diagnostic question

Reply Subscribe

Thread Tools

Search this Thread

Jun 19, 2001 | 12:19 PM

ford427

Thread Starter

New User

Joined: Jun 2001

Posts: 1

Likes: 0

diagnostic question

I have a 79 Ford 460 cid f250. My question is this. As I pull each spark plug wire, the motor audible changes sound except for one cylinder. Why is this? I have replaced the plug and wire for that cylinder. Replaced the cap and rotor, The cylinder compression is within spec. The cylinder is getting spark, the plug looks ok.
Any ideas why this one cylinder does not cause the motor to miss or make an audible change ?

Jun 19, 2001 | 01:02 PM

Franklin2

Moderator

Joined: Jan 2001

Posts: 56,965

Likes: 2,725

From: Virginia

diagnostic question

You have done a good job checking everything. The only thing that comes to mind is one of the valves is not opening.
broken rocker arm?
bent pushrod?
cam lobe worn flat?

Jun 19, 2001 | 04:08 PM

fordzrule

Mountain Pass

Joined: Jan 2001

Posts: 130

Likes: 0

From: Ozark Arkansas

diagnostic question

mine does that to i cant figure it out. i have replaced plugs and wires and the cap and rotor.

Jun 19, 2001 | 06:55 PM

shortbedford

Junior User

Joined: Apr 2001

Posts: 71

Likes: 0

diagnostic question

you need to chk the compression dry and wet and compare the results to the other cylinders. You could also ck for a vacum leak on that cyl. chk all the vacum hoses real close for cracks or splits.check around the intake where the intake and head meetyou need to get a spray bottle with water to do this some people use carb cleaner but i find this to easy to give you a false reading because its so volitale. i believe you will find a vacum leak if everything else cks out including the bent push rod and worn cam lobe. hope that helps!!

Jun 19, 2001 | 07:02 PM

dave186

Senior User

Joined: Jan 2000

Posts: 238

Likes: 0

diagnostic question

Does the engine run good and have good power? Seems to me, if a pushrod is bent or cam lobe flat, it wouldnt run worth a crap.

Dave
http://www.davesmonsterpit.com/dmp31.gif

Jun 19, 2001 | 07:59 PM

otto

Posting Guru

Joined: Dec 2000

Posts: 1,686

Likes: 1

From: Racine WI

diagnostic question

I agree with dave186

Jun 19, 2001 | 11:46 PM

75fef100xlt

Junior User

Joined: May 2001

Posts: 50

Likes: 0

diagnostic question

A V-8 can run pretty smooth missing one or 2 cylinder. I've run with 7, doesn't run like crap, just a little weaker

Top 10 Ford Truck Tragedies

Joe Kucinski

AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make

Brett Foote

Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!

Michael S. Palmer

Ford's 2001 Explorer Sportsman Concept Looks For a New Home

Verdad Gallardo

10 Best Ford Truck Engines We Miss the Most!

Joe Kucinski

2026 Shelby F-150 Off-Road: Better Than a Raptor R?

Brett Foote

2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!

Michael S. Palmer

10 Most Surprising 2026 Ford Truck Features!

Joe Kucinski

Top 10 Ford Trucks Coming to Mecum Indy 2026

Brett Foote

5 Best / 5 Worst Ford Truck Wheels of All Time

Joe Kucinski

Jun 20, 2001 | 08:58 PM

otto

Posting Guru

Joined: Dec 2000

Posts: 1,686

Likes: 1

From: Racine WI

diagnostic question

I can see a v-8 runnin smooth with a plug not firing but a valve not opening would cause some vibration or other unwanted noise i think, maybe you have a dead cylinder, do a compression check

Jun 20, 2001 | 10:55 PM

#10

Franklin2

Moderator

Joined: Jan 2001

Posts: 56,965

Likes: 2,725

From: Virginia

diagnostic question

He said he checked it and it was ok.

Jun 21, 2001 | 11:10 AM

#11

beartracks

Lead Driver

Joined: Nov 2000

Posts: 6,623

Likes: 342

From: Albuquerque

diagnostic question

I once had a badly burnt exhaust vavle and didn't even realize it untill I happened to notice the exhause on that side making the old spitting noise.

1977 Ford F-100
400m/c6
280,000 miles
Stock on the outside
modified/rebuilt everything

Jun 21, 2001 | 11:15 AM

#12

heavymetal

Junior User

Joined: Aug 2000

Posts: 59

Likes: 0

diagnostic question

Hey Beartracks
Like your choice of wheels.... Are you in the gallery?

HeavyMetal (Rod)
1977 F100 429CJ bored 30 over, Heads milled 30, edelbrock performer cam, intake, lifters, valve springs, Flat top forged pistons, polished and ported, Holley 750 Legacy, Hooker Super Comp. headers with dual Hooker Comp. exhaust and Hooker dual resonators, B&M C-6 racing tranny, with a TCI Breakaway 2600 flash stall converter, 9" rear with 2-72 gears.

Jun 21, 2001 | 01:05 PM

#13

beartracks

Lead Driver

Joined: Nov 2000

Posts: 6,623

Likes: 342

From: Albuquerque

diagnostic question

[font size="1" color="#FF0000"]LAST EDITED ON 21-Jun-01 AT 02:07 PM (EST)[/font][p]Dont have a digital camera yet but I'll get there eventually. Let me elaborate on my specs. I can't park next to a new one without the guy wanting to trade me. How do you like your tranny/converter? I'm planning ahead.

1977 Ford F-100
400m/c6
Crane Hydralic Roller, Ported, Polished, Forged, yada, yada, yada
280,000 miles
Stock on the outside
modified/rebuilt everything

Jun 21, 2001 | 11:31 PM

#14

heavymetal

Junior User

Joined: Aug 2000

Posts: 59

Likes: 0

diagnostic question

I like the tranny fine. If I had it to do over would have stuck with a B&M converter with a stock stall. I have a little wooden bed that I built on the back. No weight on the rear. I could break them loose with a stock converter and worn out 429, not that it is done up I really don't need to wind it up to take off. Going through towns I have to turn the stereo down so I can listen and try not to lay a scratch. Or not to powerslide the corners which is easy to do.
Mine is in the picture gallery, but is an older picture, before the new bed. Send me an email, if you would like to converse more on this subject.
HeavyMetal (Rod)
1977 F100 429CJ bored 30 over, Heads milled 30, edelbrock performer cam, intake, lifters, valve springs, Flat top forged pistons, polished and ported, Holley 750 Legacy, Hooker Super Comp. headers with dual Hooker Comp. exhaust and Hooker dual resonators, B&M C-6 racing tranny, with a TCI Breakaway 2600 flash stall converter, 9" rear with 2-72 gears.