Need help with this engine problem...lol

Zack

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Need help with this engine problem...I THINK I FOUND THE PROBLEM!!!

My beater breaks up under load...especially when its hot out.
Just swapped new coils in, engine has 20in of vacuum, tps ramps up voltage just fine and the fuel pump maintains 40psi under all conditions.
No visible wiring harness problems, new plugs and squeaky clean maf.
I even took the egr out of the equation and that didn't help.
Im stumped!

I've had a bad FRPS before but not symptoms like this.
The car idles smooth as glass but sometimes sounds like it has a dead cylinder when cranking.
 
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Silverback

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Please define "breaking up"? Misfire, back fire, "snap crackle pop".

Define under load? WOT, going up a hill, passing another car, what RPM range?

Perhaps a fouled injector(s) or poorly responding one.

BTW, my car seems to have a noticeable improvement in city MPG since you repaired the engine.

Regards,
 

Flyn

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I checked around the web and saw answers ranging from Battery failing, fuel filter, timing, over rich fuel delivery or timing chain. No idea if any of these are applicable Zack, just throwing them out.
 

massacre

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When you say "beater" I'm lost lol.

With you it could be several vehicles...
 

justbob

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Curious, is the ALT putting out good numbers? Battery load tested? Bad IAT sensor in the MAF? (Stock??)

Mine had the exact same intermittent issues and it was a combination of weak COP's and a fuel pump on its way out slowwwwwly.

Not sure of your set up on this car?
 

Zack

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Its got 4:10's and a tune. I logged FP and it held steady.
New fuel filter.
New COP's
Its acting like my Cobra did on the dyno when it had low battery voltage....brand new battery and volts are 13.5+
I want to swap the MAF but wouldn't you know it...im fresh out of spares
 

Zack

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Did a compression test:
All cylinders are around 180psi with the exception of #6 at 150psi.
Checked it again and it was 145.

I know its not the shortblock because this was in a different car running fine.
I had the heads done when I swapped it in this car.


Im HOPING its a valve spring thats the problem. I also put a stethescope on the drivers cams cover and there is definitely a noise thats not normal.
Ill pop the cam cover tomorrow and report back.
Maybe Ill get really lucky and find a follower that popped off and got lodged in the spring.
 

scca_stang

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could be a collapsed "lifter" or poor oil supply to a "lifter"(I know mod motor guys call them something else, but I am sure you know what I am talking about)
 

Zack

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Air escaping past the exhaust valve in #6.
Fuck my life.
Its gonna suck doing this job with no profit!!!
 

Zack

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Cylinder head is off but nothing visibly wrong...wtf.

I know im not crazy.
Lack of compression and air blowing out the exhaust pipe when the hole is compressed with air.
Ill let the machine shop.figure this one out.
 

massacre

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Sorry to hear Zack, hope it an easy (cheap) fix.
 

hellraiser319

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Sucks, hopefully its an easy fix... engines though, you may not see it, but a couple thousandths are a mile... I'm curious to see what the verdict is though.
 

Zack

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Nothing wrong with the head.
The more I study the piston in #6 and #7...it appears as though there was never a good seal between the two. The areas at the top are clean like a bit of coolant washed them off...maybe hole to hole leak as well....which would explain why I heard it out the exhaust because #7 exhaust valves were open when I pressurized #6.

Only on my car...lol
 

Silverback

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Does this mean a faulty head gasket, a warped head or head bolt torque no longer uniform or tight enough.

I think you saw that on Mark's car a few months back.
 

Zack

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Does this mean a faulty head gasket, a warped head or head bolt torque no longer uniform or tight enough.

I think you saw that on Mark's car a few months back.
Yes I did.
Dont have a clue what happened....gasket didnt show any signs of leaking.

The only thing I did different (i think) is coat the bolts liberally with 30w oil.
Normally I just throw them in and tighten.
 

Zack

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Just got in from putting it back together.
Ill test drive it in the morning, but I already know it runs much smoother than before.
 

Zack

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Got to drive the car and nothing has been fixed.

Its too damn hot out to give a fuck right now.
 

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