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GMC Jimmy Misfiring, Backfiring, Spark Plugs

Our 1993 GMC Jimmy started building up carbon in the EGR Valve. We Seafoamed it, but that didn't seem to help. We later put a new gasket on the EGR that has a screen on it. That has seemed to fix the carbon problem.

As of right now, it keeps fouling spark plugs. It sounds like it has a huge cam in it, which I'm taking as it not running on all its cylinders. When I take the plugs out, they seem to have gas on them. Any idea on what's causing it and how to fix it?
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Comments

  • lynderaelynderae Posts: 4
    First off let me say thank you for youre help with camshaft position sensor in distributor. I have also replaced the coil, the truck ran like a champ yesterday. Today however, I didnt get out of the driveway and it started misfiring. It is rainy today, but it was wet out yesterday. I cant figure this out, any help would be appreciated.
  • repairdogrepairdog Posts: 948
    Did you change the cap/rotor to rule them out?
    Crank sensor is under the front of the motor and they can act up without a code or the connector can get wet/dirty. Any SES light and codes?
  • frschevyfrschevy Posts: 2
    I have a 04 chevy blazer 6 cyl 4 wheel drive.
    I purchased in Jan 07. (39,000 miles)
    Its been back to the dealer 4 times for stalling.
    I'm just driving down the road and its shuts off.
    I still have power but the engine quits.
    so for all that has been done is (replaced)
    the distributer cap and roater,the coil and something attached to it. They can't figure it out. I don't get any
    check engine lites. Im pritty sure the problem is electrical,but who knows. Can anyone help this is driving me crazy.
  • repairdogrepairdog Posts: 948
    Running too rich so look at the CPI and nut kit (injection and hoses) under the upper intake. Posts on that and how to look at can be found by a search in the forum. Do you smell gas also? Hows the oil consumption - if high look at clogged PCV or worn valve seals - never stated the mileage. Then air filter should be clean also and vent to other valve cover attached and good.
  • It has 175,000 miles on it. And yes, I do smell gas when I run it. I replaced all the spark plugs and it still seems like it is misfiring. Thanks for the information. I will look into it.
  • quickfoxquickfox Posts: 2
    How to change middle sparkplug on driver"s side of 1996 Jimmy with 4.3 V6- problem is steering shaft blocking acess
  • repairdogrepairdog Posts: 948
    2 ways used and 1 is short plug socket and open end wrench thru the wheel well or 2 is unbolt the steereing shaft at the flex and move the shaft - change plug and reinstall shaft.
  • jlflemmonsjlflemmons Posts: 2,240
    You can also use a 3/8 socket, an adapter from 3/8 down to 1/4, use a 1/4 extension, and come in through the wheel well. Using the adapters and thinner extention gives enough play to get around the shaft. Just barely, but enough.
  • after replacing the thermostat because of it overheating now there's a noisy lifter- could this be caused from the engine getting too hot? it also due for an oil change. :confuse:
  • repairdogrepairdog Posts: 948
    Oil and filter and hope the lower intake gasket isn't leaking into the valley. Keep a close watch on the reservior - fill it to the hot line when cold and look at each day and make sure its not dropping. No leaks either so look around. Replace the radiator cap with a new one now also. Hope you flushed the system out with that new thermostat and refilled with 50/50 Dex cool mix.
  • WELL WE CHANGED THE OIL AND THE FILTER- BUT THE LIFTER NOISE IS STILL THERE! WHAT DO I CHECK FOR NEXT? :mad: :confuse:
  • repairdogrepairdog Posts: 948
    Look for water dropping - #1 cause on 4.3 is the lower intake sprays a fine mist into the valley and the lifters make noise. You will normally NOT see any water in the oil when this occurs only the res dropping and morning lifter noise. Then if thats stable you got the engine so hot that you cooked some oil on or in a lifer or two so go buy some lifter cleaner that gets added to the oil and follow the instructions. Often takes 100 plus miles to quiet down, assuming no water getting in.
  • GOOD NEWS IS THERE ISN'T ANY WATER GETTING IN!YOU WERE RIGHT ABOUT IT BEING BETTER ONCE THE ENGINE GET WARMED UP! I'LL PUT SOME OF THAT LIFTER CLEANER IN IT TODAY & I'LL LET YOU KNOW IN A COUPLE OF DAYS OR SO THE RESULTS! I'M PRETTY CONFIDENT THAT THE RESULT'S WILL BE "GREAT"! WHEN SHOULD THE OIL BE CHANGED AGAIN (3,000 MILES)? THANKS FOR ALL OF YOUR HELPFUL INFORMATION!! :shades: :) :)
  • ONE MORE QUICK QUESTION- COULD THE SERVICE ENGINE LIGHT STAYING ON NOW BE CAUSED FROM THE STICKY LIFTER??? LAST TIME IT HAD COME ON WAS BECAUSE THE GAS CAP WASN'T ON CORRECTLY & I ALREADY TRIED THAT AGAIN. :confuse:
  • repairdogrepairdog Posts: 948
    Get the code read out at any Advance or AutoZone for free to know. Read the instructuions on the lifter bottle as some require a change sooner, some don't. I do all mine every 3000 and only use the Valoline MaxLife 10w-40 now as my 4 are all over 100k miles. Do not use the $2 oil filters either - I have used the mid grade Fram Toughguard ones for years or best is WIX or NAPA Gold - forget the ones with Teflon in them. Hope all works out noise free!
  • YOU SAID THAT 4 ALL WITH OVER 100K MILES- WHAT KIND OF VEHICLES ARE THEY?? ALSO THE BOOK THAT CAME WITH MY JIMMY SAY'S TO USE 5W-30 OIL IN IT. MY JIMMY ALSO HAS A LITTLE OVER 100K MILES NOW. AS FAR AS THE NOISE- WHEN I STARTED IT THIS A.M. (COLD) THERE WAS NO NOISE. I DIDN'T EVEN PUT THE LIFTER STUFF IN YET. I JUST DROVE IT YESTERDAY ABOUT 45 MILES AFTER THE ENGINE WARMED UP SO THE NOISE WAS GONE, BUT THE LIGHT WENT OUT FOR MOST OF THAT TIME & THEN IT CAME BACK ON. I'LL LET YOU KNOW WHAT HAPPENS THOUGH! THANKS AGAIN!!
  • repairdogrepairdog Posts: 948
    All Blazers and after 100k I switched to 10w-40 MaxLife as all the bearings and seals have worn and I'm in FL so always hot! Great if the lifters already are quiet - new oil must have flushed the sludge stuff off.
  • daylyndaylyn Posts: 12
    My Jimmy drives fine around town. I've just replaced cap and rotor, spark plugs, O2 sensors, and catalytic converter.
    The problem is every time I try to drive up a steep incline the truck will lose power, then chug and sputter like it's gonna die. If I turn around and go back down the hill, the sputtering and chugging stops and she runs fine again! What is going on? Any suggestions?
  • repairdogrepairdog Posts: 948
    Assuming no SES light on and codes present.
    Change the fuel filter and if then check the fuel pressure.
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