Street chip to race chip question?

[Boostisgood]

I am currently running a 93 oct street chip w/ 20 psi. I am experiencing serious stutter, and cutting out above 4,500 RPM's......mostly in the 1-2 shift and the 2-3 shift. It feels like im floating the valves. This will occur so i let off and then occasionally the car will run terrible under normal driving for a few seconds. Like i blew a head gasket or something! Then it will clear up and drives like a champ again. MY QUESTION IS? Could my problem be the street chip? Is my boost too high for the (street chip) injector cycle to keep up? Would a race chip possibly clear this problem up. I have had the same problem on my last 3 turbos(stock, TA-49, PT-54).....same 93 oct chip and same 20 psi. Please help me out!

 

[blackbuick87]

Your valve springs are toast.

 

[Boostisgood]

Anybody else agree? Not trying to be a jerk but i wanna make sure before i rip the succa apart! Thanks

 

[BoostKillsStres]

Is there anyone close that you could try swapping coil packs and control modules with? You can try ohming the coil towers but that only works part of the time. I found an intermittant short in one pair, sometimes perfect sometimes nothing. Might also try another set of plug wires and plugs depending on miles.

 

[blackbuick87]

Are you running the stock valve springs? If you are you will need to replace them anyways because there is no way they are going to handle the power you plan on throwing at them in the future. You said yourself it sounds like valve float. If it has been happening for a while the valve seats and valves may need to be freshened

 

[Scott231]

Originally posted by Boostisgood
I am currently running a 93 oct street chip w/ 20 psi. I am experiencing serious stutter, and cutting out above 4,500 RPM's......mostly in the 1-2 shift and the 2-3 shift. It feels like im floating the valves. This will occur so i let off and then occasionally the car will run terrible under normal driving for a few seconds. Like i blew a head gasket or something! Then it will clear up and drives like a champ again.

If it continues to run like sh*t "under normal driving [conditions] for a few seconds" then it isn't because the valves are floating at, say 2,000 rpms. That's pretty unlikely don't you think?

MY QUESTION IS? Could my problem be the street chip? Is my boost too high for the (street chip) injector cycle to keep up?

I don't know how many times I will have to state this...but here goes again. It is impossible for the chip to be the problem! when the car runs fine 99% of the time.

Would a race chip possibly clear this problem up?

Definately not.

I have had the same problem on my last 3 turbos(stock, TA-49, PT-54).....same 93 oct chip and same 20 psi.

Well, it definately isn't the turbo's fault either. Sounds more like an overworked ignition (overheating problem causing a short or break in an internal circuit). However, as blackbuick87 pointed out, if you have the original 17 year old valve springs...you NEED to change them.

 

[Boostisgood]

I had the motor gone through about 2 years ago. New LT1 valvesprings! So its not the chip.....ok. Tested the coil module.....appears to work fine. I have put brand new plugs and wires in a month ago. The valvesprings and valves are the only thing that hasnt been checked! I just figured the LT1's would last a lttle longer than 10,000 miles. Guess not!

 

[Scott231]

Ahh, but do you know if the valve springs were installed correctly? (i.e. right heigth and the same heigth for each), but that wouldn't explain your problem.

How did you check the coil? Measuring resistance simply identifies really, really dead coils. Marginal coils can only be identified by using Caspers Spark Simulator tool which allows you to test at various RPM levels.

Valve springs can easily be checked at a machine shop if it comes down to that.

 

[Night Train]

Maybe I'm missing something here, but you might be running too much boost for that turbo on pump gas and you could be getting serious knock. I didn't see you say that you were getting any, though. You do have a knock detector, right? Also, you didn't mention if your scan tool indicated a lean condition or not.

Bob

 

[Boostisgood]

No knock what so ever! I use a scanmaster. I run leaded race fuel when i run the car. The car seems to act up more when it is launched from a stop. When i ease into it it doesnt do it as bad!

 

[dthrock]

George hasnt been able to figure out what the problem is? I would think he could have found whats going on with it. If you need to try something else I have an extra ECM and directscan we can hook up and do some recordings to see whats going on. My engine is in the shop now, hope to get it back into the car this week. Sure hope I dont have these kind of problems as Im going to have close to your present setup once its finished. Give me a yell email if you need anything.

Dave