AFM and Idle Issues (With Some Fuel Pump Issues Thrown In)

[KevAndAndi]

1981 FI. Driving home in October from PO's house, the car stalled a few times at toll booths and traffic lights. When I got the car home, I noticed the fuel pump buzzing loudly when the key was in the "on" position (before starting). Subsequently learned that is not normal (neither the loud noise nor the running of the pump before starting). Replaced the fuel pump, which is now much quieter but of course it still comes on as soon as the key is turned on.

Yesterday, for the first time since garaging the Spider for the winter, I decided to run it for awhile, fiddle with the idle, and take a look at the AFM. Started right up in 32 degree weather without giving it hardly any gas pedal. I seated the idle speed screw completely and then adjusted the throttle stop screw to attain the lowest idle possible. Could not really get it idling below 1000 without stalling, but adjusting the idle speed screw attained a non-stalling idle at around 1200 - 1300. I understand this is somewhat high.

I had already removed the aftermarket cone-type air filter. I examined the AFM flap through the intake. The flap never opened, no matter how long the car idled. When I pushed it open with my finger (causing the engine to start stalling), I noticed that the AFM flap's spring seemed to offer more resistance than could be overcome by air flow. The flap wasn't sticky, it just seemed too resistant.

I guess the next step is to open the cover of the AFM. Any thoughts as to what I should be looking for at this stage? One thing I'll examine is whether the contact in the AFM that energizes the fuel pump has been rendered permanently closed by someone's having bent the arm that is designed to keep the contact open until the engine is running and the AFM flap opens. Perhaps a PO has done a neat trick by making sure the pump runs even though the flap never opens? Can the resistance of the flap be adjusted? If so, how would one know how to set it? How is the engine running well without the AFM flap opening? Is this related to the high idle that is necessary to prevent stalling?

[spider2081]

Here are some links for FI troubleshooting. You may have read them. If not they are good reading.

http://www.njfiats.org/joomla/index.php ... &Itemid=70

[wizard124]

My 2 cents.........

If it runs well throughout the RPM range, then don't mess with the AFM! There is spring resistance, the flap should not open at all at idle. There is a plug on the AFM that covers an air bypass screw. This screw allows in the air needed at idle. It is pre-set and should be fiddled with as a last resort.

When you pushed on the flap, this signals the ECU to program more gas. But, the throttle plate was still closed (or nearly so). You induced a rich condition and the stalling you experienced is to be expected.

Go online and find a Bosch L-jetronic tuning guide....very specific in order and trouble shooting. This is Alfa based but among the best I have seen: http://www.hiperformancestore.com/Ljetspider.htm

edit: this link is better: http://www.hiperformancestore.com/Ljetronic.htm

[KevAndAndi]

Here are some links for FI troubleshooting. You may have read them. If not they are good reading.

http://www.njfiats.org/joomla/index.php ... &Itemid=70

Thanks! I'm printing all these and adding them to my "Fiat bible" binder.

[KevAndAndi]

My 2 cents.........

If it runs well throughout the RPM range, then don't mess with the AFM! There is spring resistance, the flap should not open at all at idle. There is a plug on the AFM that covers an air bypass screw. This screw allows in the air needed at idle. It is pre-set and should be fiddled with as a last resort.

When you pushed on the flap, this signals the ECU to program more gas. But, the throttle plate was still closed (or nearly so). You induced a rich condition and the stalling you experienced is to be expected.

Go online and find a Bosch L-jetronic tuning guide....very specific in order and trouble shooting. This is Alfa based but among the best I have seen: http://www.hiperformancestore.com/Ljetspider.htm

Thanks! I have seen that one and plan to work my way through the troubleshooting procedures, especially Brad's. I note that he suggests removing the idle speed screw, cleaning it, and making sure the spring and o-ring are intact. I have not yet done this, but will do so tonight. I suspect there is a problem with the spring and/or o-ring, as the screw turns much too easily and almost certainly will not hold a setting under engine vibration.

One thing you said completely puzzles me, though: If "the flap should not open at all at idle" then how would the system energize the fuel pump (in the way it was designed to do)? I thought the opening of the flap closes the contact that energizes the fuel pump.

[azruss]

I had issues with my idle staying consistent. It would eventually die or would die when i stepped on the gas. I pulled the idle adjustment screw as it was seated all the way it was dirty and the o-ring was a goner. I clean it and replaced the o-ring from a metric o-ring kit. I then reseated the screw and set it per Brad's instructions. The situation was greatly improved. I have it set now so my idle is right at 1000. The car will idle all day long like this. I do find i have to mess with that screw every now and then. The o-ring i used doesnt hold the screw very tight as i can adjust it with my finger. Once off idle, the car runs great.

[KevAndAndi]

I had issues with my idle staying consistent. It would eventually die or would die when i stepped on the gas. I pulled the idle adjustment screw as it was seated all the way it was dirty and the o-ring was a goner. I clean it and replaced the o-ring from a metric o-ring kit. I then reseated the screw and set it per Brad's instructions. The situation was greatly improved. I have it set now so my idle is right at 1000. The car will idle all day long like this. I do find i have to mess with that screw every now and then. The o-ring i used doesnt hold the screw very tight as i can adjust it with my finger. Once off idle, the car runs great.

Thanks! The more I ponder and read about it, the more I think there's a good chance that my idle problems are either caused or exacerbated by this screw. I can also adjust it very easily with my finger. Do you have the o-ring AND the spring? If the screw is loose, I wonder if some Loctite purple would help. Or would potentially sucking fragments of Loctite purple into the cylinders not be a good idea?

[lanciahf]

While idling spray brakeleen around the idle screw. If the idle changes you need a new o-ring. Also it is a good idea to check all rubber connections using this method. Injector seals, Big AFM tube, AUX hose etc...

I would not rip apart the AFM until you solve your high idle.

[bradartigue]

If you're going to rely on things I wrote don't download that 2002 manual. It has some errors - and is amazing the thing is still out there (it was online for about a month). Use this:

http://www.artigue.com/fiatcontent/Arti ... 124_MM.pdf

[KevAndAndi]

On the way home tonight I was thinking about the idle speed screw and the o-ring and it occurred to me: Could one of the o-rings I bought to fix the bathroom faucet fit that screw? After all, the faucet was metric (and Italian). Well, I pulled out the idle screw and found that it was gunked up, as was the orifice, and that the faucet o-ring was a perfect fit. I didn't have the time or materials to clean the orifice, but just replacing the old, hard o-ring and cleaning off the screw enabled me to get the idle down to 1000, from around 1250.

At some point, I'll crack open the AFM and see if it's the cause of the fuel pump turning on when the key is turned on.

[lanciahf]

cause of the fuel pump turning on when the key is turned on.

That is usually caused by rewiring the double relay under the glove box, or bypassing the relay and direct wiring the pump to the ignition switch.

The relay should control the pump, either when the starter is engaged or the flap moves in the AFM to trigger the pump.

[spider2081]

I think you could unplug the AFM and then turn the key on. If the pump does not run there is a good chance the AFM switch is internally bypassed. Often it only requires bending the arm of the switch under the black cover. If the fuel pump continues to run with the AFM unplugged the cars dual relay/fuel pump wiring has been messed with.

[KevAndAndi]

cause of the fuel pump turning on when the key is turned on.

That is usually caused by rewiring the double relay under the glove box, or bypassing the relay and direct wiring the pump to the ignition switch.

The relay should control the pump, either when the starter is engaged or the flap moves in the AFM to trigger the pump.

Thanks, those are other possibilities, though I'm hoping it's simply a bent contact arm in the AFM. My AFM flap never moves, so I presume that means there's another air leak (besides the idle speed screw o-ring) and/or the door tension is too high.

One other thing I noticed last night after cleaning the idle speed screw and replacing the o-ring was that my pushing the AFM flap partway open caused the RPMs to increase. Before, with the bad o-ring, the RPMs decreased. Then and now, fully opening the AFM flap causes the engine to stall, but I thought the difference in the result from partial opening might be significant.

[azruss]

It's my understanding that plumbing o-ring are not built to withstand exposure to fuels and oils. Any o-ring for automotive or hydraulic application should be ok.

[wizard124]

One thing you said completely puzzles me, though: If "the flap should not open at all at idle" then how would the system energize the fuel pump (in the way it was designed to do)? I thought the opening of the flap closes the contact that energizes the fuel pump.

Looks like I shot off my mouth without thinking... You can see in this picture how little the flap opens/arm moves to close the fuel pump contact.