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1G Running lean after boost leak fix

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91lzer

Proven Member
60
18
Aug 22, 2022
Penticton, BC_Canada
So the other day I fixed a large boost leak from the throttle body and my car started running very lean. My A/F gauge reads 18.0 and off the charts at WOT and 16.5- 17.0 at idle. I couldn’t figure out what was making it run lean and so I loosened the TB to make a boost leak so I could see if that was the problem. And with a boost leak the car runs perfect. I think the previous owner tuned the car with a boost leak. Any suggestions on what it could be or how I can fix it?
 
Well....you retune it.
If your statement is true lots if measure air was escaping and now it isn't. Seems very straightforward from a diagnosis point of view.
 
Okay, that's what I thought. do I need a DSM link to get the car tuned?
You say the car runs perfect with a boost leak. Are you basing your statement off the A/F gauge reading? If it was tuned by the previous owner and doesn't have DSMlink, what was used to tune it previously and is it still on the car? Fill out a vehicle profile so we know what we're working with here.
 
You say the car runs perfect with a boost leak. Are you basing your statement off the A/F gauge reading? If it was tuned by the previous owner and doesn't have DSMlink, what was used to tune it previously and is it still on the car? Fill out a vehicle profile so we know what we're working with here.
Yeah Im basing it off the A/F gauge, but it also runs nicely with the boost leak. The car has an EPROM
 
Update, the previous owner never tuned the car and he said the car has always ran great for 14 years. Anyone know what it could be? I would need to get a ECM link to tune the car.
 
If it was flashed with a boost leak, you either need to reflash it, return it to stock, or go aftermarket. Nothing else is going to fix AFRs if you don't want a leak.
 
Your profile states it has a 16g. Do you know if it's still on stock injectors? I'm assuming stock MAF since it's untuned? I would take the AF reading with a grain of salt. Also I would take a step back, assess everything, and go from there.

Find out what has "actually" been done to the car before moving forward.
 
Your profile states it has a 16g. Do you know if it's still on stock injectors? I'm assuming stock maf since it's untuned? I would take the AF reading with a grain of salt. Also I would take a step back, assess everything, and go from there. Find out what has "actually" been done to the car before moving forward.
My bad, I meant to put 14b😂 the turbo housing says TD04. And yeah stock injectors and the stock maf is modified. Ive been talking to the previous owner and I got some more info about the car.
 
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How has the MAF been modified? What kinda MAF? Pull one injector and take a photo and maybe we can help identify what it is. Owner should have given you a complete current mod list of said vehicle so you're not guessing. It's kinda challenging to fix an issue when you don't know what you already have....
 
I don’t know too much about it but it’s a 1st gen Technomotive stage 3 chip

If my memory hasn't failed me Technomotive didn't make any tuning related changes other than disabling fuel cut. I know that Jeff O has in the past tweeked TMO chips to make tuning mods. I've done the same for people, so you would have to look at the contents to know for sure.

If it was flashed with a boost leak, you either need to reflash it, return it to stock, or go aftermarket.

Flashing isn't the right term for reprogramming a 1G ECU.

While it might have Flash (29FXXX) or EEPROM (28CXXX) for a 27XXX series EPROM replacement, it's far more likely to have a UV erasable 27XXC EPROM or the one time programmable version of same.

In any case the chip needs to be removed for the ECU board to be reprogrammed rather than "Flashed" like the 2G Black Box ECU.

With this vintage mods, I wonder if there isn't an SAFC hiding under a seat or in the glovebox.
 
I used the term generically. While technically may be incorrect, it's still better than using the plural "headers" to refer to either a single header or, worse yet, a manifold :p
 
How has the MAF been modified? What kinda MAF? Pull one injector and take a photo and maybe we can help identify what it is. Owner should have given you a complete current mod list of said vehicle so you're not guessing. It's kinda challenging to fix an issue when you don't know what you already have....
Yeah that’s quite true, after contacting the previous owner over the past few days, I have put together a list of the things that have been done.

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I can't tell 100% if that says INP-008 or INP-009. Look at the other side and see if it says B390L or B450L. The Blue ones are usually the INP-009 B450L for the 1G turbo manual cars but in some pictures the normally gray INP-008 B390L 390cc injectors for the 1G turbo automatics look blue.
 
I can't tell 100% if that says INP-008 or INP-009. Look at the other side and see if it says B390L or B450L. The Blue ones are usually the INP-009 B450L for the 1G turbo manual cars but in some pictures the normally gray INP-008 B390L 390cc injectors for the 1G turbo automatics look blue.
They say 009. I already put them back in my car. Is it necessary to look at the other side?
 
I don't know what a "stage 3" chip would even do when the car is running 450cc injectors and thus likely a 14b. It's possible, being a TD05H, it could also be a 16g but 450cc injectors would be seriously undersized at higher boost. We'd need the numbers on the compressor housing opposite of the TD05H casting mark.

At this point, I'd crack open the ECU and see if it's even what the previous owner says it is.. something about this smells funny.
.. and either find yourself a stock ECU or a 1G link eeprom.
 
I don't know what a "stage 3" chip would even do when the car is running 450cc injectors and thus likely a 14b. It's possible, being a TD05H, it could also be a 16g but 450cc injectors would be seriously undersized at higher boost. We'd need the numbers on the compressor housing opposite of the TD05H casting mark.

At this point, I'd crack open the ECU and see if it's even what the previous owner says it is.. something about this smells funny.
.. and either find yourself a stock ECU or a 1G link eeprom.
These are the two numbers I found opposite of the tdo5 mark. I can’t make out what the 2nd photo says but maybe you can.

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Yes....most people didn't chip these to run stock injectors so it's most likely the car thinks it's running bigger injectors than it really is. Pop the ECU open. Normally, the spec for the chip/Eprom will be on it.

Okay, thanks man!

What do you mean by spec for the eprom? And I’ll get around to doing that tomorrow when I have some time

I have a theory. The previous owner set the boost controller to 13 lbs but the car had a large boost leak so most of it was escaping. If the system had no leaks and I'm running higher boost levels, then the stock injectors wont be sufficient causing the car to run lean. But there was a leak causing the boost pressure to escape and the car ran fine like that. So would decreasing the boost fix the problem?
 
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Do you have wideband gauge that you're basing this off of? Is there a fuel pressure regulator (afpr) on the car? It's possible previous owner just used afpr to "make it run right". DSMers weren't that sophisticated back in the day.
 
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