86 SVO overboosting

[scenario]

When I floor it I am overboosting and the yellow oil light and buzzer sound mementarily. I even had a backfire a couple of times. What could cause this. I replaced the vacuum hoses that go from solenoid to turbo. There were 3 hoses I replaced.

The part number on the solenoid is E5ZE-9K378-AB. I was thinking of replacing it but can not seem to find one. I dont know if it is bad or not.

I did some research but am still a bit confused on how all this works. Not really sure what the solenoid does or does not do.???? Problem could be elsewhere.

[65ShelbyClone]

Does it overboost on the "regular" fuel setting?

The boost control solenoid opens a passage to the wastegate circuit. When the solenoid is open, it releases pressure through a metering orifice in the t-fitting on the compressor housing. It then takes 14-15psi to open the wastegate instead of 10 because of the "leak."

[scenario]

Yes it is overboosting on the "Regular" setting.

[Patrick]

The latest similar complaint ended up being a bad wastegate actuator diaphram. Pump a wee bit of air (~10PSI) into the actuator with a mityvac and see if it leaks.

[SVOTim]

If you have a extra vac/air port on the turbo compressor housing blocked off with a rubber cap, check it. Could be cracked. That was the cause of my overboost issue, moons ago.

[scenario]

Ok here is the update.

I pulled the actuator rod off the WG arm and tested with air. Actuator works as it should.

The wastegate is stuck and I can not turn the arm. This is a problem with the wastegate itself. I can not get it to move at all by hand, not even a bit. I am going to try to put visegrips on it and then try to move it and hopefully I can work it free.

Anyone have any suggestions???

I am starting to think I may have to pull the unit off which I REALLY do NOT want to do. Should I try spraying with PB or something????

[scenario]

After some real convincing with PB Blaster and some hard raps with a hammer and long chisel, I worked it free constantly going back and forth. I may have slightly bent the WG handle that the actuator rod attaches to. There was nothing I could do. It was either all or nothing bc it was not moving.

I do not know how much the WG travels from closed to open. I would say the handle is moving 45 degrees atleast. I soaked it with more PB Blaster when I was finishing up and will reattach it all tomorrow. I will also play with it a little more to see if it gets even more loose. It is turning by hand pretty good though.

I am hoping it just locked up from sitting for 15 years and now that it is free and will be driven often it may stay that way.

[oneowner88lx]

Glad you found the problem. That waste gate arm does not move a whole lot. The flapper inside the elbow housing, when it opens, hits the back of the inside of the elbow fairly quickly restricting its movement. As long as the waste gate is held shut nice and tight with the actuator hooked up you should be good to go.

[65ShelbyClone]

Something that might help is getting some graphite powder worked in there between the wastegate shaft and housing. A 2000°F anti-seize compound may also be an option provided it won't affect the O2 sensor.

[MikeFleming]

Take the two nuts and flange off the downpipe. Unplug the O2 sensor connector. Carefully loosen and remove the five 13mm hex bolts that hold the outlet elbow to the turbine housing (Note these are NOT normal hardware store bolts!). Clean all the surfaces of rust especially the dump hole in the turbine housing. Clean everything up (180/220 grit paper) and run a tap through the bolt holes (8x1.25mm). Then re-assy the outlet elbow and bolts using a high-temp graphite/moly lube on the bolts. Bolts go to 164 INCH-LBS - less than 15 Ft-Lbs. Re-connect the downpipe flange and nuts.

Do this every 30K miles.

You can attempt to add some lube to the wastegate flapper shaft hole, but nothing will last very long (like minutes to maybe a few hours max).

[oneowner88lx]

I would be afraid those bolts would snap off inside that hot side housing if he tried to take that elbow off.

[MikeFleming]

^ DOH! Take them out when they're cold!

It's always a good idea to have spares.

[scenario]

Problem solved. Here are a few short video clips of boosting without any lights or buzzers going off!!!! YAY!!!!!!!

[65ShelbyClone]

Problem solved. Here are a few short video clips of boosting without any lights or buzzers going off!!!! YAY!!!!!!!

That pretty well dispels any myths about turbo lag, huh?

[MikeFleming]

Those vids reminded me of some dyno dash shots a few years back. Thought I'd share.

[oneowner88lx]

Nice job getting that problem solved.

[scenario]

Thanks to all. NOW this is the car I remember!!!!!!!!!


When I bought this car there was no such thing as the internet. There were no kids car seats (if there were I never saw them....LOL). My children until last month (thats when I resurrected the SVO) never saw a lap belt before. Every car they have been in has had 3 point seat belts in the rear. They think the lap belts in the rear seats are the COOLEST thing they ever saw and they think its like a ride at the amusement park.


I love this car. It just wants to GO! and GO FAST!!! Handles great, nothing better than that turbo spooling up......

[MikeFleming]

And another SVO back on the road!

Congrats on getting it running properly again!

[Larry_S]

My car is overboosting. I have the boost lines capped off at the T fittings and only have a line running directly to the wastegate. I also connected wastegate directly to the vacuum tree to try that. The gauge approaches 18 psi with full throttle applied. The wasegate arm moves roughly .2" - .25" with 10psi applied. Full scale on the psi side of the gauge is 10psi. Note the vacuum line is not connected in pic the intent of pic is to show the capped off t fittings. When tested I connected the wastegate to the t fitting and also tried connecting to the vacuum tree.

P1020283.JPGboth states.jpg

http://mc2.gotdns.com/photo/photo_th...745f6973737565

[MikeFleming]

From the video you posted earlier, some of the bolts mounting the turbo outlet elbow are falling out. Fix that first.

On another note the wastegate diaphragm spring is weak and opening too far under 10 PSIG (spec is 0.015") but that will cause a lower boost setting, not a higher one.