Comment

Comment by THOMAS E EVERAGE JR. on July 12, 2009 at 7:45pm

THANKS ,I WILL TRY THOSE,BUT I HAVE NO SMOKE OUT OF THE EXHUAST?
IT JUST HAPPENS WHEN U GIVE JUST ALITTLE GAS OF WHEN COME TO A STOP,SOMETIMES IT DIES,BUT WHEN I UNPLUGGED THE MAPP SENSOR IT RUNS LIKE A BRAND NEW SURBURBAN EXCEPT EVERY ONCE IN A WHILE IT WILL JUST DIE,BUT IT U PUT U FOOT INTO IT ,IT WILL RUN LIKE A BAT OUT OG HELL,WHEN U GET UP TO SPEED ,U CAN FEEL IT LOSE AND GAIN POWER ,I JUST DONT THINK IT A BAD CINLINDER

Comment by Kevin Lee on July 12, 2009 at 7:44pm

Forgive me, I forgot one other thing. You said the misfire happens just off idle, part throttle. Try unplugging the EGR valve, plugging the vacuum hose to it. If it goes away, the valve is opening too soon. The cause for that will be either a weak valve, or partially clogged exhaust, causing too much backpressure

Comment by Kevin Lee on July 12, 2009 at 7:38pm

OK, Thomas, that means it is a throttle body engine. Going by what you have already done, I will say there are a couple possibilities left. One, you have a vacuum leak, like a bad hose, or even around the intake manifold. I use either a can of brake cleaner or carb cleaner to spray around and see if you make a change. If not, the problem most likely is engine internal. To pnpoint the cylinder, have a friend put it in gear and LIGHTLY brake torque the engin until the misfire happens. while holding it there, you take well insulated pliers (they do make spark plug wire pullers for this) and take one plug wire off at a time. The cylinder that doesnt change when taking off the wire is the problem cylinder. The next step would be to check static compression on that cylinder. With the tester, it should be around 120 to 150 PSI. Under 100 PSI, you have a weak cylinder for sure. You can also "read" the plug from the misfiring cylinder. If it is very white, no deposits at all, it is either lean on that cylinder, (the vacuum leak) or even possibly getting coolant into the cylinder, effectively "steaming" the plug clean. If it is black, the cylinder is weak, and cant effectively burn the fuel. If it is oily, have a lot of flaky deposits, you have engine problems for sure, like faulty valve guides, or even bad psiton rings. Hopefully these suggestions get you on the right track

Comment by THOMAS E EVERAGE JR. on July 12, 2009 at 7:26pm

1993

Comment by Kevin Lee on July 12, 2009 at 7:21pm

Thomas,
One, what year is your Suburban? Secondly, unplugging the MAP (Manifold Absolute Pressure) sensor will cause the computer to default to open loop status, and fatten up the fuel mixture.That is covering up the misfire, giving you false diagnosis. That is also why it dies when the A/C is on. I can give you a lot more ideas, but need to know what year it is so I know the setup.

Comment by David Foster on July 12, 2009 at 4:15pm

thanks, i will keep that in mind. the engine is due for a rebuild soon. it has 345,000km on it so when its rebuilt im adding some goodies to it

Comment by Kevin Lee on July 12, 2009 at 2:35am

Good to hear that the intake isnt leaking. If it should though, use Fel-Pro gaskets. They came up with a superior design over te stock ones. Just make sure the intake isnt pitted too bad around the coolant ports, and it should be fine after that. Just some info if you will ever need it

Comment by David Foster on July 11, 2009 at 8:15pm

ended up cutting the tube to get it out of the intake
manifold

Comment by David Foster on July 11, 2009 at 8:12pm

thats it exactly! intake gasket luckily seems to be good

Comment by Kevin Lee on July 11, 2009 at 5:39pm

I know exactly what you are talking about. I have torn many of those apart for intake gaskets leaking. It comes off the left exhaust manifold, up the back and follows the intake where it goes into the left front

• ‹ Previous
• 1
• …
• 158
• 159
• 160
• 161
• 162
• …
• 191
• Next ›
• Page