Oh, would you look at that? It's a big 4.7 2007 Jeep Grand Cherokee um I believe it's an Hotel 706 somewhere it's in there. It sounds like it has a pretty bad misfire. I Started off, the customer completes the engine lights on. uh, runs rough.

Let me show you what's going on. The engine light wasn't flashing but I just started it up, pulled it in because I didn't want any problem to correct itself. So let's grab a scan tool under Joey on the inside what it's worth but sounds like we're going to get a misfire code. I'll tell plugged in so you see how the engine light's flashing key on engine off.

so if you see that on a Chrysler that indicates that somebody's reset the codes and the drive cycles not finished. So that's a really neat feature they add you just go key on engine off. You wait a little while if the engine light goes out, your drive cycle is done. if it just stays on I'm sorry, maybe if it stays on steady doesn't flash your drive cycles done.

but if it begins to flash your, your drive cycle is not current. So um, so you can see it flashing here. Just free tip for you. Probably really hard to tell on the video only putting gear here.

Perhaps you can hear it, but it's shaking pretty good. I mean I Don't know if you can see the hood trimmer or not. Definitely feels like a misfire here. It is exhausting so let's take him.

Shut it off here. we'll just go key eyed. engine off I don't I don't think you can Flash The Toads Let's see a BTC report po304, cylinder 4 misfire and a 138 I Believe that's for an O2 sensor none. Okay, let's see if the computer agrees.

So if you're working on Chryslers a lot of times you can do the Uh 3T Cycles So on off, on off, on and in the on position with three key Cycles and that will flash your codes for you on a lot of Chryslers They kept that feature for a lot of years, so we're just going to do a uh well, we won't have to do a whole fall scan. Let's just find the ECM here. We're going to look at some misfire data I Assume it has it in this year. We'll see what we see and see if it's I Mean it sounds like a dead mess to me.

Double check our codes here. Okay, yeah. so O2 sensor one circuit high and a po304 I Don't know if this is live misfire data and it is. Let me get it started up here.

see if this is a live reading sir. So appears. Yeah, that cylinder four is counting misfire. It's like crazy.

All right. let me go. shut it off. Okay, so cylinder four I Think yeah, these are one, three, five, seven fours over here.

Usually before they come to me, they've got all the new stuff already. Yep, and we can see already. it's got the new coil. I Assume probably a new plug.

Anybody missing the injector? tell Usually when they come here, all the parts are new. new plugs, new coil, new injector because we are always the last resort most of the time. So let's come up with a plan here folks. So when you're thinking about something like this, you know, obvious dead misfire.

You know it's not like low contribution. This thing just ain't working. Uh, you're thinking, you know what do we need? We need the four stroke suck, squeeze bang blow and we need it all to happen at the right time. and the engine has to have the ability to breathe.

So spark, fuel, compression, intake, and exhaust. so it has to have all of those and they have to happen at the right time. So that's something to consider. So what are the easiest things to check first? Um, I Like to kind of rule out base engine mechanical rate from the get-go because that's a super easy test to make right at the battery with relative compression.

so we're likely going to do a relative compression see what that looks like. If that looks good, we're going to move on. We'll check our spark, we'll check our fuel, and then, uh, you know, kind of go from there. Usually doing that will nail it down pretty quick.

We're gonna be using our picoscope. Got it hooked to the laptop over here I Took the high amp current clamp and I've got it around the battery cable the one that goes to the starter and then I Also took the Uh ignition probe here. put it on the number one ignition coil. It's just inductive so you don't have to tap any wires or anything here.

I've got stuff out of the way so this will give us a trigger to tell us where the number one cylinder is. This will show our starter draw current so we can see how relative each cylinder is to each other. and I've got it set up here. I've got 500 milliseconds on the screen.

our current clamp is in the 500 amp mode and 500 millivolts here on our ignition coil probe. So let's crank it over. We're going to put it in clear flood. We're just going to let it crank.

We'll get it, wait for them, and then we'll look at it and just see what the engine looks like mechanically relative to itself, hold the accelerator all the way to the floor, put a little plastic. All right. We should have enough data there. way more than enough.

Let me pause this. I'll admit I did not think it was going to sound like that. Okay, well we got something to think about here. So first of all, let's enhance Enhance.

Okay, so what are we looking at we're looking at. remember the blue Trace is starter current. This is the number one cylinder. so if we yeah but we can enhance even more so you can see the secondary ignition waveform.

So here's your classic. You know, secondary ignition waveform here. pretty close anyways. So just so we know where where we're at here.

Um, Anyway, let's skip all that and just go right to this. So this is cylinder One and we know the firing order on this. Every Chevy guy knows them. So it's One, Eight, Four, Three Six Five Seven Two and that starts over.

Getting One Eight Four. This is our cylinder. It's misfiring. Three, Six Five Seven Two and it appears right.

I'm just gonna double check myself on that. I am on cylinder one right driver side front and I believe that is a firing order. So One eight, Four, Three Six Five seven so it appears at number seven is taking more starter current. Uh is taking more current like it has more compression or it's or it's pushing two cylinders.

I think I know what's going on here I Said I think I know what's going on here. Let's look at this. Let's pull out the old-fashioned laptop. Let's see what's Let's see what cylinders are companions with each other.

One Eight Four Three Six Five Seven two. That's our firing order. Companion Cylinders One Eight Four Three Six Five Seven Two Companion Companion companion. Companion Four and seven are buddies.

What does that mean? That means when number four is on compression, number seven is on exhaust. What number seven is on compression? A top dead center. Number four is on exhaust at top 10. Center So let's picture this for a moment if we will.

Um, so just so we know what we're looking at here. the the current draw. So when we're cranking this engine over, the starter motor is spinning the engine over and it's coming up on compression for number one cylinder. So that draws more current on the starter service.

You know, if you can Envision It just kind of Grunt And to push that cylinder so the compression stroke and then boom over top that Center starter motor turns a little easier up on cylinder number. um, eight. You know it's putting, uh, you know, more strain on the starter, more current draw. I Could have had this scaled a little different so it would be a little more dramatic here.

But and then again, you know, coming up on number four and then coming up on number three, coming up on number five, coming up on number six. But then all of a sudden, that piston is trying to push up number seven and it is seemingly pushing twice as hard. Okay, so this would be number seven coming up on a compression stroke. But remember, at the same moment, when Seven's coming up on compression stroke, number Four is coming up on exhaust stroke.

I'll let you think about that for a minute. time's off. So what's that? Tell us. That tells us that there's about a 99 chance that the exhaust valve on the number four cylinder is not opening.

Because think about it. You know you can see on your screen like I say number seven is coming up on compression. It should be pushing with the same amount of amperage as all of these guys are. But it's not as pushing wood twice.

It takes twice the amount of starter current. Essentially, just you know. Just hypothetically looking at this. let's see.

it takes that Peaks out at 212 amps where the other current draw peeks out at 150. So you know that's quite a bit more. That's what. 50 60 more amps or so? Uh, to bring number seven up, bring seven up.

Make seven up yours. Um, so when seven is coming up on compression stroke, if it's pushing number four up with an exhaust valve that's not opening. what's that doing That's pushing two cylinders at the same time up on compression. The easiest way to verify that is to remove the number for spark plug.

If we take the number four spark plug out, this problem should go away. We would at that point we would have a blank one, eight, four. This one here will have no current draw, but number seven, therefore would be fixed fixed. I use that term loosely.

Um, so yeah. I Think the number four exhaust valve is not opening. Let's pull the number four spark plug and see what we can do from there to see if we can at least prove what we're talking about. I think any long time viewer of the SMA Channel perhaps has seen this before I think we did a video a long, long time ago on a Jeep with a 3.7 and I believe that one had two rocker arms off and it was I Don't remember if they were intake or exhaust, but it was doing some really funky stuff and we could.

We saw it immediately with relative compression I Don't remember if we ever fixed that jeep though, but I think it was a threesome I'd have to look through my records I I Think these four sevens also have similar issues I don't ever recall having fixed one uh, right off hand. I'd have to look through my archives. Let's get a 10 mil. Let's pull this out, pull that plug out, and redo our test.

I Don't know how a shop could an ignition coil on it. Seems like that would be the obvious thing that it's not, you know, just playing some swaptronics. Anyways, moving some coil around I Think you would see that the misfire was still there I'd be willing about it. Probably have a new spark plug.

We'll find out here. You don't need any tools to figure that stuff out or anything fancy. You can just swap around, plug, swap around coils and see if your misfire stays or moves or whatever. Yep, so we got a brand new champion RC 12m cc4.

She's pretty wet, smells like the gasoline. So we're just going to leave that spark plug out and then let's go redo our relative compression test there. and like I say we should see no relative compression. We should see no current being drawn on the number four cylinder.

at least very low because the spark plugs out. But what we're more interested in seeing is: does this resolve the issue on number seven? the high current draw. Because we suspect that the exhaust valve's not opening over here? Let me take and get our scope reset here. Get rid of the unenhanced.

I'm going to leave the scaling as it is right now. uh, that way it all looks the same to everybody. This is probably going to sound a little funky with that spark plug being out. If you're going to hear some whooshing thank you, that's the door I'm not slamming his door.

the door check's broken. It's got a damn good battery. that's all I know. So let's have a look at this.

I'll pop back here. a couple waveforms. oh one the Thunder where'd they go? Oh there they are I thought we lost shelves. Huh? Okay, let's enhance.

We can see we already fixed the problem. I use that term loosely and hints. So one Eight: here's where number four should be. Three, Six five seven, Two, One Eight: Four Bingo Just like that, we did a very non-intrusive test and we can 100 say with certainty that the number four exhaust valve is not opening.

we'll look at, would you look at that? Um, there may be other problems on that cylinder, but we know that for sure. so hopefully this makes sense to you. So we got starter current drawing, trying to shove that number one up and then trying to shove the number eight up. But number four.

That starter spinning nice and easy. It's got a little momentum coming down from this cylinder and it's like and then it slams back into uh, you know, number three and then Six Five Seven. This is where we we had our problem. Our quote: unquote problem.

We use our little claw hands here. Uh, before, but now we don't. So now we can 100 focus on cylinder four and we know what the heck we're looking for. That's great.

Oh, let's see what kind of job is it? Full valve cover doesn't look super fun. So what what could we do next to prove its exhaust valve not opening? So you can go at this a couple a couple ways. I Mean we already have a really good idea. Uh, you could put a regular compression gauge in here.

Okay, so when normally your compression, you'll hear the starter motor cranking over. Be like boom boom boom boom. You know it'll bump up at a normal rate, but what I would expect here? If we did, it would be like it would bump up at twice a rate. almost like a two cycle because this thing's building compression and every time that piston is coming up.

uh, you could do that. Or we could put the pressure transducer the end cylinder pressure transducer in here and then you could see. But I'm quite confident just based off our relative compression. and I'm going to look to see if these engines are notorious for rocker arm failure uh, or anything like that.

and then I'm going to get a hold of the customer and just see if they give us permission to pull this valve cover off and just have a look with our peepers now that we have some direction. now that we have a reason to spoke with a customer, they want to move forward and find out what the real problem is. They gave me permission to pull the valve cover uh, in an effort to not make the video super lengthy. I'm just going to go ahead and work on that here in between some other jobs today.

Once I get that off, we'll either discover that the rocker arm is M.I.A You know the for whatever reason is either falling off or we'll find like you know, the camshaft could be wiped out because that's the other thing that could keep it from opening. Or you know, a host of different things. So once I get this off. I'll kick the camera back on and we'll We'll keep going.

Radio upstairs, we don't get in trouble. I Just got that sneaked out of here. What a pita! to get that out of here. But would you look at that? One of these things is missing folks.

So here's our Lifter on this cylinder. Okay, that's the number four exhaust. camshaft. looks good and look at that.

that's our cam follower right there. Bingo. Bingo. That lady is your problem.

Well, it feels smooth on it. Interesting. We'll set that down for right now. All right.

Well now we need to figure out. Plan B here. what are we gonna do? Let me get some of my mess cleaned up there. it is snapped back in.

So what made it fall out? Um, I Don't know I Don't know if the valve intermittently stuck from. uh, you know, you know from a guide problem and then you know the rocker arm fell off I'm not sure I know on these three sevens. I In the past I have literally snapped them back in and then never had the car return for problems. I Mean the engine looks pretty clean on the inside, you know, despite you know some of the dirt and junk from from pulling the cover.

But oil change wise and stuff I mean it doesn't look neglected. Not a lot of sludge buildup. you know? There's literally nothing on camera when you wipe the oil off it. It's clean.

You know, looking down in the timing cover, it doesn't appear that the engine's you know, really abused or not serviced by any means. It's actually very, very clean. I would say oil's dark obviously I mean these four sevens are Big Oil burners. but I don't know at this point.

I'm going to clean stuff up I'm going to slide the valve cover back in and we're going to fire it up and see if we've fixed all this ladies problems just for a little show and tell if you're doing this on your own Jeep it's pretty easy to do. You can all I do is stick the screwdriver here in the end of the cam follower and then just you know, lightly pry against the cam as you pull the follower up through. You probably heard it snap in when I did it. They're relatively easy to pop in and you don't have to worry about your screwdriver ruining the cam or whatever else anybody's saying there in the comments.

If you are, you know, use a plastic screwdriver. You really don't need to pry that hard. They snap up in there pretty easy, but we can see that follower is is back on there now. So I guess that's it.

So that's the one that we just did I can bar the engine over I Suppose we could also just crank the engine over do a relative compression test with everything tore apart here. that shouldn't be a problem and uh, you know that's going to tell us right away. If we resolve the issue. We need you I need you.

You need me As usual. Hey I think you was wearing that mustard dress last time we saw. you must be aware all the time. No, it's like wearing a nightgown.

yeah with my with my robe too. Well not going in a rope. take a nap. All right.

we're gonna take a nap inside this car for me. All right you got the pedal to the plastic Mr though. uh what we're gonna do here folks is we're just gonna watch this rocker arm initially. Then we'll then we'll do our screen record uh with the uh, you know, uh, the what you call it the picot I Just want to see initially initially here.

um get you in a good view, go ahead and crank it. Miss Though it's going up and down, here comes the wee where we will let me get this fired up for us folks. All right, are you ready? Mr Though the plastic, crank it over? Okay, that's good. Well that's all we needed folks right there.

We don't even really need to zoom in or enhance. Um, we can see. Well, let's do it anyways. One eight four three six five seven two.

And what we're looking at here is not so much the total current draw as we are. How are each of the current draws relative to each other? So that's why they call it relative compression. We certainly can figure out you know the PSI per amp and then calculate how many psi each cylinder is, but we just need to know that they're relative. There goes 5-0 Uh, that they're all relative to each other.

So uh, that's good. We fixed it. and uh, the reason that they're relatively the same now is because we did put that spark plug back in and we can see that exhaust valve opening and closing at this point. I Have no choice really to other than to just throw the valve cover back on it, fired up, give it the old rev up, tune up, and ship it down the road.

Right, right? Just seek to remove our test equipment. Now let's get this sucker out of there. A little bit of a snug fit. Come on fella, there's that.

and there's that. So super non-invasive testing. both of them inductive. or I guess one conductive ones passages where I could have that something like that.

So we'll set that down there. I've gone ahead and put this side back together. just put the valve cover on it, put all the jiggly bits in there. I Believe everything's plugged in so we can reach in here and start it.

Now we should be able to look at our misfire counters. Contact: I Don't know if that's uh, spark plug fouled out. It's pretty smooth. We left this up on the screen.

Back out, go back in there. I did Count a couple on there. let her get kind of warmed up here and see what happens. like I say that plug was followed out pretty good so it wouldn't surprise me if there was a few up on there.

All right. good on the tailpipe now too. I know you guys probably couldn't hear it before. it's even tone.

got good exhaust juice coming out of it. Smells good I'll tell you that much. Beautiful, Awesome man tuned around town. when we come back we've got to look at that.

Cadillac that's been sick for a while. It doesn't run. it looks pretty rough so I don't even know foreign 175 750 on the clock. Engine looked pretty good internally for that kind of miles and uh, that's it folks.

So hopefully you guys see the benefit of this using the scope. Taking a couple lucky guesses and you know, leading us right to uh, the problem based on the evidence we collected. Um, granted I do think we have another video on this using a similar method on a I believe it was a Liberty, but I want to say on that one I thought it had two cylinders that were building um, high compression I'd have to look back through the archives maybe if I do I can link it to this video and then you guys can look at that. It was quite a few years ago, but I Was pretty sure that these four sevens had the same issues as the three seven.

So uh, so that's it. That's route we took and I want you guys to take that route down into the comment section, root around down there. questions come. it's concern.

CNC in the Facebook you guys know where to find us at this point. Not on Tick Tock though, remember that we're not on Tick Tock that's another scumbag and just remember viewers, if I can do it, you can do it. Thanks for watching. Thank you.