1996 GMC 350 missing bad

[CyClore]

I have a 1996 GMC extend cab truck with a 350 vortec motor. In the past the EGR vlave has been replaced twice. I have 101,000 miles on it now. I took a 100 mile round trip yesterday and at times I had all my power and other times when I would put the gas to her to pass someone the engine would rev and the damn thing would kick down but wouldn't go any faster. THis happened on and off all day. This has been cured in the past by replacing the EGR valve. I got 1 mile from my house and bam... It would barly run. I let it cool and it started fine. Tried it about an hour later and it would barly idle. I went to AutoZone today and they had to overnight one, so I will be getting it tomorrow. They mentioned I may have a bad O2 sensor. I would need 4 of them. Does this make sense tha they should be replaced? At $50 a piece and another $100 for the EGR valve I want to make sure I am doing the right thing.

At times when I start the truck it will run fine for a minute then a minute later I will give it a little gas and it will caugh and backfine. Seems if I get a little high RPM it runs a little better. I can't even drive the thing to a shop to have it put on the computer. I can't climb the hills here in North Central PA. THe Service light has only came on once. I disconnected the battery for a minute and reconnected it and it ran fine for about 1 minute, then same thing, but no service light. I tried it again this morning after sitting all night and it would barly run. HELP!!!!

I borrowed my Father's (now no longer living) 94 fullsize extened cab GMC Sierra GT w/350 and wow... I have really lost power after driving this thing. I have put her sideways more than once in the last twelve hours!!!

[95civicstr]

i have had experience with carbon breaking up in the intake and plugging the egr valve then getting free and then getting stuck again

[Jeremy-WI]

try a new fuel filter if it hasn't been replaced in a while

[CyClore]

Out of habit I get the fuel filter changed every time I get the vehicle inspected which is Every February. I did take the EGR valve of last night and saw a few deposits in the opening. With the thunderstorms last night I couldn't spend much time on it.

I know it says to clean the opening before placing on the new EGR valve. How do you recommend I do this? I was also not to happy to find that whoever replaced the EGR valve last time cross-threaded the bolt. I can see it on the bolt itself. I tried a new bolt and can only get it about 1/2 way down. I am going to pick up some washers for now until I can get it somewhere to have it retapped.

I have a friend that has a scanner. Once I get it running and hope it is the EGR valve, I am going to take it to his shop and see if there are any other errors. I am expecting to see some basd o2 sensors!

[Jeremy-WI]

When your friend hooks it up to the scanner have him check what the cam retard(or camshaft offset) is. It should be 0 degrees +/- 2 degrees and the scanners value will only be accurate after the engine has been over 1000rpms. There have been problems with worn distributor gears, but your problem doesn't sound like the result of a worn gear. Have the fuel pressure checked too, 60-66psi with key on, engine off and the pressure shouldn't fall much after the pump shuts off. You may also want to clean the MAF by spraying it with some non residue electrical contact cleaner(auto zone has it). If you get a code P1406 for the Egr, just clean it and put it back in

[CyClore]

How do you suggest I clean it? I have it off the vehicle, there were deposits near the valve, just a little, but I did get what I could.

Should I clean it with a chemical of some sort?

Sorry if that sounds like a stupid question just don't have a lot of time to work on it. Can't drive it anywhere either to get worked on.

[Jeremy-WI]

Use a throttle body cleaner on the egr and a little brush of some sort, you should be able to push the pintle in to clean the sealing surfaces

[96sierrastep]

I have a 96 but with a v6, just went through the same thing. Turned out that when my O2 sensors died, it started pouring fuel through the motor, more than it could burn, and it ended up on the front of the converter and basicallyl just melted the inside. I ended up changing the mass air flow, egr, put on a performance cat and a flowmaster, and changing 2 of 3 O2 sensors and I am still going to change the third one.

[Jeremy-WI]

96 sierrastep, you should have 4 sensors. One on each side of motor just downstream of exhaust manifold, one between where the y pipe and the catalytic and one after the catalytic

[SierraK1500]

I would take the vehicle to your dealership and have check the trouble codes in the system. I agree with everyone there but you should have it professionally checked

[96sierrastep]

Originally Posted by 96sierrastep

I have a 96 but with a v6, just went through the same thing. Turned out that when my O2 sensors died, it started pouring fuel through the motor, more than it could burn, and it ended up on the front of the converter and basicallyl just melted the inside. I ended up changing the mass air flow, egr, put on a performance cat and a flowmaster, and changing 2 of 3 O2 sensors and I am still going to change the third one.

thanks, I better find that other one.

[Jeremy-WI]

I would bother changing the O2 sensor just before or after the catalytic unless they throw a code because those 2 sensors just monitor the catalytic on vehicles with a single cat