The End of DIY Car Repair, Why New Cars are So Hard to Work On

rev up your engines all right here we have a very interesting problem the summer v8 gm engine misfires a number four and he's had an engine put in spark plugs coils even another computer and it continues to have a problem with number four the obvious things have been done let's get the giant computer out we'll take it for a road test we'll start there so we'll plug it in now we know that's working there we go smart link and we'll turn the main computer on too well this thing's got well over 300 000 miles and you get a lot of mileage a lot of weird stuff could happen so you need a fancy computer to figure it out it's even trickier because the catalytic converters were removed years ago that's not the problem but it's going to have oxygen sensor code because there's no cat anymore we'll start up here with the intelligent diagnosis it knows what it is h2 hummer this is the fanciest course into daily writing tips oh shut up you stupid phone uh we're gonna go through all the data systems here and we're gonna do not a smart scan but a system scan to do everything now it's doing a smart scan we're finding a bunch of codes that's just the beginning we'll start there now this has a misfire so that's what we're trying to figure out like i say it doesn't have catalytic converters there's gonna be some codes aren't gonna mean anything but we'll start at the top and work our way down start here there's six codes to the dsm here we go driver's recline sensor circuit well that has nothing to do with that running the lumbar horizontal center circuit malfunction again that's your seat in your back seat side bolster sensor we don't care about that heater on the left back and the right front isn't working and loss of driver module communications for the door that has absolutely nothing to do with the car running where class 2 data link malfunction another one of those deals that probably has to do with the doors losing communication hey it's got 300 something thousand miles you drive down the road the door's open and closed so i mean we don't care about that either we'll check the other one again lost communication with the instrument cluster data well that has nothing to do with it running poorly that's why i always warn people when these things age you got all these switches they all do stuff and they all break down over time dashes themselves break down over time but that isn't going to make the vehicle misfire now we'll get into something that's probably going to tell us a lot the power train and the powertrain control module as i said this doesn't have catalytic converters the oxygen sensor data is all going to be absorbed so we have to ignore all those heated oxygen sensor heated oxygen sensor heated oxygen sensors finally po300 engine misfire detected that's the only one that we're gonna care about the catalytic converters were taken off of this thing years ago and ran perfectly fine for years but it is misfired so let's go into that the first thing we want to do we know what the fault is so here we go let's look at the freeze frame here comes all kinds of information out it showed it was misfiring when the engine was 136 degrees fahrenheit so that meant it was not cold but it hadn't fully warmed up the engine load was 64 it was going 1600 rpm the long-term fuel trim on bank one it was subtracting minus 0.78 that's really not that big of a deal it was a little bit rich and the field trim on two was zero for a car with 300 000 miles that doesn't really mean anything the rpms it was doing 642 rpm it's just you know a little bit off idle but the mass airflow sensor said it was doing 48 grams a second now it's a brand new mass airflow sensor and so is the pcm it really shouldn't be that high at that low rpm they're going 26 miles an hour look at some lives at them put in gear now i'm really questioning the mass airflow sensor for one reason because this is a six liter engine it should be somewhere around six to seven grams per second and it's 9.04 at idle that's just too high we got a little clue going on there three secs the misfires it is number four you can see 14 now it's up to 18. it is misfiring well norman would say okay everything else is okay he'd replace the engine and it had the same code before i replaced the engine so i don't think we could blame it on the engine you can see the other eight cylinders you don't have any there now that's up to 16 24. it does it after a while and it goes back to zero and starts off you can see now it's zero but now it's counting them so it's actively misfiring there's no question about it this is an old vehicle right so we're gonna look at the history and it's logical when they're this old they're never gonna run perfect because here's the history throughout time cylinder one only misfired 17 times cylinder two three cylinder three four eighty seven cylinder four forty six thousand one hundred and eighty the main problem is in cylinder number four there's no if our hands about it yet it's a new engine it's got new coils new spark plugs even a new pcm the main computer's been replaced a driver could go bad in a main computer right and it could do that but he had that swapped out reprogrammed by guys at a tech college so that should be perfectly okay go back and look at some more data that was engine data one so let's look at engine data too damp shift data's good mission signals good here's something that's kind of interesting you can see bank one and bank two the average injector on time you can see that the bank two is actually a little bit lower consistently 2.9 here 2.98 here four one up to three let's look something up now this thing has new fuel injectors on it too so you can't blame the fuel injectors because they were all changed and since it's still number four misfire i want to be the odds that only the number four injector was bad in the new pack of eight and the old one here's real telling information the long-term fuel trim on bank one it's subtracting 1.5 so it's running rich and it's subtracting fuel a long-term fuel trim on bank two it's subtracting 10 which means it's running 10 times almost richer than bank one bank two is running the richest guess what's on bank two the number one four cylinder the one that's misfiring the most because bank one is the one with one cylinder and the other side is bank two so the bank that has the number four injector is the one that is running the richest it's having to subtract 10 fuel on that side now we're going to check the temperature of the exhaust manifold to see how they're firing now we'll check the top one and it's going at 237. now we'll check number four the one that's misfiring and it's about 217 220 so the misfiring cylinder is running cooler now that's not a surprise because we know that side of the engine is running too rich because the fuel trim is subtracting fuel trying to compensate for the problem if you have more fuel in an engine it will run at a cooler temperature that's why you really don't want to have an engine that runs super lean because it will run super hot and then burn the pistons out that's what happens when some fool takes the entire exhaust system off a car and wants it to go ah they run so lean they'll burn holes in the top of the pistons they get so hot this is the opposite problem it's running a little bit cool as far as it stands now it's kind of illogical just about everything's been changed the fuel injectors the computer the wiring harness maybe they weren't replaced correctly now let's check with this machine so let's go back to fuel data here and let's check out the fuel trim cell and the fuel trim learn those look kind of interesting and the injector bank one and the injector bank two select those and we'll start it up bank one has a longer on time than bank too but now that fuel trim is enabled graph it here we go if you noticed when i wrapped it up with it enabled it didn't misfire but when i took my foot off the gas it started misfiring and it disabled it i'm not driving we're doing a road test going up there now we're still in the bottom he took his foot off the gas that's why that happened we'll see what happens when he goes up the hill with misfire going up this hill let's see what happens with the fuel trim learning as we're going up the hill all right flooring so what we have here is a fuel trim problem now we got to figure out what's causing it the average is going up and down close enough even though one's always a little bit higher than the other i've used this machine to command the fuel trim on all the time it will no longer turn off until i push off to turn it on we're going up a hill and guess what it's not misfiring so here's the trick let's go into the machine and we are going to do a fuel injector balance so we'll look at cylinder power balance injector two injector three bad one injector four injector five projector six chapter seven and last but not least injector eight that one's getting a little tricky here now we're gonna reset them all now we're gonna start from scratch we'll clear the fault codes okay let's see if it did its job we'll read the default code these are permanent codes the catalytic conversion have been gone the sensors are gone so of course it's gonna trip them but notice the other codes have all disappeared that's one thing to remember you've got permanent codes you erase them and they come right back you got a problem in this case we know they're not there anymore because the cats aren't even there anymore that isn't causing a misfire those caused a lot of beer now we'll take for a spin and see what happens now you can see the long-term fuel trim on each side it's closer than what it was minus 0.78 and of course they change as you're driving but it's no longer the bank two is running a bunch different than the bank one you can see it's changed as you accelerate things go up and down that's going to happen but as you can see there this time bank one was now subtracting a little bit more fuel than bank two when before was subtracting almost 10 times as much fuel so this balancing seems to work the computer's trying to balance the system out whenever you replace anything on a modern car realize these are electronic fuel injectors nothing is perfect one is going to be off a little a few thousands from the other the computers got to figure out how much off they are so it can reset the stock and you got to do this when you replace any of the parts that's the problem with do-it-yourselfers these days if you buy eight fuel injections and throw them on one of these engines it's not going to run right because they got to be reset check this out the short term fuel trim now is zero and then it's subtracting a little or adding a little there isn't that much difference you can see here both of them are zero now it's running perfectly and you can see after they're both at zero they both went to adding two point three four that's because we're stepping on a gas going up a hill it's gotta add a little more fuel but when we were just cruising along they were both at zero you can't get any more perfect than that so what have we learned you need a fancy tool to work on modern cars and more importantly if you're going to change fuel injectors on your car today they have to be balanced by a machine like this or will never run right they're never made perfectly you got eight injectors they're never all gonna work exactly the same but the computer can compensate if one is a little bit rich it can make it fire less off if it's lean it can make it fire a little bit longer so i've got my scan tool in my backpack now and it's going everywhere with me because i used to say man you need about 50 different scan tools these days so far i have yet been able to find something that this machine doesn't work on now mind you it's not going to work on tesla's because he won't give any information out and that interface won't connect to his cars but you got a normal car it's something that a real mechanic should think about getting because if you think of all the work that was done on the hummer and it wasn't fixed that would have been bypassed a machine like this you could see well you know the fuel injection is somewhat off maybe it needed injectors yes but you would know after you put those injectors on you have to balance them don't balance them that's what you're gonna get weird misfire obviously the injector on number four was worse than the other ones you saw tiny little misfires maybe 40 over time on number one but like 45 000 on number four this is going to balance it as well as possible so if you never want to miss another one of my new car repair videos remember to ring that bell [Music] you

Channel: Scotty Kilmer

Views: 236,347

Rating: 4.9504862 out of 5

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Id: DqqW_1GGaz0

Length: 12min 44sec (764 seconds)

Published: Mon Sep 27 2021