1991 skylark dies when hot

[Owen W]

I've got a 91 skylark 3.3L that dies after idling or driving for about 20 minutes. Been chasing down the issue for about 2 months. Has new fuel pump and sender, new fuel filter, new crankshaft position sensor, coolant temp sensor and intake gaskets. At this point I'm thinking it's another sensor or injectors. Any help is appreciated.

 

[02LTD2.0]

I've got a 91 skylark 3.3L that dies after idling or driving for about 20 minutes. Been chasing down the issue for about 2 months. Has new fuel pump and sender, new fuel filter, new crankshaft position sensor, coolant temp sensor and intake gaskets. At this point I'm thinking it's another sensor or injectors. Any help is appreciated.

Have you considered that it may be a flaky Ignition Control Module? It may be malfunctioning once it gets hot.

 

[LARRY70GS]

Might be mass airflow sensor, try unplugging it and see if it still dies idling. Alternately, you could idle it until it dies, then unplug the MAF, and see if it starts back up. You'll get a CEL because the PCM doesn't see the MAF signal, but you can reset that.

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[HotZ28]

I would also be looking at the ICM, especially if it is original !

 

[Owen W]

Have you considered that it may be a flaky Ignition Control Module? It may be malfunctioning once it gets hot.

Just replaced it today, still dies

 

[Owen W]

Might be mass airflow sensor, try unplugging it and see if it still dies idling. Alternately, you could idle it until it dies, then unplug the MAF, and see if it starts back up. You'll get a CEL because the PCM doesn't see the MAF signal, but you can reset that.

1991 BUICK SKYLARK 3.3L V6 Mass Air Flow (MAF) Sensor | Shop Now at RockAuto

Exhaust & Emission Parts and More for Your 1991 BUICK SKYLARK at Reliably Low Prices. Fast Online Catalog. DIY-Easy. Your Choice of Quality. Full Manufacturer Warranty.

www.rockauto.com

Unplugged it after it died, still not running.

 

[CorvairGeek]

How many miles? This engine has the first generation Multitec injectors that suffer from decreasing resistance. Since it is a batch fired engine (vs the SFI 3800), if a single injector drops enough resistance (shorted or close too), the engine looses injector pulses and quits (common when hot). Good 3300 injectors measure 12.9 ohms on my Fluke 77 DVM. Mine were all over the place (as low as 6 ohms cold) at 190K miles. It had misfires at idle, and you could actually hear the difference in the audible 'click' of the injectors as they varied. I had no idea how much it was down on power until I put a low mileage set of injectors in it. IF a single injector shorts, it can be unplugged and the engine will restart on 5 cylinders. Cheap and easy to try each one, and no added fuel to the engine since the injector will be closed.

 

[Owen W]

How many miles? This engine has the first generation Multitec injectors that suffer from decreasing resistance. Since it is a batch fired engine (vs the SFI 3800), if a single injector drops enough resistance (shorted or close too), the engine looses injector pulses and quits (common when hot). Good 3300 injectors measure 12.9 ohms on my Fluke 77 DVM. Mine were all over the place (as low as 6 ohms cold) at 190K miles. It had misfires at idle, and you could actually hear the difference in the audible 'click' of the injectors as they varied. I had no idea how much it was down on power until I put a low mileage set of injectors in it. IF a single injector shorts, it can be unplugged and the engine will restart on 5 cylinders. Cheap and easy to try each one, and no added fuel to the engine since the injector will be closed.

Odometer says 67,000 but I'm guessing its rolled over at least once considering the state of the car. It has been idling funny since I got it, and it has had one injector replaced before I got it. I did your test of unplugging them one by one while it was hot and cylinder no. 4 injector was the problem child. Thank you so much for the help!

 

[CorvairGeek]

Odometer says 67,000 but I'm guessing its rolled over at least once considering the state of the car. It has been idling funny since I got it, and it has had one injector replaced before I got it. I did your test of unplugging them one by one while it was hot and cylinder no. 4 injector was the problem child. Thank you so much for the help!

Glad I could help!
The Buick 3300 is not smooth idling by today's standards. It is even cast for a counter balance shaft, like its big brother the 3800, but none were ever installed. Uneven injectors make it worse, and most issues seem to cause the ECM to increase the idle speed too.
The first generation Multitec injectors have the injector coil immersed in fuel. As the coating is slowing dissolved from the wires, the injectors resistance drops, and sometimes short out (as you have found).