930 turbo problem

[solarispete]

Sorry if this was already posted.. had some problems with posting this morning.

I have an 85 930 Euro spec.

Having problems with car when turbo boost is suppose to kick in, it literally drags and lose power (but doesn't stall), and sometimes spews out puff of smoke. It started happening last year and has gotten worse.
symptoms:
1) Car seems to run ok when cold, but happens when it's warmed up after 15-20 min light drive.
2) car idles high when this starts happening (around 1300 rpm)

Finally took to local porsche mechanic. He suspected WUR problem so he sent down to California to rebuilt. He reinstalled it after it got back and it ran good for 20 min and problem happened again. The rebuilt shop did confirm that the WUR's diaphragm was bad.

So, he's done the following, but didn't fix the problem
1) replaced the red fuel pump relays (in the front fuse box)
2) replaced the black fuel enrichment relay (in back fuse box)
3) checked all vacuum and found no leaks
4) replaced fuel accumulator
5) both Bosch fuel pumps were replaced back in 2011 so they are pretty new.

Any advise?

my mechanic also told me I am using wrong fuel and that maybe be causing the problem. I am using Chevron 91 (up to 10% ethanol). He told me to use 94 (no ethanol). He thinks the ethanol is bad for old classic porsches. The trouble is that not all stations carry 94 Octane with no ethanol. Also it costs $1.70 in Canada... He says it's cheaper than fixing the car.. Any thoughts on this? My friend has a 86 Carrera and doesn't use 94 and runs fine for many years, but then again his is not a 930... I don't know who to believe.

Thanks for listening!!!

[TDH888]

So what happens to your car is when you rev hard at lower gears when the boost comes in the car loose power or when your in higher gear and hitting for 100mph you loose power ?

[16Volt]

Ethanol destroys allot of the plastic fuel system components in our cars so the advice is always to avoid it.

[Alan L]

It is also bad for the fuel head I think.
Unless you can find an obvious problem - you might have to delve deep into the fuel system.
Wait and see what other options get posted. But you may have to check the fuel system performance and finally the fuel head (FD) performance. I 100% avoid using ethanol blend fuel. I would substitute with a lower grade octane if necessary, before using 10% ethanol.
Alan

[kevinkjse]

Hi Mate

Just because you replaced the red relays does not mean they are good as with the pumps, but the red relays are now made in china and produce problems, could always link them out temporary! if no change check fuel pressure

kev

[infraredcalvin]

Sounds like you have an air leak somewhere...check your intercooler seals

What color is the smoke, is it really a “puff” or is it a smokescreen? Sounds like a couple of things going wrong...

[Alan L]

Are you getting boost? Possibly a seal letting go at boost. The neck of the IC into throttle throat.
The high idle revs afterwards suggests maybe a leak. but stop using ethanol fuel. Presumably you have no AFR readings. the best thing you can do for your car is install an AFR gauge.
Alan

[WERK I]

I find it surprising you porsche mechanic did not do a visual inspection of the turbocharger itself. It's relatively simple to access (drop the muffler, remove cold air inlet tube). He could looked for damage, axial play and ease of rotation. Is this original equipment or are there mods to the engine?

[Rich76_911s]

Do you happen to have an AFR gauge on the car?

I had similar problems with my car. Boost enrichment was creating an extremely rich mixture (think 9:1 AFR's) and I had a big ol' cloud of black smoke behind me when under or approaching boost. I got kicked to the back of the line during Turbopalooza because a few members here got out of their cars sick and struggling to breathe.

If I rolled up to a hill in 3rd gear at cruising speed and added gas to the point where boost should be kicking it, I'd get a huge plume of black smoke behind me and the car wouldn't stall but it sure didn't want to go anywhere either. If I dropped a gear and got my RPM's up over 3500 it would go like crazy though.

Check all of the connections on the intake air line, from the Fuel meter, down to the turbo, up to the intercooler, and the intercooler to the throttle body. Also, check that the studs that hold the intake manifold onto the heads are torqued down correctly.

Did the mechanic also check to make sure your plastic intake spacers (between the intake and the heads) don't have any cracks? You can spray some carb cleaner around them and see if the idle picks up any. If you hear the idle jump you've found an air leak. ***Be careful spraying carb cleaner around a hot running engine***


Cheers
Rich

[Rawknees'Turbo]

Originally Posted by solarispete

S

my mechanic also told me I am using wrong fuel and that maybe be causing the problem. I am using Chevron 91 (up to 10% ethanol). He told me to use 94 (no ethanol). He thinks the ethanol is bad for old classic porsches. The trouble is that not all stations carry 94 Octane with no ethanol. Also it costs $1.70 in Canada... He says it's cheaper than fixing the car.. Any thoughts on this? My friend has a 86 Carrera and doesn't use 94 and runs fine for many years, but then again his is not a 930... I don't know who to believe.

Thanks for listening!!!

e10 is not causing the running problem - that is all we have available here in North Texas (93 octane, however, but the 91 you have will not cause what you describe) and my 1987 runs on it with no problem.

[T77911S]

check the rubber elbow on the intake that goes from AFM to the turbo. if it is soft it WILL collapse when on boost.

what fuel enrichment relay are you talking about? as far as I know your car should not have any of that crap.

check the over boost switch on IC, you could bypass it as a test. just ground the wire.

[DSM]

What’s the condition of the engine? (Compression / Leak Down Testing)
LC ENGINEERING Carburetor Tech

What are AFR’s? (Install Wideband Sensor)
https://www.amazon.com/AEM-30-4900-Wideband-Failsafe-Gauge/dp/B007ZAQLF6

What are fuel pressures?(System, Cold, Warm) (Plugged fuel return at tank?) Pressure test will tell.
911 CIS Primer - Testing: Pressures

What’s the condition of the turbo charger & seals?
Is turbo making boost? Stock boost diverter stuck open?

Entire Ignition system condition?(CDI, distributor, wires, plugs, etc)
Where is timing set? Is timing advancing?

[Carbster09]

I had a similar problem. First I thought it was the CDi box, that was rebuilt. Finally we replaced a fuel pump, which fixed it or so I thought. Later I was having issues like you talk about. At times it was almost undrivable. The red relays as noted are not made in China. I replaced these; however I also believe there could be a short behind the relay in the board where they "plug" into. In the meantime I have replaced the red and black relays a few times and now have a combination that is working excellent. Go figure!

[Carbster09]

Sorry, make that the relays ARE made in China. If anyone has a source for non-Chinese relays let me know. I will buy a handful. I also keep one of each relay with fuses in the car!

[908/930]

Are you developing any boost pressure? Do a quick check to make sure your blow off valve is closing properly.

Is the smoke Black or blue?

Also Shell V-Power premium also has no ethanol.