Can the CA Evap Sys Test Cause damage and bad MPGs?

[suprageezer]

I recently failed my smog test, then had repairs done, and passed. Ever since the first test my MPGs dropped off dramatically. This was the first time they did the Evaporation System Pressure Test, my question is, can this cause some kind of damage to a system part and reduce my MPGs?

 

[BorHor]

I don't think the actual test messed anything up. I am going to guess the repairs has something to do with it though.

 

[jdub]

It shouldn't...all the evap system does is collect gas vapor from the tank, collects it in the charcoal canister, and purges it (through the BVSV) to the TB.

What other work did they do? And, was the EFI fuse pulled or the battery disconnected?

 

[Rennat]

what other kind of "repairs" did they do?

i would check timing...

 

[jetjock]

No, the test can't cause a loss of fuel economy. Off the top of my head I don't see any failure mode of the Evap system that would either. What did you fail on the first test?

 

[suprageezer]

Thanks for the replys everyone, I'll look at the timing, anyone have a suggestion for the best timing for a stock N/A to acheive better MPGs. I'm not interested in power since there isn't much to begin with and it's a DD doing close to 100 miles a day.

 

[jdub]

Geezer - it would help if we knew what the car failed for on the 1st test and what work was done on the car. Timing may or may not be the problem.

In any case, the stock 10 deg BDTC is best. Remember the car needs to be warm, normal idle, and you have to jump TE1 and E1 in the diagnostic block to set timing.

 

[HommerSimpson]

Did they leave a vacuum hose off when they did test ? Or repairs

 

[suprageezer]

I posted two jpegs one of the fail test and one of the pass test. the repairs were. I noticed the drop in MPGs the day after failing the first test, which was a couple of days before it went in for repairs. So far the MPGs are the same as the day after the test BAD, with gas at 4.09 a gallon I need to find out whats going on if anything. One more thing it seems to idle smooth around 800rpm, and runs great LOL
Again Thanks for the help.

Repairs done
Set timing at 10° BTDC
Clean clogged evap system
Replace Idle Speed Motor
Replace Oxygen Sensor, not cycling fast enough
Clean carbon deposits from Plenum Chamber
Cleaned EGR Valve
Fix Valve Cover Leaks
R&R oil & Filter using GC 0W-30 and a Wix filter

 

[jdub]

Based on your CO2, HC and CO, it looks like you're running a touch rich, but not badly so. If the ECU was reset due to pulling the EFI fuse or disconnecting the battery, it will take a bit for the ECU to "re-learn" the feedback corrections for AFR control. If it was not reset, I would do so based on the work you had done. It would not hurt to check timing just in case the shop was not aware of the TE1 and E1 jumped requirement...if they set timing without doing this, it will be retarded for normal ops. Idle should be 700 RPM at idle for the NA motor.

Not sure why they replaced the O2 sensor...it didn't appear you were having that bad of a mixture issue on the 1st test. Same for the ISCV...were you having an idle problem?

 

[suprageezer]

yes the idle was around 1200, and I'll ask the shop if they know about the jumper during timing setting, and ECU reset monday, Thanks Jdub for the input

 

[3p141592654]

Your only issue with the first test was high NOx, almost certainly from an EGR problem. Mixture was spot on (14.7:1).

Since they then proceeded to throw the kitchen sink at it, I would check all the items replaced for assembly errors. High idle could easily be from a misplaced or missing vac hose or maladjusted TPS. Check for proper code 51 behavior.

 

[Keros]

The 7M's vacuum system isn't rocket science, but I've seen a number of 7M's, mine included, that had completely botched vacuum systems installed by someone who had NFI what went where and why.

Something easy to check anyway

 

[suprageezer]

Thanks for the input guys. I'm thinking my next move will be to drop it off at Driftmotion in the near future., long ways away but worth it.