Can't recirc. BOV

[Dhan]

Picked up a '91 TSi. Needed some tlc and now that I've got it running smooth, one of the issues that I'm trying to fix is the vented bov. It runs decent enough but I don't like the "sneeze" every time I shift.
The car still has the stock 1g MAF that the PO said was "hacked" to accommodate the vented bov. Visually, it looks the same as my turbo Laser's MAF and this TSi has no engine management as far as I know. I asked the PO and he said the guy before him did it, so he doesn't know.

So I bought a new untampered with 1g MAF to put on the TSi, but now it won't idle. Starts right up then dies. I put my Laser's MAF on, same thing- starts then dies. It only wants to run with the "hacked" MAF.

I searched to see if this has been covered before, and found a lot on venting BOVs, but it seems the only way that anyone vents is by using a GM MAFT. So my questions are: what does "hacked" mean in this case, what did the PPO do exactly, and how do I fix this?

Edit: I did put on a recirc. tube for the bov

 

[cl1ckclack]

i would think you want to either

a. leave on the "hacked MAF" as it was working.

b. recirculate your BOV, so you can use a normal MAF,

c. buy a MAFT to do the vented BOV setup right.

 

[jtmcinder]

So my questions are: what does "hacked" mean in this case, what did the PPO do exactly, and how do I fix this?

I'd love to hear the answer to this, too. I'm very interesting in learning how the MAF can (magically?) know when the BPV is open, so it knows when to under-measure the air-flow.

 

[Dhan]

i would think you want to either

a. leave on the "hacked MAF" as it was working.

b. recirculate your BOV, so you can use a normal MAF,

c. buy a MAFT to do the vented BOV setup right.

I did recirc. the bov with a new rubber hose and it doesn't run quite right between shifts when it's installed. It wants the bov vented. But that doesn't add up. It can't run with and w/o a recirc tube without doing any tuning. Like jtmcinder mentioned, the MAF itself can't detect these changes.

Of course, I could be missing something else entirely.

The only reason I'm hesitant to just put on the recirc tube and make no other changes is because I don't want this to effect the a/f ratios and cause damage. Plus, if this hacked MAF goes out, I have no way of replacing it. Plus, I'm just curious as to what is going on here.

I suppose I could just send the ecu out to ECMlink and have them convert it to eprom, then I could use Link to see what's happening with the a/f ratios. I was just hoping someone else has already come across this sort of thing before and could enlighten me.

 

[TunaTalon]

I'd love to hear the answer to this, too. I'm very interesting in learning how the MAF can (magically?) know when the BPV is open, so it knows when to under-measure the air-flow.

jtm inder it looks like your sar asm switch is stu k down on your keyboard. Try prying it up with a s rewdriver but don't use too mu h for e, you ould break off the key between the x and v.

/sarc click, bang /sarc

Stupid swit h is stu k again.

 

[Dhan]

Made some progress: the car doesn't run correctly with any of the mafs now, so I can rule that out as an issue. BOV is now a BPV with a recirc. tube, so that's covered too.

There is still a bucking and stalling issue between shifts, and erratic idling behavior while driving. Some kind of an a/f mixture problem?
I'm guessing, that starting at the injectors and working my way through the fuel rail, the filter, then back to the pump is the right way to go now. Is there something else I should be looking at?

I also wanted to swap the ecu from my 90 Laser into this 91 Talon to rule out the ecu as a problem. I read that the tach signals are different though, does that just mean the tach won't work, or there more to it than that?