OK, starting to smack of something, but don't let me lead you astray. I haven't got my spfi leftovers anymore to look at to compare so going to ask if the spfi has a separate faster idle circuit like the mpfi has on the throttle body. The mpfi throttle body non spider has a solenoid unit of about 19mm hex bar, an earth wire and a power wire.It has a rubber tip on the plunger and diverts air past the throttle blade when the power wire is energised and the speed is increased only 100 or 150 rpm. It might be for AC on load only but is on all my mpfi non spider throttle bodies.
I can imagine I'd get a hunting idle speed effect if it it had constant on/off power supply due to broken/bad connection ....but can't imagine it would keep it up so consistently as your problem.
What could give this consistency would be if it was a dicky relay acting a bit like an old basic alarm bell I made as a kid with a hacksaw blade acting as part of the switching circuit, a donger on one end of the blade to hit the bell. A magnetic coil winding would be powerwed up and conatct broken everytime the blade was attracted to the magnet - perpetual motion to ring a bell until main power disconnected ....just to explain where some of my random, cryptic thoughts may be coming from
I should have suggested plug off the inlet manifold when you pull the vacuum booster hose and every other one as you are trying to isolate the problem, not create a new one.
Oh, your PCV valve screwed in the manifold, wrist tight is enough, we all see extra thread on outside
Got an extra earth strap between block and body just for good measure ?
My thinking here is that if something is starving for a decent earth, it may have an earth but not good enough...and thinking here is when a rear brake/tail light bulbs blows, filament falls across the other circuit - one circuit is earth switched - tail, and brake circuit is power switched you get odd things, or if an earth is not good for one circuit so sucks it from a nearby source but needs to share you see funny cyclic things happen with lights esp in the blink circuit
Another thing, we had a guy with an EA82T in a wagon here in Oz, with an impossible to find problem at speed I think his was. I think it went a few thousand miles by truck or train to an expert to be sorted....things went quiet....vehicle sold on, sold on.
I ended up with a pair of heads from the troubled guy , and do not know if they were off his troubled beast but...inside, one valve was wearing unevenly into the side of the valve guide, think it could get stuck, not closed sealing properly. I had some new guides or Klines installed and running them now in my Mizpah'd EA82Mongrel
Edited by jono, 24 March 2014 - 04:12 PM.