RE: [alfa] 164S idle and stumbling problem

["Jeff Greenfield" <alfaguy@xxxxxxxxxx>]

Check the coolant temp sensor when the engine is at operating temperature.
Its resistance decreases as the temp increases.

If it is bad or out of spec, the car will be very rich, so much so that it
will probably not run at all at temp, or very badly if it runs.

Jeff

-----Original Message-----
From: owner-alfa@domain.elided [mailto:owner-alfa@domain.elided] On Behalf Of Paul
Niemczyk
Sent: Monday, November 03, 2003 1:27 PM
To: alfa-digest@domain.elided
Subject: [alfa] 164S idle and stumbling problem

Hi all,
Still trying to diagnose my 164S rough idle and
stumbling problem. I'm hoping that someone might think
of a solution. Here's the chronology:

- Brought car from NJ up to CO (2500 miles) with no
problems. Drove it up to Pikes Peak (~13,000 ft
elevation!) and down with no problems. Drove 150 miles
to Denver and back at highway speeds, no problem.

- Next day, car cranked but did not start.
- Next day, car started but ran like a tank, whole car
shook, felt like was running on 3 cylinders. Would not
rev above 3500 because was so rough.
- Had unpredictable strong fuel smells inside the
cabin.
- Following day, car started and drove around town,
fine at high RPMs although rough at idle. When at
idle, car stumbled and died, could not restart.
- Car has been blowing black and white smoke out of
exhaust, probably running rich.
- Found that I could restart the car by pulling the
fuel hose to fuel rail, draining fuel out of the rails
(about 1 1/2 cup), turning engine to burn off excess
fuel, then reconnecting hose and starting car.
- Engine light comes on, Motronic gives error code for
coolant temp sensor.

Troubleshooting:
- Vacuum leak? Seems okay. checked three hoses to
vacuum recirc canister, to valve cover, two hoses into
boot b/w AFM and throttle body, hose to fuel pressure
regulator.
- Timing? Checked timing, was okay. Aligned crank at
TDC, cams aligned to marks under valve covers.
- Distributor? Distributor is visually sound.
- Plugs? Plugs look okay.
- AFM? AFM resistance measured smoothly as flap
rotated smoothly.
- Coolant Temp Sensor? Resistance read 2.5K Ohms,
continuity of wiring harness checked and was okay.
Cleared the motronic error code, but came back next
time car started! (Why, if sensor is okay?)
- Heads? No evidence of leaking from head gaskets.
- Next step is to replace fuel pressure regulator
(coming in the mail!) to ensure no excess fuel at
rail. COULD cause rich mixture.
- Haven't inspected fuel pressure (don't have fuel
press guage), but when fuel hose was unplugged while
turning over car, fuel was coming very strong and
steady thru hose.

- Problem could be related to pressure difference
after driving up to Pikes Peak and back down.

I've had lots of varying advice, but given all the
evidence and troubleshooting, does ANYONE have any
clue what else could be wrong? Thanks much!

Paul Niemczyk
'91 164S 100k miles
Colorado Springs


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