MGB GT Misfire FIXED! (Eventually...)

Added: 2026-05-15

[00:00:00]Yes, guys. We're back in the garage.

[00:00:02]It's absolutely freezing.

[00:00:04]It's May, for God's sake. In the middle of May, and it's absolutely bloody freezing. But anyway, enough of the weather updates. Today, we've got another beautiful MGB GT in for some running issues, very strange running issues, actually.

[00:00:19]The chap says when he goes for a drive, it bogs down, it b- b- b- b- b- but then at standstill, it revs up fine. It It's perfectly fine.

[00:00:28]It revs in, revs out, revs up nice and high. As soon as you go for a drive, it just decides to go boo boo boo. I hope that's a good description. Maybe somebody's had the same thing. So, yeah.

[00:00:39]Let's go and check it out.

[00:00:41]All righty then, looking pretty nice this one, once again.

[00:00:46]It really is. It's a lovely red color.

[00:00:49]It really suits the red, actually. I'm quite impressed.

[00:00:52]Nice big twin carbs, electronic ignition, nice new coil.

[00:00:57]Now, the chap did say that he has done a couple of bits on this. He's swapped the coil out.

[00:01:02]Uh what else? He's put a new fuel pump on it. Looks like a new fuel filter, as well.

[00:01:07]That appears to be the wrong way around.

[00:01:11]If you know what you're talking about, that's definitely the wrong way around.

[00:01:14]The bulb should be the other way. So, we'll sort that out.

[00:01:17]Um he says that the carbs appear to be moving freely and everything, so he doesn't know why it's bogging down.

[00:01:24]Moving into the car, it's pretty cool in here. I really like the interior of this one.

[00:01:29]It's a really nice cream interior, matches the red really well.

[00:01:33]Looking really nice on the back, as well. This thing is pretty cool.

[00:01:37]Looks like it's got some posh brakes on it, as well. Looks Look at these bad boys.

[00:01:41]Nice drilled discs and things.

[00:01:44]Don't know if it's got posh calipers on it or what, but yeah.

[00:01:49]Right. Oh, the sun's just come out. Did you see that? Fantastic. Right, let's take it for a quick drive, and I'll show you what I'm talking about.

[00:01:57]I had to close the door earlier.

[00:01:59]It definitely was not very nice, but like I said, the sun has come out wonderful.

[00:02:23]Sunshine.

[00:02:25]Right, I'll just show you what I mean.

[00:02:27]It's running really quite well, actually.

[00:02:30]I'm really quite impressed. It's got posh gas struts on it.

[00:02:34]Now, as you can see, it is running really well.

[00:02:43]It seems to be revving up, idling nicely.

[00:02:46]There's no reason to believe that there's anything wrong with it, but I'll jump in the car and I'll show you.

[00:02:53]Okay, we're in. We're running.

[00:02:55]Hopefully you can hear me all right.

[00:02:58]Now, I'll just show you. So, as you take off, beautiful. No problems whatsoever.

[00:03:04]Slow speeds, no misfiring.

[00:03:10]Not a problem at all.

[00:03:13]Just get out onto the road and I'll show you what what it's actually doing.

[00:03:19]Let me know in the comments. I reckon somebody might be able to guess it before you watch the end of the video and see how it is fixed. Let me know what you think's wrong with it.

[00:03:27]As you used to pick up, it There we go.

[00:03:34]That's foot flat to the floor.

[00:03:37]Going nowhere.

[00:03:40]Now, as you can see, now as I first took off, I had loads of power, and then it suddenly started doing it. There we go.

[00:03:48]That's foot flat to the floor. Second.

[00:03:54]There we go.

[00:03:55]Got no oomph whatsoever.

[00:03:58]If I just give it a little bit of throttle, it seems to smooth out slightly. A few stutters there, but it does seem to smooth out very slightly on the on very partial throttle.

[00:04:13]And then as soon as you put your foot down, nothing.

[00:04:16]Not really anywhere.

[00:04:18]Let's get back to the garage and we'll see what we can find.

[00:04:28]I'm guessing fuel, carbs maybe not set up properly, too rich, advancing the timing maybe, spark plugs, spark plug leads.

[00:04:46]There we go. It's really not happy now.

[00:05:02]Okay, fellas. We all know what we need to do first and that's pull out our pipes.

[00:05:08]I think that definitely deserved a can of Oh, a can of Williams.

[00:05:13]So yeah, we're going to pull these pipes off.

[00:05:16]Swap this fuel filter around. I mean, that won't be an issue a running issue because the fuel filter is technically still fuel filtering. It's just not the correct way around cuz that is the way that it needs to be. Just had to put a cloth down. There's fuel going everywhere, obviously. Let me try and tuck them out of the way.

[00:05:40]Uh right, so cuz this has been on the wrong way, obviously if there's any particles gone inside here, they're going to be in the wrong side cuz the reason you have it this way Sorry, this way with the fuel coming in this way is because you can see stuff collecting in there, whereas on the other side, if it goes in that way, the little bulb inside, you can't see any crap. So, I'm just going to make sure just look down it, make sure there's no crap in it, give it a flush out the other way and a blow out, make sure there's no crap in there and we can put it back on the right way.

[00:06:15]Yeah, just looking inside, it looks pretty new. There's no crap in there or anything, so I'm I'm happy to put that one back on.

[00:06:22]Check out this bloody weather.

[00:06:28]Right, I'll put it back on the correct way now.

[00:06:30]Fuel flow this way.

[00:06:33]>> [snorts] >> And pop our pipes back on.

[00:06:45]All right, then. Let's start the diagnostic process.

[00:06:48]First things first, we're going to check ignition inside the distributor cap. Now, this has got electronic ignition, so I'm not too worried about the points, obviously, cuz there are none.

[00:07:00]But, if we can get the cap off and check the condition in there.

[00:07:03]I don't know if he said he had a new rotor arm or something.

[00:07:07]But, if we can just have a a little peep inside here.

[00:07:10]Uh a bit pitted, but nothing too crusty. Looks like that somebody's had a scratch there.

[00:07:20]Again, looks like somebody's had a scratch.

[00:07:23]Definitely.

[00:07:24]>> [snorts] >> Right, I'll put this back together because I'm not convinced that this is the source of our problem, so that goes back on. While I am here though, I'm going to see by just popping the little back holes off, I'll give it a suck and I'll see if it turns down there. See if we can see it. Okay, that was a good shot. So, I've just pulled the vac pipe off, obviously.

[00:07:48]You can just see the advance there. I'm going to give this pipe a good suck.

[00:07:57]And it's definitely advancing. So, we can rule that one out as well.

[00:08:01]>> [snorts] >> Old man John's coming to have a look uh to make sure that I'm actually doing stuff correctly, as usual.

[00:08:09]He's over there. Let me show you.

[00:08:15]He said he didn't want to be in the video.

[00:08:18]But, I'm going to sneak him in quick, cuz everyone loves John.

[00:08:21]Hi, John.

[00:08:23]All right, let's pop our distributor cap back on and uh not worry about that one too much just yet.

[00:08:31]Snappy, snappy.

[00:08:34]Snap.

[00:08:35]And don't forget to put our little vac pipe on the carb, as well.

[00:08:41]Okay, just to rule out the fuel delivery, he said it has got new fuel pump on it. So, I'm just going to >> [snorts] >> take this pipe off here.

[00:08:49]Pull this another pipe. There's lots of sucking and pulling pipes at the moment, isn't there? I do apologize, chaps.

[00:08:58]But, if I just pop that pipe off there, I'm just going to bring you over a nice clear container, so you guys can see the fuel.

[00:09:06]And I'll pop that right there, like that.

[00:09:08]I'm going to turn the ignition on, make sure we've got good fuel.

[00:09:12]Just to rule it out.

[00:09:14]Okay, ignition going on.

[00:09:19]Plenty of fuel.

[00:09:21]Loads of fuel.

[00:09:23]Lots and lots.

[00:09:25]So, we can rule out fuel delivery for now, because there is fuel.

[00:09:29]So, I'll just pop our pipe back on.

[00:09:33]Okay, so far, we've ruled out any nasties inside the distributor cap.

[00:09:38]Ruled out fuel delivery. We've ruled out the advance as well for when it wants to accelerate. I think next thing we're going to do I'm going to take the carbs with a pinch of salt just in case.

[00:09:51]But I think what we need to check next these leads look pretty good. So, I'm not sure if it's going to be arcing out of that.

[00:09:59]They're looking pretty good nick.

[00:10:01]Um there is one way to test it and that's when your engine is running, you can put your hands in and have a good feel and if you get a belt then obviously you've got a an arc somewhere through stuff. So, I think we'll try that next and uh brave getting a 50,000 V shock.

[00:10:20]Now, like I said, this is quick and dirty horrible way of trying to find out if you've got any spark plug lead arcing and I'm just going to dive in. The beast lies somewhere in the stump.

[00:10:31]Choose a passage.

[00:10:34]No way.

[00:10:35]I'm just touch the touch the leads just in case there's any spark that's only arcing on acceleration.

[00:10:47]Arcing out on any of these bits.

[00:10:50]But at the moment I can't feel anything, thank god.

[00:10:54]Quick and dirty.

[00:10:57]Okie dokie. I think it's time to pull the spark plugs. We're going to pull all four and check condition of each one of them.

[00:11:04]Now, they don't look brand new. Don't look like they've been changed, though.

[00:11:07]We might be onto something here.

[00:11:10]Okay, let's pull some plugs.

[00:11:13]There's a chance that these bad boys on acceleration, depending on what kind they are or how messed up they are maybe when they when the engine speeds get a little bit fast, one of them's breaking down or arcing out or something.

[00:11:29]I'm going to keep them all in the correct orientation and we'll go and check them out on the bench, see what they look like.

[00:11:38]What What do you mean?

[00:11:40]When it's on the load, isn't it?

[00:11:43]That's when they they give up.

[00:11:46]Yeah, that's definitely the the worst one. That's too bad.

[00:11:50]I'll clean them up.

[00:11:53]Change that one to that one. See how it goes till that one gets a new one, eh?

[00:11:57]Yeah, I think I'll just get a new set.

[00:12:00]Okay, after a little bit of research, um apparently you can use these uh iridium tipped spark plugs uh for this application.

[00:12:10]But in my opinion, you can't really beat a good old BP6ES NGK on these old things. I use them in all sorts of stuff, Aston Martins, E-Types, everything.

[00:12:19]Um and they work perfectly fine with electronic ignition as well.

[00:12:24]Also, the fact that this gentleman says he's not changed these in a while and they do look pretty old and crusty.

[00:12:32]I think the next sensible step really to rule it out would be to get a nice new set cuz they're not very expensive. I mean, they're only about a fiver each, if that.

[00:12:40]So, let's head to GSF, my favorite pals over there.

[00:12:43]They said they've got some in in stock as well, so we're going to pick them up, chuck them in and see if we fix this thing nice and easily.

[00:12:50]Let's go.

[00:12:52]To the trusty steed.

[00:12:56]>> [screaming] >> And we are back.

[00:13:13]Got our spark plugs. Um I'm just going to go and check out the other spark plugs, make sure that they're the same length and everything. I know that they are, but um Now, these ones are definitely the equivalent there, but not iridium tipped.

[00:13:32]Beautiful. Well, let's get these bad boys in. I think the car was running pretty well before anyway, so I'm not too worried about the mixture because the uh tips have got a very nice sandy color on them.

[00:13:43]I just think that they were breaking down under load, one of the spark plugs, number three, did we say? That one was definitely the worst one, so it's not like it's right across the whole of the the original spark plugs. It looked like just one was buggered. So, let's get these bad boys in and hopefully we'll give it a a nice little revamp.

[00:14:04]Oh, just before I do that, >> [sighs and gasps] >> as usual, there's something weird knocking about down here.

[00:14:11]Oh, what could we think it might be?

[00:14:13]It's the Vaudrey's branded beer mats.

[00:14:15]Oh, I've just knocked off the spanner. It's a Vaudrey's branded beer mats.

[00:14:20]Like, comment, subscribe if you like this kind of stuff. Uh go check out my other videos as well uh cuz there's loads of cool classic car repairs and stuff on there. Loads of revivals, loads of cool other stuff. If you haven't seen them, go check them out.

[00:14:33]And uh you can get one of these on the little shop down below as well. Nice one.

[00:14:37]Oh, look, it's just started raining again. Big surprise. This is turning into a more of a a weather channel than a bloody classic car channel.

[00:14:48]It was lovely and sunny before, and then it was pissing down, hailing, windy, rain. It's that time of year. I thought it'd be a bit warmer at the moment to be fair, being well into May by now, so yeah, a bit rubbish. In the garage, it's cold, hot.

[00:15:05]20° last week, 9° this morning. I don't know.

[00:15:12]Global warming?

[00:15:13]Maybe it's all these old cars pumping all sorts of crap into the into the atmosphere, but hey, be cool. Doesn't matter, does it?

[00:15:25]Okay, we'll just nip these down nice like so.

[00:15:29]One.

[00:15:33]Two.

[00:15:36]Three.

[00:15:40]Four.

[00:15:44]If anyone gets that reference, just chuck us a little comment cuz nobody ever bloody gets my references.

[00:15:52]Okay, we'll pop the plug leads back on.

[00:15:56]Number four.

[00:15:59]Okay.

[00:16:01]This is the moment of truth. I think we might have got this.

[00:16:04]I think we might be on to a winner with this one. Something as simple as spark plugs just not quite working under load. I think a fresh set of plugs will probably sort us out. So, let's let's go and fire it up and see what happens.

[00:16:31]Beautiful.

[00:16:33]Okay, I'm just going to let it warm up uh back up to operating temperature and then we'll go for a spin and hopefully this time we can actually get down the road and not block all the traffic.

[00:16:59]All right, fellas, she's up to temperature.

[00:17:02]Let's get out onto the the main road and see how she performs.

[00:17:11]And away we go.

[00:17:29]>> It appears It appears our problem is back.

[00:17:37]Misfire.

[00:17:46]Misfire under load.

[00:17:48]Right. That's that. Let's turn around and get back to the garage and continue.

[00:17:57]Yeah.

[00:17:58]No good.

[00:18:01]No good at all.

[00:18:05]Is that fuel?

[00:18:09]Let's leave it to just idle for a second.

[00:18:12]Let the carbs fill up.

[00:18:32]I wonder if we've maybe got a bit of a bit of a sticky needle valve in the float chambers are empty and or one of them's emptying at least on the uh front or rear carburetor.

[00:18:51]How strange is that? Okay, we're back in the garage. Let's have a little recap of what's going on. Um we did think that all the ignition system looks okay apart from the spark plugs that weren't changed. So, obviously that's first uh port of call when you come into uh a misfire under load. So, we swapped them out. That's not worked.

[00:19:10]>> [clears throat] >> On our little test drive then it it felt like it was almost running out of fuel on on maybe one carburetor, like it was misfiring, but maybe getting uh some fuel to the other two or what or three or one cuz as we know, it's got two carburetors. That feeds those two.

[00:19:27]That feeds those two.

[00:19:29]So, as I pulled it back in, it decided to just cut out completely.

[00:19:36]So, I'm thinking maybe something to do with fuel.

[00:19:41]This is what you got to do, I suppose, with these old things. You can't just plug them in with a computer.

[00:19:46]Uh I can't imagine that there's anything wrong with these new spark plugs. They were just uh a Hail Mary, really. Just chuck them in and see if it worked, which it didn't.

[00:19:56]So, I think we'll start taking these off on on the side of the carburetors. These are float bowls. There's one on each side. We'll pop them off. And the fact that it just conked out as I got back then says to me maybe one might be empty.

[00:20:12]This is all just speculation. It's just diagnostics, I suppose, and a process that you have to go through.

[00:20:18]Now, if I remember rightly, this gentleman did say that he swapped out one of the floats, if not both.

[00:20:28]So, I think we'll just double-check in there.

[00:20:31]We'll keep these screws nice and safe.

[00:20:34]He had swapped out the uh coil as well, so I doubt that's breaking down.

[00:20:40]I think what I'll do, I'll just pop off this pipe for a bit more access.

[00:20:45]Like so.

[00:20:48]Let's hope that we find no fuel in one of these float chambers.

[00:20:53]That would be really cool cuz then we can narrow down the issue cuz there's definitely fuel in here inside this bowl. That's beautiful. That's that's still full.

[00:21:04]But if there's not any in here and it's a a sticky float or a sticky needle or something, then we've diagnosed it down to a fuel issue post fuel pump.

[00:21:18]Like I said, I'm sure he said he had a a new fuel pump on it as well, so let's dive in and see if we can see any fuel.

[00:21:28]The moment of truth, fellas.

[00:21:30]We have fuel.

[00:21:34]There's definitely fuel in there. Let's take a look.

[00:21:37]Looks like the needle valve's working well as well.

[00:21:41]There's definitely fuel in there.

[00:21:43]Okay, we're going to go ahead and dive into our other little float chamber here.

[00:21:50]And see if we got fuel in there.

[00:21:53]If there is fuel, what on earth is wrong with this car?

[00:22:03]Our survey says, low fuel.

[00:22:10]Mhm. Yes, so as you can see in this end over here, we have quite a lot of fuel.

[00:22:18]If I just bring you over here and bring the torch, quite a low fuel level there.

[00:22:26]There's hardly any in there.

[00:22:29]So, whether that's just filled up as I parked up or this needle valve's not working so well.

[00:22:36]Who knows? We can investigate. There is a bit of crap in the bottom there as well.

[00:22:40]But the fact that there's no fuel in here is exactly what we wanted to see. Or very little fuel in there anyway, let's put it that way.

[00:22:48]We can clean the crap out of the bottom.

[00:22:50]I'm going to take this off, give this a blow out, give it a clean, check out the needle valve. Let's go and do that.

[00:22:56]Okay.

[00:22:58]>> [clears throat] >> So, this is our float, our have a valve underneath there as well, if you can see.

[00:23:05]And it appears appears to be working.

[00:23:08]But, if I blow in, no fuel.

[00:23:17]Yes, we found it.

[00:23:20]Absolutely no fuel going to be able to get through that.

[00:23:23]That needle valve is wide open.

[00:23:27]That That is on full flop.

[00:23:30]That float, and it appears that no fuel can get into there because I can't even blow through it.

[00:23:37]Right, let's take it apart. See if there's any crap in there, eh?

[00:23:42]Okay, so what we're going to do first is just give this a nice little blast in there, blast in there.

[00:23:47]Then we're just going to give it a nice tap out.

[00:23:54]And see what comes out. Oh, yes.

[00:23:58]I don't know if you can see that there, but Oh, yes, that's just what we wanted to see.

[00:24:06]Right there.

[00:24:08]See all this crap?

[00:24:09]That's all just come out from inside that pipe.

[00:24:15]And this stuff looks pretty new, as well. Maybe there's some remnants left from a rebuild or something like that, but this was definitely blocking the pipe.

[00:24:24]Check it out.

[00:24:29]Lots of cleanliness.

[00:24:33]Okay, now, the fact that we found all this crap in here, I'm so happy we did.

[00:24:36]Look at all that.

[00:24:38]Uh what I'm going to go do, I'm going to go ahead and take the float off.

[00:24:42]Uh take the needle out as well. Give everything a good clean out because it looks pretty new.

[00:24:48]Uh just in case there's any remnants left in there. And I'm also going to give this one a good blow out. I'll I'll disconnect it from here.

[00:24:55]I'll give all the uh float balls a nice clean out. Oh, there goes the gasket.

[00:25:00]Because there is a lot of crap in there.

[00:25:02]There really is.

[00:25:04]And as well, I'm going to pop this fuel pipe off here.

[00:25:08]Just in case there's any crap inside here. And I'll blow everything through with the airline. Make sure there's no crap in this line before the fuel filter.

[00:25:17]And yeah.

[00:25:19]Get it all back together.

[00:25:21]We'll be able to go out for a final test drive cuz I'm pretty confident this time that we're going to get it fixed up and it's going to work.

[00:25:39]All clear. No more crap. You could snorkel with this thing.

[00:25:45]>> [snorts] >> Right. I'll get all this put back together.

[00:25:50]I'll go and fetch the other one. You don't need to see that. I'll do the exact same to the other one just in case there's any crap in that one. I'll let you know if there is. And then we're going to go ahead and uh purge the fuel lines with some air and a bit of brake cleaner. I think we'll be good to go.

[00:26:16]That little tap.

[00:26:19]And now we should have a fully working float.

[00:26:28]I'm just going to use a little a small plastic syringe to just suck out any crap that might be in there. Going to take a rag and just try and cover it up slightly and give it a blow.

[00:26:45]And as you can see, nice and clean in the bottom there now.

[00:26:50]No more crap. There was loads of stuff in here.

[00:26:53]Beautiful.

[00:26:56]Right, that's the carb tops back on.

[00:27:00]And I'm going to just just give the fuel pipe a good blow out as well.

[00:27:05]Fingers crossed it doesn't all go in my face. You ready?

[00:27:09]Whoop.

[00:27:11]There we go.

[00:27:12]Nice.

[00:27:15]And there we are, the finished product.

[00:27:17]Nice and clean, all blown out, all clipped back up, fuel filter's on the right way around, fuel pipe's looking nice.

[00:27:25]I think we should go for a spin.

[00:27:27]I think we might be all right.

[00:27:31]Okay, fellas, moment of truth.

[00:27:36]She's up to temp.

[00:27:38]Let's go and see what she does.

[00:27:44]Okey-dokey, we're coming out onto the highway. It's the moment of truth.

[00:27:49]Let's go.

[00:27:52]There she goes.

[00:27:54]Revving all the way out.

[00:27:58]Oh, yes.

[00:28:01]Oh, yes.

[00:28:03]More of that, my girl.

[00:28:05]Yes.

[00:28:07]More of that, please.

[00:28:09]More of that, my girl.

[00:28:11]>> [screaming] >> She's driving wonderful. We've got the fix. We've got the fix.

[00:28:17]This thing drives absolutely fantastic.

[00:28:19]The brakes are good, suspension's good.

[00:28:21]It pulls really well now.

[00:28:25]Really nice, nice and smooth.

[00:28:31]Just goes to show a little bit of crap in a pipe somewhere can completely disable your car. So, I hope this video has helped everybody out who might be having a similar issue, running issues and things.

[00:28:46]It might be worth going and checking your pipes.

[00:28:49]Give your pipes a little bit of blow off and somebody else to do it for you.

[00:28:54]Right.

[00:28:55]Let's get it back. Let's get it back to the workshop.

[00:28:59]We'll go and finish off. This has been a success story.

[00:29:03]Really glad we found it.

[00:29:20]Driving absolutely beautiful.

[00:29:45]She's a good 'un.

[00:29:49]Yes, guys. Back once again with the common microphone. Another success story. We thought initially that it was going to be spark plugs cuz number three was a little bit funky. The chap said he hadn't changed them in a however long, a year, two, who knows.

[00:30:04]Uh turned out not to be that. That was the easy option.

[00:30:08]Turned out to be some crap in the the little feed pipe to the to the front carburetor.

[00:30:13]So, hopefully that little procedure, you enjoyed it. And hopefully it helps somebody out as well in the future if you want to go and clean out your pipes.

[00:30:20]Clean out your carburetors, stuff like that. Hopefully it helps somebody out.

[00:30:24]So, yeah. Nice one. Another success story. Thanks for watching and I'll see you on the next one.