slow idle at start

[micbrody]

First of all, just want set up the facts:
1981 FI
At least two previous owners who:
Ignition switch / fuel pump wired to run all the time in run position
The starter had a parallel circuit switch to energize starter. One would use to crank car if turning key to start did not energize starter.
AFM air bypass plug not present; I assume they screwed with it.
AFM had non-factory silicone to close cover (so they went into it)
Brake Booster had small leak
Vacuum advance diaphragm does not hold vacuum.

For the above problems:
took apart double relay; cleaned all contacts;
added a relay to separate high current starter amps away from ignition switch
checked and cleaned contacts on AFM (both fuel pump and cleaned resistor board, along with creating new "path" on resistor board for rotating copper contacts.
I capped off vacuum advance.
I also pulled cold start injector and tested. (it would go on and then shut off at a few seconds (depended on temperature of coolant). I also measured resistance of temperature probe at coolant T, both at probe; and at ECU connector

Car would start with just ignition key; however, depending on time between starts? temp of engine? temp outside if it was sitting? , I would have intermittent starting problems. It would crank, but I would have to hit gas pedal. Some days car started within 0.5 seconds/ other days I needed to hit gas and crank for 5-10 seconds

I then checked brake booster. Found it had a very small leak. It would function with car running. But if I waited overnight, most of the time I had starting problems. I figured that overnight the vacuum would dissipate; and it would be the source of unmetered air. So I replaced booster. Brakes do work better. Car still has some start issues; though idle did not wander as it did with leaking booster.

So I thought that all I had to do is go through procedure to "tune" the idle. I screwed down idle screw. I checked the electrical function of throttle position sensor. I started car. Let it go through at least two radiator fan cycles (190-210 deg). I adjusted throttle to 800 ish RPMs and locked down lock nut; and opened up idle screw to get to 850-900 (one half turn). Drove car. Everything seemed fine. very smooth acceleration.
I shut car off. I came back about 45 minutes later, and car would turn over, but the starting RPMS would be extremely low (200); occasionally it would die; occasionally it would accelerate.... but only to 600-700 RPMs. After about 10 minutes of driving, the temp was back to 190 and RPMs were at 900 on idle.

What should I do next?

[76was124]

Did you check the Auxillary Air Valve (AAV). It should be open when cold, and allows extra air to bypass the throttle plate to keep RPMs up until the engine warms.

Btw, not important, but i'm impressed it idles at all at 200 rpm, normally the dual relay would drop out long before then, killing the injectors.

[micbrody]

I did check and clean the auxiliary air valve. I removed it; put it in freezer; it opened up; ran very hot water over it , and it closed.
As for the very RPM; My fuel pump normally makes a background whining sound. When I start the car and the RPMs are low, I can hear the pump, but at a lower frequency. I was thinking about that maybe the fuel pump is not pressuring the injectors enough at start; however, the low whining might be from the alternator going slowly and screwing up the amperage/voltage. In other words: chicken or the egg first? The fuel pump , when car up to RPM is strong and constant. When I have car off but ignition in RUN position, I took air filter off and pushed on AFM door. Fuel pump immediately went on at its normal higher pitched whine.

[micbrody]

also, I forgot to mention: if car is struggling at the low RPMs, all I have to do is hit the gas and the car comes up to a higher RPM (but still only 600ish); and the fuel pump sounds normal at those low RPMs. So I don't think its the fuel pump, because that would not explain the initial 5-10 minutes of slower RPMs until car warmed up

[RRoller123]

AAV. Pull it and test, is not difficult. Do a search on a post I made "AAV Observations" (or something like that) for a couple of pics and time specs as to how it should close.

[76was124]

When you went through the idle setting, did you set your timing first, and also adjusted and test the throttle position switch (TPS)?

When you hit the throttle and the low idle raises to 600rpm, that 600 is after you take your foot back off the gas pedal correct?

is it a smooth idle or rough at 600RPM? My 81 won't idle much below 500 RPM.

Knowing the AFM has been tampered with by PO, did you check the resistances? It can definitely cause strange performance. Flap door isn't bent or sticking is it?

[micbrody]

Per AAV, I did pull and test outside of car. The openings looked roughly as someone had photographed at different temperatures.

[micbrody]

As for checking the timing, I have not done that yet (not sure exactly how to do it ); but I would think that if car starts well 7/10 times; and even after bad start, the engine performs great , that any static timing issues would cause a very reproducible and constantly noticeable problem . It is on my list of things to do .

[micbrody]

The perplexing thing is how "chaotic" the problem seems to be. Last night after car rested for three hours (probably 45 deg outside), I had same starting issue.
This morning , after car off in garage for 9 hours (55 deg), the car started immediately and came to normal RPMs. I did check the AFM door. Does not stick; easily moves and starts fuel pump. I previously did check resistance of AFM......but not sure if I did after "refurbishing" contacts. Maybe I have an intermittent contact problem on resistor board near low rpm position ; maybe relative humidity affects it. This I will check again. I think that could explain it. Thanks for the idea

[micbrody]

The only way I can see AAV causing problem would be if it's stuck closed at beginning of cold start; and when engine warms up, the need for auxiliary air dissipates.
Unfortunately, how could I check if valve is intermittently stuck? no outside indicator of the orifice size.

[micbrody]

Our friend Brad Artigue posted this for AFM on Alfa Romeo board. I think I will use these numbers as reference of resistance on AFM:
(I don't know how to post images)



http://www.alfabb.com/bb/forums/attachm ... 1260060056
http://www.alfabb.com/bb/forums/spider- ... ronic.html

[76was124]

You are correct about the AAV. It would have to be stuck closed for a slow idle when cold, but it wouldn't impact starting.

Have you seen Brad's manuals at: http://www.artigue.com/fiat/ ? They give you very good diagnostic procedures.

[RRoller123]

Just re-reading this and something from your original post may hold a clue. You mentioned that a PO had wired a separate circuit to energize the starter if it didn't start via the key/ignition switch. This is what I have not so fondly called the "click of death" and was, in my car, the result of a bad C31 connector, which is just downstream of the ignition switch. (There are a bunch of posts from me on this, rants, really). Even with the relay work you did, if C31 remains intermittent, it could be a source of the problem. You may want to try tightening up those connections and see if it works. In my car, the problem was that this connector is a non-locking type, and would work itself loose over time, causing intermittent starting. These intermittent issues are tricky.

Just offhand, might check the quality of the 2 ground connections at the air plenum. Ring connectors. If the plenum was painted in the past and the paint not relieved, that might cause a problem. Good luck, something will make itself evident eventually!

[micbrody]

I revisited the AFM. I checked the resistance of the pins with engine off. They all were within range of the Artigue stuff a few posts before. However, when I manually advanced the AFM (moving air flap), the resistance changed in very chaotic ways. It would go past 1000k and then down to 40-200ohms; it depended on where I stopped flap as to whether it was in a reasonable resistor range or out of range. Also of concern, was the fact that it did not appear linear. I disassembled AFM; and with just voltmeter leads, directly checked the resistance along the track that copper arm moves. It seems that resistance was all over the place. Just below the track area, there seems to be a "test area" for the same dark coating. That tested as I would expect: 6000ohms; but as I moved one lead towards the other, the resistance gradually and linearly decreased. I could not find an un-grooved area on the functional part of board that acted the same way. So my tentative conclusion: I need a new resistor board......
I did reassemble; tried to attach copper arm in a way to touch newer parts of board. Car still had difficulty starting; but once I got it going, it drove great. I would think if AFM was really screwed up , that car wouldn't run smoothly at high RPMs.....but maybe it would....but mixture would be either lean or rich .