Help! High AF correction at idle after turbo/uppipe install

Just finished installing new turbo, stock uppipe, PCV, upper intake manifold gaskets and turbo intake hose. Did the blow test for leaks between MAF to blowoff valve hose and it was airtight with no leak.

 

Loaded the tune from Mike Tuning Alliance and started it up. It was idling steady and solid but AF correction is 15% and AFR was 17-18.

 

We are going to check for exhaust leak pre wideband O2 sensor tomorrow. Any tips for checking for an exhaust leak? Anything else that can cause the lean reading?

 

Thanks

Edited July 12, 2020 by Scoobiidoo

Not sure if its related but, Did you re-install the boost pill in the tube off the compressor outlet ?

Not sure if its related but, Did you re-install the boost pill in the tube off the compressor outlet ?

No pill because I installed an ECBS. I sealed off the air filter hose end and blew into the BOV valve hose and no leak.

That sounds like a nasty leak. Why would your O2 sensor randomly go bad after you did those mods? What do you mean by 'blow test' exactly?

That sounds like a nasty leak. Why would your O2 sensor randomly go bad after you did those mods? What do you mean by 'blow test' exactly?

 

The blow test as prescribed by the tuner - sealed off the air filter hose end with a cap or can, take off the hose connecting to the BOV and blow into it, listens for leaks. If no audible leak, seal the hose off with your thumb and hold it for 5 seconds or so, put it up next to your ear and let go of your thumb. Should hear the air swooshing out of the hose.

 

Not saying the O2 sensor is going bad. I was saying we are going to look for exhaust leak pre O2 sensor since that's the only thing left to check that we worked on. The downpipe was dropped but I don't think exhaust leak post O2 sensor would affect lean idling.

When you say blow are you meaning with your lungs? The intake/ charge side I’m sure holds more air than your lungs. You will need to pressurize it with compressed air.

When you say blow are you meaning with your lungs? The intake/ charge side I’m sure holds more air than your lungs. You will need to pressurize it with compressed air.

 

Not my lungs but my athlete and saxophonist son's lungs He actually blew out the plastic cap the first time so I know it is a few psi worth. Plus it was an audible whooosh when he let go of his thumb seal.

Lol that’s fantastic! I’m imagining someone that can hopefully play the smoothest of Jazz, doing just that into the intake. I’ve seen leaks that don’t show themselves till about 5-6psi in the system, but that wouldn’t explain your crazy correction at idle. It does sound like an intake leak though.

Lol that’s fantastic! I’m imagining someone that can hopefully play the smoothest of Jazz, doing just that into the intake. I’ve seen leaks that don’t show themselves till about 5-6psi in the system, but that wouldn’t explain your crazy correction at idle. It does sound like an intake leak though.

 

Lol yeah I was very surprised he blew out the plastic cap the first time. I had to really tighten the hose clamp down.

 

I sprayed sudsy water on all the intake/manifold/turbo/intercooler areas before and didn't see any bubbling action.

 

Would a leaky up pipe connection cause lean running?

The more I think about it the same would apply to vacuum. I’d still pressurize it with compressed air. If you have a boost gauge, have your son blow into the hose again and I have a feeling you will be surprised at how little positive pressure he makes on that gauge. The leak may not show without a decent amount of vacuum.

I second the compressed air suggestion. First vacuum leak I ever hunted on one of these cars I started by blowing with my lungs, and found nothing. Showed up at around 5 psi, just like for blackobxt. I had high fuel trims there.

 

Watch the pressure and how fast you apply it, lest you dislodge an oil seal.

 

I'll throw this in too, though it's pretty arbitrary given the work you did. I recently had my fuel trims peg to max, went through all my diagnostics w/ good boost leak test up to 15 psi, and it ended up being a pinhole leak in a fuel line. Though, you'd probably smell that in the bay if you're running pump gas.

Taking your advice I started thinking I should check intake leak again so I hooked up a boost/vacuum gauge. It is idling with 17-18" Hg. How much vacuum are you guys pulling at idle? I am thinking if it is leaking it would pull much less vacuum.

 

Lol with the gauge upright that it. Upside down it is 16"

Edited July 8, 2020 by Scoobiidoo

I’d like to say mine is about -20 but there are a lot of things that effect that, altitude, ac on or off, temp and even barometric pressure. According to the gauge you might be alright but really the only way to 100% rule it out is by pressurizing the intake. That that much af correction I bet it’s making some noise at idle, but then again I’ve seen them that leak just right to not make noise. I’m still guessing it’s a leak, 90% of the time it’s a vac/ boost leak

I think -20 is the norm.

 

You may be able to rent a small compressor. If your going to buy one, make sure it can run air tools in case you ever have a need.

 

Think if it as a tool you'll have for a very long time.

Ok, running compressed air with a 6' hose away from the engine bay to about 7psi and we hear nothing. At that pressure it should be quite loud if there is an intake leak, correct?

You would hear a hiss or whistle, bad duck call or kazoo noise.

You would hear a hiss or whistle, bad duck call or kazoo noise.

 

No noise. Nothing at all even when spiked past 7psi. I am suspecting the "new" used catless sti up pipe gasket

I had a lean & af learning issue related to my gas pump.....it was new but turns out the o-rings weren't sitting properly and causing a leak in pressure.

 

If nothing comes out of your vaccum testing and changing the UP gasket, I would look into your gas pressure readings

I'll assume with a leak at the up pipe, that would be fairly easy to hear ?

You would definitely hear it

I have heatshields and the bottom cover on the car. Can't hear anything the way it is. Will have to do it tomorrow morning when it is cooler. Should I check all exhaust connection that I dropped? Like downpipe to cat?

 

BTW, over 8psi is not good. I have oil coming out of the oil dipstick. I hope I didn't blow any seals.

 

The fuel pump is the last thing I would check because I have a full tank of gas in it. i remembered the mess I made last year installing the DW with it 3/4 full.

I would check anything and everything that was removed and beyond that. If it’s an exhaust leak it will be loudest when it’s cold and quieter after thermal expansion. When you pressurize the intake you should block off anything that Could feed the crankcase and pull the oil fill cap as a precaution to avoid pushing out a seal. You shouldn’t have to pull the pump to check it, a fuel pressure test should suffice especially at idle

Another question, do you by chance have a wideband and have you checked live data to see if anything is doing anything weird? Failing sensor don’t always throw cel.

Another question, do you by chance have a wideband and have you checked live data to see if anything is doing anything weird? Failing sensor don’t always throw cel.

 

I have an AEM UEGO but I don't have another bung to install it. However, I did connect it to my OBD scanner and checked live view. It is showing AF correction of 7-8% short term and 14.8% long term after idling for a while.

 

As far as parts removed, intake manifold, turbo intake hose and the lot are all intake related. Other than that, I replaced the spark plugs. Dropped the exhaust manifold, front joint pipe, up pipe and downpipe.

I would check anything and everything that was removed and beyond that. If it’s an exhaust leak it will be loudest when it’s cold and quieter after thermal expansion. When you pressurize the intake you should block off anything that Could feed the crankcase and pull the oil fill cap as a precaution to avoid pushing out a seal. You shouldn’t have to pull the pump to check it, a fuel pressure test should suffice especially at idle

 

Found small leaks at the up pipe to manifold and downpipe to cat mid pipe. Reassembled and added copper exhaust sealant.

 

What is the best way to test fuel pressure? Disconnect and T in from where? I only have regular hose ends on my fuel pressure gauge. Thanks