mid-Ohio Lemans I had to adjust it down slightly after the engine had fully warmed up.

Now however, come July, I have the idle adjusted at approx. 800-900, and it stays there, even after the engine has warmed up.

1. Is it possible that the jets have "self-cleaned" from the fuel?

2. Result of still breaking in the engine after 3-4 months?

2. Is something wrong with the engine that it needs more fuel perhaps?

Vac. lines appear fine and connected, and the car runs and pulls fine.

[ZOA NOM]

Denser air during the colder months. July heat makes thinner air, less rise in idle speed when the motor warms up.

Just a theory.

[hkspwrsche]

That sounds like a pretty good guess. If it was slightly rich before. maybe check the fuel pressures and mixture now and again if it seems to go back to where it was?

[bigchillcar]

are you saying that you adjusted the idle at the first of july to 800-900 and that it's staying there now? if so, perhaps your 'basic idle' speeed wasn't set properly to begin with (too high)? if you mean that it has done this 'on it's own'..maybe with the now thinner air, your mixture is slightly richer..but now certain it would greatly affect idle. what speed did the idle used to rise to?
ryan

[H.G.P.]

Originally posted by bigchillcar
are you saying that you adjusted the idle at the first of july to 800-900 and that it's staying there now? if so, perhaps your 'basic idle' speeed wasn't set properly to begin with (too high)? if you mean that it has done this 'on it's own'..maybe with the now thinner air, your mixture is slightly richer..but now certain it would greatly affect idle. what speed did the idle used to rise to?
ryan

I had to adjust the idle (today) to 800-900 because it was idling (but not quite stalling) very low, around 100-200. It was idling way too low after cold start and when engine warm, and hot start. (All this afternoon)

The idle speed used to (since the rebuild) on cold start begin around 500, and then rise and stay at 900. It did this in all outside temperature conditions, including above 90 degree weather.

[bigchillcar]

is this engine a carbed 2.2? i'm really only qualified to troubleshoot a cis car and just realized you probably don't have that..what i do know is that with my car the 'basic idle' speed has to be set when the car is at operating temp (180 degrees) and my hand throttle is required to set cold idle speed appropriately at start. by the time my car has reached near operating temp, my idle has settled where it's supposed to be ~950 rpm. wish i could help more, but just don't know your engine. good luck!
ryan

[H.G.P.]

It has a hand throttle with I don't really use as it warmed up fast.

Origninally MFI but now converted to carbs.

I took it out tonight to test the afternoon adjustment:

1. The car ran terrific, and powerful (but it always seems that way at night to me), I did hear one backfire, and maybe a few pings before full warm-up.

2. But the idle started out low again (even after the adjustment), at around 300, but then after driving for about 10-15 minutes, settled down at about 700 RPMs for idle (with all the lights fully on).

3. The voltmeter showed good reading, with all the lights on also.

4. Weather about 60-65 degrees and very low humidity compared to yesterday.

So I'm not sure this idle is correct and why it changed from yesterday (fan belt tension seems right too)....



One other note: Is it possible for idle screws (or maybe mixture too), to have backed out? My idle screws are set way out at the current idle of 700.

[H.G.P.]

So went out today. And even after yesterday's adjustment of the idle:

1. Still drops to almost 100 RPM after 5 minute warm-up. But will not stall (but just about, like being "on a cliff" of stalling)
2. Fuel pressure excellent.
3. Volmeter reading excellent.

So then I again adjusted the idle screws again. The passenger side screw seem to make the most difference, by adjusting it about 1/4-1/2 turn, idles at about 700750 RPM, even when engine fully warmed up.

So this is a mystery to me. I'll go slither back into my hole now.