Back to bad MPG heat range causing it?

[Mooseman]

You could do an injector balance test but that requires a Tech 2 and it might not detect a slight leak in an injector.

Fuel pressure is easy to check. I know one member replaced his and it helped his MPG.

I'd wait until the PCM settles back down after clearing the codes.

 

[AzTruckGuy]

You could do an injector balance test but that requires a Tech 2 and it might not detect a slight leak in an injector.

Fuel pressure is easy to check. I know one member replaced his and it helped his MPG.

I'd wait until the PCM settles back down after clearing the codes.

I just have a feeling its either the FPR or Cat, but which one? The FPR here locally are $100+ for aftermarket no Ac Delco or Delphi. PepBoys has the BWD for about $60 after 30% off online code. I wonder if I should buy it to test it out? If its not the issue, then that's one part ruled out

 

[Mooseman]

Either are easy to test if you have the gauges. Cat is tested with a backpressure gauge. I bought this one, works fine for weekend mechs:
https://www.amazon.com/dp/B0002SQW9S/?tag=gmtnation-20

Fuel pressure can also be tested with this:
https://www.amazon.com/dp/B000R5IASC/?tag=gmtnation-20

Unless you just want to throw parts at it. The FPR should be an ACDelco or Delphi.

It's not urgent so you can buy it online.

The cat is more expensive so I'd test it before I swap that out.

 

[AzTruckGuy]

Either are easy to test if you have the gauges. Cat is tested with a backpressure gauge. I bought this one, works fine for weekend mechs:
https://www.amazon.com/dp/B0002SQW9S/?tag=gmtnation-20

Fuel pressure can also be tested with this:
https://www.amazon.com/dp/B000R5IASC/?tag=gmtnation-20

Unless you just want to throw parts at it. The FPR should be an ACDelco or Delphi.

It's not urgent so you can buy it online.

The cat is more expensive so I'd test it before I swap that out.

i assume this would work also for the FPR? id like to test it today http://www.autozone.com/loan-a-tools/fuel-pump-diagnostic-kit

 

[Mooseman]

Oh yes, and a nice little DMM that comes with it to check other electrical stuff.

 

[AzTruckGuy]

Oh yes, and a nice little DMM that comes with it to check other electrical stuff.

I'm heading to go pick it up now....I found this yesterday by our very own

So what should I be looking for?

 

[Mooseman]

I'd also check for loss of pressure. Prime the system without starting the engine and shut off the ignition. See if it holds the pressure for a while. How long, I don't know but if you have a leaking fuel injector or FPR, it will go down.

 

[AzTruckGuy]

I'd also check for loss of pressure. Prime the system without starting the engine and shut off the ignition. See if it holds the pressure for a while. How long, I don't know but if you have a leaking fuel injector or FPR, it will go down.

Got this too late to see....I did it how the video explained it and I have getting zero pressure? I first did it this way



Then I added another extension


The gauge is till at 0

 

[Mooseman]

Did you turn on the ignition or run the engine? Put the relay back in?

And make sure it's screwed in enough to open the valve in the test port.

 

[AzTruckGuy]

Did you turn on the ignition or run the engine? Put the relay back in?

And make sure it's screwed in enough to open the valve in the test port.

Yes turned the engine on...took the relay out and let it sputter ...crank a few times more to get more pressure out....put on adapters and put relay back on and crank the engine and no pressure at all...tried it with the second adapter and still no pressure ...gas comes out at the fuel pressure test point at the fuel filter...so I know there's pressure....

In this kit I noticed this rubber nipple seems to have broken off? Last person that used it?


This is the adapter that goes to the gauge



I put in there but it still give me zero reading...it must not go there and goes to another adapter...seems it tore off?

 

[AzTruckGuy]

Seems his Chevy has 0 fuel pressure also.. So what are the odds its my fuel tank again? Chevy replaced it under warranty

 

[Texan]

That little rubber nipple in your first picture belongs in
the connector for test port. The test port is like a tire
valve stem.

 

[Mooseman]

If it runs, it has to have pressure. I'd say the gauge is defective.

 

[AzTruckGuy]

That little rubber nipple in your first picture belongs in
the connector for test port. The test port is like a tire
valve stem.

Thank you Texan , I figured it out I had the nipple in backwards

If it runs, it has to have pressure. I'd say the gauge is defective.

Mooseman I'm being defective ha ha I have to laugh at my self...Ok now for a real pressure test

 

[AzTruckGuy]

Ok guys I was able to get a pressure reading and now I also have a misfire on cylinder 2.

I ran the engine, took out the relay for fuel pump and cranked over 2 times to relieve pressure and I was getting these readings

Turned on engine didn't start it



Turned it on and it was fluttering in between 50 and 60


So I took the relay off and let it sputter and then let some pressure out the gauge and then took off the pressure guage, of course it still spilt gas on me

Turned it on and then it was fine, but then I noticed it was choppy, so I took it for a spin around the block and then the SES light started blinking so I parked it in the garage and could smell something like sulfur in the cabin? and then I turned it on but didn't crank the engine and read the code



I haven't turned it back on, oh man well this is not my day

 

[Mooseman]

Shouldn't flutter so much but pressure is at around where it should be so the pump seems to be able to supply enough fuel and pressure.

Just thinking out loud, maybe removing the pressure from the system killed the already dying #2 injector but you should first do normal misfire troubleshooting. First check the coil by swapping #2 with #1 coil, clear the codes and see if the problem follows the coil or stays.

 

[AzTruckGuy]

Shouldn't flutter so much but pressure is at around where it should be so the pump seems to be able to supply enough fuel and pressure.

Just thinking out loud, maybe removing the pressure from the system killed the already dying #2 injector but you should first do normal misfire troubleshooting. First check the coil by swapping #2 with #1 coil, clear the codes and see if the problem follows the coil or stays.

Thanks Mooseman that helped it doesn't shake as much but I am still experiencing a miss and code now is P0300 Random/Multiple Cylinder misfire detected. The gold is the Delphi(original I assume?) coil and the silver is an aftermarket that was replaced on 1



This miss/vibration now is more noticeable, but I had a vibration before that was there, I thought it was the motor mounts. Turning the ac on makes it worse, like it wants to die. So my coil is bad

 

[Mooseman]

It'll show P0300 until it determines which cylinder is misfiring. You could look at the misfire count on the phone and see which cylinder is misfiring.

 

[AzTruckGuy]

It'll show P0300 until it determines which cylinder is misfiring. You could look at the misfire count on the phone and see which cylinder is misfiring.

Just took another reading, so I have to have a bad coil? Since the original was switched to C1 yesterday

 

[Mooseman]

Yep, better get one today since everything is closed tomorrow (I assume in the US too). It could have been the cause of the bad fuel trims if it was dying but not enough to trip a code.

 

[AzTruckGuy]

Yep, better get one today since everything is closed tomorrow (I assume in the US too). It could have been the cause of the bad fuel trims if it was dying but not enough to trip a code.

This prob came at good time, since I am heading up to Phoenix for a couple of days tomorrow in a rental. Ordered these coils from Amazon, lifetime warranty and good customer reviews from other Envoy/Trailblazer. Seems I have 4 original Delphi coils and 2 replaced ones. Since I have changed all the fluids, Id rather have all new coils as well https://www.amazon.com/gp/product/B00M07GQO0/?tag=gmtnation-20

Should fix the flutter that I had and maybe the MPG & P0440 issue, or at least let me diagnose better....

 

[AzTruckGuy]

Well I am glad I changed out all the coils, 2 of the coils seem recent and 3 of the coils where the original Delphi, 2 of the coils tabs were so hard to get off, I just ended up breaking the tabs off them. I was lucky I didn't break the connector, but yeah they are junk anyways



New coils compared to old




And the best part is my battery is dead, I haven't turned on the Trailblazer since Sunday and took the battery off on Friday to get to the upper arm screws....fun stuff

 

[AzTruckGuy]

Ok Battery replacement for a new one under warranty....Its running and sounds good, also the small vibration that I was having at idle seems to have disappeared and when I turn on the AC the vibration is just isn't as bad as it was before. PCM is relearning and of course Fusion is still picking up a Evap issue....comparing diagnostics yields some changes

 

[Mooseman]

Since the PCM was reset, you'll probably have to clean the throttle body (unless you already did this, it's a long thread). Vibe could also be from bad mounts.

 

[AzTruckGuy]

Since the PCM was reset, you'll probably have to clean the throttle body (unless you already did this, it's a long thread). Vibe could also be from bad mounts.

Already did it when I got the new oxygen sensors which was less than a month ago and it wasn't even dirty. Vibe is from a bad drivers side mount, but its better now with the coils, I can deal with it for now. The problem is still that damn evap issue...

 

[AzTruckGuy]

So did I just solve my P0440 code leak? Working on the rear swaybars I look up at the tank hose and it looks pinched and leaking?



So theres no visible leaks but it is pinched, I wonder if this is where the leak is?



Hose tank looks fine, but I am wondering if I should replace it as well?

 

[AzTruckGuy]

So of course there is no hose replacement by itself, you have to buy the whole unit..

Do you really have to buy the whole Fuel Tank Filler Neck? Can I just replace the hose as I have circled?

 

[Blckshdw]

If it's just that piece of soft hose, I'd replace just that.

 

[Mooseman]

I don't think it would cause a leak but it might make filling the tank a problem if the nozzle has been clicking off all the time.

 

[AzTruckGuy]

I do have issues at fill up when I run it low, I have to turn the gap pump a couple of times to keep it pumping. Its a small piece to replace and Id rather just do it, in case it could be the issue. If not, then more testing which is driving me crazy

 

[AzTruckGuy]

Ok more research done.. First I like the Trailblazer I have been putting a lot money into, but after brakes and chasing down the P0440 code, it shouldn't need anymore work(crosses fingers). GM is a piss poor on consumer recalls and warranty repairs. Seems there is a GM Service Bulletin 040604003 Part number GM 15131046 as a recommended Fuel Tank Filler hose update for the Trailblazer. Why GM didn't change this out as when they repaired my tanks and others is beyond me. Here's the part on Amazon for others see if they need this update. It will cure he fill up issues at fill up when the gas pump keeps stopping. https://www.amazon.com/gp/product/B00GUCRISO/?tag=gmtnation-20

I contacted the dealer about the P0440 code and asked for an inspection on the gas tank they replaced, I also stated why didn't GM change out that hose , while they replaced my gas tank. Also CC'd GM customer service on the email. Its a long shot for them to replace the hose for free, but its a worth a try on my end.

 

[Mooseman]

It's a TSB, not a recall. They will replace it only if customer complains and it's still on your dime if it's out of warranty.

 

[AzTruckGuy]

It's a TSB, not a recall. They will replace it only if customer complains and it's still on your dime if it's out of warranty.

Do you ever think customer courtesy repair crosses GMs mind? It maybe a TSB, but its related to the gas tank issue that was backordered so many months. Like I said before I would have been happy with a $1k repair credit vs the $2,250 they paid on my rental, while I waited for the tank to come in. But its on GMs dime, and they just don't talk to the consumer on matters like this at all.

 

[shovenose]

GM makes great SUVs and trucks but they don't know how to take care of their customers - it's been that way for a loooooong time now!

 

[AzTruckGuy]

GM makes great SUVs and trucks but they don't know how to take care of their customers - it's been that way for a loooooong time now!

Yup sent the email on Wednesday CCing Chevy customer care on the email and no response from dealer .....Next steps rear purge valve comes in today ...will install and clear code....if it comes back....filler gas hose replace...clear codes...if it comes back...tank hose....clear code...if it comes back...charcoal canister replace...clear codes...if it comes back....well than I am out of options as that is all the evp items

 

[AzTruckGuy]

The new rear purge valve did not clear the Mode 06 issues with Component ID $06 and $11 as they are related to my P0440 code I am still chasing down.

Ok since I never heard from the dealer on my request to replace the hose, I ordered it from Amazon, GM Service Bulletin 040604003 Part number GM 15131046. Unfortunately even after hose install I still have the mode 06 issues, but I did reset the PCM and will continue to see if it settles this week... Did a half fill up and the 1st thing I was able to leave the gas pump on auto fill without the hose shutting off on me and prob due to the flapper they added to the hose.



Flapper in the hose


Old Hose has no flapper


Took 5 minutes to install


I recommend this hose on all Trailblazers its just that nice, one thing that the Fusion OBD app informed was that my Trailblazer is ready for emissions testing as it wasn't before, so between the rear purge valve and hose, one of those parts did it.

So I took a 120 mile round trip to test out the hose and to see if my MPG had gone up..



The Elm327 disconnected about 4 times going on my trip the 1st 60 miles and I wasn't thrilled with the 12.5 MPG for total. One thing I noticed was the 1 sensor '(assume upstream) fluttered so much, it would not stay put. Sensor 2 (assume downstream) gave a constant reading.

Well on way back the Elm327 seemed to be better connected.



Now should I be happy with 16MPG for this trip? I feel disappointed for all the parts and work that there are going in and I am getting 16MPG...I know my tires and shocks are shot so that might help with MPG later, but I am wondering if I can get 20MPG for long trips after all my work is done?

 

[Mooseman]

If I can get 20MPG in my EXT on highway only driving, you should too, depending on gearing. I have 3.42 gears so that helps on the highway but sucks in the city.

That is good to know about the hose for those having issues with filling.

 

[AzTruckGuy]

If I can get 20MPG in my EXT on highway only driving, you should too, depending on gearing. I have 3.42 gears so that helps on the highway but sucks in the city.

That is good to know about the hose for those having issues with filling.

I'm on a limited time frame since I will be moving back up to Phoenix, Az in 2 weeks and I am trying to get everything done now, since I wont have time to play mechanic in my new place.

The last item I am going to replace is the upper hose with the kink in it, not going to replace the charcoal canister, after replacing other items that were working. I am starting to get really annoyed with this MPG and this Trailblazer, Ive just put a small fortune into this vehicle and this will diff be my last Chevy ever.

 

[Mooseman]

Well, you have to put this in proper perspective. It's a 13 year old truck with a fair bit of mileage. Stuff breaks and wears out. Can't expect it to run like it just came off the assembly line. I'm pretty sure I don't get that mileage anymore on my EXT and would probably have to dig quite a bit to get it back up there, if even possible. It's old and getting tired so I accept that I won't get that kind of mileage anymore. And trying to find the reason for a code on a system that could have a multitude of possible leak locations is a crapshoot for parts replacement.

One thing that just came to mind. Has the vacuum sensor on the fuel tank/pump module been replaced? It could be giving false readings.

 

[AzTruckGuy]

Well, you have to put this in proper perspective. It's a 13 year old truck with a fair bit of mileage. Stuff breaks and wears out. Can't expect it to run like it just came off the assembly line. I'm pretty sure I don't get that mileage anymore on my EXT and would probably have to dig quite a bit to get it back up there, if even possible. It's old and getting tired so I accept that I won't get that kind of mileage anymore. And trying to find the reason for a code on a system that could have a multitude of possible leak locations is a crapshoot for parts replacement.

One thing that just came to mind. Has the vacuum sensor on the fuel tank/pump module been replaced? It could be giving false readings.

One of the best vehicles I ever bought was a 1983 Porsche 911 Cab air-cooled, like the Trailblazer it was in the shop a lot getting repaired and trust me I was paying up the ying yang for the labor on it, but the issues where traced to parts that failed and not lets try this or that. The 911 also gave me a sh!t grin when I drove it, the Trailblazer doesn't. Its very frustrating when I am doing my own repairs and I am still at the same place I was in the beginning with no solution.





Now I have 3 Mode 06 issues and the P0440 code is not far off. The thing is there have been other members from both boards that have experienced these Mode 6 issues, but nothing becomes resolved from it. Its like there is no answer to what is the cause. The dealer is useless, hell the way they treated me and the tank issue in the first place, is the main reason why I will never get a Chevy ever again. They could have scanned the code with their expenses tools they have, I requested this as they were replacing the fuel tank..."crickets" that what I got from them.

I know your helping man, but when does it become crazy to keep throwing parts at it? If the sensor was giving false readings I wouldn't be getting bad MPG still
Found it for $11 ordered it
https://www.amazon.com/dp/B000NW4OPC/?tag=gmtnation-20