Dead throttle pedal

818 Views 5 Replies 3 Participants Last post by jstrieby, Sep 11, 2007

jstrieby

Discussion Starter · Sep 11, 2007

85 Spider Veloce, Bosch L-Jet, 67k miles, mostly oem and stock

I frequently have a 1-second stalling condition meaning that I'm moving any speed, any rpm and the engines just quits (stalls) for a second, no warning lights, no nothing, the engine just quits. When I depress the pedal or get-off the pedal the engine comes right back. Has never stopped completely. Seems as if throttle switch has poor connectivity to ecu? An infrequent symptom, possibly associated, is cold starts sometimes will not idle. A few restarts later, evrything's fine.

No Alfa I've owned has ever left me on the side of the road!

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Tifosi

· #2 · Sep 11, 2007

If the TPS was faulty/failed/dead, it would still run, just not really well, as once the ECU stops getting signal from that, it reverts to a pre-programmed mode that will cause things to run a bit rich, (closest thing to it is the idle mix position on a known good TPS), it'll also not go into closed loop or activate the VVT, but it will run.

I'd hazard you're looking more at a fuse, ground, intermittant ignition contact (switch or coil), AFM plug, or mabe flywheel sensor issue.

It might even be the fuse back by the ECU isn't quite contacting as well as it could be. (if that rattles, it'll shut down all kinds of stuff starting with the pumps and injectors)

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jstrieby

Discussion Starter · #3 · Sep 11, 2007

Thanks Tifosi!

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Tifosi

· #4 · Sep 11, 2007

Oh, don't thank me yet.

Wait for ghnl and a couple other folks to come through and either agree (in which case you're welcome) or rip my ideas to shreds (in which case, I'm sorry)

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ghnl

· #5 · Sep 11, 2007

Since he insists, I'll chime in and say Tifosi knows of what he speaks (writes).

I'd suggest looking carefully for false air (all air entering the engine must pass through thr AFM so it can tell the ECU how much fuel to squirt). Any leaks, loose/cracked/split hoses will make the AFM send faulty info to the ECU. Just a guess but how are the motor mounts? Maybe, if they are iffy, the engine is moving and opening/closing a split in the intake air ducts? Or causing an electrical connection to lose contact?

The TPS is really just a switch - not a sensor. It tells the ECU if the throttle is at idle position (or not). For the Spiders with solenoid controlled VVT it also tells the cam when to advance (about 3/4 or more open throttle). The TPS is easy to check (and adjust if needed). See Step 5 in the L-jet page - link is in my signature block.

The cold starts/poor idle could be a failing AAV or fault in the cold start system. Info about both the AAV and cold start system is in the L-jet page, too.

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jstrieby

Discussion Starter · #6 · Sep 11, 2007

Thanks!

I've replaced the rubber afv to tunnel, tunnel to throttle valve knowing these two big pieces were faulty. Hoses, both braided and rubber have been inspected and clamps tightened but not removed and pressure checked. My luck with Alfa's, 5 GTV's primarily, has been excellent. I can usually touch things, detect something loose or whatever and fix the problem but this eludes me because this is my first Spider and my first fuel inj Alfa. I drive this Spider daily. I now, thanks to you and all replies given, will now commence my first self-taught Bosch L-jet training class. Thanks Again, I'll let all know what I find.

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