stuckheng

Hi all, I'm fresh off a timing belt change and this is the next activity in line for the car. The car's a Turbo S but so far it's been having a bit of a boost issue, it has an old style Vitesse MAF that Vitesse says that have been discontinued 10 years ago, I do not have the user manual for it so I do not know it's function. Boost pressure initially never goes above 1 because a previous owner/mechanic decided to loop the turbo pressure line back to the air intake line after the MAF, this was in place of the blow-off valve, the BOV was not present. After capping off this particular connection, car was able to build boost, up to 1.2 bar, never higher. The car has smelt rich all along, in the cabin. It is unhealthy bad when the rear hatch does not close properly and does not have a proper seal. So I'm now running in this configuration and this is the next thing I'll be addressing. I've ordered in a BOV and intake manifold gaskets so I can have a look at it soon hopefully!

So far, I'm suspecting the cycling valve being faulty. So when the intake is out, I will be checking on this. I've had the intake system smoked and there wasn't much vacuum/connection leaks. I'm also not sure on the vitesse MAF's function, so that may be where another problem is. Otherwise, I'm very much open to other suggestions on places to look at once I'm in there. I've included pictures of the Vitesse MAF and also the engine configuration before the correction of the wrongly connected BOV region. Thank you!

GPA951s

John is still around search some threads and you can ask john Vitesse directly . The richness is coming from the low boost less air- same fuel= rich ..

fast951

No boost + running rich are symptoms of a pressure leak. Smoke testing the intake will show vacuum leaks, however a Pressure test will also show pressure leaks.

Once air is sucked through the MAF, it will send the signal to the DME. Which calculates the fuel needed based on target AFRs. If you have a pressure leak, the air measured by the MAF never makes into the engine (no boost). The DME has no way to know the measured air escaped the system. DME commands injectors based on MAF signal (rich AFRs as air escaped system).

The same thing occurs with the stock AFM.

Keep in mind MAF + Injectors + FPR + software all must match as a system. So if you find the root cause of no boost, and it is not a pressure leak, then it's time to investigate deeper to know the root cause of the rich AFRs.

At first, I would run a intake pressure test before making any other change.

You need a BOV in place! The hose linking the Intercooler pipe to the J-pipe is a huge boost leak. And will screw up the AFRs. Whoever did this, unless for an emergency to get home, had no clue of how the system works.

Note: I believe you emailed me some time ago. I did find the K&N filter part number for the metal MAF you have on your car. It's K&N 553+4728.

notny41

I have an older vitesse on mine too (looks exactly like yours) and my car seemed like it was running rich. Troubles on hot starts and stalling at stoplights. Although, I never had a boost issue. I replaced a few things but I think the major ones that helped me out were:

1. new throttle position sensor (old one would give me mostly good readings on my multimeter when moving the throttle through the range but a little flakey in some areas)
2. new DME temp sensor (the old one had an open resistance so it was doing nothing)

michaelmount123

This is the kind of support we can only wish for from other manufacturers/vendors. Clearly he's there to help. Hope you're listening, OP.

stuckheng

Thanks for the replies guys! Yes I did email you awhile ago John, thanks for your dedication to the community 🙂

I’ve done the smoke test, but not sure if there was any pressure during the test, will check with the shop. I suspect the wastegate being open, either due to the wastegate or the cycling valve, hence the 1.2 bar on the stock boost gauge. If the wastegate is open, it should cause the MAF to sense more air than it is going into the engine.

The BOV connection has since been capped off! Before being capped off, the car was not getting boost at all. I’ll have the proper valve in next week most likely.

I would also like to check the resistance of sensors as suggested. So far I see a pretty good guide by edredas on YouTube recently, gonna try it out.

I will be pulling off the intake manifold soon to have a look after I receive the intake manifold gaskets the coming week. Anything else I should look out for? I assume the intake manifold job would be easier/less possible to screw up than a timing belt 🤞 At the very least there’s more access and I won’t have to get underneath the car.

stuckheng

I forgot to mention one important point. The car also stalls out when I shift gear at times. I notice that when at times when I shift slower, the engine rpm falls to about 400rpm, mostly it catches back and engine continues running (sometimes showing split second red exclamation alert), there are sometimes that the engine will just die out. I can restart the engine by letting off the clutch, or by cranking while clutched in.

Does this issue sound related to the AFR of the vehicle? Or do I have to look elsewhere for this? It’s the most scary thing when it first happened, there engine went off while I was at speed, the brake booster stopped functioning and I suddenly had less effective brakes. I must also mention that this started to happen after the BOV connection changed from being short circuited to the setup without any BOV.

mwc951

Your MAF harness looks rough...
Verify your FQS setting is correct...
These were issues I had sorting out a VR MAF that's older than yours, just my 2 cents.
BTW...where'd you move the battery?

Frank@Work

Looking at the location of the windscreen wipers I’m guessing it’s a RHD. A RHD 944 has the battery in the back.

stuckheng

Yep the MAF harness looks rough. Being quite new to this, how do I check the MAF connectivity and resistance? I have a basic multimeter.

Just read up on the FQS and it seems good to at least check if anyone meddled with it. Thanks for the suggestion, what effect did it have on your car?

Quite right! The car is RHD, so the battery is at the back. When I first saw the car I thought this arrangement was aftermarket 😂

mwc951

John is a wealth of knowledge. Digest what he's suggesting and definitely start there. Search his previous posts, there's a ton of valuable info out on the forum.

The incorrect FQS setting mimicked a strong vacuum leak.
My MAF harness was 12 -15 years old and had seen better days.
Touching the MAF / harness connection would cause the idle to fluctuate badly or kill the engine all together.
The new harness made a noticeable difference in my case, idle is rock solid & throttle response seems better.
Here's what I used...
MAF Plug
MAF to factory harness connector
Got the IAT connector from efi hardware.com too. Shipping from Australia was surprisingly quick.