Luis de Prat

Symptoms are these:

Turn on the car, and when it reaches operating temperature, sometimes the turbo will not kick in on acceleration (flooring it) but the needle reads right past the middle (1 bar) mark on the stock gauge.

Turn off the car, turn it back on, and flooring it again, presto! The turbo kicks in.

Every time the problem resurfaces, I can correct it by shutting off the car and restarting it.

Any ideas as to what could be happening here?

TIA

Ski

Luis, have you checked the diagnostic port for trouble codes after the "failure", just as place to start?

gmsracing

Sounds like the computer is going into limp home mode. It will only boost to about 1.2 bar. Like Ski said, you need to diagnose what is causing it to go into that mode. I had this problem recently and it turned out to be a bad klr computer. Check Lindsey's website on how to make a cheap LED blink code tool. If you don't have access to the factory manuals they also have the codes deciphered.

Luis de Prat

OK, here's another one for the archives: problem solved!

Turns out the DME relay was original on the car (Oct 1990 date on it) and was starting to fail.

It occurred to me to replace the relay the other day when the car wouldn't start until I cranked it several times. Replaced the relay and the turbo kicks in normally and it hasn't refused to start since.

I appreciate the responses!

shortyboy

great,thread.once my car gets running,ill be sure to check the relays!

Luis de Prat

Well, it was good while it lasted. Problem is back. Including the nonstart situation.

Ideas, please!

fast951

Check the connection on top of the cycling valve. More than likely a bad cycling valve.

Luis de Prat

Thank you, thank you, thank you!

The car has around 112K km, so these items should start failing, I guess. Does the intake manifold need to come out to replace the cycling valve? TIA again!

sweanders

Yes, intake will have to come off. That is fairly simple to do though.

Rich Sandor

1 vote for broken cycling valve.

maybe a good time to change a few of the sensors while the maifold is off.

fast951

When intake manifold is off, replace ALL hoses etc. if still the original ones..

Luis de Prat

OK, so I was preparing to replace the CV with a new unit when someone suggested it's not the problem. Car has a new DME relay.

Your ideas are welcome before I pull the intake manifold to replace the CV.

TIA

black944 turbo

Sounds like either the KLR or the CV to me.

Rich Sandor

You can disconnect the line from the CV to the WG. This causes the WG to stay shut at all times, until the exhaust gases overpower the WG spring. With the wastegate shut, all exhaust gases will route to the turbine. Drive around like this for a bit and see how the turbo works. It should boost to 2+bar easily. Try not to overboost the engine by driving WOT, just give her a little gas and see if the turbo is spooling.

If it works fine, you KNOW there is something amiss with the CV.

SD Porsche Fan

Bad diverter valve?