I'm having a big problem with my 0411 (24 tooth) PCM controlled LSX race engine. It started to fall off above 4000 rpm like it was going lean. I verified that fuel delivery and tune was correct. Moved on to control problems. Changed wiring harness, CPS, and MAP sensor. No help, getting worse. No codes thrown. Pulled the engine and pan to examine the reluctor wheel and CPS gap. All looks good. So now Since I have been running with low impedance injectors I am wondering if I have failed the injector drivers in the PCM. I have been running this set up foe several years with no problem. Anyone out there burn up the ECU running low impedance injectors?

 

isn't there a reason they say don't run low impedance injectors on a stock PCM?

 

Did you read this part? "I have been running this set up for several years with no problem." Yes it can be hard on the injector drivers but the 0411 is very robust. I doubt this is my problem but I'm asking for experience with this set up from this forum. Apparently you don't have any....

 

Never ran low impedance injectors on the 411, so I cannot speak from experience, but I can say 0411's are cheap and easy to come by. It may of just burned out the PCM... Stranger things have happened. I'm sure this is a possibility. You can also drop a thread over on HPT forum to get more specific help, since that forum is dedicated to tuning, and over here there are a number of us, but the response time may vary.

I'm sure between here or there you're gonna find someone who has encountered this. I'm actually glad I don't know this through experience, like a lot of things I see on here lol.

 

"Yeah I've been running 25 lbs of boost on my stock 4.8 for a year and it blew up...maaaan I don't know what happened." It was working just fine then it wasn't.

Keep replacing parts, you'll eventually swap out the right one.

If you doubt it's your problem why the **** did you bring it up in the first place?

Do you have any data logs? What diagnosing/troubleshooting have you done?

 

Stock ecu will never be able to control low impedance injectors properly, and it's dumb to try.

 

Anybody who has run low impedance injectors on a factory PCM has burnt it up. To attempt this is stupidity, as the circuits involved are in no way robust enough to handle that sort of load. Also, your diagnostic process seems a little random.
.

 

hey hey hey guys. we shouldn't beat up the OP for doing something that everyone knows they shouldn't.

lets give him a bunch of reason that's not the problem. cause I'm thinking that's what he wants.

 

Very timely and well said!
So I'll ask: How do low impedence injectors harm the ECM?

 

Low impedence = low resistance. This means the low resistance injector causes too much electrical current to flow through the ECM fuel injector circuitry thus eventually burning up that portion of the circuit board. A normal impedance (resistance) injector won't consume as many amps.

Rick

 

OK, thank you Rick! I thought it might be along those lines, but wasn't sure. I thought it might be more complicated than that. Pretty simple, really.
Thanks again!

 

If you want to use lowZ's with a normal setup, then best option is a suitable driver box.

Less desirable option is to wire in resistors in increase the impedance, and hence reduce overall current draw. IMO this is bound to affect injector performance to some degree, but it is a fairly common approach where some OEM's use lowZ. Although they will have fully tested their setups, not just randomly thrown bits together.

 

LOL u guys are brutal....and also completely correct.

 

Yeah, low z injectors need a different type of injector driver circuit that can peak/hold the injector with higher current to keep it functioning as it should. The OEM PCM has high impedance injector drivers which does not have the current capacity nor the peak/hold functionality required for low z injectors. Just using a resistor pack will definitely work but makes the injectors open lazily without the higher current peak/hold. Long story short don't use low z injectors with the OEM PCM without a low z peak/hold adapter box, or just buy the right injectors the first time.

 

I think most of it is because of the OP's response to my first post.

Don't get mad at everyone because you are doing something that you know doesn't work. Yeah it worked for a while but it's not now. If I was so stupid to run those injectors on a stock PCM and it took a ****. I would have probably(OK most definitely would have changed the injectors first if not the PCM at the same time)

I would have done that before I started throwing parts at it and pulling the engine.

But you can't fix stupid. No matter how many parts you throw at it.

 

No prob here. Seems like today was the day of know-it-alls on the tech.

 

Let us know when you find out what the problem is.

 

That post was not directed at you. I'm sorry if you thought it was.

 

No we good. I LOLd at your last post.

 

I'm surprised MrEracer would do something like this. He is well known in the Experimental aircraft world for a plane he built called the E-Racer, based on the Rutan Vari-Eze/LongEze canard aircraft. Rather than a small 4cyl aircraft engine, he put an aluminum Buick V8 behind the cockpit. It was/is a cool plane! His real name is Shirl Dickey. I'm not spilling any secrets here.