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-   -   Crappy idle, misfire on one cylinder. (https://www.yenko.net/forum/showthread.php?t=149893)

DarrenX33 07-18-2018 02:04 AM

Crappy idle, misfire on one cylinder.
 
Anyone one have any thoughts on this?

Plug 2 is not firing. All others look fine. I tried the following to get 2 to work..

1) plug swap 1 to 2, no change
2) new plug wire, no change
3) tighten up plug, no change
4) change cap, no change
5) change rotor, no change
6) change timing, no variation of timing brings 2 back.
7) change capacitor, no change
8) watched for spark on plug while grounding it. no spark until you hit about 1500 rpm, then spark is there but looks weak. Perhaps my spark is weak all around.

Distributor was just rebuild/restored by Jerry MacNeish. I have new plugs, wires, coil, engine harnesses. Totally stumped.

Mr. Chevy 07-18-2018 03:59 AM

Maybe you have a faulty coil even though its new... Are the points ok??

Rich

Woj 07-18-2018 10:56 AM

It seems like the coil is the only thing you have left to change. Maybe swap out the coil for a known good coil? One thing I have found in the past is that most point sets, even the later GM are junk. I was told to give Echlin points a try, I did and really do like the quality of their points. I bought these at NAPA.

Good luck and let us know what you find.

1967 4K 07-18-2018 10:58 AM

Do a cylinder compression check. Could be in the valve train, hope not.

Postsedan 07-18-2018 11:12 AM

This is what I use on all my cars. As Phil said, today's points are junk.
Your very first tow ride home and you will throw away them points.

https://www.lectriclimited.com/break...nversion-85309

Dan

cook_dw 07-18-2018 11:38 AM

Was it running fine before the distributor rebuild? Swap distributors would be the first thing I'd do if the previous statement was true. If it cleared up then I would send it back. But FWIW its more than likely the points. Local autoparts store used to have points/condenser kit where the condenser was made onto the point plate and they were great. Never had an issue with them. Blue Streak was the name but I wanna say it was owned by Standard Motor Ignition or Products..

L78steve 07-19-2018 12:29 AM

If the distributor was run on a Sun machine and it tested good you can rule the Dist. out as being the problem, points included.

cook_dw 07-19-2018 12:36 AM

Never assume.. You will make an ass out of....... Well you get the point.


As the great President Reagan once said. Trust but verify.

tunes 07-19-2018 12:44 AM

Change the coil. This sounds like a friend's car last year that suddenly wouldn't run. It had a weak spark and would try to start. The culprit was the coil.

Lee Stewart 07-19-2018 01:27 AM

Would the engine experience the same symptoms if either the lifter got stuck or a valve spring broke?

DarrenX33 07-19-2018 03:19 AM

Quote:

Originally Posted by L78steve (Post 1408427)
If the distributor was run on a Sun machine and it tested good you can rule the Dist. out as being the problem, points included.

That is how Jerry does them, which is why I went with him. And I share your sentiment.

DarrenX33 07-19-2018 03:21 AM

Quote:

Originally Posted by cook_dw (Post 1408385)
Was it running fine before the distributor rebuild? Swap distributors would be the first thing I'd do if the previous statement was true. If it cleared up then I would send it back. But FWIW its more than likely the points. Local autoparts store used to have points/condenser kit where the condenser was made onto the point plate and they were great. Never had an issue with them. Blue Streak was the name but I wanna say it was owned by Standard Motor Ignition or Products..

It was running equally terrible. That is why I had the distributor rebuilt. The shaft and bushings were basically destroyed. I also have a box of vintage AC Delco points.

DarrenX33 07-19-2018 03:22 AM

Quote:

Originally Posted by Lee Stewart (Post 1408437)
Would the engine experience the same symptoms if either the lifter got stuck or a valve spring broke?

Problem is I have no, or very little spark on two. Not sure how those would factor in...

DarrenX33 07-19-2018 03:23 AM

Quote:

Originally Posted by Postsedan (Post 1408384)
This is what I use on all my cars. As Phil said, today's points are junk.
Your very first tow ride home and you will throw away them points.

https://www.lectriclimited.com/break...nversion-85309

Dan

I have the Crane ignition on standby. Didn't want to put it in but maybe I will try it. I was hoping the work Jerry did was good considering it was tested.

DarrenX33 07-19-2018 03:24 AM

Quote:

Originally Posted by tunes (Post 1408430)
Change the coil. This sounds like a friend's car last year that suddenly wouldn't run. It had a weak spark and would try to start. The culprit was the coil.

I do have another here, but it doesn't seem to help.

69L78 07-19-2018 10:48 AM

Quote:

Originally Posted by Woj (Post 1408382)
It seems like the coil is the only thing you have left to change. Maybe swap out the coil for a known good coil? One thing I have found in the past is that most point sets, even the later GM are junk. I was told to give Echlin points a try, I did and really do like the quality of their points. I bought these at NAPA.

Good luck and let us know what you find.

I have never had a problem with points my whole life. I also buy from NAPA and use the heavy duty or high perf points with the heavier spring so you do not get the points bounce at higher pm. These are Blue Streak DR2270XP - points & DR70X - condenser. The Echlin distributor cap with the copper contacts is RR165.

bbbentley 07-19-2018 01:16 PM

Quote:

Originally Posted by Lee Stewart (Post 1408437)
Would the engine experience the same symptoms if either the lifter got stuck or a valve spring broke?

I would hope and think the OP has hooked up a vacuum gauge and ruled out mechanical problems before narrowing it down to electrical? But good point to mention, should this not be the case? And, as a side note, mechanical lifters don’t “stick”. I guess I am assuming it is a 69 Z he is working on even though it was not stated. And, assuming a mechanical cam, as well.

Tommy 07-20-2018 12:32 AM

I would do a compression test and pull the valve cover. A stuck valve or hole burned in a valve will cause an engine to act this way. Also, by pulling the valve cover it is possible to find a broken rocker arm or a push rod has bent or come out of the bore (usually due to the rocker arm...


Tommy

Tommy 07-20-2018 12:44 AM

Quote:

Originally Posted by DarrenX33 (Post 1408462)
Problem is I have no, or very little spark on two. Not sure how those would factor in...



I reread first post. No spark until 1500 rpm then it is still weak? If all parts including coil have been replaced I would just drop in another distributor and see what that does.


Tommy

427_Rat 07-20-2018 02:34 AM

If one lobe on the distributor cam (for #2 cyl.) was wore down, might prevent spark at low RPM and allow a weak spark at higher RPM when points "bounce"...possibly? Just trying to think what would tie it to only #2 cyl. spark. You might check clearance of points on each distributor cam lobe or at least #2 cyl. and a couple others to see if any variation is apparent?

ORIGLS6 07-20-2018 03:26 AM

If it's on the Corvette, check your grounding.

Lynn 07-20-2018 03:27 AM

Checked the # 2 wire with an ohm meter, and compare with others? Not likely you got two bad ones, but possible.

Next step is kind of a pain, but assuming you have put an ohm meter on the two (2) plug wires you have tried, and they both show good, next step is to pull the distributor, put it in 180 out. Rotate all the wires 180. Start it up. If #3 now has a weak spark, you have pinpointed the distributor as the issue. If #2 still has weak spark, you have eliminated the distributor as the issue. Not likely the coil if it only affects one cylinder.

If you don't have a spare distributor laying around, I would be glad to send you a functioning one (won't be curved exactly right for your car, but will at least let you know if it is the distributor.

DarrenX33 07-20-2018 11:33 AM

This is on my Corvette.

67 Nova Boy 07-20-2018 02:38 PM

Have you replaced your spark plugs...not uncommon to have a plug or two go bad.

Dave
67 Nova Boy

DarrenX33 07-20-2018 10:51 PM

Quote:

Originally Posted by Lynn (Post 1408623)
Checked the # 2 wire with an ohm meter, and compare with others? Not likely you got two bad ones, but possible.

Next step is kind of a pain, but assuming you have put an ohm meter on the two (2) plug wires you have tried, and they both show good, next step is to pull the distributor, put it in 180 out. Rotate all the wires 180. Start it up. If #3 now has a weak spark, you have pinpointed the distributor as the issue. If #2 still has weak spark, you have eliminated the distributor as the issue. Not likely the coil if it only affects one cylinder.

If you don't have a spare distributor laying around, I would be glad to send you a functioning one (won't be curved exactly right for your car, but will at least let you know if it is the distributor.

Holy cow what a nice offer, and I very much appreciate that.. I do happen to have a spare distributor here with me. I am going to try and put it in. I will also consider the experiment you mentioned here. I think I will be able to solve this soon.

Carolina Dreamin' 07-20-2018 10:53 PM

Check your messages, Tom

DarrenX33 07-22-2018 03:22 PM

Ok. It was the distributor. I dropped in my old Unilite and it ran great. I have a thought as to what is wrong with it but I will wait until it is looked at. Sending it back to be checked out.

Kurt S 07-23-2018 05:29 AM

Quote:

Originally Posted by 427_Rat (Post 1408620)
If one lobe on the distributor cam (for #2 cyl.) was wore down, might prevent spark at low RPM and allow a weak spark at higher RPM when points "bounce"...possibly?

If it was a bad lobe, I don't know that the distributor machine would have caught that.....

Steve Shauger 07-23-2018 01:45 PM

Quote:

Originally Posted by Kurt S (Post 1408913)
If it was a bad lobe, I don't know that the distributor machine would have caught that.....

Also when it was being rebuilt it most likely would have been found.

L78steve 07-23-2018 04:54 PM

Quote:

Originally Posted by Kurt S (Post 1408913)
If it was a bad lobe, I don't know that the distributor machine would have caught that.....

Yes it would. You look around the whole dial and you can see the spark events of each lobe.
If one lobe is worn it would show a late spark on that lobe.

Mr70 07-23-2018 05:19 PM

True..


427_Rat 07-26-2018 12:35 PM

I think the tester would/should show it, but isolated to #2 cyl. only, and it appears to be in the distributor, just trying to think what it might be. Distributor cam lobe seems logical?
Interesting puzzle... Be glad to see the findings.

DarrenX33 07-27-2018 01:22 AM

Shipped it back for analysis and repair. I'm interested to find out myself. In the meantime, running great with the Mallory Unilite.

DarrenX33 08-06-2018 12:56 AM

Ok. So this was the root cause. Bent. Not sure how or when it happened. All I can say is that I returned it and he fixed it and got it back to me quick. I installed it today and drove it and all is well so far.

http://img.photobucket.com/albums/v3...DDC378BBD7.jpg

bbbentley 08-06-2018 01:32 AM

Thanks for follow up. Many times no one lets one know the outcome. Glad it is fixed as I am sure you are, as well.

Salvatore 08-06-2018 03:09 AM

your my hero Eddie.

enio45 08-12-2018 11:25 PM

soon, the top plate is bent? how might that effect it?

i can see the rotor contact might not be close to the tab in the cap, but was it off that much?

appreciate the thoughts?

427_Rat 08-13-2018 10:26 PM

Agree, Would think it would be off the same for every contact in the cap?


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