I am familiar with turbo lag (I am still trying to resolve a hesitation problem on my 87 Turbo RX) but I am now having an issue where the Turbo stays kicked in for an extra second after I let my foot off the gas.............its acting as if some strange force is keeping the throttle down for another second.

 

Could a maladjusted TPS be causing this? Any other ideas?

Consider what causes the turbine part of the turbocharger to spin, it is exhaust gases. So when you lift your foot off the gas, it stops the flow of fuel to the engine, with no fuel to burn, there are no exhaust gases created, therefore, there is nothing to spin the turbine. I don't know what you have done to the engine so far, so I can't say exactly what might cause the 'kicked in' effect you are experiencing. A guess would be that you are over pressurizing the induction system and after you take your foot off the gas, the system is just trying to normalize itself. Another thing to consider is inertia, it is simple physics, an object at rest tends to stay at rest, an object in motion tends to stay in motion. I could be that you are accelerating just prior to lifting your foot of the gas, the turbine is trying to spool up to catch up with the speed of the exhaust gases. So with no pressure from the exhaust gases, it now continues to spin while slowing down slowly, thus creating boost. Sounds like you have a turbo that spins freely.

I havent done any mods to the engine or turbo. This is a new problem that happened since I replaced the intake manifold gaskets (I had a major coolant leak). In the process my MAF went bad and I just replaced it with a junkyard MAF (it is running much better but still not quite right), I also readjusted the TPS and while it is within spec (as defined by chiltons/haynes) I am still getting much hesitation. I dont seem to have much power until I nurse the gas pedal to get the turbo kicked in just right........usually after about 3K RPM.

 

Odd issues..........I need a magic wand.

 

The extra second of acceleration just seems odd.......I need to better understand the wastegate valve and how it works. I have no intention of increasing the boost but I am curious as to how it is done.

 

I have worked on old Datsuns, Mercedes, Toyotas, Scouts, Jeeps........and now Subarus.........my 87 RX is the newest car I have ever really worked on. I am finding the fuel injection/computer issues to be quite confusing. It seems the computer takes over and confuses fuel/air issues that would be apparent on a carbed unit.

 

Can a MAF be slightly bad?

How much an issue can a slightly maladjusted TPS cause?

How does one check for vacuum leaks? (I have used ether in the past on carbed models)

tps wrong causing it to dump more fuel than it can burn under boost

close throttle all that excess fuel burns in the exhaust and spools the turbo briefly...

just a idea

 

also maf might not work correct or has a air leak some where causing it to run rich as well

It was all about a bad fuel injector.......a little bit of good old fashioned detective work figured it out. Now it runs great......no hesitation and lots of power!!!

 

Thanks for all your help.

 

On a side note......if anyone in the Denver area wants to join in the fun of a head gasket change on a 1982 Brat let me know. :-)

bad injector??

leaking fuel into engine or not putting fuel in ??

i am curious if i was partially close

The fuel injector was not firing at all........not exactly sure how that corresponds to the problem. Perhaps it was somehow firing as the turbo stopped.

When you let off the gas pedal, the momentary increase in intake manifold pressure is supposed to open the wastegate. Check it to see if it's sticking, the passage/valve is blocked or the hose that returns it to the intake is blocked.