328 Not Idling

Do you mean that the RPM undershoots severely during the decelleration process (like down to 500 RPM) and it stalls, but after you start it back up that it idles perfectly well at ~1000 RPM and has good accelleration?

I'm a quasi-believer in the Chevron Techron injector cleaner being a good thing for a Bosch CIS system occasionally (but would guess that your problem is not related to "cleanliness" if the behavior is as above).

 

I've had good results with Techron in my '87. But it has never stalled, only stumbled a bit when cold starting. I'd think your injectors would have to be badly clogged to stall the car.

 

Thanks for the clarification -- that symptom is a different kettle of fish (and I'll assume it's a US version 328).

I'd suggest that you first confirm/deny if the K-Jet with Lambda injection system has the +12V power that it needs to work properly. This can be done several ways:

1. The metering valve (aka frequency valve) should always be "buzzing" whenever the engine is running (see fig 57 on page 66 of your OM). If it's not buzzing/vibrating, that's a sign that you've lost the +12V power.

2. The two wires at the frequency valve are PN (beige/black) and AG (light blue/yellow) -- the PN wire should be at +12V whenever the engine is running.

3. The gizmo that provides the +12V power to run the injection system is the "Relay for protection of oxygen sensor system" (item H in Fig 64, page 72). The way this works is that the wire hooked to the 30 terminal should always be +12V (even with the key "off"). When the engine is running the contacts inside this relay should close and connect the +12V on terminal 30 over to the wires connected to terminal 87 (i.e., whenever the engine is running, terminal 87 should also be at +12V).

Just a first suggestion if the problem recurrs.

Good Hunting!

 

if you just filled up the tank, could be a fuel problem. You'll need to either drain out the fuel, or use it up fast.

if the car is ok when you keep the throttle a little open, check the throttle microswitch. You can either unplug and contort to probe the switch pins, or you can unbolt the injection ecu plate in the right side of the trunk and test the switch from there.

if you go for the switch directly, the center pin is common/gnd. When the throttle is closed, you should get zero ohms to the right pin (looking from the passenger side of car), going to infinite when the throttle is barely opened. You'll hear it click. You get zero ohms between center and the left pin at wide-open throttle, but that's not too relevant for your problem. Open/close the trottle a few times. The typical failure is a dirty microswitch inside the unit, and it's not very cleanable. Replacing the part is more reliable.

if you want to test from the ecu plate, unplug the pink/black wire from the diode (black plastic tube thing) and probe between that wire and ground. Again, zero ohms when throttle closed, infinite when slightly open.

also, try unplugging the o2 sensor so the car stays in open loop and seeing if that makes a difference.

 

Phil's given some good suggestions for the next layers of the onion to peel back, but I do want to confirm that your post means that you verified the frequency valve was buzzing during the bad running period?

 

The frequency valve working OK when the engine is running OK is a good sign that the frequency valve itself is OK, but I'd still suggest that you try to confirm/deny if it's buzzing when/if the problem reoccurs. I think it's very unlikely that the frequency valve itself is intermittent, but it is possible that the +12V power to run the FV is the intermittent factor (i.e., a flaky protection relay).

Good Hunting -- these intermittent Gremlins are the worst!

 

someone else in the 3x8 section is currently dealing with a classic problem...water leaking around the antenna - or a bad antenna drain line - winding up getting the injection ecu and associated relay contacts nice and corroded.

if you haven't already, you probably should unbolt the injection ecu plate and make sure things are dry under it, the ground connection is good, and contacts generally look clean.

the plate is under the carpet in the right side of the trunk, directly beneath the antenna. The carpet section and a piece of padding lift out, then you remove up to four bolts (10mm, if I remember right). When you turn the plate over, try to avoid stressing the thin goldish-brown wires that are bullet-connecting the exhaust thermocouple to the black exhaust ecu box...they are pretty sturdy, and the bullet connectors would normally separate before you tore the wires out of the ecu...but if you have corrosion, who knows.

hope that helps. If you don't see anything obvious, I'd leave the plate flipped over and drive around until you get symptoms, then hop out and wiggle things on the plate and connectors to see if the problem disappears.