legacycentral bbs

I am unsure about the vacuum that is suppose to be at the throtle body line that goes to the purge control solenoid. Right now I have no vacuum there. I have only 10in guage vac from right off the manifold.I have a 91 ej22t.

The nipple at the top of the throttle body provides ported vacuum; it ends up right by the throttle plate so that when the throttle is closed it's upstream of the plate. Don't bother measuring anything there.

10 inHg in the manifold at idle isn't right... How is your idle?

my idle is fine after I adjust it with the screw on the throtle body. I have codes 24 aircontrol, 35 canister purge, and 45 atomsphere presure senor. I believe this all has to do with the lack of vacuum but I have changed all vacuum hoses and still having problems.

Have you tried checking, cleaning, and/or replacing the IAC valve?

I have went through two IAC vavles just to make sure. They were both used but known to be good IAC valves. what about the pcv valve do you think that would cause a issue. It is old and comes right off of the manifold.

I suppose it's possible, even though it seems unlikely. You may as well change it -- they're like 2 bucks from Advance Auto Parts, and you're supposed to periodically replace them.

Have you checked the IAC wiring?

yes I have all the correct voltages on the IAC. I will through a pcv in there and see what happens.

I just pulled the pcv hose off and plugged up both ends to see if the vacuum would drop and it did not but I am still going to replace it.

For future refrence....put the screw back to factory setting and don't mess with it. It doesn't really do anything because your ECU will just compensate for the change.

Yeah it does actually. Your TPS sensor and IAC valve specifically (there may be more but those are the only ones I know of), depend on those screws to be exactly as they were from the factory.

Yes, your ECU will try to compensate for the adjustment if one is made, but that still won't fix everything. Because that adjustment is now off, your TPS (which has the idle switch built into it) now will give improper readings to the ECU about when the car is idling. The ECU will then, in turn, operate the IAC valve incorrectly.

The least of the problems that could result from this are a jerky throttle sensation, like I experienced. The ECU opens the IAC valve whenever it senses the throttle plate is shut, and closes it whenever it senses the throttle plate is open. So if the ECU is getting improper readings from the TPS, then it will operate the IAC valve incorrectly, possibly by closing it too late (meaning your car will jerk forward because now it's getting air from the throttle body AND the IAC valve) or close it too early (the engine will have a slight loss of power before the throttle plate opens up, and then it will jerk forward once that happens).

In short, leave your throttle body alone, and leave your IAC valve alone. This comes from someone who learned both of these lessons the hard way, costing me a new $360 IAC valve, and another (albeit used) throttle body with nothing adjusted on it.

Would these issues cause my loss of vacuum?

Possibly...

Ok I am know noticing that after setting the idle with the screw on the intake the computer will reset the idle after I turn the engine of and back on it settles at about 1400 rpm. I still have yet to find my vacuum problem and between these problems and my afc I am running really rich.

Assuming no vacuum leaks? Cam timing can drastically effect idle vacuum... all is right with that? Resent T-belt job maybe?

Just a thought
Gary

Not to long ago. How can I check it?

Timing light... Can get one for around $20-$30 at Advance or Autozone...

OK I finally got a new purge control valve and all my codes cleared. This is a beautiful thing, but my vacuum is still at 10 in. The car is idleing fine and runs fine and gets 8-9psi boost. Where am I going wrong?

I don't recall....but did you do a compression check on the engine?

no but if I had bad comprosion on the engine wouldn't I have boost problems?

I was thinking about it and if I had a leaking valve then I would have smoke during startup or when running or even when I rev up the engine. I dont have a cat it is straight pipe 3" all the way back. I only have 10" vac and mild hesitaion under load.

Finally I decided to pull the vacuum line from my bpv and low and behold it jump down to 19-20". Can I clean this valve or should I just buy a new one?

The bpv is stuck open so I just left it and plugged the vac line for know. It is pretty crazy seeing 20" and more during downshift.