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Hard starting cold

Tiny
SJHENNEN
  • MEMBER
  • 2000 PONTIAC BONNEVILLE
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 115,000 MILES
My car has had trouble starting in the cold the last few years. Two years ago I had new plugs put in it, that didn't help, last year I put a new battery in it, that didn't help. The only way it starts is if I plug it in at night and that gets to be a hassle sometimes. THE CAR TURNS OVER GREAT, BUT IT WON'T FIRE ALL THE WAY. It stutters at first and if it doesn't start, thats it, it's flooded. GOtta plug it in and wait. Sometimes if I keep turning it over and over and mash the gas peddel back and forth it stutters enough to get started, but the battery usually dies before it starts, so I have to jump it. (Usually takes at least ten minutes of trying that) It ranges on the temperature where it won't start, sometimes it won't even start at 15 degrees F. Also, after I run the car for a while and drive, then I stop and idle, a couple times this year I have smelled gasoline, so that might be related.
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Tuesday, January 12th, 2010 AT 1:19 PM

13 Replies

Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Hi, if you live in extremely cold region, a block heater is probably a must. When the problem occurs, if the engine cranks good, have a helper check for spark at the plugs, engine cranking. If that checks out, use a gage and check fuel pressure. The point is to find what your missing.
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Sunday, January 17th, 2010 AT 2:16 PM
Tiny
LIZ4RD
  • MEMBER
  • 32 POSTS
Have you found the solution to this issue. Im having the exact same problem on my 2000 Pontiac Bonneville and cant figure it out
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Monday, September 23rd, 2019 AT 10:30 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
Hello,

This condition can be caused by a bad engine coolant temperature sensor here is the location so you can change it out to see what happens. This guide will walk you through the steps with diagrams below to show you on your car.

https://www.2carpros.com/articles/coolant-temperature-sensor-cts-replacement

Check out the diagrams (Below). Please let us know what you find.

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Tuesday, September 24th, 2019 AT 11:19 AM
Tiny
LIZ4RD
  • MEMBER
  • 32 POSTS
Does the sensor go off of the coolant sensor in the dash? My coolant temp in the gauge cluster works fine and reads around 200 degrees farenheit at operating temperature.
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Tuesday, September 24th, 2019 AT 11:59 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
Yes, the upper limits might be okay its the lower limits you need to look at. This guide can help as well:

https://www.2carpros.com/articles/engine-cranks-excessively-before-starting

I would try cleaning the throttle bore as well.

https://www.2carpros.com/articles/throttle-actuator-service

Please run down these guides and report back.
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Wednesday, September 25th, 2019 AT 9:59 AM
Tiny
LIZ4RD
  • MEMBER
  • 32 POSTS
I read all of the articles and didn't see anything about coolant temp sensors? And to be clear their is a second sensor the the ECU reads?
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Wednesday, September 25th, 2019 AT 12:02 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
The gauge and computer use the same, no codes? also have you tried cleaning the throttle body? Look for vacuum leaks as well.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

and

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Please run down these guides and report back.
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Wednesday, September 25th, 2019 AT 12:07 PM
Tiny
LIZ4RD
  • MEMBER
  • 32 POSTS
I have no codes and I cleaned the throttle body last fall because I have been dealing with this problem for along time and I am getting tired of it. I have check for vacuum leaks with a propane torch but didn't find anything. It is a 2000 Pontiac Bonneville with the 3800 series 2 motor not supercharged. I have heard a lot the the intake gaskets are common to go bad. Could that act like a vacuum leak?
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Wednesday, September 25th, 2019 AT 12:17 PM
Tiny
LIZ4RD
  • MEMBER
  • 32 POSTS
I do have a live code reader and got a positive 14% to 17% long term fuel trim at idle. It acts like a vacuum leak but I cannot find it.I have searched many times.
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Wednesday, September 25th, 2019 AT 12:18 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
It could be internal such as an EGR and PCV stuck open or leaking. Lets run this test on the EGR.

https://youtu.be/DqUCbbKdWf4

The intake can be leaking as well to the inside of the engine which is difficult to detect. Also have we done a fuel pressure test here is a guide

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Please run down these guides and report back.

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Thursday, September 26th, 2019 AT 9:50 AM
Tiny
LIZ4RD
  • MEMBER
  • 32 POSTS
Okay, I will do that and get back as soon as possible.
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Thursday, September 26th, 2019 AT 10:06 AM
Tiny
LIZ4RD
  • MEMBER
  • 32 POSTS
Okay, just did all of the test fuel pressure is at 40 psi. EGR and PCV valve are working great. I just replaced the spark plugs as well (it was something that needed to be replaced sooner or later). I tried again to find a vacuum leak no go. Tested the brake booster works fine. I did a pressure test and got around 112 to 115 on all 6 cylinders. And I have got a strong white spark on all 6 as well. Something to add is I also can smell a hint of gas when trying to start the car. Maybe out of the exhaust, but I am not sure.
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Friday, September 27th, 2019 AT 9:47 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
Those compression readings are a little low, did you use OEM sprak plugs? (it makes a difference) Also the fuel pressure is a little low as well which can be the problem. It should be:

Key ON, Engine OFF 48-55 psi
Engine Running Pressure Drop 3-10 psi

I would replace the fuel pump. here is a guide to help walk you through the steps with diagrams below to show you how on your car. You will need to drain the tank.

https://www.2carpros.com/articles/how-to-replace-an-electric-fuel-pump

and

https://youtu.be/Q5MH2gnyFH0

Check out the diagrams (below). Please let us know what happens.
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Sunday, September 29th, 2019 AT 10:06 AM

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