Hi everyone

I was wondering if anyone here knows if I can test an Evap vent solenoid with a BAFX bluetooth dongle and car diagnostic pro ? I know expensive scan tools can test the evap solenoids and the system for leaks. Any advice is much appreciated 😊 thanks in advance

 

I do not know which cost effective scanners can command the vent solenoid but Les will probable help you with that.

The only purpose of the vent solenoid is to test the system for leaks by closing for the test. Most large leaks are the gas cap but eventually rotting vent lines and deteriorating gas tanks and canisters can contribute. One way to locate a difficult leak is with a smoke machine. That said, an evap leak will not effect how the truck runs but can cause problems in an inspection state.


George

 

I have no code for an evap leak but the truck runs like it has a vacuum leak. I've replaced the purge valve a while ago. Also from what I understand an evap leak can cause the engine to misfire and I'm going through gas like crazy ? Also when I open the gas cap i no longer hear negative pressure. So I'm pretty sure the system isn't working correctly so I thought the vent solenoid might be stuck in the open position. Do you think my best option would be to remove the vent solenoid and bench test it ? I just thought there might be an easier way to diagnose the vent solenoid. I dont know of it's even possible to have the valve stuck open and have no code coming back. I'm sure one of you guys would know the answer to that question ?

 

The vent valve is normally open and so is the purge valve. The only time the vent valve closes is to test the system for leaks. While the truck is running the entire evap system is always "leaking". The purge valve is varied but always open after the truck warms up. You could remove the evap valve and it wont change the way the truck runs unless it had failed shut. If your evap valve will not close it should set a large leak code during a routine evap system test.

Get your fuel trims at idle and 2500 rpm so we can see if a vacuum leak looks likely. Also what is your manifold vacuum at idle?

ALso if your fuel mileage sucks we should get your sensor values on a cold engine key on engine off and a warm running engine. Your ECT could be off.


George

 

Thanks you so much for your help George. I'll get that information. So I know that I have to right gauges pulled up. I know ECT is the coolant and MAP is manifold air pressure. Just the fuel trim I'm questioning because if I remember correctly there is more then one option. Which is the correct one I should pick ? I'm using car diagnostic pro.

 

This setup should get it done. You will only have 3 O2 sensors without the second bank 2 sensor shown here




George

 

I just seen your set up now. I didn't do all of those but I did some of them today so I'll tell you what I did and maybe it might help diagnose my problem so here is what I did ....

outside temperature where I was work today was 23.8 c
ECT Cold 23c
. Warm 92c
ECT fluctuates between 84c-96c when I'm driving and I seen -40c and 128c flash a couple of times while driving...very weird

After driving for 30 mins it was between 90c-92c

Manifold Air Pressure @idle was 35-36-37 ...just keeps going between these numbers after 30mins of driving

Short term fuel trim @ idle was 0.0 and -1.6 and everything in between would randomly come up

Short term fuel trim @2500 rpm 0.0 and -5.5 and everything in between would randomly come up

after driving for 25 mins the fuel trim is all over the place 0.0 to -14.00 .

I took a quick one min video while I was hopped on the hwy quickly to show you and my check engine light started flashing...I get a check engine light flashing sometimes and sometimes I don't but it only happens when I do over 80 kms.

it wont let me upload the video but I'll try to upload it later ...I might have to convert it to a different file format.

 

ST and LT fuel trims have to be reported together, all 4 numbers. We need them at idle and 2500 rpm in park. When you are driving fuel trims flop all over the place as the computer changes fuel cells..

I do not know how stabile the ECT reporting is with your software. If those wonky ECT values are really what the engine computer thinks it sees then we need to address that. Sensor/wiring/connectors.

A flashing CEL usually means misfires bad enough to kill the catalytic converter. We will need the total misfire number and if its high then we will need all 6 cylinders. Before getting into misfire counters CMP retard needs to be within spec (+/-2) or misfire data will not be reliable.

If you can get set up to provide the full picture that I showed that would be great. First cold engine key on not started Then idel and 2500 rpm warm engine in closed loop.


George

 

I used my cheap plug in creative hand held obd2 to get these values when I was driving but I used the car diagnostic pro to verify the numbers when I wasn't driving. The big BAFX bluetooth dongle falls out when I'm driving so......

 

I couldn't get the IAC gauge. It keeps saying analog and digital gauge unavailable. I will take a sceen shot of the values tomorrow afternoon.