80 FI Spider and no low speed idle

[dnudelman]

This spider dies below 2500 rpm
This is an 1800 transplant into a 2000 chassis with the 2000 Fuel injection and
2000 Distributor.

Symptoms:
Motor starts every time. "Idles" hunting between 2500 and 3000 when warm
Throttle stop screw all the way out. Throttle cable slack
Throttle position switch is fully counter-clockwise, turning it clockwise speeds
up the rpm. We tried to adjust the switch, circuit closed throughout range.
(Bad switch?)

Timing: Car runs best at 0 TDC (at 3000 rpm), at 10 BTDC misfires and tends to
run roughly and die.

What we've done:
Distibutor vacuum line, tried disconnecting it, no change
AFM to Intake hose. Looked for leaks, sprayed starting fluid around, no change.

During engine swap:
Cam Timing checked after new cam box gaskets.
Rebuilt injectors
New plugs
New water temp sensor (on the T)

What was used as is from the 2000 motor
Distributor, cap, rotor, control module
Spark plug wires - resistance check ok
AFM was said to be new or rebuilt

We bought this car after the PO had frozen the motor. He hit the oil pan and
kept on driving until the engine froze. He sold it and that buyer sold it to me
about a year later.

The 1800cc motor is out of a 75 that we got running and drove for a few days
around town (with carb of course). Valve clearances are within range as well as
compression.


Any suggestions appreciated.

Thanks
David Nudelman
Mercer Island, WA

[pope]

Hey,
I could be a lot of things. Did you install all the F.I. connections on the engine? Make sure that the Thermo-time switch is connected, it is down under the intake manifold between #2 and 3 and it looks like a water temp sensor. The auxiliary air regulator could be responsible for too high an idle.

Make sure the connections are correct and connected to the right sensor. What was done to the engine previously to you getting it? Were performance cams installed? What about high compression pistons. The F.I. system does not like either, only modest boosts.
Good Luck

[So Cal Mark]

the throttle switch is an on-off type, not a potentiometer so it won't read throughout its' range.
With the idle at 2500, I'd make sure the throttle plate is closed, then look for vacuum leaks. It will have to be a large leak such as the brake booster hose or aux air reg to create an idle that high.
The engine should run better with the timing at 10, so something odd is going on. Do you have the FI diagnosis manual and a volt/ohmmeter?

[dnudelman]

I checked for loose hoses today and verified that the throttle is fully closed. I tried clamping the hose to the aux air regulator and was able to bring the idle down to 2000 rpm. Then the motor died and would not restart. NO SPARK. I found that one the wires on the ignition pickup had worn through the insulation. I'll follow up with my results as soon as I've repaired the insulation and reinstalled the pickup
Thanks
David

[So Cal Mark]

the damaged pickup would explain why the engine misfired when the timing was advanced. Is the idle air bypass screw closed?

[dnudelman]

Is the idle air bypass screw closed?

do you mean what the manual calls the idle mixture screw, located near the throttle position switch?
thanks
David

[So Cal Mark]

the mixture screw is in the AFM, the screw near the tps is an idle air screw. It allows air to bypass the throttle plate, thereby raising or lowering the idle speed without touching the throttle adjustment

[bradartigue]

I sent you an email but it must have bounced since I saw you emailed me again - here is what I sent you and I'll try and call you today.

Hello David.

There are at least two different issues here. One is an electrical issue and I’ll argue you need to sort it out before even trying to diagnose the FI system. Keep in mind that the fan is not linked to the FI system at all, so the power loss you are experiencing is either because someone tampered with the wiring or the voltage drop when the fan comes on is severe enough to stop the ignition or FI system from working. A misconception about FIAT’s use of L-Jetronic is that it is somehow integrated into the motor like a modern FI system. It is not. It monitors some basic inputs (throttle rest, engine and air temp, exhaust O2 level) but little else. So when you diagnose it consider it a truly independent system; in other words, except for the coolant temperature sensor (an FI part) there is no control from or to the FI system of your fan or other cooling system parts.

Try and find your electrical problem – it is most likely a ground. Your motor should have at least four grounds, two are big – from the transmission bell housing bolt to the body and from the engine mount on the exhaust side to the body. Two are small – from the camshaft rear cover top screw on the exhaust side to the firewall and from the FI plenum hold down bolt to the firewall. The FI one typically has a couple of wires already meeting there, just run a new wire to the firewall. If you can’t picture these then I can send you images or a diagram. Also make sure the battery has a good ground strap to the body. It doesn’t hurt to unbolt the battery ground from the body and clean up both the bolt and the threads it goes into on the body. Use a wire brush and get it all shiny.

Once your electrical system is a bit happier then you can focus on FI. I would get the FI pump working off the FI dual relay again – in other words, get the wiring to the FI pump off of the direct-connect the previous owner did.

High idle in an FI system is really only caused by two things – unmetered/bypass air or open throttle plates. Sounds like you don’t have any air leaks, so I would do something like this:

Disconnect the accelerator cable.
Completely slack off the idle stop screw.
Fully seat the idle air bypass screw.
Unplug the cold start injector.
Block off every air port except the AFM leading into the FI system. Simply undo the hoses and cover with duct tape or little hose nipples. Make sure you include the distributor vacuum advance cable at the side of the throttle body.

The car absolutely should not run in this state.

If it does then the only source of air would be from the throttle. Unplug the big air hose and take a look that the throttle plate is at about 1 degree open. If so then undo the other side of the air hose and check the AFM flap; it should be closed.

If it does not run then you at least have a starting point. Get the AAR hooked back up and do the idle speed setup procedure. Do not hook up the accelerator cable until you get the car running on the idle bypass screw and stop screw alone.

[dnudelman]

Brad,
Thanks, the email must have bounced. I'll get right on this list and let you know.
Rgds,
David

[dnudelman]

Disconnect the accelerator cable.
Completely slack off the idle stop screw.
Fully seat the idle air bypass screw.
Unplug the cold start injector.
Block off every air port except the AFM leading into the FI system. Simply undo the hoses and cover with duct tape or little hose nipples. Make sure you include the distributor vacuum advance cable at the side of the throttle body.

If it does not run then you at least have a starting point. Get the AAR hooked back up and do the idle speed setup procedure. Do not hook up the accelerator cable until you get the car running on the idle bypass screw and stop screw alone.

1. It does not start with everything disconnected as mentioned in the first paragraph above.
1a. It does not start the vacuum to the regulator disconnected
2. It will start with aar hooked up as well as the cold start injector. Idle air bypass screw out 1 turn and IF you kick open the throttle a little. Idles for a less than 1 minute at 2500, then slowly drops to about 1800 and dies.
3. I took the cover off the afm and watched the needle move. The afm was about midpoint at 2500 rpm. Is this normal?
4. When I reconnected the brake booster, the car started easily and would idle continuously at 2500 without dying. There is a check valve in the brake booster with an arrow and the word "motore". I have the arrow on the valve pointed towards the "motore"

5. I'm wondering if something is amiss with the AFM. Is it shutting off the injectors? Also, the fuel pump is wired ON with the ignition switch. I had a fuel pressure guage on the cold start solenoid hose earlier and I don't recall pressure dropping at any time. I

[So Cal Mark]

the fuel pump shouldn't run until the afm flap opens slightly. I don't recall the afm flap being at the halfway point at 2500rpm. Can you control the flap by hand once someone starts the car? It could be that someone tried to "tune" the afm by changing spring tension

[dnudelman]

Mark,
1. The PO wired the fuel pump around the relay so its ON when the ignition switch is in the on position.

2. I've got the cover off the AFM, the contact lever that slides along the half circle resistor is at about 1:00 position at 2000 rpm.
3. I gently pulled the contact lever clockwise (to close the afm) and the engine would die almost immediately

Thanks
David

[rlux4]

You didn't say whether you've got a FI diagnostic manual yet. If you don't, each of us who does our own maintenace really needs to have it. There is a good one here: http://mirafiori.com/~thad/fi/
Another good source for checking the electrical components is here:
http://www.wcmotors.com/personal/Fiat%2 ... agnostics/
Here is a picture of the AFM , not running:


And this is at idle (900 RPM)


Ron

[dnudelman]

Ron,
Thanks for the pix. My afm at 2000 rpm looks like the bottom one. I do have the FI manual(s). Thanks

[bradartigue]

Ron,
Thanks for the pix. My afm at 2000 rpm looks like the bottom one. I do have the FI manual(s). Thanks

Out of curiosity did you ever put an external tachometer on your coil to see what it said? Are you sure the motor is at 2500 and its not just a crazy tach - not to doubt you because a motor at 2500 sounds fast.

Shouldn't have to crack open the throttle plate to get it to run if the AAR and idle screws are set correctly.