Question about Chevrolet Suburban

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When driving up a grade at 65+mph the car starts to shake as if the wheels were out of balance. Usually in connection with this the service engine light goes on and stays on for several days. The mechanic(not dealer) says the computer shows that the sparkplug or injector to cylinder 4 is misfiring. The car, 1999 1500 model with 250000 miles, had complete tune up in the past 5000 miles,including sparkplug wiring harness. This only occurs when the engine is at the upper end of its output. Why and what can be done to correct this problem?

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  • Chevrolet Master
  • 21,873 Answers

Well first you will need to figure out if it is fuel, ignition, or something mechanical.
Usually a miss under load is a weak spark or lack of fuel. Its possible the plug for cylinder 4 has become weak. Swapping it with another cylinder or replacing it would rule it out.
With that many miles, the injector for cyl 4 could be getting weak or dirty.

Posted on Jul 31, 2013

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Posted on Jan 02, 2017

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  • 1 Answer

SOURCE: Misfire

One question, have you replaced the ECTS (Electronic Cooling Temperature Sensor)? These cause no end of different seemingly unrelated problems on Saturns. Peice is about ten bucks and is an easy install. Just search on youtube for a how-to video. Even if that's not the problem it is reccommended to replace this peice just the same as they ALL end up going bad at some point.

If that's not a fix, start pulling plugs. Check to see if they're correctly gapped and if they have any damage/corrosion. If you're running Platinum plugs, immediatly change to a copper plug as Platinums have no place in these motors. Most people have the best luck with NGK copper.

Check to make sure that your plug wires haven't been crossed. This sounds like a plug or wire issue most likely so it has to be in that family, if the plugs are good, wires good and not crossed, sensors are fine, then time to replace your coil packs. If you've replaced everything up to the coil packs then that is most likely the cause of your dillema.


Posted on Oct 25, 2008

  • 4088 Answers

SOURCE: 2005 Jimmy 4X4, 4.3L, P300 multiple misfire. Have

Try some injector cleaner in the fuel--there might be some water in the fuel also. Check the air cleaner.

Posted on Aug 01, 2009

caroldon
  • 17129 Answers

SOURCE: The car shakes at 35 mph then as you increase

It can be the suspensions or the shock absorbers, check also the engine mountings.
i will be good to take a full checkup of all the links and suspension bushes in the car. so a full test on the shocck absorbers, test the wheel bearings the hubs and if the discs are bend even is if the balancing was done.

Posted on Sep 21, 2010

Danniboi
  • 1098 Answers

SOURCE: My 2002 Camry (4 cylinder)

Hi

Did the dealer check the crakshaft sensor? it sounds like the timing is shifting causing the misfire.
the heat can cause intermitent faults maybe not long enough for the computer to register the fault with a code.

And as a possiblity the coil pack may be arking out somewhere, has this ever got wet? or cold recently?
Regards

Dan

Posted on Dec 29, 2010

freetek
  • 5568 Answers

SOURCE: I have a 2001 Jeep

I don't know which brand of plugs you have installed, but I wouldn't hesitate to change the spark plug since during my automotive lifetime, I have had two plugs with cracked insulators. This causes electrical 'leakage' from the center electrode to ground that can cause random or permanent loss of spark to the engine. Both of them were 'Champion' brand which I now never buy.

Posted on Apr 12, 2011

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