causes of multiple misfires other than stuk valve?

[PTSchram]

Bad ticking noise, CEL on, random multiple misfires resulting in excess emissions, #4 & #8 cylinders specified, ticking noise coming from 1-7 side of engine. Pulled plug and replaced wire to #8, no dice.

Any ideas before I pull the heads?

[SUE ROVR]

If it is GEMS no, well it could always be a dropped liner

Ron

[PTSchram]

Originally posted by SUE ROVR
If it is GEMS no, well it could always be a dropped liner

Ron

The used car dealer who bought it at auction told me it had light valve noise! Initially, I thought bad rockers, until I actually heard it. He's gonna freak if I find a dropped liner.

When the liners drop, is it as obvious as it sounds?

Thanx Ron!

[LRover]

How 'bout a sticky lifter? Loose liners often leak coolent into combustion chamber so I would check for those signs.

[PTSchram]

Originally posted by LRover
How 'bout a sticky lifter? Loose liners often leak coolent into combustion chamber so I would check for those signs.

The noise is coming from the 1-7 side. The misfires are listed as 4 & 8. Either way, the heads are coming off. Good thing I have an entire new valve train I didn't need for another job.

[pendy]

Fix it the aviation way and charge them for a head job.

Aviation way:

remove valve covers and rocker arm assemblies.
use the compression tester witout its valve core
hook up shop air to a cylinder
use a rubber mallet and whack on the valve stem of the aired up cylinders valves
repeat on all cylinders
listen for escaping particle in the exhaust stream and intake
reassemble
cross fingers and start it up, higher RPM
Go have a beer and set up your next scam


All advice given freely
JP

[Puffdragon]

Most likely gunked valves.

In case you wanted the advise. Use all the old parts. All you need to rebuild the heads in shop, will be an electric drill valve seat compound, a few hones and new vavle stem seals. Only replace the vavles if they have excessive wear, or are bent.

First clean the head of all carbon. Remove all valves. Clean carbon off all valve stems with a bench wire wheel. Check for gauling.

Next hone out all valve guides with proper hones for exhaust and intake.

Then lightly oil valve stems and replace valves in head. Apply valve lapping compound to valve seat and valve.

Use an electric drill or the like on the back of the valve stem to seat each valve. You will know whne it has seated. You may wish to seat the valve a little deeper past that point. Check for a consistent grey seat mark on the valve and head.

Clean lapping compound off head and valve. Install valve stem seals with a small deep socket.

You now have heads that will perform like new, and last for at least 50k or more.


If valve seats are worn badly--------Replace heads
If valve guides are worn badly-------Replace heads
If you damage the deck on the head----Replace heads

Sorry gotta say it, no machine work required to re build heads. If you think you need machine work, replace the heads.

Minor warpage of heads is acceptable. Head bolts will easily re align the heads to the engien deck.

The above procedure is exactly how we handled heads at rover. I have never had a Head job come back for repairs relating to the work we did.

Heheeh he said head JOB

[UPOVR]

A worst case scenario could be what happened to me. Flat cam lobe

[PTSchram]

Originally posted by Puffdragon
Most likely gunked valves.

In case you wanted the advise. Use all the old parts. All you need to rebuild the heads in shop, will be an electric drill valve seat compound, a few hones and new vavle stem seals. Only replace the vavles if they have excessive wear, or are bent.

First clean the head of all carbon. Remove all valves. Clean carbon off all valve stems with a bench wire wheel. Check for gauling.

Next hone out all valve guides with proper hones for exhaust and intake.

Then lightly oil valve stems and replace valves in head. Apply valve lapping compound to valve seat and valve.

Use an electric drill or the like on the back of the valve stem to seat each valve. You will know whne it has seated. You may wish to seat the valve a little deeper past that point. Check for a consistent grey seat mark on the valve and head.

Clean lapping compound off head and valve. Install valve stem seals with a small deep socket.

You now have heads that will perform like new, and last for at least 50k or more.


If valve seats are worn badly--------Replace heads
If valve guides are worn badly-------Replace heads
If you damage the deck on the head----Replace heads

Sorry gotta say it, no machine work required to re build heads. If you think you need machine work, replace the heads.

Minor warpage of heads is acceptable. Head bolts will easily re align the heads to the engien deck.

The above procedure is exactly how we handled heads at rover. I have never had a Head job come back for repairs relating to the work we did.

Heheeh he said head JOB

Thanx KC, the heads are at the head shop getting a valve job as well. Some things I don't mind farming out.

BTW-it only took me slightly more than two hours to disassemble. I'm closin' in!

[SUE ROVR]

Dropped liners are not as obvious as they would seem. I have seen a few go for 10,000s of miles with a dropped liner and busted piston. CEL on, then CEL off, comes back on, goes off.

They are nasty at first but then the top of the piston/ring etc crap gets blown out the exhaust and it is just a mild miss, at high rpm they will actually fire!

Lucky it seems like valves for you.

Ron