Boost Issue 1994 GT

[Bazza-NZ]

Hi all,

I have been trying to sort out my twin turbo which has boost issues. It doesn't boost at all on the secondary turbo and enters into limp mode (Code 66). What happens is as soon as it revs to 5k it hard cuts and throws a code. Gets full boost on the primary then start the change over then it feels like it dies off.

So far..

I've changed over the BBOD with another unit

Cleaned AFM with MAF cleaner

Check all vac lines are connected correctly

Removed turbos to check them for any damage

New spark plugs

Running out of ideas, thoughts?

[lachlan]

One or both of the blow off valves have a hole in the diaphram. Suck on the vac line to them and see if they hold vac . If you can breath through it they are fkd

Have you got a boost gauge on it ?

[Bazza-NZ]

 lachlan said:

One or both of the blow off valves have a hole in the diaphram. Suck on the vac line to them and see if they hold vac . If you can breath through it they are fkd

Have you got a boost gauge on it ?

I'll check out the BOV tomorrow, didn't think of them. If it's the case are any twin turbo BOV compatible or will I need to check for specific part numbers?

I had one in it briefly but removed it again. Tee off the IC BOV pipe and showed 9/10 psi on primary turbo.

[les666]

Yeah I reckon secondary bov. My 94 did the same thing when I bought it. Any twin turbo bov should work. They have different coloured stickers but the only difference is the angle of the vac nipple.

[Bazza-NZ]

Thanks for the quick replies and information. I've tried them using the vac hose and they seem to hold find but I'll remove them to physically inspect them and check there direction

Just, out of curiosity, what direction should the arrow point?

[lachlan]

I believe the arrow is flow of air . So both point down .arrow points into the intake tract away from the turbos /intercooler. If you put secondary one upside down it still works but majes a funny fart /groan noise lol

You cant really tell much from looking at them . But you will be able to suck on it and see if it opens and stays open . Youll hear it click /clunk as it moves

My 94 auto has holed both bovs . The 95 manual im workin on atm also had a hole in the secondary even tho it drove fine

[Bazza-NZ]

 lachlan said:

I believe the arrow is flow of air . So both point down .arrow points into the intake tract away from the turbos /intercooler. If you put secondary one upside down it still works but majes a funny fart /groan noise lol

You cant really tell much from looking at them . But you will be able to suck on it and see if it opens and stays open . Youll hear it click /clunk as it moves

My 94 auto has holed both bovs . The 95 manual im workin on atm also had a hole in the secondary even tho it drove fine

Tested both of the BOV today and the primary turbo side has a hole in it. Didn't make a sound or hold pressure so I'll replace it this week and see if that makes a difference

Secondary BOV made clicking noises and held pressure. Appears to operate as expected.

Edited December 26, 2015 by Bazza-NZ