'86 SVO Boost Surging in Premium Mode Only

[David Eckel]

Hi, everyone. I'm new here. I just bought a 1986 SVO that for the most part is in great shape. It isn't without issues, however. My main concern is boost related. In low-octane mode, the boost builds rapidly and stays steady at about 8 psi. In pemium mode at full throttle, it builds rapidly up to 16 psi and wavers between 10 and 16. Check out this video I shot to see what I mean.

[David Eckel]

https://www.youtube.com/watch?v=7J4bDTlPzJg

[David Eckel]

I should also add that the car is utterly stock, with two exceptions. It has a cat-back Flowmaster dual exhaust, and it has an aftermarket cruise control which seems to be inoperable. And I'm sorry for the multiple posts--I can't seem to separate paragraphs with my enter key in the forum text dialog box--it does nothing. (weird!)

[David Eckel]

And no newb thread is complete or worth responding to without some pictures, so here you go!http://i176.photobucket.com/albums/w166/dfeckel/Mobile%20Uploads/2015-10/FD765767-9C66-49F6-9C18-E2CCF29E240C_zpsaisjguyo.jpg (http://s176.photobucket.com/user/dfeckel/media/Mobile%20Uploads/2015-10/FD765767-9C66-49F6-9C18-E2CCF29E240C_zpsaisjguyo.jpg.html)http://i176.photobucket.com/albums/w166/dfeckel/Mobile%20Uploads/2015-10/0BBF2FEB-F299-451D-B9C7-8FCEC578C5FC_zpsuearyibd.jpg (http://s176.photobucket.com/user/dfeckel/media/Mobile%20Uploads/2015-10/0BBF2FEB-F299-451D-B9C7-8FCEC578C5FC_zpsuearyibd.jpg.html)

[MikeFleming]

It's supposed to do that.

Needs more octane.

[David Eckel]

Thanks for the response. The car has had two full tanks of 93 octane run through it at this point, so that video was using high octane pump gas. Are you saying it needs higher octane than that to have a stable maximum boost under full throttle? I'll run the tank down low and put 10 gallons of 110 octane in there (at $8/gallon--ack!) to see if it makes a difference.

[MikeFleming]

Are you saying it needs higher octane than that to have a stable maximum boost under full throttle? I'll run the tank down low and put 10 gallons of 110 octane in there (at $8/gallon--ack!) to see if it makes a difference. Yes, correct.

Variable-boost, variable timing with interactive control. That's the design.

Boost comes up until it pings, then timing is immediately (next firing cycle) retarded until the pinging stops, while boost is also reduced (takes longer) and timing is advanced again. Lather, rinse, repeat.

There is no memory of what happened previously and there is no individual cylinder control. VERY primitive compared to engine mgmt systems today.

There are some things we can do/check to reduce octane sensitivity, aka pinging, such as reducing base timing slightly, reducing peak boost pressure, verify fuel supply (and injector balance) is proper, cooler air, clean the collected oil out of the intake track, etc.

Try one gallon of 100 octane (note ALL 110 is leaded!) into 5-10 gallons of 93. Less expensive. Or add 1-2 gallons of hardware store quality Toluene to a tankful. It'll smell a bit different but makes for a very good octane test.

[Mike S]

Did you replace all of the boost controller hoses? You may have a leak.

[David Eckel]

Great description of the boost management system. I am so new to this turbo Ford world. The extent of my turbo wrenching ends with the computer chip I had soldered into my '98 1.8t Passat. And good tip on the toluene. I may have misremembered the actual octane rating of the local station that has "race" gas. It's probably 100. I replaced only one boost control solenoid hose. It was pretty rough. The other ones appear to be replacements, i.e., fuel injector hose with screw type hose clamps instead of the crimp/pinch-type clamps on the hose I replaced.

[David Eckel]

I just put 8 gallons of Cam2 100 octane into the mostly empty tank over my lunch break. The fuel gauge was just above the empty red line, and the 8 gallons brought it up to between 7/8 and full. I ran it for ten miles to get all the lower octane run through the system and the 100 to get evenly mixed in. Result? No difference. I've ordered some shop manuals and will now begin to learn more about this EEC-IV turbo system and start checking off different possibilities. Will keep everyone updated.

[MikeFleming]

Take the charge cooler off and inspect it for oil. Clean as needed (brake cleaner, shop vac, isopropanol alcohol, drain, shop vac).

Also inspect / clean any discovered oil in the VAF (vane airflow meter) and associated hoses between the air filter element and the turbocharger compressor inlet elbow. Use the same mix listed above to clean the hoses and the airflow path of the meter (do not soak the meter! - spray and drain / dry).

[David Eckel]

Thanks for the advice. I will do this ASAP. I did notice what looked like some oil residue around the intercooler inlet, so I'm sure there's some oil contamination in there.

[MikeFleming]

Normal, expected accumulation from the PCV system.

Has a really negative effect on heat transfer inside the charge cooler and a semi-negative effect as the vapors get into the combustion chamber (oil being an octane degrader in petrol).

[Eyelawdoc]

Another thing to check is the condition of your PRIMARY wiring to the EEC IV ignition module on the distributor. I've had several stock SVO's over the years that had problems with surging under higher boost pressures that I was able to fix by replacing the old crumbling Ford factory wiring. If your wiring to the module on the distributor is original (30 yrs. old) it is probably bad. It's easy enough to check with a visual inspection. If there is ANY doubt, replace the wiring and plug.

[Under Pressure]

How is that beautiful white SVO doing Eyelawdoc?