P1128/1130 - my turn

[jpc763]

2001 986 S - 85k miles

I have been getting these codes for the past month. Car runs and idles fine.

I followed the 101 things book to clean the MAF but the codes came back.

I read on another forum to disconnect the MAF and drive the car in order to rule out the MAF. If the codes come back it’s something else. If not than it’s probably the MAF.

Is that the correct next step?

[blue62]

Originally Posted by jpc763

2001 986 S - 85k miles

I have been getting these codes for the past month. Car runs and idles fine.

I followed the 101 things book to clean the MAF but the codes came back.

I read on another forum to disconnect the MAF and drive the car in order to rule out the MAF. If the codes come back it’s something else. If not than it’s probably the MAF.

Is that the correct next step?

Those codes are most often caused by:
Vacuum leak of some type.
MAF sensor issue.
Fuel delivery issue.

The correct next step is a proper diagnosis of the issue.
So to try to help you I need to know what types of diagnostic tools you have available.

Best diagnostic tools are your senses.
Remove your engine cover and have a very good long look at the visual condition of your engine bay. Is it clean or dirty????
If it is dirty is it a dry dusty dirt???? or is it an oily residue type dirt.??????
If you have any oily residue type dirt on your hoses or any place in your engine bay then you have vacuum leaks.

Do you have a OBDII scanner???
Do you have a vacuum gauge???

If you have a OBDII scanner that reads MAF delivery in g/s and also MAF voltage.
Then you can look at the MAF signal in relation to RPM to see if it is near spec.

If you have vacuum gauge....... HOOKED UP CORRECTLY AND THE TEST RUN UNDER CORRECT CONDITIONS..... it will tell you if you have a vacuum leak.

[jpc763]

Thanks for the great info.

I am not home this weekend so cannot give the complete visual inspection. I was in there on Wednesday to clean the MAF. The engine bay is very clean. I do not remember any oily residue. The car was serviced in March.

I have a Durametric but nothing else to diagnose.

[blue62]

Originally Posted by jpc763

Thanks for the great info.

I am not home this weekend so cannot give the complete visual inspection. I was in there on Wednesday to clean the MAF. The engine bay is very clean. I do not remember any oily residue. The car was serviced in March.

I have a Durametric but nothing else to diagnose.

So with the Durametric you can check the MAF voltage and g/s.
Go into the engine module then click on actual values.
that will bring up a list of things.
Find MAF voltage.
with ....Key on but engine off..... MAF voltage should read 0.9 - 1.1 volts.
With .....engine running at idle...... MAF voltage should be 1.2 - 1.5 volts.
Let me know when your back at your car.
I will hook up my Durametric to my car and give you some running g/s figures to look at.

You can also buy a vacuum gauge for around $25.00 and I can tell you how to connect it and do a proper vacuum test with it.
If you decide to purchase one let me know I will point out the correct type.

Tell me how the car runs... do you notice anything different since the codes came up????? Does it idle correctly and at the proper RPM????
Are you using a stock air filter or is it after market????

[jpc763]

Originally Posted by blue62

So with the Durametric you can check the MAF voltage and g/s.
Go into the engine module then click on actual values.
that will bring up a list of things.
Find MAF voltage.
with ....Key on but engine off..... MAF voltage should read 0.9 - 1.1 volts.
With .....engine running at idle...... MAF voltage should be 1.2 - 1.5 volts.
Let me know when your back at your car.
I will hook up my Durametric to my car and give you some running g/s figures to look at.

You can also buy a vacuum gauge for around $25.00 and I can tell you how to connect it and do a proper vacuum test with it.
If you decide to purchase one let me know I will point out the correct type.

Tell me how the car runs... do you notice anything different since the codes came up????? Does it idle correctly and at the proper RPM????
Are you using a stock air filter or is it after market????

I am back home and just checked MAF Voltage

Engine Off - 1.01 v
Engine Idle - 1.31 v

I saw other MAF values in the list.

I have no problem buying a vacuum gauge. If you can point me to a good one I can get one and then follow the instructions to test it out.

The car runs great AND there does not appear to be any difference since the codes started appearing. Upon startup it can idle rough ~600 - 1000 then settles in at around 800 RPM (based on the notches on the gauge being 200 intervals).

I am using a MAHLE Air Filter - It was changed probably 2 years ago.

Thank you so much for your help!

[blue62]

Originally Posted by jpc763

I am back home and just checked MAF Voltage

Engine Off - 1.01 v
Engine Idle - 1.31 v

I saw other MAF values in the list.

I have no problem buying a vacuum gauge. If you can point me to a good one I can get one and then follow the instructions to test it out.

The car runs great AND there does not appear to be any difference since the codes started appearing. Upon startup it can idle rough ~600 - 1000 then settles in at around 800 RPM (based on the notches on the gauge being 200 intervals).

I am using a MAHLE Air Filter - It was changed probably 2 years ago.

Thank you so much for your help!

Looks like your MAF specs. (for those two tests) are within correct voltage range.
I will get you some running MAF specs. tomorrow or the next day.

You can buy a vacuum gauge at places like Orielly's auto parts.
Your looking for one that has around a 2 inch gauge face or bigger.
It should come with a section of hose and a fitting or two.
The most important fitting you will need is a "TEE" fitting.

Good that your using a stock air filter and not an after market like an oiled K&N they are hard on MAF sensors.

Interesting that the car runs "great" usually the car idles kinda rough when these two codes appear.
We will look at the MAF a little closer and see what a vacuum tests has to say.

[jpc763]

Originally Posted by blue62

Looks like your MAF specs. (for those two tests) are within correct voltage range.
I will get you some running MAF specs. tomorrow or the next day.

You can buy a vacuum gauge at places like Orielly's auto parts.
Your looking for one that has around a 2 inch gauge face or bigger.
It should come with a section of hose and a fitting or two.
The most important fitting you will need is a "TEE" fitting.

Good that your using a stock air filter and not an after market like an oiled K&N they are hard on MAF sensors.

Interesting that the car runs "great" usually the car idles kinda rough when these two codes appear.
We will look at the MAF a little closer and see what a vacuum tests has to say.

As I said, it starts up a little rough but settles in.

Is this what I need?

HFS (R) Carburetor Carb Valve Fuel Pump Pressure & Vacuum Tester Gauge Test Kit https://www.amazon.com/dp/B00KRJFSFQ/ref=cm_sw_r_cp_api_glt_fabc_B51EGBDZ2G3WPSEA6KRE

[Stl-986]

any auto parts store will have smaller fittings. They are usually in the Help section. Just need a smaller T. Any of the vacuum ones are what you are looking for.

[vkmotorsports]

jpc763 what happened next ? did you figure it out ? i have the same issue on my 2001 Boxster S. Had P1128,P1130 and Cleaned the MAF sensor and the P1128 came back.