Idles fine but sputters on throttle. backwards tach?

[dpoole]

I previously posted this in Spider forum. I got one response there but the problem is not solved so I am reposting here.

'82 Spider with Bosch fuel injection

Was running fine then all at once, while driving down the road, I lost all throttle. It idles fine but coughs, spits and backfires when throttled. It's not pedal linkage - does same when move throttle at the plenum. Not enough power to drive car at all. It was not a gradual thing, went all at once.

It still starts right up and idles smooth.

Strangely, the tachometer shows the correct idles but goes LOWER when RPM's go up? This began at the same time as breakdown. I assume the tach is electrical so the problem may be electrical.

I have now replaced all vacuum lines (Greg's trunk & engine silicone kit). Recently changed fuel filter and tank fuel pump. Changed the large relay next to the ECM. Main fuel pump clicks and hums for a second when turn the key, so I assume it is OK. When changing the relay, I noticed the connector with the blue/white wires is not connected to anything. I'm guessing it went to the altitude sensor and was removed by PM. Since it has always been this way, I assume not cause of my problem but is this OK?

Installed new air tube (the flexible one that connects hard plastic one to air filter box).

During silicon vacuum line install, found the evap canister had rusted through and had holes. Replaced canister.

Visual inspection of distributor and rotor looked OK. Spark plug wires appear to be fairly new by PM. Cleaned and reconnected AFM connector. Installed new coil.

I'm going through the Ljet troubleshooting guide but nothing yet. The backwards running tachometer is strange. Any ideas on my overall problem? Is there anyway to temporarily by-pass the AFM? I hate to buy a replacement if that is not the problem.

thanks.

D. Poole
'82 Spider w/ Bosch FI

[dpoole]

Also, the exhaust leaves the wet, black, sooty deposit on the ground.

[dpoole]

Problem solved. Made a little trip up to Mebane in my Jeep (which apparantly now needs a fuel pump, geez!) to borrow an AFM and magnetic flywheel sensor from Greg. It appears to have been a faulty lower magnetic flywheel sensor. Installed the good one borrowed from Greg and now have full power back; and the tachometer works correctly again. Just bought a used sensor on eBay.

Thanks to Ray in Brown Summit and Greg in Mebane for lending me spare parts to troubleshoot. I'll get the Alfa back on four wheels and make a trip to return the borrowed parts. Then, I'll start looking at the Jeep's problem.

The support of the Alfa BB comes through again, thank you!

D. Poole
'82 Spider w/ Bosch FI