help me track down a vacuum/exhaust leak please

[v8stang]

I posted a thread about this a few weeks ago. Haven't been able to figure it out since then.

Little background:

Swapped over to 47's with Shaun's 93 tune in anticipation for e85 down the road. Logs were great on 93 and car ran a 11.97 with tune/h pipe/tires.

Car then sat for a month while I was away on work. Came back and 2 wks later finally swapped to e85. At which time logs showed the O2's were trimming fuel by 15% to correct for a leak. This led me to believe it was an issue with the swap to e85. Car was untouched besides e85 and tune. It really puzzled me.

Fast forward a few weeks, I switched back to 93 and removed/reinstalled the injectors using Vaseline and sprayed carb cleaner looking for possible leaks elsewhere.
Then, a few nights ago, I logged again, and Shaun said its still showing the correction being done by the o2's.
I'm stumped here. The bay is completely stock except for a drop in filter.
I'm gonna check the h pipe this coming week, but Shaun said BOTH o2's are reading the condition, so it probably isn't the h pipe.

Ok, so my questions are:

If I take it to the dealer for this, how do I go about it?
Am I supposed to say, "Hey my tuner says I have a vacuum leak somewhere"....

Second question:
What could have caused this from sitting a month?

Thanks guys

 

[Shaun@AED]

I've found misc small leaks from the PCV system on many cars.

I've also found over time (engines breaking in) Fuel trims trend towards lean as the engine becomes more efficient as an air pump.

Closer inspection of your 8/30 Gas idle log shows .70-.83 lb/min logged at idle and 700RPM. Your log of 10/22 on Gas shows .62-.73 lb/min logged at idle and the same 700RPM. That is 13-14% difference which is exactly what I am seeing in your data logs.

Since these 2 logs are on the same tune and the Maf can not be 'clocked' we can conclude the Maf is accurate and seeing less airflow than it was in the 8/30 log. This is a clear indication that it is not exhaust leak related.

If lb/min was the same in both logs we'd look at exhaust and fueling changes (ethanol content), but the Maf is seeing less airflow than previous logs at the same RPM, yet the fueling needs are identical to the previous log. This is a clear indication of airflow bypassing the Maf.

 

[5PNTSLW]

I would start by listing all of your mods, complete list of everything you have touched on the car

Yes, you could go to the dealer and say that actually, and they will diagnose it but you will pay for it.

 

[v8stang]

I've found misc small leaks from the PCV system on many cars.

I've also found over time (engines breaking in) Fuel trims trend towards lean as the engine becomes more efficient as an air pump.

Closer inspection of your 8/30 Gas idle log shows .70-.83 lb/min logged at idle and 700RPM. Your log of 10/22 on Gas shows .62-.73 lb/min logged at idle and the same 700RPM. That is 13-14% difference which is exactly what I am seeing in your data logs.

Since these 2 logs are on the same tune and the Maf can not be 'clocked' we can conclude the Maf is accurate and seeing less airflow than it was in the 8/30 log. This is a clear indication that it is not exhaust leak related.

If lb/min was the same in both logs we'd look at exhaust and fueling changes (ethanol content), but the Maf is seeing less airflow than previous logs at the same RPM, yet the fueling needs are identical to the previous log. This is a clear indication of airflow bypassing the Maf.

Thanks Shaun, I appreciate you taking the time to type this information. I feel with that, I understand a little more of what is going on.

I would start by listing all of your mods, complete list of everything you have touched on the car

Yes, you could go to the dealer and say that actually, and they will diagnose it but you will pay for it.

Only times the bay has been touched were to install injectors, drop in filter and 2 step. All was done before the first log which showed perfect.
Aside from that, the car has h pipe, and some rear suspension. 16k on car

If its a faulty pcv system, should I still pay for the dealer to check?
The

 

[Cashbum]

I know you said you used Vaseline for the injectors but make sure they didn't fold or something weird like that. Ive seen it happen before on a neon srt4. Had a pretty large vacuum leak through the bottom o-ring of the injector. Just thinking out loud though