Okay I have finally correctly identified both the PCV valve and the hose that provides vacuum to it.

I let the car idle while it warmed up. During warmup vacuum pressure was constant at 19 inches of mercury. The engine ran smoothly during this time. The ticking noise I mentioned under the intake manifold then came back after a couple of minutes. After the noise started, vacuum began to fluctuate until the guage was getting pegged again at both ends.

I tried several times to squeeze the correct PCV hose to see if I could hear the PCV valve click. During warmup, and after the unusual symptoms appeared. I could not successfully hear the PCV valve click. The hose is hard brittle, but not cracked. I removed it and looked through it, it is unobstructed in any way.

I also placed a long screwdriver on the intake manifold near the back where the noise seemed loudest to see if I could hear the clicking noise inside by placing my ear against it. I could not hear it through the screwdriver.

So I guess we still can't rule out the PCV valve.

 

Check the belt tensioner. Sometimes a loose belt can cause knocking when tensioner hits stop.

good luck

 

The belt is in good shape. It is 9 months old.

The tensioner marks are within spec.

The tensioner shouldn't impact the vacuum pressure after warmup should it?

What should be done next?

 

Noise may not be related to vacuum fluctuations was my thought.

I would try to pinch off the vacuum lines; brake booster, EGR, PCV, EVAP supply sequentially and observe vacuum for change. If bouncing is stopped by pinching off supply, then something is wrong on that system.

If nothing, time to check valve clearances and adjust as necessary. Another way to check valves is perform a compression test to see what compression levels can be generated.

Again, are you losing any coolant? Any bright white smoke from exhaust? A leaking head gasket could produce many of your symptoms.

good luck

 

After warmup there is a strong relationship between the start of the vacuum issue and the start of the ticking noise. The ticking noise is located on the drivers side of the engine, on the rear of the engine, on the top of the engine.

We have tried squeezing the hose to the PCV valve and it did not impact the vacuum issue. I then tried squeezing the vacuum hose for the brake booster and it did not impact the vacuum issue. The EGR valve has no external vacuum hose to squeeze. So we are unable to test it.

I then tried squeezing the hose for the component where I had connected my vacuum guage. This fixed the vacuum issue. I took a picture of the component intending to upload it. However is is 789 KB which is larger than your site's size restriction which is 98 KB. My best guess is that it is the EVAP canister purge valve. Is this correct? It is on the drivers side of the engine on the rear above the intake manifold, behind the thottle body.

Does these frequently fail?

What are your thoughts on sourcing a replacement should I source it from OEM, aftermarket or a salvage yard?

Hopefully replacing it will fix the engine misfire CEL's.

Thank you very much for you all your help it has been extremely helpful and I am very grateful to have been able to have learned from you.

 

The vacuum oscillations could be a false signal. The EVAP system uses vacuum to pull gas vapor from fuel tank through evap charcoal cannister. There is a solenoid switching valve which modulates the vacuum level frequently. Since you don't have any EVAP DTC's, this possibility seems likely. The ticking noise may be the EVAP solenoid valve modulating vacuum to EVAP system.

Suggest checking vacuum from another source. Check intake manifold and throttle body for other vacuum lines.

good luck

 

Party pooper.

I moved the guage to the brake booster line and vacuum was solid 19 inches the entire 10 minutes I ran the car.

Now which direction?

 

Some progress, if no solution. We now know that leaking valves or head gasket fault is unlikely.

Missing on all 6 cylinders suggests a common fuel fault; perhaps low fuel pressure, or dirty injectors due to fuel contamination.

Fuel Pressure should be measured to confirm w/i specification.

I recently took my daughter's 2001 Celica to a local shop who ran flow tests on all 4 injectors and found two partially blocked. This was causing lean condition on two cylinders which could not be compensated w/ Long Term Fuel Trim (LTFT).

If contamination is cause of blocked injectors, then a fuel additive is unlikely to fix problem. Injectors will need to be removed, inlet screens cleared, and flushed to clear.

Lot's of good youtube videos on how to DIY fuel injector cleaning. I managed to partially clear my Celica injectors using 3 AA batteries in series and aligator clips to connect to injector. I used throttle body cleaner and air pressure to flush. LTFT decreased enough to avoid setting code. This cleared the P0171 which has been a constant companion for almost 2 yrs.

good luck

 

Check the fuel pressure from the fuel pump, or at the injector pump?

 

The vacuum guage I just bought only reads fuel pressures up to 10 PSI.

Since this pump should put out 55 psi I need to buy a new guage to read the fuel pressure.

Also, I need to make sure that I have all the proper fittings and o rings before I start taking things apart. I will need to study the Haynes manual closely, determine which are and get some before starting to take anything apart.

I bought a stethescope today to listen to the noise. It may also be useful now to listen to fuel injectors.

I haven't worked on injectors before. How difficult is it? I will search for some videos and look at them.

Does your daughters Celica have a 20R engine?