I've been chasing one problem after another trying to get my T.A. to run in time for Super Chevy this weekend in Ennis, TX. It seems like most issues have been resolved with the exception of one. Yesterday, Paul(from BP Racing) and I took the car out to try and tune a little bit after the installation of the BAP. We logged the first pass without it and it started to break up at about 4,800 rpm. To the best of my recollection the log showed an AFR of about 13:1 and IDC at about 76%(7-9 lbs/boost and on 103 VP). Detonation? I didn't think so. The temp was at 225*, though. My fans aren't coming on. It's a relay or ground problem that's being resolved today. Anyway, we logged another with the BAP at full on and it still started to break up(or pop) at about 4,950 rpm. This time the IDC was down to 72% and AFR was like 9.9:1.

So, I start tearing the car apart in my head, trying to think of what I've replaced and what I haven't, and I've replaced the opti, and added a new MSD 6A box but never changed the "COIL." Could it be? Well, I call MSD to find out what coil they recommend for a 1997 LT1 and what problems they know of with stock coils, etc. He recommended the Blaster HVC coil and then the conversation goes like this:

Him: How did you route the WHITE wire from the box.
Me: I don't remember, wait, I bought the harness with it so it was plug and play.
Him: Is the WHITE wire bundled with the rest of the wires, in other words, did you tie it all together to make it look nice.
Me: Yeah, probably.
Him: The WHITE wire is prone to EMI and will usually cause problems right at the RPM you are describing. It must be 3 to 4 inches from the orange/black wire.
Me: No shiot?
Him: I would check that first before you go buy another coil.

Have you guys experienced anything like this? Another thing is that the guy who was programming it before had the timing set at 30* up to about 5,000 and then slowly brought it down. We changed it to 28* at 4,800(i think) and brought it down from there. THAT run netted the same breaking up but at 4,500 RPM. Any thoughts?

 

I have the same damn problem at 5800 and i stumped. Like you said i fix one thing, buy another, and boom somthing else goes or needs upgraded. First i thought i was maxen MAF, but i gues since i have a 94 this is not a problem. Fuel is fine, opti new, dew mod new, and again as you i did not change coil. Im so stumped dont know what to do. I think im going to go to the dyno and see if they can help. From the readings i get from scnamaster everthing looks fine. This is the first time i have no idea what to do or try, and once again the car sits.. .. I thinking its ignition also but lots of other people have the same setup as i do with no problems. The car just dies at 5800 or so, and i have only let it do this twice or so, im scared to blow somthing.

 

What makes a 94 car unable to flow enough air to max the MAF??? That doesn't make sence

 

you say the first pass it was breaking up around 4800rpm and the a/f was 13:1 (too lean imo even for 103)

then the next time it was breaking up @ 9.9:1 a/r (too rich)

^^^either condition can cause ignition issues, both being lean and being rich

Try finding that sweet spot that most boost motors run well in 11.0:1-12.5:1 and see if it keeps doing it.

What are your plug gaps?

Fix the fan operation before you break a piston

 

I have the same type of problem too my dyno chart looks crazy up-down up -down i was told be the shop it was my accel 300 plus ignition box, so right now my car is running on the stock system boy thats fun , the spark keeps geting blown out when i get on the gas.He told me it will be correct when i bring it back in 2 weeks to put the new accel in i still made 380 rwhp with the stock ign, im hoping to cross the 400 mark so let me know what you guys find out..

Oh yeah my A/F at wide open throttle is 12.1 to 12.2 crusing around town its 14.7.

 

It seems to be the coil. The "harness" that I bought along with the MSD box runs the WHITE wire alongside the ORANGE/BLACK wire so Electro Magnetic Interference seems to be the problem(so why sell something that is designed FLAWED?). After hard wiring the box to the coil and separating the WHITE wire from everything else, Paul managed to get the car to pull to 5,500 RPMs before breaking up again. YEEHAA!! Progress!

Tomorrow I'm going to go purchase an MSD Blaster HVC coil(part# 8252) and hope that this will get us to the 6k RPM mark that I need to be at. The stock coil puts out approximately 140-160 mA. This one puts out 300 mA. Sooooo................

1) If you are having issues with RPM misses and you run an MSD box, check to see that the WHITE wire is 3 to 4 inches from any other wire, especially the ORANGE/BLACK wire.

2) Replace the stock coil if you're still running it.............although I should probably reserve judgement until I test the car with the new one. I'll post those results tomorrow night or Wednesday.

Here's my car at a glance:

1997 Pontiac Trans Am LT1
383 ci
CC305 cam
1.6 Crane Gold RRs
Racetronix single intank 340 series fuel pump
Kenne Bell Boost-A-pump (newest edition and it WORKS!)
72 lb injectors
Custom fuel rails
ATI twin-intercooled D1SC Procharger at 15+ lbs/boost
Midwest TC (being installed tomorrow along with shift kit)
F.A.S.T. (this is the shiznit)
bunch of other stuff.....................
8.5 inch slicks..............probably not going to be enough...........

 

By no means do i believe it, yet anyway! Just what i was told! Im at total battle with ECM and learning how it all works. I only know the basics , and thats from my brother, Injuneers, and 10seczs write ups. Im sure if i was as advanced as many of the members it would be no problem. Just gathering all the info i can before i buy lt1-edit/CAT. Its all a learning exp and ill take it one day at a time as i have for the past 1.5years. At this time i should get a dyno and get the pcm programed again with the new data. Right now the car sits for a bit, till i cool down. I just cant drive it unless i can pound it . As i said above not risking damage to do so either!

 

AMEN! I believe we departed from the same boat dock. If I had HALF the knowledge of some of these guys, I'd have at least 8 grand in "let's upgrade" monies. Unfortunately, I run blind and don't know when to quit getting up after I've fallen. I've had more fun/heartache with this car than one heart can stand but I love it and for me it's worth the trouble/uncontrollable laughter.

I dream of the day I can post impressive track times and not be embarrassed of having the SLOWEST blown/stroked TA on the planet.

This weekend should net me AT LEAST the SECOND slowest blown/stroked TA on the planet.

 

BAP as in Boost-A-Pump?
If so NEVER turn it above 16 Volts! Any more than that will cause a Walbro pump to start cavitating which will aerate the fuel.

Jack
Racetronix

 

Oops. That doesn't sound good. Anyone care to explain to me what "cavitation" means in lamen's terms?

 

Layman's terms:

The gears start rotating so quickly they beat air into the fuel mixture. This puts air bubbles in the fuel lines and the injectors try to squirt fuel but have to pass the bubbles as well. Not good as you can imagine. (sort of like sucking soda through a straw when you get to the bottom of the glass ... you get some soda but also get some air mixed in.) This could also happen if you run too low a fuel level in the car. During hard acceleration the fuel may move away from the fuel pick-up inside the tank and cause cavitation (starve the fuel pump of fuel) and send bubbles down the fuel line.

Not good for fuel systems and also not good for oil pump systems if your oil level get too low or you turn long hard corners such as during road racing.

Later ... Larry S.

 

Well, a couple of rings let go. 15+ lbs/boost, 103 octane, and 10:1 compression do not a happy motor make. Lesson learned. so much for "proving" to you guys that I could do what you told me I couldn't. Next combo will be more well thought out. Thanks for the info. You guys in this forum have taught me more than I could ever thank you for.........not that I always listened.