My journey in isolating a P0171 on a 2006 I6 Chevy Trailblazer. Fuel pressure test, O2 sensor, MAF, Fuel cleaner, leak detection then intake manifold gasket repair.
Thank you for posting this. I thought my surging/revving when the outside temp was 38 or below was due to the intake manifold but lucked out as it was mass airflow sensor which I had replaced 5 months earlier with an CARQUEST part. Failed, replaced with OEM and took the CARQUEST replacement part to get that piece of $#!^ off the shelf. Will donate it to a free store.
Glad I watched this first. All of the intake bolts were fairly loose. Tightened them back up, it instantly ran better. Waiting for a few more drive cycles to set everything so I can get it emissions tested now. 07 Trailblazer
I have seen a lot of people saying to tighten the bolts. Best bet is to re torque them. 5 ft pounds on the first run then 8 ft pounds on the second. You want even pressure or you will have bigger problems in the future.
U can also get to it just fine from the front with 1/4 inch 3 inch extension with 10mm socket also 1/4 inch once u get that on the bolt the extension will be resting against the firewall and u can add another 3 inch 1/4 inch extension then ur rachet I didn't have any issues came right out went right in
Hahaha I just rebuilt the top part of that engine, valve job etc so I have to take it all out. An exhaust bolt broke so to fix that had to take the head out. Yeah at first it was a pain, but I got used to the auperman stance and to that sucker out in 5 min or less. The exhaust manifold was cracked if you're wondering why I broke the bolt. So I also took out the oil pan to get tye front cover off to do proper timing. Now I am getting P0171 and 900 RPM. I will do what you suggested with the carb spray. These cars are a pain to work on without the proper tools. On that intake far end bolt I used a 1/4 inch swivel even though I also have the flex. I did torque it also using the longer extension and stuck the torque wrench underneath..Once you do it you adaptand it works out better. Anyways thanks for the video.
Great video and thank you for the advice. I had the same issue but only in the cooler months. Once the weather would get warm, the check engine code would disappear. I also changed parts here and there hoping to fix the issue with no luck. I came across your video and you stated that you wish that you had just tightened the bolts first. I thought that I'd give that a try and like yours, my bolts were quite loose too. I tightened them up and that did the trick. Thank you. :)
Check the hoses coming from the secondary air injection system. The valve is near the exhaust manifold and looks similar to an EGR valve. The injection pump is under the truck near the transmission. A hose melted on mine under the truck leading to a p0171. I changed the 02 sensor, #1 fuel injector, all the intake gaskets etc.
Great job explaining and demonstrating the need to know warnings. I’m headed into this job as gas fumes are present. I will try the starter fluid suspecting a leak. But the tips are great. Nice job. Did you find a “fuel pressure regulator atop the fuel rail? Seems most issues are with smelling gas it’s leaking. Wish me luck, Man. Steve Plymouth MA
I have a 2005 Chevy trailblazer with a P0171. The STFT is 19.5% and the LTFT is 211%. My son was driving 37mph when the code hit. I previously did spray carb cleaner around to check for vacuum leaks (I learned that in high school). I also removed and cleaned the throttle body. Sometimes when he turns into a parking lot at a slow speed his truck with turn off. Very frustrating.
Hi Po, when you say 'turn off' do you mean it electrically goes dead? Does the engine stall with dash lights still on? Does it restart immediately or do you need to wait? Does it act the same with a full fuel tank? Any codes? Can you recreate it? Need more info but my guesses would be loose battery terminals, a failing alternator, a faulty/weak ground, or your fuel pump is getting spotty. My suggestion would be to get the charging system checked for free at Autozone, Run a can of fuel cleaner thru the tank. Check the fuel pressure (loaner gauge from Autozone), Good luck man!
OK, for the LTFT of 211%. Sounds like you have a massive air leak or a bad sensor. Since you say you checked for air leaks, seems like a sensor problem. I would replace the sensors with OEM/AC Delco parts. One at time. MAF then O2 sensor. That my two cents. Good luck. Also, perhaps such a high STFT is stalling the engine at low speeds??
How did you finally manage to get that clamp on the lower intake hose off. The struggle is real. Trying to remove it without taking the intake off and not having much luck. I can get it to turn but not slip off.
Yeah I am going through the P0171. I did the smoke test and the only leak was through the hose at the SAI valve. I rebuild the head and valve job recently. This happened after. So the intake was torqued at 89in/lb. The TB was cleaned and gasket replaced. I just ordered the PCV hose that is cracked. Could not find a leak with the carb spray. The fuel pump is new. Didn't check the pressure yet. Car runs great. I have 900 rpm issue. When that happens the downstrwam O2 variates 0.1 to 0.9 aswell as the O2 upstream. After the code is active the O2 stay at .7 or .8. STF goes from negative 10 to positive 10 I actually saw a 19 there briefly. The long term trim actually goes to 9 on acceleration and goes to 3.1 on deceleration. So I am not really sure what is next.
Hi gyong, been a while since I dealt with the p0171. I would doubt it's fuel pressure issue if the car runs well at full throttle. My mind tends to the MAF sensor - is it OEM? Did you clean it regardless? Assuming you disconnected the battery to ensure the Throttle Body relearn would take place. Would be really crappy if it was a fuel injector since they are so hard to get to in this truck. Did you run some high quality fuel injector through the tank? You can measure the resistance/ohms on the injectors by disconnecting the connection plug - I have another video out here which explains the pin-out and what I found. The fuel line schrader valve is right there behind the AC cross over bar if you want to connect a direct hose to try to clean the injectors. My other thought would be, and this is a big reach, is your battery voltage up to spec? Good luck man! Let me/us know when you have it figured out. Be cool - pay it forward. :-)
Thank the stars you Put this up so basically that air intake needed to be replaced correct? I believe I am having the exact same issue my truck is telling me I have a large vacuum leak
Gadgeto, my enthusiastic advice is to do the leak test with starter fluid or carb clean around all the intake components before you do anything else. If you do find a leak in the intake manifold area, then try tightening all ten bolts of the intake manifold - especially the ones closer to the firewall. Once you tighten/retighten, re-run the leak test. If you still have a leak after tightening the bolts you are going to need to remove the entire manifold to access then replace the manifold gasket. I guess your intake could have a crack/leak in the plastic manifold itself but I suspect that is very rare.
On mine, the rear bolts were all loose, each one was a little looser in sequence to the rear. The rear ones were really loose, to a point where I could turn using just my fingers. However, the bad news is, tightening all the bolts still did not help me in my case. I'm leaning toward the Air Solenoid Check Valve as documented by another RU-vid video.
Trying to be helpful...I would do the leak test using some carb cleaner just to make sure you are not having an intake manifold like even after tightening the bolts. Very easy to do and it may save you from working all the other potential issues. Good Luck!
Food for thought: Instead of Loctite on the bolt threads, would backing out the bolts one by one and re-installing with a wave washer or star washer not work?
Es, I don't think oil in the intake would cause white smoke coming out the oil fill cap. My guess would be a faulty valve stem seal causing exhaust gasses to slip past the exhaust valve stem and into the valve-cover/head area - hence the smoke coming out the oil fill cap. That's my guess. Does it puff out when the engine is running? If you put your hand over the oil fill cap is there pressure trying to push your hand away? If so, could be the valve stem seals or a bad valve?
Before you dive into all the work to replace the intake gasket, I recommend you first try to tighten as many intake bolts as you can (especially those nearest the windshield).
Yeah you can only get to like 4 out 10 bolts without removing everything. and if you gotta remove everything anyways might as well replace the gasket as inexpensive as it is. looks like i might have to try this. ive done everything possible to fix my failblazer. it runs but its rough. trying to extend the life as much as possible like everyone else here 😂
Yeah seems like a nightmare! Would of been a good time for the valve cover gasket while that intake was off Good old GM However these engines last a long while !!
I have an 05 envoy. Changed out the manifold gasket and air intake gasket. Couldn't get the last bolt on near the firewall. I have a p300 error code still. Could that back bolt be throwing off multiple misfires?
Adm, I would spend the effort on getting that last bolt near the firewall tight. I threw a blanked over the engine and laid on top of the engine to reach back with my right and left hands to get that bolt in. Others have said you can get that bolt through the wheel well. Regardless, that bolt deserves to be in. Now the p0300 is a tough one. I think I would look at the fuel injector connector (make sure it is clean) - see one of my other videos on the connector. I would also throw a few bottles of Techron fuel cleaners in the tank. Also, consider going to autozone and getting a test gauge to test the fuel pressure. You can rent it for free and the test port is really easy - right on top of the engine with a little shchrader valve. I would also test the battery at autozone - it is free and low or varying voltages can really mess up your troubleshooting. One last thought, how old are your plugs? They are very easy to get to so I would just replace them just to rule them out. Good luck man.
@@krgetler the funny thing is that once I put everything back with the new gaskets I did a scan tool test and I initially got a p306. So I erased the code and drove until the light came back on a few hours after . Did another scan test and I got a 300 code only. So erased the code again drove it and light came on again . This time its just a 306 code 2x. I changed the #6 fuel injector and the plugs are 3 weeks old. Im going to try to get to that bolt first.
I finally got that bolt tightened! But i still have p306x2 error code. Could it be the ignition coil harness for 6th cylinder or maybe its the actual valve? Not sure what else to do
@@thesuccessfulmind7180 Adm, my thoughts..... swap the coils, swap 3 and 6 and see if the code moves. Swap the plugs, swap 4 and 6 and see if the code moves. Did the 6 plug gap look right? Do a compression test of #6 cylinder and pray it is good - free loaner gear from AutoZone. Run some big-time fuel injector cleaner (you may need a mechanic who has the equipment) right into the fuel rail schrader valve just behind/below that stupid cross engine AC tube. Problem still not found? See my other video on how to measure the resistance across the fuel injectors without taking the intake off. If you have a bad fuel injector it is a pile of work because you have to take the intake off. Good luck man! Let me know what you find out.
