I'ma go ahead and agree with you that it's probably the FPR. That's the only time I've ever smelled fuel under the hood of mine, and they are known to fail/leak after a while. Mine was leaking intermittently but I finally found a tiny bit of dampness under it so I replaced it. Better safe than going out in a blaze of glory like a rolling Viking death ritual.
Hint of fuel in air intake
Good afternoon.
I was cleaning the airbox, snorkel and air guide along with changing the air filter and noticed a very slight smell of gas. A hint if you will. Could a failing fuel pressure regulator be the culprit?
I know if draws vacuum from the resonator box on top of the engine. I removed the box and there was no fuel in there, but it also had a slight aroma of fuel. I'm not getting a code and I haven't lost any fuel economy. I'm going to pull the line later and smell if it has a fuel smell. If I recall correctly, if it smells of fuel the diaphragm is leaking and the unit needs replacing?
What else might be causing the fuel smell? PCV system issues?
Thank you.
I was cleaning the airbox, snorkel and air guide along with changing the air filter and noticed a very slight smell of gas. A hint if you will. Could a failing fuel pressure regulator be the culprit?
I know if draws vacuum from the resonator box on top of the engine. I removed the box and there was no fuel in there, but it also had a slight aroma of fuel. I'm not getting a code and I haven't lost any fuel economy. I'm going to pull the line later and smell if it has a fuel smell. If I recall correctly, if it smells of fuel the diaphragm is leaking and the unit needs replacing?
What else might be causing the fuel smell? PCV system issues?
Thank you.
1 - 20 of 22 Posts
At this point a blaze sounds better. Driving home from work last night and I get a reduced engine power and check engine light. Pull the code and it's P1515. I need to get home and a tow was going to be to expensive. Pulled the ECM fuses for a minute, started up no problem and ran fine until almost home. Same thing happened 2 more times, much closer to each other.
I'm thinking FPR still as well as the accel pedal. Going to replace both tomorrow and hope this handles it. Throttle body will also get a good cleaning as well and I'm going to finally install the oil/water separator in between the crank hose and the intake.
I'm thinking FPR still as well as the accel pedal. Going to replace both tomorrow and hope this handles it. Throttle body will also get a good cleaning as well and I'm going to finally install the oil/water separator in between the crank hose and the intake.
Pull the vacuum line off the FPR and see if fuel runs out. Or, take 3/16" i.d. section of vacuum line (about 6 feet) and connect one end to the FPR and then stick the other end into your mouth if you do not have a vacuum pump. If doing this by mouth, proceed carefully to gently suck on the vacuum line to see if the FPR holds vacuum (remember you do not want to get a mouthful of gasoline.
If the diaphragm is good, you'll be able to create a vacuum and it will hold for many seconds.
Good Luck!
If the diaphragm is good, you'll be able to create a vacuum and it will hold for many seconds.
Good Luck!
I pulled the line yesterday with my mechanic friend and their was no fuel seepage. Started the truck (REP light was back off) and revved it a few times. No fuel leaked out and it was able to rev each time I hit the pedal.Pull the vacuum line off the FPR and see if fuel runs out. Or, take 3/16" i.d. section of vacuum line (about 6 feet) and connect one end to the FPR and then stick the other end into your mouth if you do not have a vacuum pump. If doing this by mouth, proceed carefully to gently suck on the vacuum line to see if the FPR holds vacuum (remember you do not want to get a mouthful of gasoline.
If the diaphragm is good, you'll be able to create a vacuum and it will hold for many seconds.
Good Luck!
This is why I'm perplexed by all of this. Part of me thinks it's the pedal because twice within the last few times of driving when I let off the gas the truck kept accelerating slightly like my foot was still on it. So either the throttle body is gummed up again (I did notice some oil on the S hose under the resonator), which will get it cleaned out tomorrow anyway when I remove the I take, or the pedal is bad and is mismatching commands.
Maybe I'm chasing a gremlin and I'll be stuck with a truck in the shop. Hopefully tomorrow the rain is done and I can get out to it and get it done.
OK on the FPR being good.
Good Luck tomorrow with cleaning the throttle body and the oily S hose. Hopefully the gremlins will get flushed away!
Good Luck tomorrow with cleaning the throttle body and the oily S hose. Hopefully the gremlins will get flushed away!
Slight smell of petroleum in the air intake system wouldn't bother me too much. Reversion from the intake valve, PCV fumes could each account for that. An oiled-gauze air (K&N or similar) filter would do it, too.
Connect a scan tool, see what the gas pedal sensors are up to. I'd expect one to start at 5 volts, and drop as the pedal is pushed. The other will do the opposite, start low and go up to 5 volts at WFO.
No idea why you'd install an oil-water separator in the PCV system. If you've got that much oil and water in the crankcase fumes, something is wrong that needs actual repair.
Connect a scan tool, see what the gas pedal sensors are up to. I'd expect one to start at 5 volts, and drop as the pedal is pushed. The other will do the opposite, start low and go up to 5 volts at WFO.
No idea why you'd install an oil-water separator in the PCV system. If you've got that much oil and water in the crankcase fumes, something is wrong that needs actual repair.
I have an air raid cold air intake system that uses a dry filter. It's not a heavy fuel smell. I just noticed hints of it when I had the CAI off. For the oil, I'm not getting a severe amount of blowby. The oil water separator is more a catch can to mitigate the oil getting up and in than anything else.
Update:
Pulled the air intake stuff off to access the throttle body. It was as clean as it had been when I last cleaned it. No oily buildup or carbon.
I put the key into the ignition, turned it to on, didn't start the truck and had my son step on the accel pedal. Butterfly opened slightly, even when fully pressed.
I then started it, hit WOT (it took a few seconds longer to rev up beyond 2000, which I'm assuming is due to the intake being off), but the butterfly still barely opened. I'm going to change the pedal now and see if that improves it. Otherwise, throttle body?
Also did the vacuum test of the FPR by sucking on the tube. No fuel went into it and it held a tight vacuum. I'm going to say the FPR is still good.
Pulled the air intake stuff off to access the throttle body. It was as clean as it had been when I last cleaned it. No oily buildup or carbon.
I put the key into the ignition, turned it to on, didn't start the truck and had my son step on the accel pedal. Butterfly opened slightly, even when fully pressed.
I then started it, hit WOT (it took a few seconds longer to rev up beyond 2000, which I'm assuming is due to the intake being off), but the butterfly still barely opened. I'm going to change the pedal now and see if that improves it. Otherwise, throttle body?
Also did the vacuum test of the FPR by sucking on the tube. No fuel went into it and it held a tight vacuum. I'm going to say the FPR is still good.
Update:
After swapping the pedal the butterfly barely opens, even at WOT. It also started making a rattling/crunching type sound which I assume is the gears being done for. I also manipulated the butterfly with my finger and could hear the gears at a point and feel the grittiness.
It's amazing how I was still able to make it home with the throttle body all messed up. Resetting the PCM was a temporary fix that worked long enough to get home. It's crazy that resetting the PCM was enough to clear the mismatch and let it still drive. This is why I'm hoping the throttle body is the only issue here.
I'll update again tomorrow when the part arrives and I get it installed. Anything I should look at once the throttle body is installed? WOT should open the butterfly all the way, stuff like that.
Also, the Haynes manual I have doesn't mention a formal relearn procedure is needed, so I'm assuming let it idle for 5 minutes, drive it around for about 30 minutes at various pedal positions and speeds, and then it's considered learned.
After swapping the pedal the butterfly barely opens, even at WOT. It also started making a rattling/crunching type sound which I assume is the gears being done for. I also manipulated the butterfly with my finger and could hear the gears at a point and feel the grittiness.
It's amazing how I was still able to make it home with the throttle body all messed up. Resetting the PCM was a temporary fix that worked long enough to get home. It's crazy that resetting the PCM was enough to clear the mismatch and let it still drive. This is why I'm hoping the throttle body is the only issue here.
I'll update again tomorrow when the part arrives and I get it installed. Anything I should look at once the throttle body is installed? WOT should open the butterfly all the way, stuff like that.
Also, the Haynes manual I have doesn't mention a formal relearn procedure is needed, so I'm assuming let it idle for 5 minutes, drive it around for about 30 minutes at various pedal positions and speeds, and then it's considered learned.
Ooof. Crunchy gears, no bueno. I hope that does the trick! Just saw a YouTube short of a guy taking one apart to lube the gears... that's all good I guess but I'm pretty sure I wouldn't bother. Thanks for the update 👍🏻
The oil water separator is more a catch can to mitigate the oil getting up and in than anything else.
Proving you have no reason to install a "catch can".Pulled the air intake stuff off to access the throttle body. It was as clean as it had been when I last cleaned it. No oily buildup or carbon.
I totally agree with you --- a 'catch can' is lowering the river and not raising the bridge.Proving you have no reason to install a "catch can".
It's not a good idea to treat a symptom without FIRST knowing what the problem is - and then if you decide that swinging a dead cat around your head at a cemetery crossroad at midnight - is a good thing to do --- so be it.
You will have actually chosen to ignore a basic truth that is inconvenient to you and you'd rather do things the way the original engineers set things into motion.
BTW: the throttle plate should NOT open full-wide - WOT unless the MAP sensor has sufficient vacuum on its piezo element to tell it that the PCV system can still operate.
It will NOT allow the vacuum to drop to less than what is needed to create a vacuum in the CV side of the PCV system.
With the engine not running, you will never be able to open the throttle electronically - or physically.
If you DO force the throttle plate open - you run the risk of damaging the drive/driven gears - which I think you just done-did.
Don't force things to move unless you are sure you really really want to run the risk of $$$ damage.
I love you guys so much.
You're all focusing on the wrong part. The fact that the PCV hoses were essentially clean shows me that mine is breathing right and doesn't need a catch can/oil separator. The occasional capful of Berrymans B12 on the regular is all she needs.
I'm more concerned about this throttle body thing. It was crunching before I tried to move it manually. It crunched on the few tests I did with my son to see it open and close. You could hear the gears crunch in the cabin.
Does it sound right that it's chewed up like that but I was still able to reset the PCM long enough to drive 15 miles like normal with no pedal issues or power loss?
To then reset the PCM by removing the fuses and then drive like normal for another 6 miles without any noticable issues?
And then reset the PCM again and drive without issue for another 5 miles until I got it home?
Does the computer need to see a certain amount of mismatches between the pedal position and the throttle position before it hits the REP light and cuts down the power?
Is there another component I should be looking at, or does the system in question really just consist of the pedal, PCM and TB like the diagram in the Haynes manual?
You're all focusing on the wrong part. The fact that the PCV hoses were essentially clean shows me that mine is breathing right and doesn't need a catch can/oil separator. The occasional capful of Berrymans B12 on the regular is all she needs.
I'm more concerned about this throttle body thing. It was crunching before I tried to move it manually. It crunched on the few tests I did with my son to see it open and close. You could hear the gears crunch in the cabin.
Does it sound right that it's chewed up like that but I was still able to reset the PCM long enough to drive 15 miles like normal with no pedal issues or power loss?
To then reset the PCM by removing the fuses and then drive like normal for another 6 miles without any noticable issues?
And then reset the PCM again and drive without issue for another 5 miles until I got it home?
Does the computer need to see a certain amount of mismatches between the pedal position and the throttle position before it hits the REP light and cuts down the power?
Is there another component I should be looking at, or does the system in question really just consist of the pedal, PCM and TB like the diagram in the Haynes manual?
As the old Johnny Cash song goes, "one piece at a time".
I think you're on the rite track. Definitely need to replace the stripped-out throttle body, no question. Give it time to relearn, then test drive it and go from there.
That's my 2 cents, keep the change ya philthy animals.
I think you're on the rite track. Definitely need to replace the stripped-out throttle body, no question. Give it time to relearn, then test drive it and go from there.
That's my 2 cents, keep the change ya philthy animals.
Does the computer need to see a certain amount of mismatches between the pedal position and the throttle position before it hits the REP light and cuts down the power?
Is there another component I should be looking at, or does the system in question really just consist of the pedal, PCM and TB like the diagram in the Haynes manual?
With the lesson learned from the screaming deaths of people in run away vehiles like Toyotas, GM wasn't gonna let that happen.
Death by cheap engineering lawsuits would not be good press releases, so the first sign of even a glitchy mismatch IN THE FOOT PEDAL would trip the REL.
I cannot speak for a "Failure-to-comply" at the throttle motor as being a life or death situation IF there was less than a significantly correct digital return of info from the throttle plate position sensor.
IOW ---> glitches in the foot position readouts, no matter how small, would AT LEAST trip a Boolean Flag at the first sign of trouble from it; but from there the trip to REP-land would be quick and merciless.
But glitches from the throttle plate readings ---although still important --- would be perceived less: "death defying" and therefor would be not as likely to go REP on ya.
The only reason for a mechanic to have a Haynes Manual ..... would be for comic relief.
Is there another component I should be looking at, or does the system in question really just consist of the pedal, PCM and TB like the diagram in the Haynes manual?
With the lesson learned from the screaming deaths of people in run away vehiles like Toyotas, GM wasn't gonna let that happen.
Death by cheap engineering lawsuits would not be good press releases, so the first sign of even a glitchy mismatch IN THE FOOT PEDAL would trip the REL.
I cannot speak for a "Failure-to-comply" at the throttle motor as being a life or death situation IF there was less than a significantly correct digital return of info from the throttle plate position sensor.
IOW ---> glitches in the foot position readouts, no matter how small, would AT LEAST trip a Boolean Flag at the first sign of trouble from it; but from there the trip to REP-land would be quick and merciless.
But glitches from the throttle plate readings ---although still important --- would be perceived less: "death defying" and therefor would be not as likely to go REP on ya.
The only reason for a mechanic to have a Haynes Manual ..... would be for comic relief.
Update:
New throttle body came in. Install was easy since everything was already off from yesterday. Put everything back together and performed the relearn.
Start and let idle for 3 minutes. Turn off for 60 seconds. Run at idle another 3 minutes. Turn off and you're done.
Took it out for a drive and it felt good. Better than before. Snappier with the new pedal and throttle body combo.
Drove around for a bit at various speeds and idles, with AC on and off, with defrost on and off, etc. with no issues. Idles went up and down as expected.
Most importantly, after 30 minutes of driving around, no more Reduced Engine Power light. All the power is back and the beast feels good again.
Thank you all.
New throttle body came in. Install was easy since everything was already off from yesterday. Put everything back together and performed the relearn.
Start and let idle for 3 minutes. Turn off for 60 seconds. Run at idle another 3 minutes. Turn off and you're done.
Took it out for a drive and it felt good. Better than before. Snappier with the new pedal and throttle body combo.
Drove around for a bit at various speeds and idles, with AC on and off, with defrost on and off, etc. with no issues. Idles went up and down as expected.
Most importantly, after 30 minutes of driving around, no more Reduced Engine Power light. All the power is back and the beast feels good again.
Thank you all.
Glad to hear it, nice job!
That's what we like to hear . 
1 - 20 of 22 Posts
Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum
A forum community dedicated to Chevy Trailblazer and GMC Envoy owners and enthusiasts. Come join the discussion about performance, modifications, troubleshooting, towing capacity, maintenance, and more!
Full Forum Listing
Explore Our Forums
Top Contributors this Month
View All
Ravalli Surfer
158 Replies
chem_man
125 Replies
metalmike187
84 Replies
Recommended Communities
