Low power, lean conditions (cracked air intake tube) GM

Low power, lean conditions (cracked air intake tube) GM

1997 chevy blazer with the hesitation problem this came from another garage before we started looking at it fuel pump new fuel pump was installed new mass airflow is installed distributor cap plugs wires rotor and still has the problem so we’re looking at it and what I did instead of showing the test drive we just took it for a test drive did a wide open throttle run and I’ve shown you guys this with dirty mass air flows and how we use the o2 at wide open throttle to see what kind of condition we have whether it we’re getting enough fuel or not and what we found is our hesitation problem on this vehicle was in fact a lean condition if you look at both the o2 s you will see that during the test drive as we’re accelerating as noted by the mass airflow grams per second increase and the throttle position sensor at wide open both upstream Oh two sensors are lean the entire time that we are at wide open throttle concerns for that would be primarily dirty mass airflow secondary would be fuel pressure both of those parts were replaced if you look at the mass airflow peak reading you see 150 grams per second that should be good I’m not thinking the mass airflow is going to be a problem so we’re going to go after fuel pressure and see what our fuel pressure looks like are we doing a fuel pressure check on this 97 blazer you’ve got a gauge connected nice to GM gives us a Schrader valve on the back of that air cleaner housing there’s a straighter so got the gauges connected we’re going to do a snap throttle test it’s not good enough to check static fuel pressure ever you always want to check it under a load situation right now at idle we have about 54 psi which is pretty good the key with this test is when you stop it you want to make sure that it doesn’t drop off on a snap so we see pressurize it should not drop when I snap this so oppressor increase it was okay to drop mower on a diesel but during the exile you want to make sure that it rises by 61 psi I’d like that to be a little bit higher I think but 54 Dido 61 psi wide open throttle it didn’t drop on a stop or lean condition does not look like a fuel pressure problem at this point so we got to keep moving continuation on our lean condition again before this vehicle came to us had a new mass airflow put in a new fuel pump and with it running with it running lean with good fuel pressure we focused on the mass airflow again just doing a visual inspection you know making sure here are the arrows pointing in the right direction I’ve seen people put these in backwards and it is and as we’re looking at the air intake tube what do you know we see a crack in the air intake tube and it was pretty bad when I took the air cleaner out you can see it when I open it up surprisingly that we had 150 grams for a second a wide-open throttle on this vehicle I would have expected this to be a little bit a little bit lower voltage or a little bit lower frequency which would affect my grams per second reading but um yeah it definitely needs an air intake tube we’re gonna temporarily duct-tape this and take it for a ride and see what our numbers look like on a test drive and see if we fix this vehicle or if I caused this problem when I pulled the air cleaner off and it was a small crack I think I may have made it worse when I pulled the air cleaner off and kind of split it more than than what it actually was but I’m pretty sure this is gonna take care of it okay this is the after shot of our test-drive after temporarily fixing our crack in our air intake tube with duct tape and what you notice right away on this is during this run where we we’re accelerating so we hit white up and throttle right here you notice that the o2 this is the bank 1 sensor 102 is rich the whole time the bank 2 sensor 1 is rich the whole time and we’re getting a peak grams per second number now of 197 so that 150 number I use for most vehicles you know it doesn’t always apply there are variables this one hitting almost 200 grams per second you see we had a clear increase in the air flow through this sensor as indicated by the fuel the correct amount of fuel we’re getting now looking at the o2 sensors is telling us that that is a fix this vehicle just had a cracked air intake tube

About the Author: Michael Flood


  1. Great video,showing how data analysis helps you identifying drivebility problems.I'd do smoke test first,whenever hesitation is present.I understand this video is to show how to use data.Anyway ,great job,keep'em comming.

  2. @magrisers Thanks for your comment and I agree a smoke test would have been good too. Honestly a simple good visual inspection would have been the best method. I preach that to my students all the time, yet I didn't perform one on this truck. Anyway I posted this one because within the video I showed the proper way to test fuel pressure and also wanted to re-enforce the O2 at WOT test.

  3. Good video. What will the other shop charge the customer? Obviously the new MAF, plugs, cap, fuel pump, etc… weren't needed.

  4. @beefystik Thats for your comment and I'm glad people are talking about my channel! Hope you enjoy the rest of them. More videos coming soon for sure.

  5. @DZydrunasC Yes. So what do you think the original shop did? Tell the customer it needed the parts and charged them an arm and a leg? Those parts and labor must have added up to $500!!!! I watched another vid from ADTP Training, or something like that, that showed a turbo car with a tricky problem, so tricky the original shop replaced the fuel pump AND TURBO that weren't the problem.

  6. @enix2k6 Yes you can do that however for this truck Fuel trim was normal at idle and low speeds. This was because the tear in the boot opened up under load due to engine torque. So this engine ran lean under loads only.

  7. @JUDGERAMBO Yes and volumetric efficiency of the engine. (Intake-exhuast, cam design, number of valves per cylinder, bore and stroke, turbo or supercharger etc.)

  8. Hey, you wouldn't happen to know if you can jumper an OBD2 port to access the stored codes like you could with the OBD1 systems? 98 Jimmy.


  9. @xIntoThePitx No you can't but you could get it scanned at a local part store and give me the codes and I could try to help you

  10. @ScannerDanner – Ah ok, wasn't sure. I'm cheap and prefer to save money instead of spend. I don't know of any shops that will do a 'free' scan, they all want an hour's labor of $80+tax, for something that takes 5 mins. But, I do know a few ppl that will do it for free, just a pain to line up schedules and the 1.5hr round trip. I see OBD2 scanners on sale all the time, just haven't jumped on one yet.

  11. @xIntoThePitx Your in Canada, here in the states the parts stores offer free diagnostics. Don't get me started on how ridiculous that is. If you keep watching my videos you will see that you cannot replace a part for a code. Anyway let me know if you can get that info.

  12. @ScannerDanner – Free diagnosis must be nice, but I don't see how they make money off it, unless they get you to agree to them fixing the problem when they waive the diagnostics fee. Yes, that's true you can't just throw parts at a code, but knowing the codes is an excellent pointer in the direction. I've been having long crank-start times which I minimize by letting it prime up. Colder the weather, shorter crank times. With CEL on, it starts no problem by defaulting the prob component

  13. @xIntoThePitx Well they call it "free" but all they do is scan it and then try to sell you a part based off of the code. It is a big scam. Check your fuel pressure (55-65) must be at least 60 during cranking. No start will occur under 50 on your system(not typical). make sure fuel pressure holds on shut down, if you have a bleed down problem (leaking psi reg.) this will also give a long crank and rough idle.

  14. @ScannerDanner EGR will stick open on these also. Watch my GM EGR flow video about 3/4 in shows how to unstick a linear EGR. not your car but same valve. Also all of these testing procedures are in my book.

  15. @ScannerDanner – Yes, I'm certain there's an issue with the EGR. I have e-test reports that show it. These linear egr's aren't the most reliable things GM offers, and these 4.3s are good at carboning up, just like your 3.1 blocked passage video. A long time ago I seafoamed it and think maybe that dislodged some carbon and it got forced into the egr port. Do you think those 'screen' egr gaskets are worth getting, seeing how I'll need to replace the gasket anyway.

  16. I also have a 97 Blazer . Do you have a video showing how to test this particular MAF and the EGR with "normal" volt meters? I can't afford the professional setup you use in your videos. I just bought an Innova 3160b Scan Tool so I can read my own codes and the first use pulled P0300, P0175, and P0420. This is after I replaced plugs/ wires, cap, rotor, EGR valve and Coolant temp sensor. I need to test the MAF and O2 sensors before proceeding to back pressure test. Thanks for the vids so far.

  17. Watch my two part GM MAF sensor testing videos. I show how to do it with a DMM in those videos. (you are limited in what you will see though)

  18. Thanks Scanner. I'll look for them. I since learned that the scan tool I have also does live data. It's just not as nice as your set up. Now I just need to learn how to use it.
    Any idea what might be causing the 3 codes I posted? The Air Intake is in good shape, no cracks or tears. After the tune up it should be running better than it is. I'm leaning toward MAF or O2 sensor(s) with a possible partially clogged CAT.
    Any help is much appreciated.

  19. great videos paul. this cracked hose sympthon is not the same as vacuum leak. what about fuel trim numbers at idle. would be high and improve a higher rpm. thanks paul.

  20. I just installed new headlights in my 94 explorer and when I removed the intake tube the entire bottom of the tube near the end on the MAF side was torn clean open with a hole about a half inch wide and two to three inches long. I wondered why my idle was rough and surging for so long and it turns out that the problem was just the deterioration of the original tube.

  21. hm…so, basically, the "un-metered" air was entering the engine…was not a dirty MAF…but it could ve been…hm, those 150g/s kind of screwed this good video…do it again!

  22. My father in law's 2009 Nissan Sentra had similar performance issues but only a lean code on the 4 cylinder. First thing I think when I see these lean codes check for intake leaks, from the air cleaner box to the intake manifold. Lo and behold, split as big as this in the inlet duct, same place l as this. Got this replaced l, no codes no performance issues have returned.

    Hadn't seen your video till today, as I fixed this issue some months ago.

  23. Sorry for shouting! This is one of my first videos and what you don't see is I am teaching to a group of students at a technical college. I needed to project my voice to them and was a newbie with the camera mic, and how well it picked up my voice. I've since fixed this. But there are some other videos from 2011 and 2012 where I can't watch them either, it's so annoying. But if you can get past those parts, my content has always been great. Thanks for watching! Now go watch something newer before you write me off okay? 🙂

  24. GM vortec emission troubles are almost always vacuum leaks. I use cigar smoke blown into small vacuum tube near the ABS module. After sealing intake upstream of the maf sensor and blocking the CVT. Blow smoke into the system ill reveal all leaks. I found my butterfly shaft leaking slightly as well causing a po174 code

  25. Typical GM product. I still have the original air intake hose on my 1991 Ford Escort with 131k miles. The 2013 Chevy Sonic has a cracked air intake hose at 54k miles LOL

  26. I have this exact problem on my 2014 impala. Would you say that duct tape would be a decent temp fix until I can buy a replacement part?

  27. I had a cracked hose too and the difference is night and day with a new intake hose, no more hesistation or low power, it was probably running like this for a couple years

  28. I think jiffy lube broke mine trying to check the filter, and didn't tell me lol. It started hesitating a lil bit, later on that day.

  29. 2003 Saturn ion won't idle past 2000 rpm, sounds rough when trying to idle past it and the speed thermometer stays at 0 mph while driving and won't go more than maybe 15 mph

  30. I have a Pontiac G3 (same engine as Chevy Aveo) Engine light was on so I took it to my mechanic. He put a new MAF sensor on and nothing changed. He wanted me to leave it for a few days so he could figure out what was going on but that wasn't an option so I took it home. I had the hood popped to put in some windshield washer fluid and looked at the outlet hose past the MAF sensor and sure enough it was cracked almost all the way around. I wrapped duct tape around it until I can pick one up. Watched a tutorial online and it looks like a very easy fix. Thank you so much for your video! YOU ARE THE MAN!!!!

  31. I recently bought a 2008 Honda Accord and I noticed in the engine bay that there is a piece of tape covering a couple of the ridges on the intake tube. Now my engine light came on and the P0420 code came on. Should I replace the tube first and run diagnostics to check the functionality of the o2 sensors?

  32. 2008 Mitsubishi Lancer ES 2.0L had a cracked air intake Throttle tube, and duct tape solved the problem. The engine was hesitating and even stalling at lights (very embarrassing). Thank you for your video mate.

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