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Ok guys i’m new here and this is my first post. Been watching Eric for years now and finally took the jump to create an account. So here’s my issue, had my service engine soon light checked and gave back an evap small leak code. I have had this code before and it turned out to be my purge solenoid. This was the first thing I checked. When I checked, It was stuck open and purging the tank at all times. What hinted me to it was hard starting after fill up. Checked the solenoid with a switched ground and sure enough it had bit the dust. Got the replacement part and installed. The issue now is that I am getting a constant signal from my pcm to turn on the purge valve and its mimicking the symptoms described above. I checedk the new part and it switches on and off with applied voltage as it should. Next thing I did was plug a test light into the connector. I am receiving full power when the ignition is in the run position. This has got me stumped. Is there another sensor that would make the pcm tell the purge solenoid to open on cold start or am I looking at tracing down a bad ground? If i remember right, this solenoid is ground switched correct? Any help would be greatly appreciated because this issue is tanking my mpg.
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I watch ETCG, scannerdanner and South main auto. I see Eric from south main auto on a shop version of Mitchel a lot for diagrams for a hefty price. On, etcg there is an advertisement for Mitchel for the DIY and I believe you can subscribe to your car specific from 10 -40 dollars depending how long you want info on all systems, months to years. Much better than Hanes manuals which I only use for torque specs, but diagrams can be found in those at local parts store. I would start out first with google search specific to car and component diagram sometimes in google images to see what comes up for free. check out local library and ask the help, you would be surprised what they can get from other librarys.
OK from what I have read, it is ground switched from the pcm and from earlier testing I know its getting a constant ground. So my next step should be to test the signal wire from pcm to solenoid for continuity?
Basically unplug it from pcm, hook test light to possitive and see if its being grounded somewhere else.
If you get to the PCM easily, you can unplug it from the PCM and see if the ground remains inwire from other open. You could check for continuity. check for bent pins, corrosion in fuse box as SMA just put out a video on a chevy cobalt with weird grounding. I know this is not much help but it will be finding your diagram and chasing down the ground circuit to see if it is a problem in wires or the PCM. Just by chance, does that solenoid have more than one ground on it.
Nope has a 12v feed and a switched ground. From my recent testing ti appears the circuit is in tact and in good working order. Borrowed a diagnostic tool and the sensor receives signal. When toggled on it comes on and it goes off when toggled off. Now im really confused on what could be causing the pcm to tell the sensor to remain 100% open all the time?
Electronics are not my specialty for sure but I would guess some parameter is telling the PCM to turn on the purge valve, obvious I know.
My next step would be to figure out under what conditions the purge valve is opened and look down that route. IE: Evap system its self. What is the computer seeing that is telling it to turn on the purge valve. Or is it an intake/ fuel issue. I dont know but would love to hear others thoughts and what you get figured out.
Would a bad vent solenoid cause the purge valve to vent constantly. My circuit checked out ok and I doubt its the pcm because I can toggle the purge valve on and off with a scanner. Something is telling the evap to vent. Its going to be a p.i.t.a if its the vent solenoid because its on the tank. Just so happens gm thought it would be a great idea to shove the tank way up in the car above the muffler. Yay me lol. Any input is appreciated. Also gonna clear the code and let the check engine light comeback and give you guys the code.
I have a 99 Monte and its seems like these years of GM made everything hard. To change my battery requires removing the front sway bar, fuse box, Window washer tank and air box just to remove battery and hold down. I replaced intake gasket and called for fun to dealer to get quote and they wanted 1150..Took me about 7 hours with hand tools. Profitable 7 hours
Sorry, done ranting. Vent valve should be open at rest and closed only with signal from PCM. I agree if you can control at PCM, that is a good sign. I know the canisters can clog up with gas that has been overfilled to much and dampened charcoal, etc but I don’t know how to test that. The vent valve should be able to blow through when disconnected.
That is one way of thinking and maybe your direction. In your research, what engine conditions cause the purge valve to open? Sorry I am not much help. I am a DIY with old car mechanic experience learning on the new cars as I go. Glad to discuss it out with you but hope others out there will help…..
Well guys I found the problem. The ground switch side for the purge valve is grounding out when i move the harness. Now to find a diagram for the wire. If anyone can assist me in this I would greatly appreciate it.
Nvm guys I found a link. Here it is http://www.firebirdnation.com/forums/topic/342426-links-94-and-98-factory-manuals/
has everything for the fourth gen firebirds.Well bad news, I need a new pcm. I traced the wire down and found that the pin for the purge valve is always grounded car on or off. Its supposed to be a switched circuit. 🙁 Well thanks for all the help, Im going to unplug the valve for right now and drive it as is until I can afford to buy a pcm and get it programmed.
Sorry to hear the bad news. Check out online auto salvage yards. I have had good luck with autowrecking.com for cheap pulls and shipping. They have a warranty but verify before getting. Best of luck.
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