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Author Topic: 1993 Cobra... Popping/misfiring intermittently  (Read 29596 times)
kilby91
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« Reply #15 on: August 12, 2015, 10:03:11 am »

Did a compression test last night, with a borrowed Snap-On compression tester. I did the test with a cold engine, all plugs removed, battery charger hooked up to battery, fuel injectors unplugged, with throttle blade open.

All cylinders were in between 120-125 PSI...

I know that's low, and that I should have done the test on a warm engine... Since this engine was built for boost and is 8.5:1 compression and has a cam setup for turbo, I guess that low cranking compression would be expected.. Right??

Once I get this missing problem figured out, I will start gathering parts for a blower install... I would like to get it running as efficiently as I can like it sits though.

Thanks,

Richard
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kilby91
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« Reply #16 on: August 13, 2015, 04:33:03 pm »

While doing some rear end suspension swapping around yesterday, I dropped the fuel tank to see exactly what is going on back there.. Looks to be a pretty solid fuel system. Its got an aftermarket fuel pickup with AN fittings and braided lines to a Professional Products 225LPH external pump with a Russell check valve, and a Russell fuel filter in line, and large braided line all the way to the rail.

This really doesn't have much to do with my missing problem, just wanted to update for anyone who might be wondering about the fuel setup.. Not sure why it wont hold fuel pressure with pump off?? But, no big deal I guess... 
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Joel5.0
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« Reply #17 on: August 16, 2015, 09:52:43 am »

FPP bleed-off is usually caused by the FPR or the FP design of the check-valve. As long as it primes correctly and pressure is within spec KOER, no problems should be present.

That cranking compression readings are too low and might be in the Quote-Unquote "threshold" area for intermittent misfires to show. Anyway, have you tried doing a couple of test-drives with the distributor locked (28°-30°) and SPOUT plug removed? Since cylinders 7 & 8 are the ones showing in the cylinder balance test, make sure you route the spark plug wires as shown/explained at http://sbftech.com/index.php/topic,4596.0.html. LUK
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ACRONYMS:
LUK  LMK  JIC  BTSTDTRT  YCYDYP  NFI-YTM  SPOBI, and the classic... DILLIGAS

'86 Mustang GT, X-303 cam, Holley DP 700, RG Tran., 289 Heads   Ford Smilie 2


Quote from: Joel5.0
The right to be stupid is inalienable for sure however, there is no such thing as a right to impose stupidity onto others
Great Thoughts will Overwhelm a Feeble Mind
There is never money to do it right, but there's always money to do it over.
Knowledge based on external evidence is unreliable.
He, who doesn't ask, does not deserve an answer.
A mind is like a parachute it only works when it is open.  (oldmanjoe)
If you can't explain it simply, you don't understand it well enough. (Albert Einstein)
Tuning on a Dyno for the track, is like swim practice in a bathtub.
I can explain it for you, but I can't understand it for you. (90lxcoupe)
The proof of understanding is the ability to explain it. (H. Torruella)
Ignorance is bliss, but stupidity is orgasmic.
Fraud and falsehood only dread examination. Truth invites it. (Samuel Johnson)
The chaotic resistance of the opponents leads to the conclusion that they are not prepared to meet the challenge. The problem is already much more psychological then technological. [Bojidar Djordjev]
Individuals are rational and humane... Crowds are reactionary and barbaric. (Jason)
The person who says it cannot be done should not interrupt the person doing it. –Chinese Proverb
Nothing sways the stupid more than arguments they can't understand - Cardinal de Retz
kilby91
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« Reply #18 on: August 19, 2015, 11:18:27 am »

Well, this car sure is confusing.....

I changed back to the stock distributor, instead of the Richporter unit that I bought.. I think I might have had the richporter a tooth off. With the stock one back in place it has ran great in the last 50 miles while I was testing it..

I know that being a tooth off hasn't been my problem the entire time, cause I have had the dizzy in and out probably 10 times and i normally don't make stupid mistakes like that..  But, for now its running good again...

Strange!!!
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kilby91
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« Reply #19 on: August 19, 2015, 02:09:13 pm »

https://www.youtube.com/watch?v=uw3MLSmW2UA


Short clip of the car running in the carport...
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thunderjet302
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« Reply #20 on: August 19, 2015, 03:26:10 pm »

I have heard (and experienced) aftermarket TFI and PIP components being garbage compared to the Motorcraft equivalent. I'm not surprised it runs better with the stock distributor.....
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1988 Thunderbird LX: 306, Edelbrock Performer heads, Comp Magnum 266HR cam, Edelbrock Performer RPM intake, Edelbrock 70mm TB, 80mm PMAS slot MAF, 30lb injectors, FMS stainless shorties, 2.5" exhaust, AOD with 2800 PI converter, 8.8 with 3.73 gears, 31 spline Traction-Lok, 31 spline Moser axles, subframes.
2011 Focus SE, 2012 Mustang 3.7, 2017 Honda Accord EX-L V6
kilby91
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« Reply #21 on: August 19, 2015, 03:37:59 pm »

I agree.. But in my case it was running bad in the first place, that's why I bought the other distributor!
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thunderjet302
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« Reply #22 on: August 19, 2015, 04:43:53 pm »

Ghost in the electrical system?  Huh?
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1988 Thunderbird LX: 306, Edelbrock Performer heads, Comp Magnum 266HR cam, Edelbrock Performer RPM intake, Edelbrock 70mm TB, 80mm PMAS slot MAF, 30lb injectors, FMS stainless shorties, 2.5" exhaust, AOD with 2800 PI converter, 8.8 with 3.73 gears, 31 spline Traction-Lok, 31 spline Moser axles, subframes.
2011 Focus SE, 2012 Mustang 3.7, 2017 Honda Accord EX-L V6
Joel5.0
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« Reply #23 on: August 30, 2015, 10:40:33 am »

I agree.. But in my case it was running bad in the first place, that's why I bought the other distributor!

Looks like you had the symptom caused by two items. When you installed the new distributor and fixed the original cause, the new distributor took over as the new cause. .... it happens, BTSTDTRT.
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ACRONYMS:
LUK  LMK  JIC  BTSTDTRT  YCYDYP  NFI-YTM  SPOBI, and the classic... DILLIGAS

'86 Mustang GT, X-303 cam, Holley DP 700, RG Tran., 289 Heads   Ford Smilie 2


Quote from: Joel5.0
The right to be stupid is inalienable for sure however, there is no such thing as a right to impose stupidity onto others
Great Thoughts will Overwhelm a Feeble Mind
There is never money to do it right, but there's always money to do it over.
Knowledge based on external evidence is unreliable.
He, who doesn't ask, does not deserve an answer.
A mind is like a parachute it only works when it is open.  (oldmanjoe)
If you can't explain it simply, you don't understand it well enough. (Albert Einstein)
Tuning on a Dyno for the track, is like swim practice in a bathtub.
I can explain it for you, but I can't understand it for you. (90lxcoupe)
The proof of understanding is the ability to explain it. (H. Torruella)
Ignorance is bliss, but stupidity is orgasmic.
Fraud and falsehood only dread examination. Truth invites it. (Samuel Johnson)
The chaotic resistance of the opponents leads to the conclusion that they are not prepared to meet the challenge. The problem is already much more psychological then technological. [Bojidar Djordjev]
Individuals are rational and humane... Crowds are reactionary and barbaric. (Jason)
The person who says it cannot be done should not interrupt the person doing it. –Chinese Proverb
Nothing sways the stupid more than arguments they can't understand - Cardinal de Retz
kilby91
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« Reply #24 on: October 20, 2015, 10:02:38 am »

Haven't driven this car much in the last couple months, but got it out yesterday and drove it around.. It still does the exact same thing...

It is great to drive and runs great, except for the low RPM miss and the stuttering under WOT... Im at a loss.... Asking Asking
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Joel5.0
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« Reply #25 on: October 20, 2015, 11:43:36 am »

Suggestions if you can:
1. Take a clip of the car running with the symptoms and the camera aimed at the tachometer.

2. Remove SPOUT, set timing to 28° - 30° BTDC, leave SPOUT off and run the car taking another video clip.

LUK
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ACRONYMS:
LUK  LMK  JIC  BTSTDTRT  YCYDYP  NFI-YTM  SPOBI, and the classic... DILLIGAS

'86 Mustang GT, X-303 cam, Holley DP 700, RG Tran., 289 Heads   Ford Smilie 2


Quote from: Joel5.0
The right to be stupid is inalienable for sure however, there is no such thing as a right to impose stupidity onto others
Great Thoughts will Overwhelm a Feeble Mind
There is never money to do it right, but there's always money to do it over.
Knowledge based on external evidence is unreliable.
He, who doesn't ask, does not deserve an answer.
A mind is like a parachute it only works when it is open.  (oldmanjoe)
If you can't explain it simply, you don't understand it well enough. (Albert Einstein)
Tuning on a Dyno for the track, is like swim practice in a bathtub.
I can explain it for you, but I can't understand it for you. (90lxcoupe)
The proof of understanding is the ability to explain it. (H. Torruella)
Ignorance is bliss, but stupidity is orgasmic.
Fraud and falsehood only dread examination. Truth invites it. (Samuel Johnson)
The chaotic resistance of the opponents leads to the conclusion that they are not prepared to meet the challenge. The problem is already much more psychological then technological. [Bojidar Djordjev]
Individuals are rational and humane... Crowds are reactionary and barbaric. (Jason)
The person who says it cannot be done should not interrupt the person doing it. –Chinese Proverb
Nothing sways the stupid more than arguments they can't understand - Cardinal de Retz
kilby91
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« Reply #26 on: October 20, 2015, 11:56:28 am »

Thanks for the reply.... I will do my best to get a video as soon as I can...

I haven't noticed anything funny with the tach while the miss/stutter is happening, but haven't really focused on it either...

One strange thing the car did yesterday:

It was the 1st time I have cranked the car in almost 2 months... Cranked great, idled great, ran great... Then about 20 minutes into my drive while sitting at a red light, the  car develops a hard miss... Like hitting on 7 cylinders miss... I creeped up the road to a parking lot, and popped the hood to check for a loose plug wire or injector. Didn't find anything loose, but when I fired the car up again the hard miss was gone, but the pesky on going stutter that I have always had returned??? It was weird and im not even sure if they were related, but that is how it happened... Its got to be something small/stupid because the car runs great in every other aspect... DRIVING ME CRAZY!!!
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kilby91
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« Reply #27 on: October 21, 2015, 09:05:16 am »

That video link should be a quick video I made yesterday of the car. The video starts in 2nd gear, then I hit 3rd for just a second, then shift to 4th and roll into the throttle. It breaks up so bad around 3,500 rpm that the camera starts to shake. You can hear it through the exhaust as well.

https://www.youtube.com/watch?v=blD09xfi3_4


This video is a second gear pull as well. You can hear it stutter a couple times right around 5,000 rpm..

https://www.youtube.com/watch?v=Rsj5Pg4XZC0
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kilby91
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« Reply #28 on: October 21, 2015, 01:53:24 pm »

When I get home today, I will remove the SPOUT and try again..


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kilby91
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« Reply #29 on: October 22, 2015, 06:47:28 pm »

Didn't get a video, but it runs substantially worse with the SPOUT removed and timing locked at 28*... The tach didn't act any different than it did in the videos above. With the timing locked at 28* it missed all through the RPM range and sometimes felt like a hard miss... I didn't run it long, maybe 10 minutes around some back roads.. 
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