Missing a cylinder - please help me figure why - Page 2 - FFCars.com : Factory Five Racing Discussion Forum
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post #31 of 80 (permalink) Old 10-14-2019, 09:02 PM
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Quote:
Originally Posted by sread View Post
If you can truly hold your hand on #8 exhaust tube and it is not hot, it sounds like the exhaust valve is not opening...
Nope. If the exhaust valve was not opening he would have it blowing back through the intake.

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post #32 of 80 (permalink) Old 10-15-2019, 06:30 PM
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I'm dying to find out the answer to this now. Wish I had some input.

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post #33 of 80 (permalink) Old 10-16-2019, 06:26 AM
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Just Thinking...

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Originally Posted by JKleiner View Post
Nope. If the exhaust valve was not opening he would have it blowing back through the intake.

Jeff
If the exhaust valve is not opening, and the intake is, then there would be a charge of air/fuel on the intake stroke, and a solid compression reading. If the mixture is ignited, and can't escape through the exhaust valve, the first time it happened there might be some blow back when the intake opens again, but with the cylinder full it can't draw another charge of air/fuel and would not fire again, resulting in a cold header tube.

Just snow balling the thought, that is what I see as a possibility.

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post #34 of 80 (permalink) Old 10-16-2019, 11:16 AM Thread Starter
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Thanks again for all the suggestions!

I have not had too much time this week to tinker, but I did try the following:
  • Leak down test. Put pressure on #8 and it seems intake and exhaust valves are tight. Only hissing was out of valve cover. Tried to do the same on #1 and it seemed to be about the same.
  • Swapped the distributor and TFI module with another used one I have had on the car before. No change in how it runs.

I guess I will have to pull the intake now to see if there is some sort of blockage - could do the same for the exhaust I guess. It will also allow me to get my endoscope camera in there to take a look.
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post #35 of 80 (permalink) Old 10-16-2019, 01:03 PM
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This is so intriguing with so many possibilities. Perhaps someone should be running a book on it 🙂. I would have put money on an over fueling injector causing the cylinder to be flooded, but I believe that has been discounted now.

Hopefully the endoscope will bring an answer.

Best of luck, Nigel in South Oz
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post #36 of 80 (permalink) Old 10-16-2019, 01:16 PM
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I was half jokingly thinking "shop rag stuffed in #8 intake runner" -

It still sounds like ignition to me though, did you double check wire routing and ensure that there is no crossfire/spark leakage? (run car in pitch darkness, look for sparkles)? Are you sure that #8 is the ONLY failing cylinder and that you haven't cross-wired it with another cylinder (firing order, are you sure it's correct for your engine/cam?)?


What EFI system specifically is installed, and can you post a link to the SCT chip specs? (I have a Quarterhorse, and there are LOTS of ways to mess it up)



Intriguing puzzle, please keep us posted!

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post #37 of 80 (permalink) Old 10-16-2019, 02:07 PM
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How long has the car been running in this same configuration, before changing anything? How did the symptoms first appear?
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post #38 of 80 (permalink) Old 10-16-2019, 06:33 PM Thread Starter
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Quote:
Originally Posted by tim-in-oakton View Post
I was half jokingly thinking "shop rag stuffed in #8 intake runner" -

It still sounds like ignition to me though, did you double check wire routing and ensure that there is no crossfire/spark leakage? (run car in pitch darkness, look for sparkles)? Are you sure that #8 is the ONLY failing cylinder and that you haven't cross-wired it with another cylinder (firing order, are you sure it's correct for your engine/cam?)?


What EFI system specifically is installed, and can you post a link to the SCT chip specs? (I have a Quarterhorse, and there are LOTS of ways to mess it up)



Intriguing puzzle, please keep us posted!

I am now running with a different distributor cap and wires just to check if that was the cause. I will try to put the original set back on and check it. I am fairly sure that the wires did not get crossed while I was racing down the track though

I will try to double check the temperature on each of the exhaust exit pipes. The temperature was a bit varied, but #8 always sticks out as not raising until the heat bleeds over from the head.

I like your idea about the chip - yesterday I called the tuner who installed it and dialed it in on the dyno to see if they have and any similar experiences with this chip on a Windsor engine (Revolution in Baltimore). They said that they had never experienced that (other than one that came in with a cam lobe that was self destroying and therefore not firing on one cylinder). He also mentioned that the chip/ECU does not control ignition on individual cylinders.
One idea though is that there is a selector wire where I can change maps. There is a map that says go back to stock tune. Perhaps I should try that.
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post #39 of 80 (permalink) Old 10-16-2019, 06:48 PM Thread Starter
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Quote:
Originally Posted by sread View Post
How long has the car been running in this same configuration, before changing anything? How did the symptoms first appear?
I have run this configuration since I put the AFR heads on two years ago. The car has also been on the track a couple of times, plus a long drive down to the tail of the dragon this summer. So lots of miles on it both cruising as well as getting beat on on the track. The only change I have made recently is to add electric power steering (one of the Saturn Vue units).

The car ran good the first 20 minute session of the day on the track. On the second session I had only done a couple of laps - although this session I turned the heat up a but, but always shifted before 6k rpm. There are a couple of turns where you run it up to 5-6k rpm in third before getting on the brake. When I got on the gas after the second quick bursts I could feel that I did not get the same throttle response, the sound had changed and there was a slight vibration. I did not notice any bang/rattle when it happened.
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post #40 of 80 (permalink) Old 10-16-2019, 07:11 PM
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Gonna throw this out there. Did the cam break?

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post #41 of 80 (permalink) Old 10-16-2019, 07:35 PM
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Quote:
Originally Posted by KRUSTY990 View Post
Gonna throw this out there. Did the cam break?

krusty
That's a thought. If it broke at the end then only the #8 would be affected.
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post #42 of 80 (permalink) Old 10-16-2019, 07:57 PM Thread Starter
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Quote:
Originally Posted by sread View Post
How long has the car been running in this same configuration, before changing anything? How did the symptoms first appear?
Quote:
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That's a thought. If it broke at the end then only the #8 would be affected.
When I turn the engine by hand the valves do open and close - I guess theoretically if the there was a fracture it could make the broken end run along and slip once the engine runs. Not sure how likely it is, but at this point I am open to any idea!
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post #43 of 80 (permalink) Old 10-16-2019, 11:57 PM
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If you have physically witnessed both valves opening while turning the engine over, then I am just as stumped as everyone else. I had a similar issue but mine was blowing tons of smoke out of the exhausted. Turned out to be an intake valve wasnt opening, and the engine was sucking oil down through the intake valve stem. Could the rocker arm be cracked, and when you saw the movement you were only witnessing the pushrod side move and not the valve tip side on the exhaust valve?

On a side note - did it run correctly when you switched to a different distributer (isaw you mention planning to swap them but wasn’t sure if you carried it out)? I’ve seen (well, read on forums) instances where a piece of the internal distributer comes loose/cracks and wont throw a good spark to one cylinder but functions well otherwise. I’ve had issues with my MSD distro where it will build up heavy carbon on a couple of the posts. I’ve also heard of posts cracking inside the cap (invisible) which would throw a weak spark to one cylinder.
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post #44 of 80 (permalink) Old 10-17-2019, 12:11 AM
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I once had a bad lifter that presented some very strange issues, sort of like what you're experiencing. Might be something to check, even if it appears to be working when turning the engine over by hand (at running RPM it may not be doing its job).
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post #45 of 80 (permalink) Old 10-17-2019, 02:55 AM
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Just my 2 cents.....
My son has a 70 Chevy pickup with a small block in it. It did something like this. It had a dead #6 cylinder and we did pretty much everything you have already tried. When I pulled the valve cover the rocker arms looked like they were working correctly. After scratching my head for a bit, I rotated the engine a few more times and that's when I noticed that the intake rocker was rocking as advertised... the issue was that the nut had backed off the stud and the rocker was moving but not pushing the valve down like it should. New stud and lock nut cured the issue.

On the issue of the cam being broken.... it is possible to have a cam brake straight enough that it will catch enough to moved the valves when turned by hand, but once force is applied (engine running) it will slip and that cylinder will be dead.

Just my thoughts here.
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post #46 of 80 (permalink) Old 10-17-2019, 04:54 AM
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Don’t think it can be a broken cam. The 302 is an interference engine design. If anything messes up valve timing the piston and valves would meet. Your compression is good and the leak down test showed no airflow through intake or exhaust hence, no bent valves.

Watching with interest to see the final resolution to this problem!

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post #47 of 80 (permalink) Old 10-17-2019, 01:45 PM
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You need three things for a running engine, fuel, compression and ignition. I was sure you had a dead plug, but you said replacing it made no difference. Did you verify that you had good spark?
Someone said a broken camshaft, well no, not in the sense it broke in half, but a wasted lobe is possible. You posted the answer I believe in an earlier reply " (other than one that came in with a cam lobe that was self destroying and therefore not firing on one cylinder). He also mentioned that the chip/ECU does not control ignition on individual cylinders."
You need to check the rockers on the dead cylinder, either one has backed off, or a lobe on the cam is damaged.

Last edited by rich grsc; 10-17-2019 at 06:57 PM.
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post #48 of 80 (permalink) Old 10-17-2019, 04:04 PM Thread Starter
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Thanks again for the good input! I will pull the upper intake and valve cover tonight and give it a good inspection
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post #49 of 80 (permalink) Old 10-18-2019, 12:42 AM
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What about a collapsed hyd lifter?

Never assume it is only one problem. More than once on my car, there was two problems at the same time.
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post #50 of 80 (permalink) Old 10-18-2019, 01:56 PM
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That sounds like a good probability - but wouldn't there be a significant tapping noise? Pretty sure it is something mechanical - seems like fuel and spark have all been covered
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post #51 of 80 (permalink) Old 10-18-2019, 04:54 PM
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I can't wait to hear the solution. If the compression, leak down, and valve motion is good, it's mechanically sound, no need to pull the heads. PS, the leak down test will show bubbles in the radiator if you have a bad head gasket. It will also whistle in the intake or exhaust with a bent/burnt valve. Loose rocker indicates bad cam or rocker/stud or pushrod. You can see broken springs, etc.
Swapping the injectors and injector wires are great tests to locate a bad injector or wire or ECU issue. I would have bet on the plug wires.
I think it might be a bad intake gasket. Is the plug wet with gasoline or antifreeze or both? That could cause the misfire. Maybe your scope can see something at the head/intake location.
Closing the throttle at high RPM spikes the vacuum in the intake/cylinders. Race motors occasionally break rods - they are pulled apart as the crank tries to yank the piston away from TDC at high RPM with high vacuum readings, also hard on bottom rod bearings. You may have pulled the intake gasket out of position.
PLEASE keep us posted.
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post #52 of 80 (permalink) Old 10-19-2019, 03:58 AM Thread Starter
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Update: Pulled the upper intake and valve cover off to give the rockers, pushrods etc a better look on #8. I have attached some pictures, and all seems to look good. It looks like the valves timing are about right relative to the piston position. I was able to put the endoscope into the cylinder, and it does not look like the piston has been in contact with the valves – at least judging on looking at the top of the piston.

With both valves closed there is no play in the rocker. I am able to turn the pushrod by hand even if it is pretty tight.

So if it was collapsed lifters would the internal spring in the lifter be able to open the valve when the engine is turned by hand and then “collapse” or keep the valves from opening at all when the engine is running?

What is the best way to diagnose that? I am almost tempted to run the engine without the valve cover and see what the valve do. It will probably be an oily mess but what else to do?

The spec for the valve springs are: 150# seat, 400# @ 0.66" max lift. I replaced the lifters two years ago with original Motorcraft when I put the AFR heads on.
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post #53 of 80 (permalink) Old 10-19-2019, 03:03 PM
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If you are going to start it up without the valve cover, I have had good luck with a couple of heavy rags across the top of the valve train, less the ones I want to see.

Depending on the spray, you should have a couple of minutes before it gets messy. I put the edges of the rags inside the valve cover lip.
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post #54 of 80 (permalink) Old 10-19-2019, 05:08 PM
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Danish, just a thought. The underside of the pictured rocker appears to have been binding in several places. Most rockers, I've ever seen, appear to be smoother/ better finished, than yours appears. Just my 2 cents worth, Irwin.
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post #55 of 80 (permalink) Old 10-20-2019, 12:22 AM
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Is the tip roller pin coming out of that rocker arm on the the right?
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post #56 of 80 (permalink) Old 10-20-2019, 01:25 AM
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Also, the rocker laying on its side - it looks like some part of the fulcrum shaft or bearing is protruding underneath the snap ring - at about 2 o’clock in the picture.
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post #57 of 80 (permalink) Old 10-21-2019, 06:01 AM
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Running with VC's off

FWIW, small clip on wires with a rubber tip are available that clip to the rockers and plug the oil hole . . . just so you can idle the engine with the valve covers off.

Doc
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post #58 of 80 (permalink) Old 10-21-2019, 03:17 PM
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A couple of observations from your pictures. You have full motion of both valves. This indicates your cam, lifters and pushrods appear to be fine. Since you have the rocker off, pull the pushrods and roll them on a flat surface. Any bend will become readily apparent. Valves sticking open can cause a miss but on our engines it would result in valve damage. You don’t have that because your compression and leak down tests were good.

I would keep chasing fuel and ignition problems and since you’re this far apart change the intake manifold and gaskets.

Good Luck

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post #59 of 80 (permalink) Old 10-22-2019, 12:05 AM
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Any chance the high revs could have sucked out the intake gasket? Any coolant in the oil and/or can you do a coolant system pressure check to see if its leaking into the motor?

Weird problem. Best of luck with it. Scott

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post #60 of 80 (permalink) Old 10-23-2019, 10:05 PM
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This is like a whodunit mystery. I’m betting on a fuel injection issue. You have spark and you passed a compression check. All that is left is fuel to provide the bang and heat.
You can have the following issues
1. You can have the ECM call for the fuel, power delivered to the injector, and the injector not fire.
2. You can have the ECM call for fuel ,power is delivered to the injector and the injector does not spray enough fuel .
3. You can have the ECM call for fuel, power is NOT delivered to the injector, but the injector is capable of firing if it received power.
4. The ECM does not call for the fuel for that cylinder.

Sounds like you moved injectors around so I would check the power going to #8 injector to see if it’s there power and if it has enough to fully engage the injector.

If the power is good then it may be time for a new or reprogrammed ECM.
Good luck, I can’t wait to see what caused this.
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Last edited by Brewha; 10-24-2019 at 04:56 PM.
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