Wierd Shudder - CEG Archives

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All was fine last evening and this morning I put back on my Strut Bar and started the car up. It had a wierd shudder or miss or hesitation at about 2k rpm's. It feels like a vacuum leak or a spark being blown out. I also threw a CEL. It will build boost but it doesn't act like it want so hold it. I have NGK TR6's with .035 gap. I looked for about a half an hour for the leak, to no avail. I am going to Street Flight tomorrow to use the OBD2 scanner. I am planning to get a new/upgraded Blow-Off (Bypass) valve tomorrow. I have three suspicions... Let me know what you all think.
1. Vacuum Leak due to boost pressure popping seal.
2. Spark being blown out or fouled plug.
3. Bypass valve is failing (cheap-ass Bosch that is in the kit) due to boost pressure.

Important to note- this stumble happens in all RPM ranges and not nessecarily only in the boost range.

I would guess its a vacuum leak. Spark blowout usually only happens at higher RPMS, and since you said the stumble is happening in all rpms, I would eliminate that. I've had vacuum leaks, and it causes some weird stuff to happen.

Good Luck finding the problem.

I told Chris to check the POS valve since you're only hitting 7 lbs. He has a line on some custom pieces. Also, since you just put the bar back on and now it is missing, having you checked to make sure you didn't crak a plug wire or are grounding out on the coil pack on the back side of the motor since I'm assuming your bar goes right over the top of it? Always check the last thing you did when a new problem arises that wasn't there before.

Rick

I am a Super Jack-ass..

I found the problem. I had popped one of the plug wires loose from the rear bank, while putting on my strut bar. While under no load, the wire would arch and make the ignition. When under a load the plug would miss all together. Duh!

Oh well, in the process of trying to fix it, I picked up a really kick-ass Bypass Valve that is billet aluminum which caused me to pick up another LB of boost.

I still have some tuning to do, but I am heading in the right direction.

BTW- My CEL read "Error with RAM" or something like that. I assume that the Chip was not alowing the computer to diagnose the loose wire. Anyone got an idea???

Hehe, a swing and a home run for Buckshot!!! LOL

I'd try clearing the computer and seeing if you get another CEL Jason. BTW, what did you guys get for a # last night on the dyno?

Rick

Jason, did you get the RFL BOV that Chris told me about, and does it vent back into the system or to atmosphere?

We got him an upgrade for the bosch. It vents back in. The RFL bov's are all gone and I don't think we will try another one.

I've still got the vortech supplied bypass valve. Is that a bad thing? It holds 10 psi, no problem. Why is it supposed to be such a bad peice?

Just curious

I'm interested in a upgraded BOV can you tell me more info?

Why did you gap to .034 wasn't the correct supposed to be .054 that's what mine are at.

Originally posted by fst4dr:
I've still got the vortech supplied bypass valve. Is that a bad thing? It holds 10 psi, no problem. Why is it supposed to be such a bad peice?

Just curious

The bad thing is that they are so varied in the "preset" boost that they allow. Some hold 6, some 8, some 9... If your's is holding it's rated 10 psi, you have nothing to worry about until it doesn't hold that pressure any more when the spring wears out.

Kaiser can let you know more about the brand name on the Bypass Valve that I am now using. It is a quality Billit piece and feels solid. If you hold the Bosch in your hand it is like nothing at all. I pushed my finger into the valve portion and I really don't see how it reseats itself. It is a POS IMHO. I did not like the idea of having a $3000 S/C with a $.35 Bypass Valve. The new one is good for #10+. FYI- They are hella easy to change out. I have it hooked in as a Bypass not a Blow-Off. It recirculates back into the intake. I have heard good and bad about venting it back into the atmosphere. I will experiment at a later date.

The gap is smaller on the plug because the smaller the gap the harder it is to have your spark blow out. The SVT Lighning (which comes with Single Plats) is gapped at .040. This is a blown vehicle out of the box.

BTW- I did not have time to re-dyno since adding the new BOV. More later this week.

I dont think you can vent it to atmosphere, unless the new one works differently. When the car is idling (pulling full vacuum) the valve is open, so it is like having a huge vacuum leak

And yes I did experiment with it and found out the hard way

Kaiser and I are working some things out where Buckshot Motorsports might be a supplier of the new BOV's. The valve can be made to work either as a bypass or blowoff if you have a heavy enough spring to keep it closed at idle. Basically it just takes playing with to make it work as one or the other rather than to vent it back to the intake like the bosch piece. I'm planning on doing this as part of my aftercooler kit that is being engineered right now.

Rick

Sounds like a winner. Keep me informed of your progress.

BTW- Buckshot, you were right. I just figured that I would give you bragging rights on your astute diagnosis.

Thanks!

Originally posted by kinger:
Why did you gap to .034 wasn't the correct supposed to be .054 that's what mine are at.

I would not gap the plugs at the stock setting on a boosted car!

Spark blow out is a major concern.

Vortech recommends .032 or something like that. It runs great at that gap, but wears out the plugs pretty quick. You can get away with .040, which is about were I am at right now. It still runs great. .054 is way to big.

Originally posted by DemonSVT:

Originally posted by kinger:
Why did you gap to .034 wasn't the correct supposed to be .054 that's what mine are at.

I would not gap the plugs at the stock setting on a boosted car!

Spark blow out is a major concern.

My Bad guys I'm running .045 must have been dsylexic..

Originally posted by kinger:

Originally posted by DemonSVT:

Originally posted by kinger:
Why did you gap to .034 wasn't the correct supposed to be .054 that's what mine are at.

I would not gap the plugs at the stock setting on a boosted car!

Spark blow out is a major concern.

My Bad guys I'm running .045 must have been dsylexic..

We will call you "The man with the big gap". In Native American, that would be "One With Large Gap"

Originally posted by Rev. Po-Jay:

Originally posted by kinger:

Originally posted by DemonSVT:

Originally posted by kinger:
Why did you gap to .034 wasn't the correct supposed to be .054 that's what mine are at.

I would not gap the plugs at the stock setting on a boosted car!

Spark blow out is a major concern.

My Bad guys I'm running .045 must have been dsylexic..

We will call you "The man with the big gap". In Native American, that would be "One With Large Gap"

Funny I knew a girl with that nickname once. I never did figure out how she got it?!?

Doh!

There are no poles (no pun intended) in my reach, long enough to touch that one.

BTW- Once I fixed the plug wire I cleared the code. It did not come back on... Yet. I re-gap the plugs tonight. I will gap at .035... We shall see how that goes.

My boost seems very "surgey" at the top. I am thinking that I am blowing out the spark. What do you guys think?