I have a 2000 jimmy 135000 runs perfect,changed intake gasket do to leak, back together ran with multiple misfire changed distributor i was told they had problems with those.Truck run perfect again but has nocking noise,change distributor again still there. Any help would be very mutch appreciated thanks. Bobby
I would have tried new pLugs and wires and using fuel injection cleaner in the regularly. You could also check to see that the Mass Airflow Sensor was not damaged.
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If there is a vacuum leak from the intake gasket. It is possible it will kill those cylinders. Take some wd40 and spray around the intake gasket on that side. If the engine runs better it's problem the intake gasket at fault. Try getting to the bolts and tighten all bolts see if that helps. If not spray around larger vacuum hoses and check for a leak and repair as nessary..
If a random multiple misfire code appears , and electrical system checks out Ok, need to do a fuel pressure test at the fuel rail (Drivers side) if checks out ok, it very well can be sticky fuel injectors.If injectors leak by can cause to much fuel dispursed into engine, sometimes a bottle of lucas fuel injector cleaner will do the trick, opens up the poppets (injectors) although the (Spider Injector) has an electrical pulse that is supplied from the ECM (computer.) The spider injectors definitely go bad some sooner than others! Not a pleasant job also an expensive job if u are not doing it yourself! If your vehicle was fine before this started happening go back over everthing u have done, check each wire out with a noid to see if spark is correct ( A noid plugs into end of the wire that goes onto the sparkplug, check each wire one at a time, u can purchase a noid for this vehicle at your local autoparts store) Not saying this is definitely the problem, there are many things that cause these problems,crank sensor, cam sensor, tps mass air flow map sensor intake leaks and vacuum leaks etc etc,u can check for leaks by spraying down intake and vacuum lines with a can of carb cleaner, look for a change in the idle when u are spraying it down How do we know? been thru it all to often! GOOD LUCK! 1998 GMC Jimmy 4.3 Liter Vortec V- 6.
Sounds to me that you may have a vacuum leak or leaks.
You can spray starting fluid,spareingly on and around the intake while the car is running.
And look and listen for the engine to rev up, replace and or tighten hoses or gaskets.
Be careful to not have anything,loose fitting to get tangled up while the engine is running.
55 psi that may be a little low but would that cause a misfire on cyc 3 only?
NO that would affect all cylinders not just one . Do a compression test on # 3 cylinder .
If you get ck engine light on , you have a cyl. number
that misfires , ck vacuum leaks on intake manifold around that area aspecially intake manifold gasket.
vacuum leaks, plugs, check the wires for corrosion on the coil packs, the 3800's are known for corroded contacts there, also a common problem is the intake gasket leaking near the egr valve, check to see if it is wet around where the egr valve enters the intake manifold, check for fuel pressure, and make sure all the sensors and vac lines are plugged in properly
Check to make sure you have the firing order correct. If so, go ahead and remove each wire to isolate the misfiring cylinder. From what I can understand from your post, it seems that so far, you have done everything correctly. Did it run well before you did the gasket? Running rich can be a product of a vacuum leak as well. To find it, spray some carb cleaner around perimeter of manifold, and near any vacuum source. If idle changes, that's where the leak is! If its leaking from the new gasket, you might consider, loosening up the bolts and re-tightening them in a cross pattern, side to side, beginning at the center, working towards both ends. split the torque value and tighten twice: if value is 30lbs, do once at 15, the second time @20. I hope this helps. Good luck
Its common for spark plugs to get severely fouled after intake manifold leaks due to coolant entering cylinders. Sounds like you had experienced this because you stated a severely overheated engine. This is the first place to start... there could be other issues but this is the order to go in.then p.c.v valve, wires and mass airflow sensor. Hope this helps.
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