Engine loses power around 5000RPM

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Offline GoodysGotaCuda

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Re: Engine loses power around 5000RPM
« Reply #120 on: February 10, 2008 - 07:23:29 PM »
A scope won't do you very good if you cannot read it properly. I wouldn't bet that MOST shops these days even have one without a pile of dust on it. Not saying its not a good diagnostic tool, however it is a lost art it seems unless you find a really old-school guy.

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Offline Jacksboys

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Re: Engine loses power around 5000RPM
« Reply #121 on: February 10, 2008 - 11:05:01 PM »
A scope won't do you very good if you cannot read it properly. I wouldn't bet that MOST shops these days even have one without a pile of dust on it. Not saying its not a good diagnostic tool, however it is a lost art it seems unless you find a really old-school guy.



That is what I am afraid of.   :2thumbs:
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Offline ntstlgl1970

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Re: Engine loses power around 5000RPM
« Reply #122 on: February 11, 2008 - 02:44:43 AM »
I am not sure.  It is a mechanical pump and I do not have a guage.   :dunno:
Not sure, I will have to test it at some point.  :2thumbs:
Not sure, I do not have anything hooked up to a vacuum.
Not sure,  I will have to check this also.  :2thumbs:



Also, if an O2 sensor sees a bunch of oxygen, then it would read Lean. 

Spend 5 bucks on a vacuum/fuel pressure gauge, you could eliminate about 15 possible problem sources. Buying an oscilloscope would be a complete waste of time since you don't know how to read it.
70 Cuda, 7.0L Gen-III Hemi, Viper T56 w/9310 gearset, 3.91's, Megasquirt MS3x v3.57, Innovate wideband, Firm Feel upper arms, torsion bars, springs and strut rods, QA1 DA shocks. I did everything on this car except the fancy paint stuff and I drive it...and I can't seem to stop messing with it....

Offline Moparal

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Re: Engine loses power around 5000RPM
« Reply #123 on: February 11, 2008 - 04:33:23 PM »
Are you sure your valve springs are good?  If they are week, they will not open and close quick enough and it possibly could make you think your tach is going nuts by causeing valve float.  Seems you should have found out something by now. How is your oil pressure? 

Offline Jacksboys

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Re: Engine loses power around 5000RPM
« Reply #124 on: February 13, 2008 - 03:03:02 PM »
Are you sure your valve springs are good?  If they are week, they will not open and close quick enough and it possibly could make you think your tach is going nuts by causeing valve float.  Seems you should have found out something by now. How is your oil pressure? 

Oil Pressure is great, I forget the exact psi but it does not go down at all when the rpm is up.

I know I should have figured it out buy now.  Sometimes I get a little lazy on my days off since they are few and far between right now.  :sleeping:

I do not think it would be valve float since the problem rpm changed by 1500 rpm when I changed the distributors a few months ago.  :dunno:
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Offline dodge freak 2

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Re: Engine loses power around 5000RPM
« Reply #125 on: February 13, 2008 - 11:43:49 PM »
I did not tell you to buy a scope, I thought you should find a place that has one. This way you know if its in the ignition or not.

As for nobody having one anymore, not so sure about that. I seen on E-bay a newer snap-on scope that has anti-lock brake system checks and other high tech new car stuff.

These young auto tech guy's are trained very good. Your motor would be like a price of cake from some to work on.

I can not see it costing more than $100 to get it look over by a pro.

You are going to spend that much and maybe more by guessing what it could be.

If you are hell bent on doing it yourself, then I would replace the wiring. Thats from the mopar box, that plug with the 4-5 wires-it does not have points, right? It could just be a bad wire-how old is it? That would explain the heat making it worst and getting worst with time. When you swap dist. you moved some of those wires around. They get rusty inside and you can not see the bad area. The wires are very thin too.

A new one cost like $20....heres a link for you...

http://store.summitracing.com/partdetail.asp?autofilter=1&part=DCC%2D3690152&N=700+4294925143+4294839065+400172+4294841558+115&autoview=sku

At least if you change it and its not it, it was old any how and could go bad at any time
« Last Edit: February 13, 2008 - 11:51:17 PM by dodge freak 2 »

Offline dodge freak 2

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Re: Engine loses power around 5000RPM
« Reply #126 on: February 13, 2008 - 11:54:06 PM »
And yes, remove that tach too. Thats not the best brand either.

Offline Jacksboys

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Re: Engine loses power around 5000RPM
« Reply #127 on: February 14, 2008 - 12:37:36 PM »
If you are hell bent on doing it yourself, then I would replace the wiring. Thats from the mopar box, that plug with the 4-5 wires-it does not have points, right? It could just be a bad wire-how old is it? That would explain the heat making it worst and getting worst with time. When you swap dist. you moved some of those wires around. They get rusty inside and you can not see the bad area. The wires are very thin too.

A new one cost like $20....heres a link for you...

http://store.summitracing.com/partdetail.asp?autofilter=1&part=DCC%2D3690152&N=700+4294925143+4294839065+400172+4294841558+115&autoview=sku

At least if you change it and its not it, it was old any how and could go bad at any time



The wiring is new also, so I doubt it was a rust issue, but I may consider trying another one after I go through the distributor. 

I do not see it as guessing and wasting money.  Every time I replace something and find out that it was a good part, it goes in my trunk so I have a spare if something breaks on the road.   :2thumbs:
1971 Dodge Challenger:  360/904/3.23
   
Success is the maximum utilization of the ability that you have. - Zig Ziglar

Offline dodge freak 2

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Re: Engine loses power around 5000RPM
« Reply #128 on: February 14, 2008 - 01:22:11 PM »
Well thats cause you are young. One day you look at all that stuff in the trunk and shake your head.

On to the high speed miss. Well no, if the wiring has been changed I doubt thats it.

You are stuck not knowing where abouts the problem is. If the carb main jet air bleeds are dirty-carbon, dirty, cobwebs, that too will cause the motor to break up.

I would say changed the pick up coil in the dist. but you switch dist. so they both could not be bad..highly unlikely.

Good luck, hope you find whats wrong soon....

Offline dodge freak 2

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Re: Engine loses power around 5000RPM
« Reply #129 on: February 14, 2008 - 05:41:27 PM »
You want a another wild guess-I hate guessing games-check this link out, they repair MSD spark boxes-not sure which box you have, just assumed its Mopar. They say a MSD box can limited a motors RPM to 3500-5000. Heck thats sounds like your problem, heres the link....

http://techwest.ipower.com/index.html 


The MSD ®Ignition box failures are sudden and without warning to the driver. The normal senerio is as follows; the vehicle is doing just fine, then without warning the engine is limited to 3500rpm to maybe 5600rpm. The throttle response is sluggish at best, and the engine acts as if it has just lost all of its performance.

Offline matt63

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Re: Engine loses power around 5000RPM
« Reply #130 on: February 14, 2008 - 06:44:13 PM »
You can either trouble shoot ie get it scoped or change parts (beg/borrow/steal is cheaper than buying).  I think carb, ignition, distributor, coil have already been suggested as parts to swap out first. I don't think there are any other choices here.  :)
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Offline Jacksboys

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Re: Engine loses power around 5000RPM
« Reply #131 on: February 15, 2008 - 02:30:47 AM »
Well thats cause you are young. One day you look at all that stuff in the trunk and shake your head.


 :bigsmile:   :2thumbs:


If the carb main jet air bleeds are dirty-carbon, dirty, cobwebs, that too will cause the motor to break up.


I completely cleaned out and put new gaskets in the carb about a year ago, so I would not think that would be the problem.


You want a another wild guess-I hate guessing games-check this link out, they repair MSD spark boxes-not sure which box you have, just assumed its Mopar. They say a MSD box can limited a motors RPM to 3500-5000. Heck thats sounds like your problem, heres the link....

http://techwest.ipower.com/index.html 


Sounds interesting, but I have the Mopar ECU.   :2thumbs:
1971 Dodge Challenger:  360/904/3.23
   
Success is the maximum utilization of the ability that you have. - Zig Ziglar

Offline dodge freak 2

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Re: Engine loses power around 5000RPM
« Reply #132 on: February 15, 2008 - 11:39:31 AM »
The air bleeds on the carb are towards the top. Gaskets have nothing to do with them. Stick a fine wire in each one to be sure they are not clog.


The problem with guessing is you think whats been changed can not be it. My 1 month old MSD plug wire touch the header and was miss firing only @ wide open throttle and only after 15-20 mins or more time. Turn motor off, 20 mins later ran fine till it was very warm.

Well I had a MSD 7 box, so dumb me thought the box could be going because my battery went dead a week before and I needed to jump start it. MSD tech told me that can damage the box, send the box to them.

Put my old MSD 6 box back on. Motors running great now, all the time. Even drove it for 1 hour straight.

2 weeks later my MSD 7 box comes back-no problems found!

Put box back on and the motors misfiring again!  Called MSD saying  thats its bad and was not fix. MSD told me no way, it was tested for 4 hours.

Well that did it. Only thing it could be is my 1 month old wires-I changed the cap, rotor, pick up coil because they were old.

Yep, I got my omh meter checking each wire and then I see a crack in the spark plug boot. Put a different wire on, problem solved.

What happen me and MSD thinks, is the 6 box was not strong enough to find the ground but the 7 box was.

I wasted time, money and felt like a fool yelling on MSD tech line. They did send me 2 brand new wires for free.
« Last Edit: February 15, 2008 - 11:44:25 AM by dodge freak 2 »

Offline Jacksboys

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Re: Engine loses power around 5000RPM
« Reply #133 on: March 07, 2008 - 04:30:01 AM »
I just wanted to let you know that I have been very busy lately and have not had time to mess with anything.  It was even hard for me to get on here these last few weeks.  I did take the Challenger for a ride Thursday because I had to go to the bank, so at least it still drives good at low RPM.   :2thumbs:

Hopefully I can have an update soon.
1971 Dodge Challenger:  360/904/3.23
   
Success is the maximum utilization of the ability that you have. - Zig Ziglar

Offline dodge freak 2

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Re: Engine loses power around 5000RPM
« Reply #134 on: March 07, 2008 - 01:06:19 PM »
That stinks! Don't work too hard, maybe a break from your ride would be good anyways.

I tell you, gut feeling-since it sat for a while, then drove fine at low rpm's I would bet-without looking at it-its weak valve springs.

You know about the rope in the cylinder head trick to change those springs right. New springs would cost $60-$70, thats not much and they do get weak over time so even if its not it won't be a total waste.
« Last Edit: March 07, 2008 - 01:10:18 PM by dodge freak 2 »