1992 Camaro Z28
L98 5.7L V8 350ci. Mild Cam, no cats. Headers.

BEFORE Nov of last year my avg was 180km/per fill up.

November of last year I have my engine tuned (dealer) up and was getting approx. 235km per tank full (Well 1/4 tank or so left). At the time I had no cats running.

Few weeks ago I put the cats on to get thru aircare and then had them install Flanged straight pipes which are a bit longer and larger in diam. The dealer then retuned the car back up as the car had to have the timing DROPPED to get it to pass aircare.

Ever since I put the straight pipes back on, retuned back up, I've noticed since then my gas plumets to around 180km per fill up like it was BEFORE.

I discovered that the air tube that goes from the PCV valve to the TPI is split around 1 1/2" long at the very end were it pushed into the nipple of the TPI throttle body. It was BARELY even on it, basically hanging there. I pushed it back on and complained to dealer that I was getting the same gas mileage than I had BEFORE they did the timing.

They claim the car is likely running lean because of this tube allowing air in.

[Pic found on google]



Is this true? If this tube is allow air in (passenger side) will it effect my gas usage??

 

Yea that could cause bad MPG, any vaccum leak like that will cause problems

 

That would have no effect because it is only the air supply to the PCV system and air is supposed to go into pass side cover anyway
You would have a vac leak if hose was open between the PVC valve and the intake

If however you have the PCV valve installed in the pass side cover then that is WRONG.

Air is supposed to go from TB to pass side cover , through engine , out PCV valve in drv side cover to the port on the intake

 

I disconnected the tube while the car was running to see if the car would start to run differently. And the moment I removed the tube, I noticed absolutely no change in how it was running. I assumed it would start to shake or idle up/down, or stall.

 

My car has the tube in the same way as the above pic. I've looked and there does not seem to be anything wrong with that set up. GM documents, and engine diagrams, including exploded views for the 91-92 Camaro has the same setup. I don't see what is wrong. Are you sure about this?

 

I think you misread my message. I never said the PCV was on the passenger side rather the TUBE that goes from the Throttle body.

 

From post #1
"I discovered that the air tube that goes from the PCV valve to the TPI "

 

The plastic fitting in the pass side cover is just that; a fitting to adapt hose to cover
PCV valve is in drv side cover and is metal

If you do actually have the valve in pass side then there would be no airflow so nothing would change
Valve would one way flow to TB which has no vac,
If valve is in drv side then it is already sucking air in through the engine so nothing would change.
As noted above , only disconnecting line between the valve and intake where there is actual vac
present will affect the engine ; big vac leak

 

I see.. So a leak from the hose from the TB to the CCV (or so GM terms it) would NOT effect my gas?

What would? Everything to do with fuel, ignition, timing, has been either replaced or tuned.

 

The PCV valve controls the airflow through the engine.
So long as that is functioning correctly ,CCV should not be your problem
Has anybody pulled the ECM codes to see if anything showing?

 

There were no codes when they checked which is why they were baffled as to why it was failing aircare. There only hope was to retard the timing at the time

 

Are you running a cooler t stat? They are known to cause poor mileage. I'd get a 195* stat.

 

so its not the PCV line leaking its the crankcase breather line that was leaking, so being that you right it wouldnt cause a problem

 

Just did a fill up (had about 1/4 tank left).

Distance Driven : 210km
Fuel Used: 41.714L
Cost $ 62.49Cdn & 1.496/L

Calculates to 19.9 liters per 100km
fuel cost is $0.3 / km

ALL CITY driving! Rarely drive over 50KM and coast as much as I can.

 

Does anyone know where to get a correct replacement for this hose nowadays?