Low-Key-Oly-fd

Sup names Tino, and i just recently picked up an fd, 93, car is silver, 5sp i love it! awsome car,
anyways, i drive it and when i reach 4500 the boost gauge dies off, 10 psi, the slow to 0 no power past 4500,
i looked under the intake manifold, and there is 1 sensor that bolted to the intake top plenum, and 2 or 3 plugged vacum lines, i was told that there might be a cracked vacum line also?? anyone know were to start? or the line the would usually break?? i bought a 50 ft roll of vacum line and someone told me to do a complete replace of all the lines??

i dont know any help would be much appreciated!! or any locals?? thanks..

rynberg

You need to perform basic turbo system troubleshooting. Check the FAQ thread for the link (under T).

The first thing to check would be the line and check valve running from the y-pipe to the pressure chamber. The check valve often fails/breaks.

ncfd1

secondary turbo problem look under faq's and start there

recon fd

It may not be aturbo problem, if your lucky. This was happening to me. I think you may have a waste gate issue. This is how it was explained to me by my friend. When your W/G lets off the 2 psi to drop to 8 ,during your normal 10-8-10 pattern, your waste gate is getting stuck open for some reason and not closing which in turn all of your boost is just being wasted into your atmosphere. This may be it or it may be not, but it is something to think about.

goodluck,
josh

dgeesaman

iTrader: (7)

The story you are relaying from your friend is generally incorrect, but yes it is true this "turbo problem" is generally a problem with the widgets that control the turbo and not the turbo itself.

The 10psi below 4500 indictates that the wastegate is probably functioning fine.

To get full boost above 4500rpm, 3 major things must happen:
1) the Turbo Control Valve opens and feeds the secondary exhaust.
2) the Charge Relief Valve must close.
3) the Charge Control Valve must open.

Since you see 0 psi above 4500, it suggests 2) is the problem. If this valve hangs open, all the boost can leak out into the airbox, resulting in 0psi. I think problems with 1) and 3) tend to still produce some boost, either delayed or reduced, but not consistently 0.

Try disconnecting this from the airbox so that it releases air directly to atmosphere. It should start making a BOV noise at 3500rpm, and stop whooshing at exactly 4500 - if you hear air rushing above 4500, that's the sound of your boost leaking. If this happens, reconnect it to the airbox and post that this is the case and we'll try to figure out what's causing it to stick open.

Dave

Low-Key-Oly-fd

also, it seems to work randomly , i just changed alot of vacum lines and made sure they were all in the correct posisions.. i just did a 3rd gear pull and it pulled all the way to 8 or, 7.5 u know, but i will go check the valves right now good idea, that thought did not cross my mind!!,

EDIT :::::::::::::::::::::

ok I checked the valves, the lower valve when pulled acts like a normal valve, closes and, release`s pressure off throttle, and the top valve i rev`d it to 6,000, and when i release the throttle it dose no blow off yet no air comes out on the rev or , down reving,.

???????????????????

Low-Key-Oly-fd

also when it does work for a second over the 4500 mark, it dosent hit 0 instantly it creeps to 0 though quickly, ? turbos are new though so ??

dgeesaman

iTrader: (7)

The lower valve (the ABV) appears to be working properly. The turbos are fine. The problem is in the solenoids, valves, hoses, etc that don't get replaced with the turbos.

To properly test the upper valve (the CRV) you're not listening for sound after you let off throttle. Simply start accelerating full throttle from 2500rpm to 5000 or 6000. (4th gear at 45mph should be a good starting point). The valve should whoosh from 3500-4500 while you're under throttle. At 4500 the sound should cut off sharply. It should not be whooshing when you let off the throttle ever.

If it passes that test consistently, then do this:
A) after the test run, disconnect one of the hoses running to the black pressure tank on top of the engine. Air should rush out.
B) then trace the vacuum line running from the vacuum tank (the black tank almost hidden under the alternator) and disconnect that hose. You should hear lots of air rushing in.

Dave

Low-Key-Oly-fd

yah the valve wooshes when ever i let off throttle. "when i dont get boost" but if it boosts correctly" somtimes it does not woosh.. so sometime it cuts off at 4500 sometime it does not, the Upper valve.. and also im missing 2 of the upper tanks, i got them from the lastowner but the are not bolted or plugged in

dgeesaman

iTrader: (7)

Yeah, if you're missing the pressure tank or vacuum tank your system is not going to work. You need to get under that UIM and reconnect things exactly per the diagram. Make sure you're not looking at the A/T version of the diagram - the M/T has only one pressure tank and one vacuum tank.

Dave

Low-Key-Oly-fd

ahh this vacum diagram looks different then the one i was going off of, i will switch things around tonight after work and post the results, thanks for that diagram dave,




Best regards Tino.

Low-Key-Oly-fd

ok i did that vacum diagram.


HOLY ****..... thank you very much for the help........ I owe u some dinner....


it was the air bypass staying open :-)

riptor

now thats what i like to see guys...problems getting solved . once again why i love this place..lol. glad u were able to diagnose ur prob low-key.
-steve

HDP

iTrader: (2)

How do you fix issues on a car you plan to sell... get FREE help from people on a message board and pocket the $$ you would have spent at a repair shop.

Low-Key-Oly-fd

i own my own import shop, but i know Nothing about rotary`s.. the car is the daily driver, and i came to the boards to fix it and have fun!! especially at pir lap days, putting the cage in next week