Vehicle shutters and hesitates at cold starts in mild degree weather

Tiny
COOLOLDS85
  • MEMBER
  • 1989 BUICK REGAL
  • 2.8L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 56,000 MILES
My vehicle for the first time since I replaced the leaking old thirty year old clogged fuel injectors is still shuttering and hesitating at cold starts at 60 degrees or higher weather. When it’s frigid it starts with no hesitation at all. After it shutters on me it feels like the engine wants to shut off on me but the computer regulates the idle after a couple of seconds and smooths it out.

I did research and think it may be the coolant temperature sensor because the coolant temperature sensor sometime doesn’t pull a engine code when the sensor is bad. It also regulates fuel and air mixtures in the airs atmosphere if the car is running lean. It can also smell like unburned fuel at cold starts which I am smelling. After I drive to engine temperature it’s back to normal. I didn’t let the engine warm at operating temperature because I had to clean the garage out to move the car out of the drive. I just parked it around the corner and shut car off. Came back later to bring it back and it did it the second time.

Here’s what I replaced all last year:

- Spark plugs and spark plug wires. I did notice one of the spark plug wires have a small hole in one.
- Idle Air Control Valve
- Coil Packs and ICM
- TPS Sensor
- Map Sensor
- Fuel Filter
- Fuel Pressure Regulator
- Fuel Injectors and o ring seals
- Air filter is still good too and throttle body bore is clean

Before buying a coolant temperature sensor should I reset the Idle air control valve do the relearn and drive it?
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Tuesday, February 5th, 2019 AT 7:58 PM

5 Replies

Tiny
HARRY P
  • EXPERT
You don't have to buy a coolant temperature sensor to test it. I'm attaching a series of images containing how to test the engine coolant temperature sensor and where it is located. All you need is a decent multi-meter. Here's the one that I own: https://www.amazon.com/gp/offer-listing/B000X5TSUA

In reality, to me it sounds like you have a decent sized vacuum or intake air leak somewhere. As it warms up, the leak changes, and so does the performance of the car. The computer can only do so much to try to compensate for such a leak, but it tries. Here's a link to our guide on looking for an air leak: https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

And here's a video on running this test: https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge. Try it out on a cold engine and hopefully it'll point you to whatever the problem is.

Hopefully these tests will get you fixed up. Let us know what you find and we'll go from there.

Harry
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Tuesday, February 5th, 2019 AT 9:07 PM
Tiny
COOLOLDS85
  • MEMBER
What is the correct voltage reading you should get for the coolant temperature sensor? I didn’t see the readings in the information. I also did replace all the vacuum lines along the intake manifold and intake plenum. Could intake plenum gaskets or intake manifold gaskets cause this to happen?
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Tuesday, February 5th, 2019 AT 10:42 PM
Tiny
HARRY P
  • EXPERT
Sorry, I'm not sure how it happened but those are the wrong images. I'm reloading them now. The voltages and resistance values are in the correct images. Yes, intake plenum and manifold gaskets could cause an issue like this. They would be allowing extra, unmetered air into the system, which the computer may or may not be able to adjust for.
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Wednesday, February 6th, 2019 AT 3:45 AM
Tiny
COOLOLDS85
  • MEMBER
And how about the intake manifold air temperature sensor? I did more research related to my concern and it said when the car has troubling cold starting that sensor isn’t letting the computer give the right readings.
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Wednesday, February 6th, 2019 AT 6:30 AM
Tiny
HARRY P
  • EXPERT
Regarding air temperature sensor readings, I'll have to dig further later on. But here's what a quick check on Prodemand turned up.
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Wednesday, February 6th, 2019 AT 5:39 PM

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