Under boosting 1997 850 t-5 after replacing parts

Post by **Sveedy** » 17 Apr 2023, 18:59

Neil, you know more about these cars than I do. I was taking a shot in the dark, which upon further thought, is probably a miss. If he's got boost, but at higher rev's, then the wastegate must be holding pressure. Seems like the spring in the CBV might be wrong.

Post by **scot850** » 17 Apr 2023, 19:14

That is why I am wondering if there is a difference between the old style 850 and newer V/S/C70 style TCV's. It may be a combination of if you use the older style it may work ok as that is what the CBV is set up for, or if you use the newer one you may have to adjust the CBV to work with it. I am out of my depth there!! LoL!

The only other thing is the pipes are not connected to the correct ports on the TCV or there is a leak in the vacuum or turbo pipework requiring longer times to spool up.

Neil.

Post by **matthew1** » 17 Apr 2023, 20:00

What RPM is peak boost? I think mine was mid 4k.

Post by **hausmeister** » 18 Apr 2023, 04:33

If the boost controller/tcv is suspect then you migth want to get a different one, see also here
viewtopic.php?p=483876#p483876

I can only recommend it.
Regarding boost, my car was very laggy for a long time. I fixed it over time doing different things.
(Now, since it is an automatic, it pretty much always is in boost (depending on throttle) as soon as the torque converter slip lets up.)
- finding and fixing boost leaks
- adjusting wastegate spring a bit tighter
- getting a new tcv and shortening hose lengths. if the hoses are too big and long it will cause issues in my experience with the tcv control lagging behind

Hope you can find the problem. Even with the stock ecu the car is quite peppy from the go.
Not sure if that is what you mean by underboosting though.

buggzz · Post by **buggzz** » 20 Apr 2023, 20:49

Sorry for the late reply, I swapped the ipd tcv with the round one that comes off the turbo model, and after some more testing It fully spools up at 4500. But I do sometimes feel like its lacking some power, it feels like fuel is getting shut off. And the tcv is pretty far from the original starting point its closer to the intake for the airbox like at the front of the engine.

Post by **scot850** » 20 Apr 2023, 22:45

The TCV should mount near the airbox. The later style hangs off the engine side of the airbox near the air inlet pipe to the turbo.

Late spooling or weak could mean the CBV needs adjusting or the diaphragm in it has a hole in it. Also you will need to check all the pipe work and intercooler for leaks.

Finally I would check the fuel pressure at the rail. Should be in the region of 43 psi. When was the fuel filter last changed?

When were the sparkplugs last changed and the gap set to .028"? When were the distributor cap and rotor last changed or the plug leads?

Neil.

buggzz · Post by **buggzz** » 26 Apr 2023, 21:32

The cbv has been replaced, was a pain to do but got it done around the same time i replaced the tcv. The fuel filter was replaced around 4 months ago as well as the fuel pump. And how do I check the PSI on the rail. But about sparkplugs I need to replace those soon, since I have no clue when the last time they were replaced. Thank you!

Post by **scot850** » 27 Apr 2023, 08:17

There is a valve on the LH end (driver's side) of the fuel rail that looks like a tire valve. You test the pressure there.

Neil.

Under boosting 1997 850 t-5 after replacing parts

Re: Under boosting 1997 850 t-5 after replacing parts