The car runs fine when driven normal. But when i get on it, it seems to cut out everytime @4800-5200rpm in every gear. Sounds like i have a standard and can't shift. I have MSD Dizzy, MSD Coil, MSD Digital 6, MSD wires, and champion plugs. I have replaced the ECM, TPS......and tried running the car with the MAF unplugged....still same problem. I have also replaced the control module in the msd dizzy with another i have laying around. Any help or suggestions to try would be greatful. THANKS

 

also i have unhooked the msd and just ran the stock hei and still had the same problem.

 

just drove it around with the "brown" wire disconnected, and the car seems to drive "decent" til 4000rpm where the motor and timing just seem complete crap and poppy. The timing with the "brown" wire disconnected is advanced to 10-11* I'm running a 355 with a stealth ram and 30lb injectors. heads are Edelbrock Vic Jr's fully cnc-ed and my cam is an edelbrock with .575 and .585 lift and 234 / 238 duration. I don't know if this info is nessecary, but if it helps at all u have it ...... HELP PLEASE.....

 

5000rpm is normal for an L98 to start to choke. It can't breathe.

 

Are you running a stock chip or a custom one. If custom, the rev limiter can be set in the chip (it's about 10K RPM by default).

If it's a stock chip, there's no way it's gonna run that engine and intake combo, you need a custom chip for that setup.

 

 

Hey Vern its Aaron from NTTGA....lol.... Its a custom chip. it ran in the car for almost a month right. This is the reving problem that I have had for a while now and can't figure it out. As for the motor......its fully built. If you need specs....just ask

 

TTT

 

have you checked it for running lean? if the fuel pressure is dropping that can certainly cause the same issue.

 

yes i have a scanner and it all seems fine...thats the wierd thing.....what next? what do i need to look for?

 

What you describe sounds like the valves are floating. That is a pretty agressive cam, might need better valve springs.

 

You wouldn't happen to have the MSD-6AL box would you?

if you do that box has a rev limiter built into it, they call it a "soft touch rev-control"

 

its nothing caused by the mechanical part of the motor. Its in the electronics somewhere......sensor of some sort......and i have the MSD Digital 6....and the rev limiter is turned off.....like i said before i ran my stock hei stuff and get the same problem

 

Aaron, this is Pantera61 from NTTGA. What program are you using to scan the car? Maybe someone on here can take a look at the final scans with you incase you have overlooked something.

It sounds like the ignition system to me. Do you have another coil that you can throw on there?

 

Personally, I have never had good experiences with champion plugs. In fact, if I get a car in for a performance problem, and it has Champion plugs, the first thing I do is replace them. Fully 80% of the time, this solves the problem.

Your results may vary.......

 

Hi, Aaron! I knew it was you, recognized the name.

There are only 2 rev limiters available - one in your MSD box, and one in the prom (fuel cutoff RPM, normally set about 10k RPM by default). So if it's neither of those, then it has to either be fuel restricted, ignition, or the runners/plenum. Since the car ran right for a month, then I doubt it's the air restriction possibility.

Has anything at all been changed since it "ran right"?

The scanners don't tell you if your fuel pressure is low (bad FPR, pump, or filter). However, they should show the O2 voltages and BLM's. How are those looking at WOT and 4500+ RPM? Injector duty cycle can indicate a problem there as well.

If not there, then it would probably be an ignition problem. Daniel suggested a new coil, and that's where I would start if the fuel stuff looks good. Coils are notorious for going bad, especially with a hotter ignition box installed. And MSD coils are very well known for their short lived benefits. I've got one right now that's about 8 months old. That's some kind of record for me. MSD boxes are also real hard on ignition modules in the dizzy. They can act really strange like this when they start to fail as well. I'd also check for carbon tracking in the dizzy cap and for slop/play in the dizzy shaft.

But my first guess is either the coil or ignition module since it ran okay for a while. Both can get weak enough they can't cycle or fire quick enough at higher RPM levels.

But I still think you're also gonna be air flow restricted with LTRs at 4800 RPM..... JMO though.

Like Daniel said, need to see some datalogs to be able to help much. What did you use to data log? I've got DM and TP, you can email me your log file and I'll see if I can see anything obvious in it. Just let me know when you're about to send it so I can make sure it gets through our firewall/virus scanning stuff. Otherwise I might not even know you sent it if it gets blocked.

Good Luck, and let us know how you progress on this one!

- Vern

 

well.... i did swap out coils and that wasn't it. I also tried swapping the ignition module from another dizzy that i used before. I guess i could try a brand new module. I haven't had any successful scanner programs for the laptop. I gues the parts i have don't work????? I have just been scaning with an EZ - Scan tool. I will try getting my scan stuff to work and see if i can send a file........any other sugestions?

 

Only other idea was to tape a fuel pressure guage to the windshield and see what it does when you hit the high RPM problem.

AS far as scanning goes, you have the laptop. TunerPro is free, so all you need is a data cable. Try www.moates.net if nothing else.

 

Since you already changed the coil out, I would then suggest checking all of the fuel system. Starting with a new filter and check the fuel pressure.

Are you losing any power or stummbling after 4800rpm? What about heat, are you building a lot of heat after WOT or in the upper RPMs?

Does the pump prime when you first turn on the key? If so, does it sound sick? My fp sick and lasted about 8 months and just wouldn't die, but it would lean out really bad after 4500rpm, which could be the same as yours.

Vern mentioned TunerPro, I will back it up since that is what I use. It was one of the only scanner tools that I could get to work. The other was Ease, but you have to purchase their cable and software and that is about $300.

 

do u know if there is anybody in the area (close to arlington where i live ) That might already have a cable. I bought one online and can't get it to work. It detects the aldl but not the pcm...??? i have no clue......

 

Well, Phil lives in Arlington, but I don't know if you can borrow his. Send a pm to zghost on NTTGA.net.

Let me know if what he says, I might be able to lend you my AutoProm while I'm out of town, but I will have to get it as soon as I get back in town to finish tuning mine.