09 ss starts, won't run...

[pisco]

Ok it's time to throw in the towel and ask for help.
Brief intro since I have yet to start a build log..
Brandon aka Pisco...(long story) from Nebraska, chassis #220 shipping soon extended city with an 09 ss donor 83k? miles

I'm trying to make my donor run before I rip the wiring harness apart. The crash broke upper map, lower map wires, evap solenoid, intercooler, and radiator.
The engine will start, run for 5-20 sec and die.
If I keep it revving it will keep going a bit longer..
I unplugged upper map, spliced lower map wires, and sealed as many vacuum leaks as possible. This seemed to help a little (it had zero pedal response prior)
plugged in my buddies snap-on modis ultra and no significant codes present (nothing that should prevent running)
any input at all before i replace map sensors?

 

[ctuinstra]

When you say unplug the upper map, you by chance aren't referring to the MAF? The MAF being unplugged is going to make it run like junk.

 

[Ross]

Find and fix the air leaks on the intake, and a the exhaust (these throw off the O2 sensor).

Fuel pressure issue?

 

[pisco]

Find and fix the air leaks on the intake, and a the exhaust (these throw off the O2 sensor).

Fuel pressure issue?

I've watched that video on finding leaks... well done!! I'll probably do something like that when it's time.
I didn't check fuel pressure

When you say unplug the upper map, you by chance aren't referring to the MAF? The MAF being unplugged is going to make it run like junk.

no I wish I had tried it though, with the Intercooler tank broken (patched it with duct tape) I'm sure map is inaccurate
my problem is it seems to run fine and rev fine (as long as I keep it above 2200 rpm) as soon as it droops or if rhythm is off slightly it will just shut off.
I've never seen a car do this before.

I think my next step is to replace the map sensors and bypass the intercooler with a pipe

 

[Ross]

If the map sensor was bad, it would probably throw an engine code. There is 2 of them on my LSJ engine, one was broken on my engine (from the accident the totaled the Cobalt). The tube that lead to the intake vacuum was broken off, and the map sensor was now reading air pressure outside of the engine... which is exactly what the other map sensor is reading. Anyhow, my engine ran with this broken map sensor. I had to unbolt the map sensor to find the broken tube.

 

[Desert Sasqwatch]

The turbo engine should run just fine without having boost pressure, so thinking the open intercooler is the problem is incorrect. My 08 SS/TC had a broken intercooler from its accident and ran fine with the MAF disconnected. It would idle and rev up without any problems. From the description of your problem sounds like a lot of unmetered air is getting into the intake and leaning it out when your at low rpm. Search and fix the air leaks first before investing in new sensors.

 

[ctuinstra]

The turbo engine should run just fine without having boost pressure, so thinking the open intercooler is the problem is incorrect. My 08 SS/TC had a broken intercooler from its accident and ran fine with the MAF disconnected. It would idle and rev up without any problems. From the description of your problem sounds like a lot of unmetered air is getting into the intake and leaning it out when your at low rpm. Search and fix the air leaks first before investing in new sensors.

I don't understand this, you are saying the it should run fine with the MAF disconnected yet suggesting there is unmetered air getting in. Isn't the MAF sensor for metering the air getting in? I agree there can be and unmetered air getting in causing an issue. But with the MAF disconnected, ALL air now is unmetered (and just running off of default tables). Also with the MAF contains the intake air temp and with it disconnected, it reads the intake air as being infinitely cold.

 

[Lonny]

When we went to upgrade Matt's turbo Goblin we hooked up HP tuner and found that the MAF was not reading. It had a couple of wires that were broken internally.
It had never worked the whole time it was in my orange Goblin either.
We fixed the wires and it would not run worth a crap. After a whole lot of doing everything wrong we found an article that talked about how to make sure you have clean, undisturbed air flow for your MAF. It said that if the MAF is to close to the turbo inlet that the air flow is not able to be measured properly.
We extended the MAF and filter up near the tank and it all started working.
With the MAF reading properly the two things I noticed was the fuel milage got better and it had way better throttle response.
Other than that it still raining great.
The MAF was not working in the smoking tire Goblin video.

 

[ctuinstra]

When we went to upgrade Matt's turbo Goblin we hooked up HP tuner and found that the MAF was not reading. It had a couple of wires that were broken internally.
It had never worked the whole time it was in my orange Goblin either.
We fixed the wires and it would not run worth a crap. After a whole lot of doing everything wrong we found an article that talked about how to make sure you have clean, undisturbed air flow for your MAF. It said that if the MAF is to close to the turbo inlet that the air flow is not able to be measured properly.
We extended the MAF and filter up near the tank and it all started working.
With the MAF reading properly the two things I noticed was the fuel milage got better and it had way better throttle response.
Other than that it still raining great.
The MAF was not working in the smoking tire Goblin video.

This is true if the MAF has failed and them ECM determines this and then it runs off of the VE tables and assuming they (VE tables) are fairly close, the engine will still run but not ideal. Now if the MAF is disconnected, it also contains the intake air temp sensor and now the car is not only not metering air, it thinks that the air is extremely cold and therefor throws off the tune completely. If the MAF is "working" but very inaccurate such as Lonny was talking about with it being placed in the wrong spot, it doesn't error out and the ECM keeps using the data although the metering data is bad, again causing the engine to run bad. Many different scenarios with different results. This can lead to confusion, including my own.

As part of the tuning process, we purposely cause the MAF to fail by lowering the fail point to below normal. This way we force the car to run strictly off of the VE tables to tune those in the best possible. We ran our car off the VE tables for a couple of weeks until we got it dialed in. However, if the VE tables are not "tuned" well to your conditions, the car can run like crap.

Keep in mind, there are two parts to the MAF.

1. The MAF sensor itself
2. Intake air temp sensor

So the MAF being bad is one thing. Unplugging it is another.

Disclaimer: This is my knowledge of the SS/SC and the turbo set up could be completely different. I'll never pretend to be a turbo expert.

 

[pisco]

When we went to upgrade Matt's turbo Goblin we hooked up HP tuner and found that the MAF was not reading. It had a couple of wires that were broken internally.
It had never worked the whole time it was in my orange Goblin either.
We fixed the wires and it would not run worth a crap. After a whole lot of doing everything wrong we found an article that talked about how to make sure you have clean, undisturbed air flow for your MAF. It said that if the MAF is to close to the turbo inlet that the air flow is not able to be measured properly.
We extended the MAF and filter up near the tank and it all started working.
With the MAF reading properly the two things I noticed was the fuel milage got better and it had way better throttle response.
Other than that it still raining great.
The MAF was not working in the smoking tire Goblin video.

this is what I was thinking, triggering it to go to a limp mode and all air being unmetered.

 

[pisco]

I don't understand this, you are saying the it should run fine with the MAF disconnected yet suggesting there is unmetered air getting in. Isn't the MAF sensor for metering the air getting in? I agree there can be and unmetered air getting in causing an issue. But with the MAF disconnected, ALL air now is unmetered (and just running off of default tables). Also with the MAF contains the intake air temp and with it disconnected, it reads the intake air as being infinitely cold.

The way I understand it is with a maf working and hooked up it meters the air coming through it, with massive vacuum leaks it meters x% of the air throwing the mixture off accordingly. Unhook it completely and the computer decided to ignore that adjustment and run by default value.

 

[ctuinstra]

The way I understand it is with a maf working and hooked up it meters the air coming through it, with massive vacuum leaks it meters x% of the air throwing the mixture off accordingly. Unhook it completely and the computer decided to ignore that adjustment and run by default value.

Yes, BUT, remember if you unhook it, you are also unhooking the intake air temp sensor and the car no longer knows the temp of the air and may read it as infinitely cold and run terribly rich. If you had HP Tuners, you could cause it to error out and not use the metered air data and still us the temp sensor.

The only other option is a bypass harness or removing one of the wires to the MAF sensor part of it.

 

[pisco]

Just to be clear... the goal isn't to leave it this way just verify my donor does run.
I tried it when I got off work and it worked, unplugged the maf hooked up the jump box in the trunk and it fired right up and idled.
It was running quite rich and backfired when revved but it ran!

 

[ctuinstra]

Just to be clear... the goal isn't to leave it this way just verify my donor does run.
I tried it when I got off work and it worked, unplugged the maf hooked up the jump box in the trunk and it fired right up and idled.
It was running quite rich and backfired when revved but it ran!

PERFECT!