High RPM breakup

Hey guys I have a problem that I never really noticed untill after I put the blower on my car. It seems like an ignition problem to me, but I don't know what to do.

Some details from after the blower install, and while tuning:

Opti had 35,xxx on it
Crane HI-6
Crane LX92 coil
new Taylor wires
new NGK TR6 plugs (checked the tips, all tight)
stock MAF (screen still in it)
LPE/Accel 58mm TB

Here is a dyno graph from then:
http://performin.homeip.net/images/hosting/joshdyno.bmp

Since I thought it was the Opti going south, I replaced a few items:

NEW GM opti (from a dealership)
New (again) TR6 plugs (checked the tips, all tight)
New (used) engine wiring harness (changed for other reasons)
New Bosch O2 sensors
Edelbrock 58mm TB.

The car is still acting EXACTLY like it was before.

BUT

A shop here in town recently had this exact problem with a heads/cam 97SS. Our dyno graphs looked almost exactly alike after 4500 rpm.

Some things about that car:

New opti
stock ignition
tried new coil, and ignition module
added Delteq-NO CHANGE
traced all the engine grounds-all checked out good.


Have any of you experienced this? What else should be checked?

Any and all help is greatly appreciated!!!!

Thanks,

Oh, and the car is not setting ANY codes.

My sheet from last night looks just like that. I'm gonna try replacing the coil and plugs with a smaller gap.

My sheet from last night looks just like that. I'm gonna try replacing the coil and plugs with a smaller gap.

Let me know how it turns out....how soon you going to do this?

Tonight - not sure when i'll dyno it again tho - maybe on Friday

Here's a pic of mine - I think i'm worse off than you tho

http://www.cardomain.com/ride/252001/7

Here's a pic of mine - I think i'm worse off than you tho

http://www.cardomain.com/ride/252001/7

WOW! Your's is really bad...it doesn't seem like yours is the same problem as mine...

Yours also starts out low, then jumps up drastically. Mine is gradually going up, then goes erratic.

Do you have a way to scan the pcm during the dyno run? Check for knock. What do you have the spark plugs gapped at? If the gap is too big, you're blowing out the spark. I would try to lean out that air/fuel ratio as well. :)

Now that's a dyno graph. (http://www.flp2win.com/cart/templates/featured/mitchscar/mitchsdyno.jpg)

Do you have a way to scan the pcm during the dyno run? Check for knock. What do you have the spark plugs gapped at? If the gap is too big, you're blowing out the spark. I would try to lean out that air/fuel ratio as well. :)

Now that's a dyno graph. (http://www.flp2win.com/cart/templates/featured/mitchscar/mitchsdyno.jpg)

I would agree...hopefully I will have a graph that goes that high in the near future! But in the meantime:

I have Autotap, and there is 0 knock retard...we have 17-18 degrees in it at WOT. The plugs are gapped at 0.035".

I envy you and your car, BADST95!!

I would agree...hopefully I will have a graph that goes that high in the near future! But in the meantime:

I have Autotap, and there is 0 knock retard...we have 17-18 degrees in it at WOT. The plugs are gapped at 0.035".

I envy you and your car, BADST95!!


Thanks for the kind words! It's not cheap to make that kind of graph. :)

Is your car a stick or an automatic?

Thanks for the kind words! It's not cheap to make that kind of graph. :)

Is your car a stick or an automatic?

No problem man! :)

My car is a 6-speed.

No problem man! :)

My car is a 6-speed.

I almost wonder if the clutch is slipping... that might possibly create a "spikey" graph.

I almost wonder if the clutch is slipping... that might possibly create a "spikey" graph.

I would consider that, but I know that that's not it...I've had clutch problems in the past (or so I thought), and it turned out to be just tire slip on the rollers. I have a new Stage III in it, and MT Drag Radials on it now, and there is no sign of slippage (even put 2 people in the trunk for one pull-no change). You can even feel it on the street at moderate throttle, no boost, where the tires are spinning.

I would consider that, but I know that that's not it...I've had clutch problems in the past (or so I thought), and it turned out to be just tire slip on the rollers. I have a new Stage III in it, and MT Drag Radials on it now, and there is no sign of slippage (even put 2 people in the trunk for one pull-no change). You can even feel it on the street at moderate throttle, no boost, where the tires are spinning.

Spec? Is the clutch broken in? Did you put 500 miles on the clutch before putting it on the dyno? Your car is not going to spin the tires on the dyno. If the car is properly strapped down, it's not going to slip. My car didn't spin the tires on the dyno. :)

I fixed my high rpm break up by swaping out my MSD coil for a stock one and replacing my ignition module with a AC Delco replacement.

Spec? Is the clutch broken in? Did you put 500 miles on the clutch before putting it on the dyno? Your car is not going to spin the tires on the dyno. If the car is properly strapped down, it's not going to slip. My car didn't spin the tires on the dyno. :)

Well, oddly enough, it was spinning the tires on the dyno. That's why I thought it was the clutch originally. I put the SPEC in it, put 650 miles on it, and strapped it down, and did the same thing...then we put 2 people in the trunk, and it actually made power! :mad: I was running some worn out Bridgestone Potenza street tires, so I guess that's what did it. Put some ET Streets on it and didn't have a problem after that, just the miss.

While on the dyno you can feel the hesitation and bucking, so I wouldn't think it's tire or clutch slippage.

Well, oddly enough, it was spinning the tires on the dyno. That's why I thought it was the clutch originally. I put the SPEC in it, put 650 miles on it, and strapped it down, and did the same thing...then we put 2 people in the trunk, and it actually made power! :mad: I was running some worn out Bridgestone Potenza street tires, so I guess that's what did it. Put some ET Streets on it and didn't have a problem after that, just the miss.

While on the dyno you can feel the hesitation and bucking, so I wouldn't think it's tire or clutch slippage.

Hmmm... how do you expect me to help when you keep giving contradicting my ideas? ;) Maybe that Crane box is bad??? :)

Hmmm... how do you expect me to help when you keep giving contradicting my ideas? ;) Maybe that Crane box is bad??? :)

:D Sorry! There's just so much info that I have that I couldn't put into one post, or it would be a mile long! ;)

I was thinking of the box, so I'm going to try putting a stock coil back on it, and bypass the box and coil. See what that does. I'm also going to replace the opti extension harness, to see what that does.

I have seen those Crane boxes take a dump before. Maybe that's the problem. I'd switch it back to stock to double check.

Well guys, I found my problem! It was the vacuum line going from the intake to the fuel pressure regulator! It had been pinched at one time, and had a hole in it. Replaced it, and wala! Went to the track yesterday, and had 0 problems! Ran a new best also, times in sig!! :D

Just wanted to let those that had subscribed to this thread what I found! :cool: