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91 Buick Park Avenue wont start in cold

Hello, I’m stumped on this one. I bought a 91 Buick Park avenue about 2 years ago. It’s been really reliable and I’ve replaced a few parts but over all she runs great. I’ve replaced the starter, battery, idle air control valve, throttle position sensor, she has new spark plugs and wires, and basically tune up. I know she’s got a bit more work to go but as of right now the issue is once it started getting cold here she only wanted to start sometimes. When it snowed and was really cold she didn’t want to start at all. Today it’s 51 out today and she started right up and drove normal. I’m at a loss of what it could be. Maybe another sensor? Any thoughts or help would be greatly appreciated.

What happens when you try to start it and it does not.

Dash lights? Starter motor turns over the engine, or does not? Engine turns over for many seconds but does not start? Starts but does not run?

Its the cold…old cars get lazy sometimes. Seriously, what grade of motor oil do you use? I use 5W30 in my 19 year old Toyota and she starts right up.

My 30-year-old Toyota pickup started balking recently. I took the top off the air cleaner, shot in a dose of carburetor cleaner (for the priming, not the cleaning), and it started right up. This is a cheap and convenient diagnostic that points to a slowness in my fuel delivery system. And it’s better than struggling to start. I’ll diagnose it better later.

It sounds like it is caused by too lean of fuel/air mixture. Cold starts require much more gasoline be injected during cranking compared to warm starts, especially when the ambient temperature is cold too. My Corolla is similar vintage so yours may use a similar method. There’s a sensor that measures the coolant temperature, and that information is used to control the injection time for a separate cold start injector to spray more gasoline in proportion to how cold the coolant is. There’s also a thermal timer in that gadget, which heats up during cranking & switches off the cold start injector after a certain amount of time (proportional to the temperature) to prevent too much gasoline from being sprayed. If your ParkAve uses a cold start injector (newer models don’t) , your problem might have to do with a fault in one of those two parts. Do you have a repair manual that explain how the cold start function is handled on that car?

Low cylinder compression and/or spark problems are another common cause of this symptom. It sounds like you are keeping your car in good repair, but still, it might be time to do a compression test.

I think a 91 GM will just have a coolant temp sensor, and the computer will add more fuel if it detects the engine is below a certain temp. Works that way on an early 90’s GM truck engine at least. There’s a “coolant temp sensor” that tells the computer the engine temp. And there’s another sensor that sends the engine/coolant temperature to the temp gauge in the dash. Similar on my 2004 Buick with a 3800 V6. They didn’t change things up much for a while, apparently. The coolant temp sensor is a good guess if it’s only slow to start when cold. Although I assumed “cold” for that sensor meant an engine that hadn’t been started rather than a cold ambient temp. Anyway, would be a good thing to check. GM CTS is pretty simple to check, but I have forgotten how! Should be able to Google it, though.

Yep, I’m with Scrapyard. Provided compression and everything else is ok, I’d suspect either the coolant sensor as described or the air sensor. You really need to have a computer hooked up though to see what the sensors are actually reading though when cold to be sure, or just replace parts and see. Neither one is expensive but get the right coolant sensor for the engine, not the gauge. I needed to reference the service manual to figure out which one was which.

Easy enough to check, but the main problem with the ECTS theory is that I don’t recall anyone ever reporting here that they found a faulty one in their car. That sensor seems to be pretty reliable.

I’ll admit I’ve never had a faulty CTS either. But I did have a poor electrical connection to the CTS on one vehicle. Seems reasonable to test it and it’s wiring since the slow start condition is temperature related, though. I wouldn’t recommend just going out and buying one on a guess.

I had a bad one. That’s why I know it takes endless cranking to start when cold. But thats why you put it on the diagnostic computer first to see what it is actually reading compared to what it should be reading. Of course that’s one in a 1.5 million miles so yeah they are reliable.