Hesitations and Ignition Related Issues.

NotLaw

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So bringing this out of my Fairlane thread to a place it might actually get seen, I've got an ignition issue with the Fairlane.
To quote from the Fairlane thread:
...
A week or so before I F-ed up the diff, I had an issue where I was accelerating, hard onto the interstate (talking WOT, 6000 rpm shifts, etc) and at approximately 5200 RPM in second gear, I got a hard judder from the engine, like the ignition was cut. It sounded like I had slammed into a rev limiter at full chat. Repeated hard ignition cuts. I backed off for a moment, and got right back into it and it was smooth up to my 6000 rpm shift.


I never had the issue again, and a little poking around in the ignition and fueling system revealed nothing. I could not reproduce it, so I shrugged it off. After all, a problem that cannot be reproduced is not a problem.


On my test drive of the diff yesterday. the problem came back and in full force. The difference is this time, It did it while I was cruising at 75 mph on the interstate. Almost felt like the engine tried to stall at 2800 rpm, flutter, rough hesitations, something that felt like a massive back-fire, the lot.


I checked my spark plugs and they told me that I was running ultra lean, (and a check of the Adjustable Part Throttle screw in the Q-Jet confirmed this, it was practically bottomed out) so I fattened up the mixture a bunch, and went on another test drive.
I also checked and confirmed the ignition timing at 14? initial advance, and 30? mechanical advance all in at 2500 rpm or so.


No change.


This morning I pulled the distributor cap off, and found this:



It doesn't really look too nice in there at all. This is the original Skip White cap and rotor that came with my dizzy when I bought it somewhere around 20,000 miles and and engine ago.


I'll replace it, and see where things go from there. It's definitely feeling like an ignition problem though.
Maybe a Ignition Module? (if the cap and rotor don't fix it)
...

And a video of the issue, that I filmed on the first drive after replacing the Distributor Cap and Rotor with Napa Echlin parts.


The video is in 2nd gear, cruising at about 40 mph, and starts just after I put my foot to the floor.
[/QUOTE]

Going back out to the car later, I noticed this:

about .125" of up/down movement in the shaft. Is this normal? could it even cause this kind of issue?

I pulled the dizzy out of the engine and looked over it, I did not see any unusual wear on the shaft, gear, or housing. Everything looked OK.

I also recorded this video, which shows that under no load, the ignition system works just fine.

I topped out at ~4700 RPM or so, per my Innova digital timing light. The engine was not hot anymore (having been about 4 hours since the last drive) but it was not cold either.


As for specs:
Engine is a rebuilt 302 with a Comp Camps Nostalgia+ flat tappet cam with 15000 miles since the rebuild.

Spark plugs and wires were replaced at the rebuild, and gapped at .040"

Distributor is a Skip White HEI conversion distributor, first installed into my old 298 engine in August 2013. Power is supplied to it by using the original ballast wire to trigger a relay, sending +12v direct from the battery along a 14 gauge wire. This is the same setup that has been on the dizzy since almost day one.
The ignition module is a replacement Autozone one, replaced about 1.5 years ago.
Coil is the original Skip White coil, and the cap and rotor are of course, new.


I can consistently reproduce the issue by putting the engine under heavy load in any gear, though I cannot say I have ever noticed it under 1900 RPM. The temperature of the engine does not appear to make a difference unless it has had a whole night to cool off. My first drive this morning took about 15 minutes before I started having the issue. Every test I have made during the day today I have been able to reproduce it immediately.

Thoughts? If the end play is not a typical cause of this kind of issue, my next step is probably going to be an ignition module.
It's what I replaced the last time I had strangeness with the ignition, though I can't remember what that strangeness was now...
 

GRtak

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Have you checked for a vacuum leak?
 

NotLaw

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Only two vacuum lines on the whole engine, everything else on the carb is plugged

One, which is ported vacuum from the carb, that goes to the vacuum advance,
and the other is the line that goes to my vacuum gauge.

My vacuum gauge is reading normal vacuum for this elevation, between 9 and 12 inches of vacuum at idle (cam) 14 inches at light cruise, and around 22-24 inches at off throttle. I'll double check the two lines and all the vacuum caps though.
 

NotLaw

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I did some testing of the vacuum line situation on the car. As I said, I've only got two, the ported line to the distributor, and another line off the back of the carb (normally for the power brakes I think) that I feed into my vacuum gauge.

I blocked off both of those ports, and triple checked all my caps on the other lines (they were good still) and went for a test drive. No change. Missing under load, over 1800 RPM.

I also tried wiring the secondarys shut, no change; and switching the vacuum advance to manifold vacuum, which if it changed anything, just made it very slightly worse.

I did take it up to 4000 rpm or so in first gear, (using reasonably light throttle, no more then 40% at any point) and it ran smooth as silk. I should have hit it hard at that RPM to see how it would behave, but I was on main street at the time, and I'm not sure it would have been much appreciated, I was getting enough attention as it was screaming down the road at 4 grand :mrgreen:


My next test is going to be to bypass the relay feeding the dizzy 100%, and just apply direct voltage to it.
I'm also going to check my fuel filters and fuel flow, per a recommendation on another forum.
 

ScarFace88

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I was actually thinking this was a fueling issue when this first came up, is the fuel pressure in spec?
 

GRtak

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There are also intake gaskets and the carb itself that can leak.

Scarface may be correct too.
 

Spectre

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Autozone modules have been known to be bad out of the box. Also, check the HEI pickup itself, not just the module.
 

NotLaw

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Spectre, I replaced the AZ module (which was running fine in the car for the last year or so) with a BWD unit from Oreillys. Probably just as shit a part, but it works equally well as the old AZ unit. IE: the car starts, runs and drives, but this issue persists.


For today's update, I started by hooking up my Autometer Air/Fuel ratio gauges that I had purchased just before I exploded the diff a month ago (one for each bank, with O2 sensors installed in the header collectors, parallel with the ground.
The gauges showed that I was still running stupid lean at idle, which I quickly adjusted to a less retarded mixture of 13.5:1, from the 18+:1 that I started with.
A quick drive round the block showed that I was cruising around town at ~13:1, and WOT at 2000 rpm in 2nd dropped the mix to 10:1, and immediately induced my popping misfire issue.

Despite the gauges saying that I was running rich in at least one situation where I could cause the issue, I pulled my fuel line off and ran the pump. Fuel flow was good, no air or anything in the line, but pressure was rather low. I could hold my thumb on the end of the fuel line and barely even notice the pressure (note: the fuel line in this car is 5/16)

I thought carbs were supposed to only be 4-7 psi anyways though?
I'll see if I can't rent a pressure gauge of some kind from one of the parts stores tomorrow anyways, be good to have an actual number.
If the gauge doesnt reveal anything, or if I can't get one, I do have a spare new fuel pump I can swap in. I still need to check the filters too.

Anyways, Even with the possibility of not enough fuel pressure, I find it hard to wrap my mind around the idea of borderline lack of fuel (or even absolute lack of fuel) causing this harsh, sharp, stuttering misfire in a carbonated car. If it was fuel injected, that makes sense, but with a fuel bowl providing at least a small buffer, I would expect a different feel of misfire. I've run the fuel bowl dry before (accidentally leaving the pump off will do that after all) and it's never felt like this.

I also ran the fuel bowl dry so i could take the fuel line off for my test today by way of running the engine with the fuel pump off. While it was draining away, I let it idle for a time, as well as brought the RPM up a bit. As rather expected, as the fuel level in the bowl dropped, the AFR for both banks got increasingly lean, until it stalled out from lack of fuel.


Another test I ran was to hook the +12v of the dizzy straight to the battery with a new wire, no change.

I checked the voltage output of the alternator as well. 12.7 at idle, which is not unusual for a old car that is still externally regulated like mine (though i did replace the regulator with a electronic one ages ago)

I get 13.8 or so if I give it basically any throttle though, right on the money as far as I am concerned.

I also checked some resistances on both the HEI coil, and the pickup coil in the dizzy.

Per this post I found via google there should be more than 0 ohms, and less than one ohm between Tach and Batt terminals on the coil, I read 1.8 Ohms.

He also says there should be between 6000 and 30000 Ohms between the Batt terminal, and the carbon pickup inside the cap. I read a dead open, but I am inclined to think this is a method or tools issue, as the car does still run, just not right in every situation.

I also checked between the pickup coil's two leads and ground, per this site and it was dead open, as it should be. I started running out of light before I could complete the tests on those two pages, but I will continue in the afternoon tomorrow. I also plan to take the coil down to one of the parts stores so I can compare side by side Ohms between my old coil and a new one.
 

Spectre

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Have you verified ignition timing since replacing the module?
 

NotLaw

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I rechecked all the timing.
14 initial
32 all in at 2500 (and I checked, it held 32 up to at least 3800)
52 with vacuum by 2500, holding steady up to 2500.

I also checked the fuel pressure. Between 5 and 6 psi constantly under all loads. It flutters a bit while the issue is occurring.
 

Spectre

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It sounds like it's an intake backfire, then? Intake backfires change the pressure in the carb venturis and that affects fuel flow.

Might want to use your timing light as a spark detector and see if any of the plugs are not firing when the issue occurs.
 

NotLaw

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Well, the problem is very much not solved, but I am 98% sure I know what the problem is.

I noticed yesterday as I was driving back to Oriellys to return the fuel pressure gauge I rented that the misfire problem seemed to be getting worse. It was now happening with even moderate throttle, and accelerating up a even a slight hill was enough to induce it.
While I was in Oreillys, I saw the MSD cut to length plug wires, and decided that since I've rather intended on going that kind of route anyways ever since I redid the engine a year and a half ago, that I would just bite the bullet and buy them.

When I got the new plug wires in, there was actually, for the first time in this process, an improvement.
The misfire went from happening even with moderate throttle (I'll assign an arbitrary 50%) to only happening with a little heavier throttle (say, 65%)



With this little sign of improvement, I went looking for spark plugs.

I asked for Autolite 26's, since I've been running Autolites in this car since the day I bought it, and it turns out they were on sale.

When I pulled the old plugs out, they were gapped between .032" at the smallest, and .045" for the biggest, though the majority were right around .040" ?.002

There was no visible damage or issues with them

Overall shots of the old plugs. All 8 are in order, right to left.


And individual shots of the old plugs
1. 2. 3. 4.
5. 6. 7. 8.


I installed the new plugs today after gapping them to .040, which is a bit more than my ford book recommends.

After installing the new plugs, there was a marked improvement to the issue. Now I would only get misfires at much heavier loads and I could even go WOT, for a short time, before inducing the misfire.

This is what gave me an idea. I retarded the initial timing to a silly number, only 3?.

The problem went away. :mrgreen:



I pulled 1st gear up the steepest hill in town all the way to 6100 RPM. Smooth as silk.

Of course, with only 3? of initial, the engine is not very happy during transitions, particularly from idle to moving. there's a bit of a bog. It actually reminds me of the turbo lag in my Saab. I clutch out and start moving, and it slowly accelerates, then all of a sudden wakes up and grabs your balls lol.
I suppose the bog could have something to do with how rich my idle is at the moment too. That fluctuates between 12.5 and 13:1 AFR...


Ever since I discovered the large amount of endplay in the distributor, I have been wanting to contact Skip White (the vendor) and see what they have to say. I've always been too busy during the day with work, and by the time I get off work and remember to call them, It's been after their hours. I was able to call today though, and while none of their techs were still there, I found out that they'll be in tomorrow, so I'll be giving them a call for sure.

I'm finally on the trail of this damn problem. :mrgreen:
 

syncview

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Play in distributor is sideways or up And down?

Also increasing the plug gap will put more stress on the ignition system

Your problem sounds more like a fuel delivery issue. First thing to check is the fuel pressure
 

Dr_Grip

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Any news from Skip White? Running a Skip White dizzy myself I am curious as to how this plays out.
 

NotLaw

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When I called Skip White, their tech indicated that this amount of play is not entirely unusual, but that he didn't think it could cause this issue. He also said they would be happy to send me a replacement if I want to send my old one back.

For now, since the issue is no longer reproducible with the initial timing backed off to 10?, I have just ordered a distributor gear shim kit which will get my play down to .025"

We'll see what happens.

I did make the misfire happen once yesterday, but I was not able to reproduce it. The problem is still there, lurking in the background.
 

NotLaw

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Well, Time for a status update on this.

Long story short, I replaced the fuel pump, re-jetted the carburetor, and replaced the distributor with a new Pertonix unit, and this car is still broke to :censored:


I shimmed up the dizzy, and if anything, It made it worse. Rather then waiting for 1.5 or more weeks to get a replacement dizzy that may or may not have been any better, I chose instead to accelerate one of my future upgrade plans, and go to a quality aftermarket small cap dizzy. (the small cap is absolutely necessary for another future upgrade; space reasons:whistle:)

I went with a Pertronix Flamethrower and E-Core coil from Summit.

Once It came in, I got it all installed, timed to 36? all in mechanical timing at 3000 rpm, and went for a test drive.

At first, everything seemed OK, I made a WOT run all the way up to 5500 RPM, and all was well.

The next time I got into it though, at around 3500 RPM, the problem came back in full force, and everything went downhill from there.

At this point, I was absolutely crestfallen... and Pissed lol

With no obvious direction to go, I went down the other path of fueling.

I knew that I was running very rich (10.5:1) at WOT, and that needed to be fixed regardless, So I ran some numbers and picked some new primary jets and secondary rods that should have brought my WOT fueling back to where it ought to have been.

The car had #73 jets in it, 49M Primary Rods, and DA Secondary rods.
The numbers showed me that these were around 16% too big, so I backed off to #68 jets, and DH secondary rods.

I installed these at the same time as I replaced my fuel pump with a new one (my spare ended up being a old pump, i had already used the spare to replace the electric pump on the K5, oops)

The new fueling and pump brought my AFR at WOT closer to where it should have been, but it was hard to get my cruise AFR into spec, (primary rod is too big now) and it also induced a lean spot at 2500-2800 rpm.

So, I picked the wrong parts, not unusual for someone who is still gaining experience in tuning Q-jets, but did it fix the problem?

Of course it didn't

No change to the problem, but at this point, my friend told me that he thought it felt more like a backfire then a misfire, and after further thought, I think I agree with him.

Right now it feels less like hitting a rev-limiter, and more like hitting a damn brick wall.

With the fueling obviously not effecting the backfire, I went back at the timing, and brought my all-in timing down to 30? and disconnected the vacuum, advance, as this at least covered up the problem before.

This time? it made it worse of course.:dunno:



So, that bring the tale up to last week. This last Tuesday, I rented a compression tester and started testing the engine. The results were as follows:
Code:
[U]Cyl #     |   Pressure (PSI)
   1      |      105        
 [B]  2[/B]      |      [B]5          [/B]
 [B]  3 [/B]     |      [B]35         [/B]
   4      |      105        
   5      |      115        
   6      |      115        
   7      |      100        
   8      |      115        [/U]


Keeping in mind that on the SBF, the cylinders are counted as follows:



I put some oil into cylinders 2 and 3, and compression only increased perhaps 2 or 3 psi, not enough to indicate a failed ring or scored cylinder wall in my opinion.

This morning, I pulled my passenger side valve cover, and then all the offending rocker arms (one at a time) and inspected things.

I found no issues, and there is perhaps a .030" variance between the closed valve heights (measuring from spring cap to spring seat)

That is a small enough variance for me to attribute to inaccuracies in measurement methodology or differences in the cut of the valve seat.

My current popular theory is a fractured or cracked valve, which is closed and mostly sealed up on a cold engine, and opens as things get hot, but I am not sure this theory adequately explains the intermittent-ness of the problem, nor the fact that it happens at different RPM's, and adjusting the ignition timing also effects it.


Another issue I take with this whole damn thing is how can an engine with so obviously low compression on two cylinders run so smooth? My old engine in this car had little to no compression in two cylinders too, and that thing ran obviously rough.

I'm baffled, and while I really, really would like an explanation that does not require me to disassemble the entire damned engine, it's looking like that might be the next step.

Maybe I'll have to accelerate my head upgrade that I was planning on doing in a few years...
 

73GMCSprint

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Where the compression is low on 2 adjacent cylinders, I would think you need to rule out a head gasket problem.
 
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