Chevy Trailblazer has rough idle and poor fuel economy (fuel filter change)

Changed the fuel filter on my 2003 Chevy Trailblazer. This truck has been amazing, but lately it developed a rough idle. The rough idle almost sounded like it was going to stall sometimes and the fuel economy was getting terrible. I tried changing spark plugs and it didn't work so changing. Fuel pressure was within spec, but I still suspected maybe the fuel filter was clogged. Watch the video to see if it resolves the problem.

[@jayrenner211]

Fuel filter (every 30K) Then Throttle body cleaning, ignition coils, spark plugs every 100K even if you think you don't need it, do it.

[@allensshenanigans348]

I agree with keeping up on maintenance. Thanks for watching. Please support the channel by subscribing.

[@blackericdenice]

It’s not a diesel. You only need to change the fuel filter about every 120k miles.

[@627miko]

​@blackericdenice 1 year late but still Chevy calls for 30k fuel filter intervals. It's $50 at the dealer or $20 for a wix on rockauto. (NAPA filters are also wix, so those are pretty good value depending on the price) why would you not just do it every 30k? Sure it's not needed but it's cheap insurance for bad gas or some goofball putting stuff in your tank.

[@blackericdenice]

If you are still having this problem. Change the map sensor. I have a 2004 and I just changed my part. No I didn’t have a check engine light and the engine ran fine.

[@SkyMuffinz]

What else can I do for fuel milage I changed filter and regulator air filter map sensor

[@blackericdenice]

@@SkyMuffinz Nothing. A GM tune the TB engine to pull like a v8 truck engine. It does a great job of doing that. Like a v8, it drink gas.

[@allensshenanigans348]

What are you getting for fuel mileage?

[@tssiddiqui]

very nice, got the location and the filter change.

[@adamvalenzuela6626]

My 2003 Trl blzr bougt it new changed plugs ones never changed fuel filter. All exept one coil have i changed. But now 2023 my trl blzr stalls at stops. But runs good on the road. Thanks for the video.

[@allensshenanigans348]

Thanks for sharing. Please support the channel by subscribing.

[@rolisaenz]

To prevent that high pressure fuel spray off, you can remove the FUEL pump relay in the engine fuse box, i think is relay 41, run the engine till it stalls, then when working below the truck, you can see a cap in one of the connectors, it is the fuel pressure relief valve, just put a pen or something so you can get out any remaining pressure , that way when you unhook the fuel lines, yo do not get that surprise fuel spit out.

[@allensshenanigans348]

Did that and ran it until it died. It still had pressure.

[@rolisaenz]

@@allensshenanigans348 idk what happened then, i saw other videos where they use the valve to relief the pressure so just little fuel come out.

[@sully4536]

@AllensShenanigansd Get Some CRC Sensor friendly map sensor cleaner and throttle body cleaner and clean the throttle body if you haven't already I bought my 2004 same color as yours for $600 Cleaned the throttle body put a hot battery in it and drove it home still daily is now it just rolled over 207k and still runnin like a top trailblazers are like a sore dick you can't beat em

[@billlee1724]

😂😂 like a sore dick ya can’t beat ‘em hahahaha, 260k and 137k going strong, got two 4.2s !

[@billlee1724]

Put 200k on the older one and only needed about 3 starters and maintenance lmao

[@stanleyplock1181]

My 2004 BMW 325i only got 15 MPG since I bought it 5 years ago. I cleaned the MASS AIRFLOW SENSOR and I'm getting around 30+ now!!! (It never threw a fault code for anything. Including Oxygen Sensors.)

[@allensshenanigans348]

The trailblazer 4.2l engine doesn't have a mass air flow sensor. Thanks for watching. Please support the channel by subscribing.

[@sfh2050]

I replaced all six plugs and 4 coils. Car runs fine very stable but it randomly hesitates (like a cough) for split seconds ONLY ON IDLE. Any suggestion will be highly appreciated. No codes on OBD by the way.

[@allensshenanigans348]

Check for vacuum leaks. Thank you for watching. Please support the channel by subscribing.

[@bash7102]

Put a bottle of Marvel Mystery Oil in on the next fill up. Take off and clean throttle body. Take off and clean mass airflow sensor.

[@sfh2050]

@@bash7102 i got a code for upstream o2 sensor.

[@bash7102]

@@sfh2050 Maybe try to clean or replace EGR valve? Not sure unless the sensor is bad or cat stopped up a bit. I know I used some CRC intake valve cleaner one time that made a world of difference in my truck. You spray it into the throttle plate while holding gas around 2000 to 2500 rpms.

[@darrellpickering8535]

Should've seen if it would've restarted to drop the fuel pressure even further & left the fuel cap off. There's around 50 psi on those lines. If you still have rotten mileage check the top of the tank. The metal barbs the fuel pump has are prone to rusting & pinholling. Since that pump sits in a depression, it's hard to see or even get a hand into. Scope works great tho. If you feel/see fuel there the tank needs to be dropped.

[@allensshenanigans348]

Thank you

[@debradale6305]

I have a 2002 envoy and for the last year or so my gas mileage has gotten worse. But never sputtered or slowed down until 2 days ago I was on the open road at around 55 mph and all of a sudden it began sputtering and slowing down. I thought it was out of gas so I pulled over and shut it off. Someone brought a gas can and put a tiny bit of gas in it, I don't believenit was enough to make a difference because when I cranked it back up there was no hesitation in cranking. Normally when you run out of gas it takes a little bit of time for it to crank. I was about a mile from a gas station and it ran fine and I put 4 gallons in it. When I took off it ran well for about 5nmiles and began sputtering again and slowing down. I pulled over and sat for a few minutes and cranked it up again and it went 5 more miles and did the same thing. I did this for around 15 miles and managed to get it home. The fuel filter was replaced and it seemed to be fine until the next day I cranked it up and drive it around 10 miles and it did the same thing. So I turned around and drove back towards my house. I had taken the gas cap off and it seemed to run better. But when I reach the road to my house it began sputtering much worse than it had before and it would not move while idling like it had done the day before. This time I smelled a weird smell and the digital readout on the dash flashed the stop engine message which had not happened before either. I managed to get it home. I'm not sure where to start looking for the problem since I already replaced the fuel filter. I have little resources or money to fix it. Does anyone know what the problem might be from your own experiences with a 2002 envoy?

[@garyhouse3134]

My 2004 trailblazer was doing the same thing as yours the catalytic converter was plugged up

[@debradale6305]

@@garyhouse3134 I have read so many articles and watched so many videos that give a long list of things to check before replacing fuel pumps because it can be something much cheaper to fix, like my brother had this happen to his truck and he replaced so many things but it ended up being a bad ground wire. Once he fixed that everything was fine. I don't realize these cars had such bad reputations until I had this problem. If I take it to a mechanic will a diagnostic machine tell me what is wrong? I have one of those you can use at home but it isn't showing anything

[@garyhouse3134]

There's a port by the fuel filter you can check the fuel pressure at. O'Reilly has a fuel pressure test kit you can rent to check the fuel pump thinking it has to be around sixty psi. I drilled some holes at the front of the converter to see if that was the problem it had lots of dust and rust that was plugging it up when running when motor shuts off the dust falls back down allowing it to start and run again till dust plugs up all the little hose in the converter.

[@TerminusHostilia]

Debra, the friendly staff and members over on GMT Nation forums can help you get to the bottom of it. You seem a stickler for details and it would make you a nice fit over there. Best of luck!

[@debradale6305]

@@TerminusHostilia how do I contact GMT Nation?

[@garybrown9719]

why trailblazer get terrible gas mileage

[@billyjames7343]

I didn't see a jack stand. If your making a video for others to follow your instructions..you should at least tell them to never crawl under a car supported by just a jack..block it up or use a jack stand for safety. Otherwise..good video!

[@deadpresident78]

🤣

[@arizonadon5644]

Ours idles rough with the AC on......300 mile highway trip yesterday was down on power a bit and downshifting itself (on cruise control) on hills it really shouldn't have had trouble with...it's an 06 with the filter in the pump module... Supposed to leave on a 1700 mile trip across the Rockies in a couple of days.......Anxiousness.... Not good!

[@allensshenanigans348]

I hope your trip went well.

[@McChevy]

Thanks for the video... Just one question... Was a engine light on?

[@allensshenanigans348]

No it wasn't. Thanks for watching! Please support the channel by subscribing.

[@williammedlock798]

Just changed fuel filter. Still low rpms. Rins rough

[@allensshenanigans348]

Check for vacuum lines unplugged or damaged. Change MAP sensor. Pull and check the condition and color of the spark plugs.

[@joekrim6557]

Sign of clogged filter

[@fernesal]

I need to do that. Did it solve the problem? Runs better? Better mpg?

[@allensshenanigans348]

Yes. The rough idle and almost stalling during idle went away. The fuel economy only slightly. I believe it was the original fuel filter.

[@estelapena52]

thanks

[@wildangel0229]

Good video. Is it the same for a 2005?

[@allensshenanigans348]

I believe the only difference is the port for checking fuel pressure is located in the engine bay. Thanks for watching. Support the channel by subscribing.

[@jesusadame4364]

Mine sputters a bit in the am after I hit 40 mph I'm trying this next thanks

[@jerrynorm9631]

Thanks I'm going to try this just put 50 bucks got 14 gallons and drive 36 miles a day to work for two days I need more gas in the last 3 weeks I spent 340 dollars taking my son to work I'm trying this or get a new car it's 2005

[@johnpanikowski7821]

older models dont have an external fuel filter and they are internal with the fuel pump

[@joeysantillo8977]

2009 envoy has no external fuel filter.

[@innovativeintelligence4172]

Did it help the mileage ? I know I need to change mine

[@allensshenanigans348]

From 11 to 12 mpg to 15 to 16 mpg in town.

[@karenvanderwall6684]

You should watch before posting. Didn’t see you taking filter off

[@allensshenanigans348]

Sorry you missed that part. It's between 6:00 and 6:17. The filter is on the frame so it was really difficult camera angles.

[@MrArob826]

I enjoyed it, but a bit nervous about trying to do the same

[@allensshenanigans348]

Just give yourself enough time. It isn't too bad. Please subscribe to support my channel!

[@allensshenanigans348]

Just give yourself enough time to finish the job. It isn't too difficult. Recommend starting on the passenger side. Please subscribe to support the channel!

[@allensshenanigans348]

Please support the channel by subscribing!

[@juliangoings8923]

Auto zone w won’t even let me buy this part for me tb

[@allensshenanigans348]

I think I got mine at O'Reilly.