Chasing vacuum leaks and goes no where

[theWalkinator]

Long time looker but first time posting.

2001 boxster 2.7, got 4 codes, P1126, P1133, P1128, P1130.

I know this has been beaten to death but for the life of me I just cannot find where is the leak, here is what I have done so far:

1. Cleaned throttle body
2. Replaced AOS
3. Replaced MAF with Bosch one

Smoke tested from the intake duct right after the MAF, find no other leaks except a very small leak from the resonance tube nipple which is the pivot point of the resonance flag, I use a cap and epoxy to seal the nipple and no leaks after it is sealed.

Here are some data points from my scan tool:
EOBD mode:
MAF 2.75 g/s
Bank 1: STFT 1.562% LTFT -0.781
Bank 2: STFT 3.906% LTFT -0.781

Porsche Mode:
Bank 1 FRA 1.00 RKAT 4.17
Bank 2 FRA 1.00 RKAT 4.50
MAF 10.1kg/h at 1.27v

So definitely the car is running lean and idle is unstable, it surges up or down every few seconds, but smoke tested multiple times, no leaks in engine bay, no leaks under the car and no leaks in frunk brake booster area. Also did multiple times battery disconnected and reconnected, turn key on for 1 minute the pull the key out, wait for 10 seconds then start the car to force ECU to re-adapt, still no luck, clear the code and short drive for like 20 minutes codes come back. Car still drives fine even with those codes.

The only thing that I didn't do is to test fuel pressure, my HF fuel pressure test kit does not fit the Boxster fuel rail schrader valve so need to buy another one.

What else? The vacuum reservoir? If the vacuum reservoir starts building up vacuum then loses it, would that cause idle to surge and fuel adaptation codes to be thrown?

[S50Sinner]

While you wait for a pressure sensor that fits (please let me know which one you get and if it fits, I need one too), you can check fuel flow rate at the filter under the car. There are some solid YouTube videos on it, all you need is a jug/jar of some sort that you can measure with and someone to turn the key while you're under the car. I would try it before and after the filter. Flow is half the equation, but it could give you some insight into what's going on. You could also try adding some fuel system cleaner to your tank.

[JFP in PA]

Time for a smoke test …..

[theWalkinator]

Originally Posted by JFP in PA

Time for a smoke test …..

I have smoke tested many times and found no leaks, I smoke tested from the intake tube right after the MAF. Do you think I should smoke test from second air pump charging hose?

Okay now I got new fuel pressure test kit and it works this time, it is 1/4" fitting.

Here is the fuel pressure:

Static: 2.8 ~ 3 bar
Idle: 3.3 bar

So fuel pressure at idle is good, but static is low, when turn the key to ON position, it went up to 4 bar then dropped back to 3 bar, after couple of minutes, it dropped to 2.4 bar.

So what gives? Fuel pump is leaking?

[theWalkinator]

Okay, I just did fuel flow test with my Launch X431 scanner which has "Fuel Pump Relay Final Stage" test function, it can activate fuel pump with key in ON position, this is nice so I don't have to jump the fuel pump relay, here is the results:

- At the supply line before the fuel filter, 20 seconds got almost 1 liter of fuel out, that's way exceeded 30 seconds 850ml specs
- At the return line, got 900ml running fuel pump for 30 seconds, but the fuel came out was yellowish, looks like dirtier than the fuel dumped from the supply line, I guess I need to replace fuel filter then.

Also removed vacuum line from fuel regulator, no fuel dribbled out so guess the fuel regulator is good.

Also pulled the Y vacuum splitter out of the vacuum reservoir and used a hand vacuum pump to test the vacuum reservoir, it cannot hold vacuum, so this means the vacuum reservoir is bad and need to be replaced?

Since fuel pressure when engine is off is at 2.8 ~ 3 bar (spec is 3.8 bar), could the fuel pump is still the problem that the check-valve is bad even the flow is good?

Will order new fuel filter and new vacuum reservoir.

[theWalkinator]

Okay so the new vacuum reservoir arrived today, I tested the new reservoir with hand held vacuum pump and it holds vacuum fine, the old one in car does not hold vacuum, so I just pulled out the vacuum hose goes to the old reservoir and connected the hose to new reservoir on top of the engine with a silicone hose then cleared the codes and started the car, the car is still running lean, RKATs for both bank are pegged at 4.5% still! Also hooked the hand held vacuum pump to the hose that connects to the vacuum reservoir and it holds the vacuum too, so the new vacuum reservoir does not help to resolve running lean issue. I am out of idea what to check next.

[theWalkinator]

My car is 2001 2.7, the original MAF is Bosch F 00C 2G2 064, the replacement MAF is also Bosch, the part number is 0280 218 055/986 606.125.02, I ordered it from RockAuto, and before I ordered it, I double checked FCP Euro and Pelican Parts, they all show this MAF for my car, is this replacement MAF not the correct one?

Also, my codes are
P1128, P1130 Adaptation idle range Below Limit Value
P1126, P1133 Adaptation lower load range Exceed Limit Value.

I searched and saw someone posted that for P1128, P1130 Adaptation idle range Below Limit Value, the car is running rich and ECM is trying to take fuel away and reaches the limit, and STFT is around 25% and RKAT is pegging at 4.5%, I am confused, is the car running lean or rich? If it is running rich then that explains why there is no vacuum leaks detected.

The causes for P1128, P1130 Below Limit Value could be:
– Incorrect signal from MAF sensor
– Fuel pressure too high
– Fuel injector leaking
– EVAP canister purge valve open

So
- Incorrect signal from MAF - wrong MAF sensor?
- Fuel pressure too high - Pressure tests at the fuel rails are fine, idle 3.3 bar, engine off 3.5 bar
- Fuel injector leaking - how to test leaking injectors? the car only have 33km so leaking injectors seems unlikely
- EVAP canister purge valve open - EVAP vacuum leaks cannot be detected by intake smoke test, correct? the purge valve is under driver side intake manifold so that is my next thing to check, how can I check it without fighting to remove it ?


I also add that the car was running fine but the codes popped up after I cleaned throttle body, not immediately after but for a while it developed rough idle and eventually those 4 codes popped up.

[JFP in PA]

Originally Posted by theWalkinator

My car is 2001 2.7, the original MAF is Bosch F 00C 2G2 064, the replacement MAF is also Bosch, the part number is 0280 218 055/986 606.125.02, I ordered it from RockAuto, and before I ordered it, I double checked FCP Euro and Pelican Parts, they all show this MAF for my car, is this replacement MAF not the correct one?

Also, my codes are
P1128, P1130 Adaptation idle range Below Limit Value
P1126, P1133 Adaptation lower load range Exceed Limit Value.

I searched and saw someone posted that for P1128, P1130 Adaptation idle range Below Limit Value, the car is running rich and ECM is trying to take fuel away and reaches the limit, and STFT is around 25% and RKAT is pegging at 4.5%, I am confused, is the car running lean or rich? If it is running rich then that explains why there is no vacuum leaks detected.

The causes for P1128, P1130 Below Limit Value could be:
– Incorrect signal from MAF sensor
– Fuel pressure too high
– Fuel injector leaking
– EVAP canister purge valve open

So
- Incorrect signal from MAF - wrong MAF sensor?
- Fuel pressure too high - Pressure tests at the fuel rails are fine, idle 3.3 bar, engine off 3.5 bar
- Fuel injector leaking - how to test leaking injectors? the car only have 33km so leaking injectors seems unlikely
- EVAP canister purge valve open - EVAP vacuum leaks cannot be detected by intake smoke test, correct? the purge valve is under driver side intake manifold so that is my next thing to check, how can I check it without fighting to remove it ?


I also add that the car was running fine but the codes popped up after I cleaned throttle body, not immediately after but for a while it developed rough idle and eventually those 4 codes popped up.

The fact that the codes you are seeing is an impossibility (overly lean and rich at the same time) says something is wrong. Most likely problem is that you inadvertently "upgraded" to the later MAF (part number ending in 125 01 or higher) when you replaced the original MAF, which REQUIRES the DME be recoded in order for it to work properly, which requires access to a PIWIS system.

[theWalkinator]

Originally Posted by JFP in PA

The fact that the codes you are seeing is an impossibility (overly lean and rich at the same time) says something is wrong. Most likely problem is that you inadvertently "upgraded" to the later MAF (part number ending in 125 01 or higher) when you replaced the original MAF, which REQUIRES the DME be recoded in order for it to work properly, which requires access to a PIWIS system.

Right, that puzzled me as well, but with my original MAF I also got those 4 codes, so I will put the original MAF back and replace the vacuum reservoir which is bad then reset ECU and test drive the car to see if codes comes back again.

[theWalkinator]

Looks like I get rid of P11298 and P1130 codes after I replaced vacuum reservoir, however, 10 miles short test drive still got P1126 and P1133 (lower range adaption exceeded limit).

I also replaced fuel filter, man it is dirty, I mean very dirty, the gas came out of old fuel filter is very dirty cloudy and has some black sediment after let it siting for a while so definitely it needs to be replaced. After replaced fuel filter, I re-tested fuel pressure, engine idle 3.3 bar, right on the spec, engine off, it gradually creeps up to 3.5 bar after couple of minutes, and 10 minutes later it still holds on 3.5 bar. I also removed the return line but it does not seem to loose the fuel pressure, I did what you said, block off the return line and pressurize the fuel system, still around 3.5 bar so I think neither the fuel pump nor the injectors are leaking.

I was also able to test the EVAP purge valve (under the driver side intake manifold), my scan tool is capable to turn it on and off, so I hooked my hand vacuum pump on the EVAP hose from the throttle body, it held vacuum, then used my scan tool to command the valve to open, I heard a click and immediately the vacuum dropped to 0 so the EVAP purge valve is good.

I also tested fuel regulator by pulling the vacuum hose off the fuel regulator when engine is idling, no change of fuel pressure and I can feel the vacuum suction from that small vacuum tube.

After replaced the fuel filter, I took a quick 10 mile test drive, P1126 and P1133 came back in pending, so I unplugged MAF sensor and clear the code, took another 10 mile quick test drive, fuel trim seems to be fine and no P1126 and P1133 code, does that point to the MAF sensor?

The MAF sensor I got from Rock Auto is Bosch 98660612502, however, my car is 2001 model but production date is in September 2000, so should the MAF sensor be 99660612400?

I will do another smoke test, but I really don't think it is vacuum leak issue, P1126 and P1133 are lower range code not when the car is idling so if there is any small vacuum leak it would more likely present at idle (P1128 and P1130) but at higher RPM small vacuum leak can be neglected, correct?

So that comes down to either the MAF sensor or the fuel pump, but I am still thinking it is the MAF sensor's fault, I need to correct MAF sensor which might be 9966061240, thought?

[AK986]

Originally Posted by theWalkinator

Right, that puzzled me as well, but with my original MAF I also got those 4 codes, so I will put the original MAF back and replace the vacuum reservoir which is bad then reset ECU and test drive the car to see if codes comes back again.

Hey, i'm running in to the similar issue with my 98 Boxster. I checked the car for vacuum leaks by using the smoke detector ,and couldn't not find any.

Any updates on your progress?

[theWalkinator]

Originally Posted by AK986

Hey, i'm running in to the similar issue with my 98 Boxster. I checked the car for vacuum leaks by using the smoke detector ,and couldn't not find any.

Any updates on your progress?

I replaced vacuum reservoir and that helped to get rid of P1128 and P1130 (idle below limit) codes, but P1126 and P1133 (lower range exceed limit) codes still present.

I also replaced fuel filter which is really dirty (fuel came out of the filter is cloudy and contains fine black sediments), after replaced fuel filter, I re-checked the fuel pressure, idle at 3.3bar which is right on the spec, but engine off fuel pressure is kept at 3.5bar which is 0.3 bar lower than the spec, but I don't think it really matters. Also replaced the spark plugs with NGK Iridium plugs as well as spark plug tubes since they are leaking oil and might also leaking vacuum, but all that didn't resolve P1126 and P1133 codes.

Other things checked:
1. Checked vacuum at the Y hose connector, it holds vacuum
2. Fuel regulator, pulled out the small vacuum hose from the fuel regulator, it is dry no fuel came out, the small vacuum hose has suction so both fuel regulator and vacuum are good.
3. Checked EVAP purge valve with my scanner and a hand vacuum pump, I can command the valve open and close, when it is closed, it holds the vacuum but when I command it open, the vacuum drops to 0 so that ruled out the EVAP purge valve.

I also tried with the MAF plug disconnected, P1126 and P1133 codes did not show after 10 miles test drive, so at this point I think most likely it is the wrong MAF sensor that I bought from RockAuto which is 98660612502, though all online sellers (FCP Euro, Pelican Parts, RockAuto, etc.) give this MAF sensor as the correct one for my car, but the original MAF sensor in the car is Bosch F00C2G2064, I couldn't find anywhere that this MAF sensor fits my car or any boxster, except one eBay seller who has a list of Bosch 99660612400 but the item picture shows Bosch F00C2G2063. My car is 2001 2.7L but the production date is in Sept 2000 so 99660612400 might be the correct MAF sensor for my car, this website https://www.eurospares.co.uk/Porsche/Boxster_986/Boxster_986_(2001)/PartDiagrams/106-000/AIR_CLEANER?ref=7 listed both 99660612400 and 98660612500 fit 2001 boxster 2.7L.

If 99660612400 won't resolve the P1126 and P1133 then the last thing is the fuel pump?

[theWalkinator]

Okay so I took the air filter out and used a inspection mirror to inspect the MAF sensor housing from the air box, what I found was that the honey comb mesh screen is half missing and the other half is very dirty and mostly clogged, and it happens on the MAF sensor hot film side blocking the air flow. I remember someone said in the forum that he found a cigarette pack and some other stuff stuck there causing his car throwing those fuel mixture codes, this might also be the reason that I got these codes.

I will remove it from the car when I have time and see if I can savage the MAF sensor housing. Besides to prevent foreign objects to get into the intake tube, does that honey comb mesh screen has any other purpose? I mean it certainly can reduces amount of air into the intake tube comparing without it, correct? So if I remove the half remaining screen, would also cause more air into the intake than the design?