Rough Idle, low power, and engine dies at stoplights

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searya
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Rough Idle, low power, and engine dies at stoplights

Post by searya » Sun Jul 08, 2018 4:18 pm

Hi my 84 Pini Azzurra was running fine. The next day I started it up and it ran rough, gave little power uphill and would die a stop lights.

Looking for ideas. So far I have checked:

Fuel pressure at the cold start injector (looked good)
Looked for vacuum leaks using proprane (found none)
Replaced Fuel pump and filter
Blew through and ran water through the fuel valve above the rear axle
Replaced Spark Plugs
Looked for spark arcing in the dark
Checked compression on 2 cylinders both at 150 (still plan to do the other two)
Sean
1984 Pininfarina Azzura
Saint Louis, Mo
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bartigue
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Re: Rough Idle, low power, and engine dies at stoplights

Post by bartigue » Sun Jul 08, 2018 7:04 pm

Check the ignition timing with a timing light.
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Brad Artigue
1982 Spider 2000
I've restored, worked on, sold, bartered, and bled for:
1970, 1979, 1980, 1981, 1982 124 Spiders -- 1969, 1970 850 Spiders -- 77 X1/9
http://fiat.artigue.com
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rridge
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Re: Rough Idle, low power, and engine dies at stoplights

Post by rridge » Sun Jul 08, 2018 8:16 pm

Runs fine one day and runs badly the next. Nothing touched in the engine compartment between episodes. No new fuel. What things can change overnight? Timing belt can skip a tooth on startup. Rodents can chew through wiring. The resistor in the FI temp sensor can go flaky...

My vote would be temp sensor. Put a VOM on the FI temp sensor. Sits on the front of the coolant tee with an FI harness plug. Do a search for the correct ohm range and a way of bypassing a bad one.
Richard
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searya
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Re: Rough Idle, low power, and engine dies at stoplights

Post by searya » Sun Jul 08, 2018 8:53 pm

rridge wrote:
Sun Jul 08, 2018 8:16 pm
Runs fine one day and runs badly the next. Nothing touched in the engine compartment between episodes. No new fuel. What things can change overnight? Timing belt can skip a tooth on startup. Rodents can chew through wiring. The resistor in the FI temp sensor can go flaky...

My vote would be temp sensor. Put a VOM on the FI temp sensor. Sits on the front of the coolant tee with an FI harness plug. Do a search for the correct ohm range and a way of bypassing a bad one.
Thanks I did the test and the sensor is at 1.5 ohms. Gonna do a search now for proper resistance.
Sean
1984 Pininfarina Azzura
Saint Louis, Mo
searya
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Re: Rough Idle, low power, and engine dies at stoplights

Post by searya » Sun Jul 08, 2018 8:59 pm

bartigue wrote:
Sun Jul 08, 2018 7:04 pm
Check the ignition timing with a timing light.
I don't have a timing light but will try to find someone that does.

I did check the coil (Magneti Marrelli AEI200) and found the following:
Primary Ohms: 2.1
Secondary Ohms: 10,950

looking at the service manual it says Primary should be between .75 and .81 could that be the problem?
Sean
1984 Pininfarina Azzura
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Re: Rough Idle, low power, and engine dies at stoplights

Post by spider2081 » Sun Jul 08, 2018 9:25 pm

looking at the service manual it says Primary should be between .75 and .81 could that be the problem?
Sean
if you touch the leads of your ohm meter together chances are it does not display 0.000 What ever the number is that it displays when the leads are touching each other needs to be subtracted from the resistance measured. The meter displays the resistance of its own leads.
searya
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Re: Rough Idle, low power, and engine dies at stoplights

Post by searya » Sun Jul 08, 2018 11:00 pm

Good point. I touched them together and got 1.4 so sounds which would put me at a net .7 so likely good there too.
Sean
1984 Pininfarina Azzura
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searya
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Re: Rough Idle, low power, and engine dies at stoplights

Post by searya » Sun Jul 08, 2018 11:28 pm

bartigue wrote:
Sun Jul 08, 2018 7:04 pm
Check the ignition timing with a timing light.
If I can't come up with a timing light is it okay to do by ear? Can I break anything by loosing it up an turning it?

Also, thanks for all the tips on this forum and your guides! I just read your fuel injection tune up guide and ordered your book from Amazon.
Sean
1984 Pininfarina Azzura
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Re: Rough Idle, low power, and engine dies at stoplights

Post by friedman » Mon Jul 09, 2018 8:15 am

Pull the distributor cap and see what the pickup wires look like. They are very frail and easily break or fry off the insulation.
Carl in Virginia
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bartigue
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Re: Rough Idle, low power, and engine dies at stoplights

Post by bartigue » Mon Jul 09, 2018 8:53 am

I'm saying check, not saying change. Don't change anything until you've narrowed it to a problem area or run out of options.

Richard is right about the forward temp sensor; a couple of things there: if the coolant is low it can read incorrectly, and they do go bad without warning about once every 20 years. If the sensor is older than you can remember then it is cheap insurance to replace it anyway, I consider it almost a maintenance item and do it with the timing belt.

The frayed ignition wiring may be a cause, it is usually reflected in the tach jumping around nervously. You can check the wiring by removing the cap as noted above.
-----------------------------------------------------------
Brad Artigue
1982 Spider 2000
I've restored, worked on, sold, bartered, and bled for:
1970, 1979, 1980, 1981, 1982 124 Spiders -- 1969, 1970 850 Spiders -- 77 X1/9
http://fiat.artigue.com
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