Hi everyone,

I recently purchased my 2005 R53 about 2 months ago. The previous owner had the car in to a mechanic about a month before that for a P1498 code. They replaced the supercharger air duct and green gasket then.

Once I took over ownership I noticed that if I started the car cold with the A/C off I would get a P1498 pending code along with an EML light. The car ran fine, with no power loss. If I kept the A/C on with a cold start there would be no EML or pending code.

On a warm start with or without A/C on there would be no EML at all.

I changed the intercooler boots (badly cracked) and the fuel pressure regulator vacuum line (also cracked). The problem still persists and it seems like as the weather is cooling down in the mornings for my commute, even with the A/C on the car will occasionally throw the EML/Pending P1498 code.

I suspect a vacuum leak and will do a smoke test this weekend, but just wanted to get some input on any other common vacuum leaks?

Also I checked vacuum pressure when the engine is at warm idle and it seems to be stable around -9psi. Does that sound about normal, or would that indicate a vacuum leak? I ask because there seems to be conflicting reports of normal warm idle vacuum being either -9 or around -15 psi. I am concerned because I don't want to burn a valve or cause any damage like that.

Thanks in advance!

 

So a little update:

Cold engine idle vacuum pressure with A/C off is about -6psi.

Warm engine idle vacuum pressure with A/C off is about -9psi.

I believe this would either indicate a vacuum leak that seals up when the engine is warm, or a lazy MAP sensor (when cold). I will have to see about testing the MAP sensor, but it seems very easy to get at.

Is the vacuum pressure supposed to be the same when the engine is cold vs. when the engine is warm? Could someone test this if they have access to a boost gauge or an OBDII scanner with app for their car?

Thanks.

 

I think it would be different upon cold start due to the higher idle?

At least on my car the cold start idles higher than normal for a minute or two --- if your car is the same then that would affect the readings.

At warm idle (my idle seems to be right at 900 or so rpm), I get 19.0 - 19.6 inHg.

 

Hopefully a smoke test will show you a vacuum leak. I’d be suspicious of the recent repair to the intake duct and green gasket. It’s possible they didn’t seat the gasket well (IIRC the best procedure is to put the gasket on the supercharger then put the duct in place, not to put it on the duct first). And It’s really common to damage one of the vacuum lines coming out of the duct, too. One runs to the MAP on top of the engine (not the TMAP) and it’s really common to damage or unseat that line and not notice, since it runs up underneath the sensor. In any case, good luck. Vacuum leaks can be a pain to find.

 

Thanks for the input! Just rigged up a smoke test and found smoke billowing out the oil cap and one of my new DDMWorks silicone intercooler boots. So my dad found a piece of rubber to sandwich between the clamp and intercooler boots, so we fixed that leak. Going out to the store for a new oil cap o-ring now!

 

Alright so I wanted to wait until this morning to post after a true colder morning start.

So yesterday afternoon after fixing the vacuum leaks (oil cap oring and intercooler boot) I cold started the car and no EML or check engine. Vacuum pressure started around -7psi and increased to -9psi within 5 minutes. Car ran great, it was around 86F outside ambient temperature.

This morning I cold started and the car (around 74F ambient temps) and vacuum pressure again started at -7psi and slowly increased to -8.8 to -9psi within 5 minutes. The car threw the EML and P1498 pending code again after a few minutes of idling.

Are these pressures normal for a cold start? Since they seem the same from this morning and yesterday afternoon with the only difference being the EML and pending P1498, I am starting to think the problem isn't a vacuum leak. I'll go get a new throttle body gasket tomorrow and clean that. May as well do the blow through valve since its in the same area...

Any other tips? I'll do some Googling to see if there is a way to test the Oxygen sensor out of the car. It kind of makes sense that it could be throwing things off because I believe the car runs in open loop without O2 sensor readings for a few minutes on cold start and then goes to closed loop using the readings? If so, that would explain the light coming on after a few minutes of the car being started.

If I ziptie the BPV "open" all the time would that be an accurate test to see if the code comes back upon cold start?

EDIT: Tested the BPV by putting my hand on the linkage, it has very good resistance and seems to spring back as it should. Tomorrow morning when I start the car I'll see if it can open up anymore (I believe it should be completely open but since the car is complaining of too much air I'm guessing it could potentially not be opening all the way of dirty). Also decided to put the car in front end service mode tomorrow and just double check the shop's work on the supercharger duct and green gasket along with all the vacuum lines that attach to it.

I'd appreciate any thoughts, thanks!

 

Just a quick update -

I put everything back together and after a few colder morning starts I have no EML. To recap what I did, I changed the BPV and throttle body gaskets, and cleaned both. I also fixed an air leak on my intake hose and a couple other small vacuum leaks that I found using a rigged up smoke tester and some soapy water. I also patched my supercharger duct a bit with RTV. Not sure if that was needed since the leak was before the MAP sensor, oh well.

Moral of the story - do a smoke/pressure test and use lots of soapy water. Seems like there are quite a few small places for air to leak from.

 

The 9 psi is low and indicates a vacuum leak, of some sort. The pcv may be the problem. it is on the passengers side and behind the intake horn.

 

Hmm okay that is interesting. After putting everything back together I don't have an EML light anymore. Maybe it is because I disconnected the battery for a few days so the computer is still learning? I've put over 100 miles on the car since all the work and still no EML light. What should vacuum pressure be a warm idle? I already changed out my PCV with a new one. Pressure/vacuum test reveals no new leaks either.

I guess time will tell if the light comes back on. Thanks!

 

Curious. How has this situation panned out so far ? Unfortunately in previous post, a myrid of things were done to eleviate the issue so not able to pin point what step or proceedure may have cleared this up.

Your thoughts ?

Thanks!!

 

So I think it was a few of the small vacuum leaks that were causing the issue (none of which really impacted the way the car drove). As far as troubleshooting I found the best way for me was to first visually inspect everything that is accessible when the car is in front end service mode. I replaced everything I could see that had cracks in relation to the vacuum system. Next I would try to smoke/pressure test the car to pinpoint any smaller/harder to see leaks. I rigged up a small smoke tester device that I can take some pictures of for you this weekend if you need.

So in recap, I replaced these items which I believe where contributing to my P1498 code and ultimately helped to fix the combination of vacuum leaks:
Intercooler boots (DDMWorks Silicone)
Vacuum line from fuel pressure regulator
Supercharger BPV gasket to intercooler horn
Throttle body gasket
RTV sealant on the plastic seams of the supercharger duct/charge pipe

Hopefully this helps, I haven't had the code since I last did all this work on the vacuum system. Let me know if you need any more information or pictures!