random misfire 96 5.7 vortec


milo54
02-04-2006, 08:06 PM
I have a 1996 silverado with 5.7 vortec engine. Truck runs fine in cold weather. Warm weather and damp weather I get random misfires under light load. Under load the misfires stop. If I unplug the egr valve the problem goes away. I replaced the egr valve and the map sensor but this did no good. The chevy dealer had me run a can on infector cleaner thru but this also did not help. Please help as the chevy dealer is also stumped.

speedindevil
02-04-2006, 08:37 PM
check the cheap stuff first, and how many miles are on the truck? anyway, start with the plugs and wires first, if you haven't already, if you already did, then, check all of your cylinders for compression differences, maybe it's a sticky valve, have you gotten any codes out of this?

milo54
02-04-2006, 11:01 PM
The truck has 114,000 miles on it and I did replace plugs, wires, cap, and rotor. The compression was checked by chevy dealer and was good. The only code that appears is a p0300, random misfire

Mr. Smith
02-05-2006, 08:12 AM
The truck has 114,000 miles on it and I did replace plugs, wires, cap, and rotor. The compression was checked by chevy dealer and was good. The only code that appears is a p0300, random misfire

Google random misfire, read and troubleshoot from there.

wafrederick
02-05-2006, 03:11 PM
Pull the distibitor,mark the distribitor before pulling out.The timing is not adjustable.It might be a worn out distibitor gear.Did one last week,could not find the miss and pulled the distribitor.Found out the distribitor gear was worn out,put another one in and the miss was gone.

sivadnar
02-07-2006, 02:30 PM
Any missing coolant? Does the engine compartment smell sweet after driving it for a while?

I had this exact problem on my 98 5.7. It stumped a local mechanic, etc. I think the intake gasket was leaking... A leaking intake gasket is a very common problem on these motors.

speedindevil
02-07-2006, 08:50 PM
Try putting a timing light on it and slightly rev the engine up and down, just a touch, this should tell you if there's any slop in the timing stuff (distributor gear) if it jumps around a lot right after revving also does it have a crank pos. sensor and/or a cam pos. sensor? Not too familliar with the newer chevy engines, if so check those too.

wafrederick
02-09-2006, 09:05 AM
You cannot set the timing on a vortec 350 with a timing light,The timing is not adjustable.You set the distribitor with a scan tool such as a GM Tech 2,etc if you pull the distibitor and make sure mark it before pulling out.The cam sensor is inside the distribitor anyway.

samthecarman
02-09-2006, 04:58 PM
the couple of expierences i have had with random misfires, if you have all the old stuff try putting them back on one at a time to see if you got a bad distributor cap, wire etc... (working on a buddy's 97 silverado and the brand new distributor cap had a manfactures defect, got another one and it went away). if that does not solve the problem, I would run the fuel injector cleaner again, my truck all of the sudden decided to throw a light, p0300 and the fuel injector cleaner worked. you may have to do it twice to make sure. run the tank until almost empty, put the injector cleaner in there, drive for approx 30 miles and then fill the tank w/gas and add another bottle of injector cleaner. i would check all the stuff mentioned above before i would pull the distributor but that is just me. hope this helps

98 5.7 rdm.misfire
01-23-2011, 11:32 PM
I OWN A 1998 Z/71 5.7 VORTEC K 1500 SAME ENGINE. :smokin: RANDOM MISSFIRE IS CAUSED WHEN THE KNOCK SENSOR IS BAD, IT SENDS INFO TO THE COMPUTER TO ADVANCE OR RETARD THE TIMING. I HAD THE SAME PROBLEM A LOT OF GUESS WORK AND MONEY FOR NOTHING. THE SENSOR IS LOCATED ON THE PASSENGER SIDE OF THE BLOCK BESIDE THE FREEZE PLUGS IT SCREWS IN BUT DRAIN YOUR ANTIFREEZE 1ST. ITS A EASY FIX WITH THE TRUCK ON JACK STANDS. $32.99
FOR THE KNOCK SENSOR AND ABOUT 30 MIN. JOB.
MY TRUCK WAS RANDOM MISSFIRING UNDER LITE LOADS OR A HILL.
NAW WITH 160,000 MILES
ON IT, IT RUNS BETTER NAW THAN IN THE PAST 8 MONTHS AND BETTER FUEL MILLAGE TO.. CHRIS.....

Ikeepitreelz
11-16-2011, 09:35 AM
i own a conversion van with the 5.0L Vortec and spent so much money trying to get the misfire code off, changed wires,cap,rotor,spark plugs and nothing, started getting intake manifold leaks so i changed the gaskets ,sill had the same code, now frustrated I did a lot of research and found out that Chevy's C.F.I (central fuel injection) is very troublesome including in the 4.3L v-6 engines, the remedy for some people is paying a lot of money to replace the stock unit with a stock unit, but i found out they make an plug and play unit that eliminates the cranky C.F.I unit to a Multi Port Unit, each cylinder gets it's own true fuel injector instead of a "poppet valve" which tends to stick after a lot of miles, I changed the Fuel injection unit and the throttle is more crisp now, where as before engine seemed sluggish, supposedly mileage improves with this system, installing is not hard at all if you have some basic tools, ratchet,extensions and a lot of patience if it's a van (no room). but on the trucks it's very easy, oh yes and the system comes with a new fuel pressure regulator that is attached, I highly recommend this changeover and while your at it buy at least 3 cans of throttle body cleaner, i can't tell you how greasy and cartooned up the intake caller was, and anyone with high mileage might want to change the intake gaskets while your down there anyway, spray all passage ways to remove any carbon build up, I also purchased an upper intake manifold which is relatively cheap, $70.00 by Dorman products, the fuel injector conversion unit is $299.00 made by GP Sorensen, google it and you will find their catalog, Autozone should carry it and it got good reviews when i researched them, your other option is going to the Chevy dealer but you will pay about 600 plus dollars for the same system. i hope this can be a bit of help. attached are some pics of the new system.

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