This thread could turn into a bit of a tome.
To be fully open here, I have a 2ZZ which was done around 5 years ago and has been absolutely sweet to me. The only faults I've had were a broken driveshaft (oops) and a weeping rocker cover which was kindly fixed for free, despite the engine change having been done 18 months previously.
I've not used the car much this year. Mostly the monthly meets at Caffeine and Machine which are around 50 mile round trip. The last one was at the beginning of August. I filled the tank in July and have just over half a tank of fuel in.
When going to C&M in August, the car didn't quite sound right. Not horrible right, but not quite right. It was due a service, so I gave it new oil, plugs, filter. Did the usual - checked the coolant levels and so on. Turned it over and it sounded OK and I hoped a decent Italian Tune Up would fix it.
So on Sunday, I had a car show in Lancing. Around 120 mile round trip.
I got 10 miles up the road and it sounded horrendous. Lumpy and labouring under load. The engine was burbling rather than the TTE exhaust. I turned round and came home.
It sounded a bit like the time I played around with an induction kit with my 1ZZ, so my first go-to was the air intake. Checked all the hoses - no splits. Took apart the CDA filter, expecting to find some acorns or a mouse nest. Nope. Intake was just groovy. Took the MAF out, the O ring disintegrated. Found another one. Cleaned the MAF. Still the same.
So next up, fuel. Took the fuel pump and filter out. The filter was not only filthy, but had a micro crack on the top. Ordered a new one and fitted.
Sounded even worse. Took it out on the bench. Cleaned everything, including contacts and put it back. Sounded better, but back to square one.
Ordered a cheap Chinese MAF, just in case. Reset ECU. No difference.
It was at this point that
@mikek sent me a short whatsapp:
Air fuel spark
Ooh, hadn't considered that whilst cleaning the engine bay, some water might have seeped down a coil pack (it's a common problem on the 2ZZ).
Not just a little water, quite a lot of water. Well that would be causing a problem.
Dried it out thoroughly and cleaned with contact cleaner. Gave the spark plug a good check and it looks just fine, so no damage done (it wouldn't have reached the actual plug, just the coil pack).
OK, so now it sounds about 50% better. But it's still not well.
Checked the trims. 16.41%. That's not great. Should be + or - 5%.
OK, so leaving the ECU to reset overnight.
Reading through a few posts on here and Spyderchat, I've also ordered a new improved fuel pump.
TLDR:
- Checked air intake thoroughly
- Fuel filter cracked, replaced
- Water in spark plug chamber, dried out, coil pack thoroughly cleaned and dried
- Swapped out MAF
- Checked all other spark plugs and coil packs - all OK
So next up, reset overnight, replace MAF with the Denso one, replace fuel pump.
Any other suggestions, very very welcome!
Noises:
Under no load, a burble - mostly now fixed.
Under load, what I can only describe as a BRRRRRRRRRR sound.
It probably isn't this, - it's not the 'classic' symptoms, but sometimes it's different. Check the crank timing sensor earth connection, bottom edge of timing cover. Dirty or loose...?
To my mind, if cleaning up the coil pack helped 50% I would try swapping them out for known good ones. What would be the chances of two things going wrong at exactly the same time? Failing that, injectors.
Sounds like a vacuum leak somewhere just not a big one and not in the obvious places.
Quote from: Pete McCue on September 29, 2026, 08:52To my mind, if cleaning up the coil pack helped 50% I would try swapping them out for known good ones. What would be the chances of two things going wrong at exactly the same time? Failing that, injectors.
As it happens, I had a couple of them spare. I replaced them a couple of years ago, because 2 were cracked.
Doesn't sound like injectors either. That would mean the car was running on 3 cylinders. It's not that kind of sound.
Quote from: Craigjm on September 29, 2026, 09:40Sounds like a vacuum leak somewhere just not a big one and not in the obvious places.
Does seem like this. The 2ZZ uses a concertina pipe (which I've taken out and checked). I'm tempted to simply run it out of the back of the car, because the only bit I can't get to is the intake above the wheel.
Quote from: Gaz mr-s on September 28, 2026, 23:48It probably isn't this, - it's not the 'classic' symptoms, but sometimes it's different. Check the crank timing sensor earth connection, bottom edge of timing cover. Dirty or loose...?
I'll check that. I remember Carolyn mentioning it on another post. But I'm not sure it would have this impact. I'd expect it to be cutting out.
There's so many possibilities here. You just have to work through them systematically. The fasult does seem to be somehow related to your giving it all a good clean-up?? The old coilpacks that you put in could be struggling.
I can say that a poor earth on the crank sensor will make it struggle as the revs go up, it won't just cause the engine to cut out.
Quote from: Carolyn on September 29, 2026, 11:20There's so many possibilities here. You just have to work through them systematically. The fasult does seem to be somehow related to your giving it all a good clean-up?? The old coilpacks that you put in could be struggling.
I can say that a poor earth on the crank sensor will make it struggle as the revs go up, it won't just cause the engine to cut out.
That's what put me off the immediate earth theory - it was lumpy at tickover too.
I'll investigate that later.
I did change the coil packs a year or two back with known good ones, because 2 of them had cracked.
Agree with systematic. I mean, changing some of the things like filters and pumps are always good maintenance for a 22 year old car that's done 160k (and a 24 year old engine that's only done 65k)
I feel that stripping down the entire induction system right through to the throttle body is probably next.
Then check every single pipe for splits.
My big worry of course is that the intake manifold is split/gasket failed or so on. Because that's an engine-out job and I don't have those facilities.
Intake manifold is not an engine ot job. Fiddly, yes, but you can get it loose enough to change the gasket. However, it's not likely to be the gasket.
'Known good' used ones that have been in for two years are no longer 'known good'. Are you showing misfires on your OBD?
Quote from: Carolyn on September 29, 2026, 12:19Intake manifold is not an engine ot job. Fiddly, yes, but you can get it loose enough to change the gasket. However, it's not likely to be the gasket.
'Known good' used ones that have been in for two years are no longer 'known good'. Are you showing misfires on your OBD?
No. OBD is absolutely clean as a whistle. No faults.
Plugged it in last night, got it lovely and warm and took it out for a quick spin to make sure no faults came up.
It's somewhat sluggish, but I can get it into lift, even.
As above, though, trims were awful at +16.41%. Normally doesn't go above 5.
Lazy O2 sensor?
Quote from: Carolyn on September 29, 2026, 15:21Lazy O2 sensor?
I did wonder. Genuine Denso ones that I think are about 4 years old.
I did take a video last night. This might give more....
Well, wouldn't you know it. It's leaning towards a failed PCV valve.
A suggestion I read was to block the hose from the PCV valve and turn it over.
I put an M8 bolt in it, which fit lovely and snug.
Turned the engine over. Sounded great. Immediately improved.
I have a new one coming tomorrow, because I had a feeling it might have never been replaced and I read a post from
@Ardent earlier that said they should be replaced after 30,000 miles. The engine has done close to 70,000.
@Carolyn as I didn't have any good known spare coil packs, and seeing as one of them had got wet, I ordered a new set and replaced them. Denso ones seemed to be in short supply, so I've got Bosch ones. Looking at the old ones, it looks like they may have been a mix of Denso and cheap Chinesium.
The new fuel pump turned up today and with a bit of fettling, it fit and runs well.
So all of this diagnosis has cost a fortune, but these are serviceable parts, so worth replacing.
I'll probably be back tomorrow, complaining that it didn't fix it. But for now, it
might have done and that's enough to let me sleep tonight.
The only other thing that's coming in the post is a throttle body gasket. I was going to take it off and see if it was working properly. Definitely something worth keeping in the workshop.
Last time I had a problem with the throttle body, someone sent me a known good one so I swapped it out.
I can't remember if I reconditioned the old one (which I should). I did order the JIS bits especially and don't think I've ever used them.
Well, that's absolutely banging! New PCV and the car is as good as ever.
No idea how and why the old one failed, but that's the nature of cars.
They are a 30,000 mile item.
And cheap as car parts go.