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Discussion Starter #1
My 92 164L has been running rough when cold (temp in the mornings is around 15-20F) for the past couple of weeks. Up until today, it would clear up after 2-3 minutes. But today after running about 30 minutes or so, it was still running rough, but intermittently. I originally thought it was electrical (a spark plug or ignition wire) so I tried disconnecting each plug wire one at a time while idling roughly. It died each time I disconnected one, so don't think it's a plug or wire.

Where should I start, to track down the problem?

Thanks
Joseph
92 164L
 

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Change the cold start coolant temperature sender which screws into the thermostat housing? Looking aft from the front of the car, it's the left hand one of the two senders.
 

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The connector to the ECU temp sender is a known problem due to the wires being too short and strain put on them if the engine rocks too much. Sender could be fine, but the connector wires having an intermittent connection.
 

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Change the cold start coolant temperature sender which screws into the thermostat housing? Looking aft from the front of the car, it's the left hand one of the two senders.
The connector to the ECU temp sender is a known problem due to the wires being too short and strain put on them if the engine rocks too much. Sender could be fine, but the connector wires having an intermittent connection.
Both of you guys talking about same Bosch 2-wire coolant temp sensor which serves as a "cold start" sensor. It should have about 4000 ohm resistance when engine cold and about 400 ohms when engine hot.

It is the hidden one under top radiator hose in mid thermostat housing not the temp gauge sender next to timing belt cover.

You may have to jack up car, remove wheel and front inner fender liner to get to it. It has a wire lock in connector.

I test engine running cold with a spare CTS plugged into the wiring Bosch connector but not installed in thermostat housing. Engine should run smoothly with high sensor resistance as that is what enriches fuel mixture when cold.

Once engine is fully warm engine should run if you disconnect sensor.

If you can't get smooth idle when engine warmed up, you might want to print off timing template and check cam timing.

See this link for doing timing check: http://www.alfabb.com/bb/forums/164...ecking-alfa-164-12v-v6-engine-cam-timing.html
 

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Discussion Starter #7
I tried replacing the coolant temp sensor (lower one on thermostat housing) as suggested by Steve and Del, with another (used) one. Got same results. When I hook a meter up to either, I get momentary readings, from 600 to 1800 ohms. I don't know if they should be constant readings, but I doubt they are both bad.

Anyway, what other suggestions does anyone have? It feels like it is running on 5 cylinders when started cold, gradually gets better as it warms up, but is still intermittently misfiring, especially under acceleration. At times, runs completely normally, so can't be cam timing.

Joseph
92 164L
5 speed
 

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Remove the distributor cap and inspect the insides for carbon tracking or damage. Also, carefully inspect the rotor for any signs of damage/burning. Bad caps and rotors are common problems that can cause seemingly random/intermittent/temp sensitive problems. When it's very dark, open the hood with the engine running and look for any signs of a spark plug wire arcing.

Have you checked the wires to the blue connector to be sure they are not damage/strained/broken?

Your ohm values aren't right. What temp was it when you took those readings.
Here's the charted test values:
 

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fuel filter??? Lots of reasons I wont waste your time with but I have seen where cold weather gets em wonky. As mentioned the sensor wiring and connector is where I'd look as well. ciao, jc
 

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I tried replacing the coolant temp sensor (lower one on thermostat housing) as suggested by Steve and Del, with another (used) one. Got same results. When I hook a meter up to either, I get momentary readings, from 600 to 1800 ohms. I don't know if they should be constant readings, but I doubt they are both bad.

Anyway, what other suggestions does anyone have? It feels like it is running on 5 cylinders when started cold, gradually gets better as it warms up, but is still intermittently misfiring, especially under acceleration. At times, runs completely normally, so can't be cam timing.

Joseph
92 164L
5 speed
Are you sure you changed the hidden Fuel Injection coolant temp sensor (CTS) in mid-thermostat housing between the two radiator hose's inlet and outlet or did you change the temp gauge sender next to timing belt cover? You pretty much need to remove front wheel and front inner fender liner to see that blue or cream colored Bosch CTS and to be able to safely change it.

See Chazzy's old post showing where both sensors are located on 164 V6 engines:

http://www.alfabb.com/bb/forums/790300-post14.html
 

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Also use of thread sealing tape or some sealers on the threads will disrupt flow of the electric "bits". Best to install them "nekkid". ciao jc
 

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Discussion Starter #12
"Remove the distributor cap and inspect the insides for carbon tracking or damage. Also, carefully inspect the rotor for any signs of damage/burning. Bad caps and rotors are common problems that can cause seemingly random/intermittent/temp sensitive problems. When it's very dark, open the hood with the engine running and look for any signs of a spark plug wire arcing.

Have you checked the wires to the blue connector to be sure they are not damage/strained/broken?

Your ohm values aren't right. What temp was it when you took those readings.
Here's the charted test values:"

Roadtrip,
I checked the cap and rotor first thing. Both look fine and are less than a year old. I'll try the arcing test tonight. Wires to the connector are good. I got the same ohm results with both of the temp senders I have, but I'll try the one that is out of the car tonight with a different meter to see if it is any different. Temperature at the time I was testing it was around 40 F. I did what Steve suggested and connected one to the wiring without installing it. Still had the rough running. Let the car warm up, still with the uninstalled one hooked up, and the idle rpm was way high, about 2000 rpm. Applied heat to the sender and the idle immediately went down, so I know temp is affecting the sender.

Joseph

Joseph
 

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Discussion Starter #13
"Are you sure you changed the hidden Fuel Injection coolant temp sensor (CTS) in mid-thermostat housing between the two radiator hose's inlet and outlet or did you change the temp gauge sender next to timing belt cover? You pretty much need to remove front wheel and front inner fender liner to see that blue or cream colored Bosch CTS and to be able to safely change it."

Steve,
Yes, I changed the correct one. I removed the upper radiator hose and was able to change it. Lost a little coolant.

Joseph
 

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Brainstorming here, but how about getting a 6K ohm resistor and plug it into the blue connector, simulating a cold engine. That way also, you can manipulate the connector to see if there's an obvious break in the wire.
 

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OK then just get a good CTS with about 3k to 4K resistance at about 68F cold and just plug it into Bosch connector and see how the engine idles cold if old sensor is the problem engine should run smoother and maybe a little rich once warmed up.

You don't need to even install it as it does not have to be grounded to work like the gauge sender has to be to keep the red overtemp light out.
 

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Discussion Starter #16
Solved the problem today. Turned out to be oil leaking past the seal around the spark plugs on cylinders 1 & 2, and shorting out the plugs. Cleaned out the oil in the spark plug well, put in new plugs and it runs fine again. This is the second time this has happened, so I know I need to replace those seals. Does anyone have them available?

Joseph
92 164L
5 Speed
 

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"Turned out to be oil leaking past the seal around the spark plugs on cylinders 1 & 2, and shorting out the plugs"

Oil doesn't short out spark plugs, as it is a dielectric fluid. Many a 4 banger Alfa has been run fine for k's of miles with oil in the exposed sparkplug wells (ask me how I know this, lol). Same for the V-6.

What most likely cured your problem were the new clean unfouled plugs. Works every time, esp if they are the NGK Iridium's.
 
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