Question about 2000 GMC New Sierra 1500

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5.7L keeps backfiring, wont start

The dropdown menu only went until 2000 but really it's a 1991, has been tuned up in last 10,000 miles, was running fine, parked it for 10 days, now it won't start. It just backfires a few times while turning over and won't start. I put the battery on a trickle charger for a bit so its all juiced up. Still no results. Recently replaced EGR valve and Map sensor.

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  • Master
  • 1,448 Answers

Check cam sensor

Posted on Mar 27, 2014

6 Suggested Answers

6ya6ya
  • 2 Answers

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Posted on Jan 02, 2017

  • 1118 Answers

SOURCE: 1994 GMC Jimmy hard to start and runs rough when first started

did you do a fuel pressure test? if you havent do it its cheep an at least you can elimanate that. if thats not an issue, then there is only two other things crank sensor, and if there is one cam sensor.

Posted on Feb 02, 2009

blueextc3221
  • 15935 Answers

SOURCE: 1998 chevy pickup V8 130.000 miles running very

The Exhaust Gas Recirculation (EGR) valve is an important part of the exhaust circulation system of a vehicle. EGR valves have been in use in the United States since the 1960s, when car companies were seeking ways to increase the efficiency of vehicles while also decreasing pollution. When the EGR valve is clogged or malfunctioning, it can cause irregularities in engine performance such as rough idling or valve knock, indicating that the EGR valve should be inspected.
The EGR valve works by routing a small amount of exhaust back into the combustion chamber, where it can be reused. This is done for a number of reasons. The primary reason is that a certain temperature is required in the combustion chamber, and exhaust is much warmer than air taken in from the outside. As a result, the engine need not work as hard to heat the combustion chamber to optimal temperature. The second reason is that the use of an EGR valve helps to reduce nitrogen oxides, which will combine with elements in the atmosphere to form smog.
Many EGR valves are mechanical, and simply have a small valve which opens to allow exhaust into the combustion chamber and closes when it is not necessary, and to keep the air mixture optimal for combustion. Some mechanical versions will not open until there is sufficient back pressure, ensuring that the valve will not be open when the engine is idle or warming up and needs a higher concentration of oxygen for combustion. Electronic EGR valves are also available, and use electronics to regulate the valve.
If the EGR valve is stuck open, it will essentially cause a vacuum leak, leading to inefficient combustion, rough idling, hesitation, and sometimes stalling in extreme cases. This is because the car cannot combust on carbon dioxide from the tailpipe alone-it needs atmospheric oxygen as well. If the combustion chamber is flooded with exhaust from an open EGR valve, it will not function properly. To check and see if the EGR valve is stuck open, have someone idle a parked vehicle with the brake on while you examine the plunger shaft to see if it is stuck open.
If the EGR valve is stuck closed, emissions of nitrogen oxides will rise, and the car may start to knock. Spark knock happens when the fuel mixture in the combustion chamber ignites before it has been reached by the explosion in the cylinder, resulting in a disruption of the engine timing. In this instance, the engine should be warmed up and revved to see if the EGR valve will move.
In both cases, simple repairs are possible. The EGR valve can be clogged, and a simple cleaning of a mechanical EGR valve may solve the problem. In the case of an electrically controlled EGR valve or a more complex mechanical problem, replacement of the valve may be needed. The EGR valve is an expensive motor vehicle component, and care should be taken to ensure that it needs to be replaced rather than repaired. A reputable mechanic should advise you appropriately.
Failure to repair or replace the EGR valve will not lead to a life threatening condition, although it will reduce the life of your car and increase the potential emissions. Especially in areas which require smog testing, an automobile with a malfunctioning EGR valve may not pass.


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Posted on Mar 26, 2009

  • 232 Answers

SOURCE: 1991 gmc med duty truck with 454 tbi ,backfires, no power.

By module do you mean computer? There's nothing wrong with it. Yea, replace all ignition components with new ones. New cap, rotor, wires and spark plugs.

Posted on May 18, 2009

  • 38 Answers

SOURCE: 1999 GMC Yukon seems to backfire once in a while

look for vac leak at egr valve, when cold spray carb cleaner on and see if it speeds up the eng

Posted on Jun 27, 2009

  • 713 Answers

SOURCE: my 99 gmc jimmy wont

no it does not have the self diagnostics on it. i had a 1998 model jimmy and i had to replace the junction block under the hood because was doing the same gm said it was in the bridges in the block were the fuses are. no codes would ever show in the computer. i picked one up from the salvage yard to replace it with and it fixed the problem. if you do this it has to come out of the same identical vehicle and the numbers on it have to match.

Posted on Aug 28, 2009

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