1995 GMC Sierra Truck doesnt want to go at first

Tiny
GDPRESTON
  • MEMBER
  • 1995 GMC SIERRA
  • V8
  • 2WD
  • AUTOMATIC
  • 215,000 MILES
When I drive my truck cold and give it some gas it doesn't want to go. Instead it acts as if I'm not giving it any gas at all and take a few seconds then responds. This just started happening recently. This morning when it happened it was followed by a loud popping noise under my hood. I couldn't make out the noise. I replace filters regularly i.E. Fuel, air, oil. It hasn't been too long since I changed plugs, wires, and distributor either. Any ideas?
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Tuesday, March 31st, 2009 AT 3:33 PM

8 Replies

Tiny
IMPALASS
  • EXPERT
Hello -

To better assist you please tell me if your model is a pickup C1500, or K2500 etc. Also your engine size in liter and the 8th digit of your VIN.
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Tuesday, March 31st, 2009 AT 4:48 PM
Tiny
GDPRESTON
  • MEMBER
Thank you. Sierra 1500 5.7 liter and the 8th digit in VIN is K.
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Tuesday, March 31st, 2009 AT 5:03 PM
Tiny
IMPALASS
  • EXPERT
Hello -

Thanks for the info.I am looking at the C1500 model.

Do you know how to read the trouble codes on your vehicle?
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Tuesday, March 31st, 2009 AT 5:58 PM
Tiny
GDPRESTON
  • MEMBER
I don't have a hand held tool to plug in underneath my dash. I don't have an service engine soon light. I know the truck has a lot of miles and I have drivin it pretty hard over the years. I have taken very good maintenance care of it though. Changing oil religiously. It always seems to act up most in the mornings. Like I stated when I give it some gas it just bogs down and does nothing for about 2 sconds, then starts accelerating. Once it is warmed up it runs ok. Not like it used to.
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Tuesday, March 31st, 2009 AT 7:24 PM
Tiny
IMPALASS
  • EXPERT
Sorry about that - hit the wrong button.....now this time with the figures.........

As far as a tool..........from what I can see on your model, you don't need one.........just a paper clip.......If your connector under the dash doesn't look like the figures below then we will go a different direction.

Obviously this has been a great vehicle for you and you have taken great care of it. Yes, it does have some miles on it but that is okay..........but it is normal to have a few things start to go wrong too..........

Also, the light doesn't have to be on to have thrown a code. If the truck can help tell us what is wrong, that is even better. It may not show us anything.

So this is my thought............I tell you how to check the codes...........once you check that if there are no codes then we look at the several sensors that could cause the problem you are stating and, it could also be your fuel pump too........

Please remember a MOST important thing while doing this test.

DO NOT START THE CAR ONLY TURN THE KEY TO THE POSITION THAT ALL OF THE DASH LIGHTS COME ON.

AGAIN, DO NOT START THE CAR.

Okay, first do you have a 12 pin or 16 pin DLC?

If you have a 12 pin then I need you to take a paper clip and put one end into terminal B and the other end into terminal A.


http://www.2carpros.com/forum/automotive_pictures/248015_F1_5.jpg



If you have a 16 pin then I need you to take a paper clip and put one end into terminal 5 and the other end into terminal 6.


http://www.2carpros.com/forum/automotive_pictures/248015_F2_5.jpg



I have attached how you check for codes. See if it makes sense to you. The big thing.....DO NOT START THE CAR!

Once you have your paperclip in as above for either the 12 or 16 pin....then do the below.

You then turn the car on to where JUST the lights on the dash come on ONLY.....DO NOT START THE CAR!

Watch your check engine light.

The first flash is the first number and the second flash it the second number. So you sit with paper and pencil and count the flashes. It will flash the same number 3 times and then go to the next if there is one. It should always start with 12. So for 12 it will be:

Flash (1) pause flash, flash (2), longer pause.... Flash (1) pause flash, flash (2), longer pause.... Flash (1) pause flash, flash (2), longer pause....

Now from this point on watch and count the other numbers. Say it is 31. It would be:

Flash, Flash, Flash (3) pause flash (1) longer pause.... Flash, Flash, Flash (3) pause flash (1) longer pause.... Flash, Flash, Flash (3) pause flash (1) longer pause....that would be code 31.

The second you see it repeating itself, then turn the car off and immediately remove the paper clip or jumper wire so you don't forget.

Again - I cannot stress enough......DO NOT START THE CAR.

Now if you get the codes tell me what they are. If you do not, then we will check the other items Lord willing if the manual has test for them.

Some of the items that can cause hesitation are bad sensors: MAP, TPS, MAF, ECT, Vacuum leak, weak fuel pump.

So, again, my thought is first let's check for codes..........

Your thoughts?
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Tuesday, March 31st, 2009 AT 9:00 PM
Tiny
GDPRESTON
  • MEMBER
Great. Thanks for getting back with me. I have printed out the 12 and 16 pin DLC pinouts. I will go and get the code (if any) later this morning and get back with you. Great directions by the way. Don't worry, I will not start my truck with the paper clip in.
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Wednesday, April 1st, 2009 AT 8:01 AM
Tiny
GDPRESTON
  • MEMBER
OK. I did what you said. The only code that I got was 12. It kept coding 12 over and over and thats it. Thanks.

Garry
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Wednesday, April 1st, 2009 AT 9:18 AM
Tiny
IMPALASS
  • EXPERT
Hello -

Thanks for checking on that Garry

Well, no codes......

I would first check under the hood for any signs of something shorting out since you said popping or, it may have been a backfire which may be it is not getting enough fuel.

Please check all of your vacuum hoses to ensure none are loose, cracked, split. If you don't find anything there.

I have attached the chart for checking the Engine Coolant Sensor.


http://www.2carpros.com/forum/automotive_pictures/248015_Coolant_1.jpg



I have attached the charts for IAT and MAP sensor. If they are good then I would get my fuel pressure checked.


http://www.2carpros.com/forum/automotive_pictures/248015_Map_IAT_1.jpg



Have you ever changed your fuel pump?
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Thursday, April 2nd, 2009 AT 7:37 PM

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