ajs88

What causes this and how do I fix it? At WOT, on the 18 psi setting it spikes at 18 then bounces down to 15 then jumps up and down from 15-18 psi like 2 or 3 times per second...Any ideas what is going on here? It has an aftermarket boost controller which I havent ever touched and thats the only turbo related aftermarket component.

Also it misses a lot at idle and smokes only on start up and WOT passes. I am thinkin the oil is coming from the valve seals, and the miss is just a fouled plug due to the oil...

What do you guys think?

ajs88

I am refering to an 86 svo btw

mg man 75

When was last time of a tuneup? Motorcraft parts are the ones most recommended. Knock sensor maybe killing the boost since you say it has miss. If get rid of idle miss will probably get rid of wot problem. Have you check fuel pressure. 39psi at idle with vac line off. With boost should build 1psi of fuel for 1psi of boost. May have do like me and run gauge out from under hood and drive to check that last part. Check all vac lines and boost lines for cracks and leaks. Is vam to turbo hose stiff? Should be. If soft will collapse under boost from turbo sucking on it. Check timing 10degree BTDC with spout out. Good luck Maurice

ajs88

o wow, thanks a lot! I would look into everything this weekend. The car pulls 20in. of vacuum at idle so I know mechanically it is in great shape. I just bought the car not too long ago, and I am unsure of the vehicle history. It has an aftermarket fuel guage on the rail and aftermarket boost gauge.

I know there is a tsb on intake gasket manifold leaking but I wouldnt think those would be faulty. What vacuum lines should I pull off? All of them?

mg man 75

?tsb what is that? On checking fuel pressure just the small vac line on fuel regulator on the fuel rail. Then should have 39 psi at idle. If not ok check fuel filter and pump etc. If ok note fuel pressure with vac line on [it probably will not be 39psi now that is ok] then get gauge so can see it when driving. Then get boost and then add 1psi of fuel pressure for every 1psi of boost. Example. 10psi of boost equals 10psi more of fuel pressure of the base pressure [pressure at idle with vac line on].

trashline

Id also check for a boost leak from your intercooler hoses. Dont just do a visual, squeeze them and flex them. Boost leaks can force open orifices at certain psi's vs other psi's. Dont forget your vacuum hoses become pressurized when you are in boost.

a miss can be caused by a bad gapped plug, fouled plugs, a bad tfi/pip... almost anything.

There should be a spring in the VAM hose.

I would do a tune up since it sounds like it is needed, as recommended from above, and then I would pressurize your intake system to find any leaks.