jQuery not supported.



Engine misfire 97 350 vortec.

Engine misfire 97 350 vortec.

Postby Chevydude37 [OP] » Dec 12 2011, 2:47am

Hello,

I have a 1997 chevy k1500 with the 5.7 v8. I have a misfire on cylinder number 2. If the spark plug wire for cylinder number 2 is connected it will backfire intermittently, and the truck runs better with it unplugged. I have checked the compression on this cylinder and it read 150 psi. I changed all sparkplugs and wires, cap, rotor, distributor was replaced not too long ago due to a previosly worn distributor gear. I even took the upper intake manifold off and swapped number 1 and 2 injectors off of the "spider assembly" and it still misses on number 2 cylinder. The missing occurs at idle and throughout the rpm range.

Anyone have any ideas? I appreciate anyones help in advance!
Original Poster
Chevydude37
Newbie
Newbie
Posts: 4
Topics: 1
Joined: Dec 12 2011, 2:27am
Years of membership: 2 years of membership2 years of membership
Location: Florida
Year: 1997
Make/Model: Chevrolet Silverado
Extra Info: k1500
Group Membership:
Registered users

Re: Engine misfire 97 350 vortec.

Postby ASTE25 » Dec 12 2011, 6:00am

I know this idea does not really follow your compression test results, but, have you checked to make sure you do not have a camshaft that has a lobe worn down?
Jordan
ASTE25
Shifting into Sixth Gear! [L3]
Shifting into Sixth Gear! [L3]
Posts: 11012
Topics: 19
Images: 5
Joined: Jan 03 2011, 6:37am
Years of membership: 3 years of membership3 years of membership3 years of membership
Location: New Market, Alabama
Year: 2015
Make/Model: ...Not an owner
Group Membership:
Automotive Technicians
Member Extraordinaire
Registered users

Re: Engine misfire 97 350 vortec.

Postby themutt101 » Dec 12 2011, 1:59pm

I'd check the polarity between the points on the cap. I've seen them at work with newer caps on them and there is polarity between two points within the cap that you cant see just by looking at it. If you have another cap you can use just to test it I'd try that.
User avatar
themutt101
Automotive Technician
Automotive Technician
Combustion on 1 piston [L2]
Combustion on 1 piston [L2]
Posts: 120
Topics: 22
Images: 1
Joined: Mar 07 2011, 4:40pm
Years of membership: 3 years of membership3 years of membership3 years of membership
Location: Vermont
Year: 1999
Make/Model: GMC Sierra
Extra Info: 5.3L 4x4 1500
Group Membership:
Automotive Technicians
Registered users

Re: Engine misfire 97 350 vortec.

Postby Chevydude37 [OP] » Dec 12 2011, 8:44pm

I have not checked the camshaft lobes. I did readjust the valve lash with the directions in my haynes manual though. Is there an easy way to check for worn camshaft lobes?

I do have an extra cap. I'll try that today and post results.
Original Poster
Chevydude37
Newbie
Newbie
Posts: 4
Topics: 1
Joined: Dec 12 2011, 2:27am
Years of membership: 2 years of membership2 years of membership
Location: Florida
Year: 1997
Make/Model: Chevrolet Silverado
Extra Info: k1500
Group Membership:
Registered users

Re: Engine misfire 97 350 vortec.

Postby ASTE25 » Dec 13 2011, 1:08am

You probably got a valve too tight when you adjusted them. On the old small block chevy I always adjusted them with the engine running (hydraulic lifters, of course). If you are not comfortable doing it that way, or do not how to do it that way, just start with one cylinder on TDC (compression stroke) and loosen the rocker untill you can twist the push rod with your fingers. Then tighten the rocker until you have no clearance between the push rod and the rocker arm. Then tighten the rocker an additional 1/2 to 3/4 turn. Do that for each cylinder after you have brought it up to TDC, going in the firing order (1 8 4 3 6 5 7 2). After you have all 8 done you should be good to go. To check for a worn camshaft lobe, you can use a dial indicator to see if the pushrod is lifted to whatever the specs for your engine calls for.
Jordan
ASTE25
Shifting into Sixth Gear! [L3]
Shifting into Sixth Gear! [L3]
Posts: 11012
Topics: 19
Images: 5
Joined: Jan 03 2011, 6:37am
Years of membership: 3 years of membership3 years of membership3 years of membership
Location: New Market, Alabama
Year: 2015
Make/Model: ...Not an owner
Group Membership:
Automotive Technicians
Member Extraordinaire
Registered users

Re: Engine misfire 97 350 vortec.

Postby Chevydude37 [OP] » Dec 13 2011, 2:11am

Thanks for the replys guys. I didn't get to changing the cap today but I will give that a try asap. If that doesn't work I will try to readjust all the valves and see what happens. I do not have a dial indicator yet but if other options do not work I will get one. My dad says he took a big u turn and then it all the sudden started doing this??? I dont understand
Original Poster
Chevydude37
Newbie
Newbie
Posts: 4
Topics: 1
Joined: Dec 12 2011, 2:27am
Years of membership: 2 years of membership2 years of membership
Location: Florida
Year: 1997
Make/Model: Chevrolet Silverado
Extra Info: k1500
Group Membership:
Registered users

Re: Engine misfire 97 350 vortec.

Postby ASTE25 » Dec 13 2011, 3:14am

Well, you have to have three things to get combustion: Fuel, compression and spark (at the right time). As long as you are getting those, it should run fine. If you know what cylinder for sure has the miss, then that makes it easier to figure out since you just have to work on one. As far as the valve adjustment, since it is only one cylinder that is misfiring, I'd just mess with it and leave the others alone.
Jordan
ASTE25
Shifting into Sixth Gear! [L3]
Shifting into Sixth Gear! [L3]
Posts: 11012
Topics: 19
Images: 5
Joined: Jan 03 2011, 6:37am
Years of membership: 3 years of membership3 years of membership3 years of membership
Location: New Market, Alabama
Year: 2015
Make/Model: ...Not an owner
Group Membership:
Automotive Technicians
Member Extraordinaire
Registered users

Re: Engine misfire 97 350 vortec.

Postby Chevydude37 [OP] » Dec 14 2011, 7:02pm

Well guys, I have it running right now. Turns out there was no "new cap and rotor" installed. It was just swapped with another cap and used the same rotor. I sandpapered the contacts down on both and it runs like a dream now. Sure wish I would have known that bit of into before I started taking the upper intake manifold off...
Original Poster
Chevydude37
Newbie
Newbie
Posts: 4
Topics: 1
Joined: Dec 12 2011, 2:27am
Years of membership: 2 years of membership2 years of membership
Location: Florida
Year: 1997
Make/Model: Chevrolet Silverado
Extra Info: k1500
Group Membership:
Registered users

Re: Engine misfire 97 350 vortec.

Postby ASTE25 » Dec 14 2011, 9:05pm

Good to hear you got it fixed.
Jordan
ASTE25
Shifting into Sixth Gear! [L3]
Shifting into Sixth Gear! [L3]
Posts: 11012
Topics: 19
Images: 5
Joined: Jan 03 2011, 6:37am
Years of membership: 3 years of membership3 years of membership3 years of membership
Location: New Market, Alabama
Year: 2015
Make/Model: ...Not an owner
Group Membership:
Automotive Technicians
Member Extraordinaire
Registered users

Return to Engine

 

  • Similar topics
    Replies
    Views
    Last post

Common search terms

engine work right guys misfire vortec installed getting anyone same thanks help still make

It is currently Oct 31 2014, 6:49pm

  • Sponsor
Login  •  Register
SHOP TALK (Live Chat)
Engine Forum
EngineThis is where all of our engine discussion and conversation takes place. Talk about engine diagnostics, adjustments, modifications, performance and care. Motor tuning and repair to gain horsepower and fuel efficiency.
To create a new topic in Engine, click this button:
Previous topic Next topic
Sitewide News Sitemaps & Feeds

Who is online

Users browsing this forum: No registered users and 11 guests