Rough idle

[treeroy]

Last week I fitted a decat manifold to my car (rather, my local garage fitted it). Today at a traffic light I noticed the car is rough (I would describe as lumpy?) at idle.

Is the manifold likely to be causing this issue? Or might it just be a coincidence. It is *possible* that it was doing it before fitting the manifold but if it was, then I didn't notice it. But I rarely run the car at idle as I don't normally drive in traffic.

It's going between 700-900 rpm every now and again. It was shaking a bit when in traffic earlier which is why I noticed it; I've stopped for a while on my drive and it's not shaking but it is not staying at a constant RPM.

I understand that normally rough idle is an issue with air filter or spark plugs. But is it possible or likely that the manifold caused it?

[Ac1962]

aside from checking for air induction leaks , maybe something got disturbed fitting the manny. Check the MAF O ring for wear/splits or if the MAF housing has come loose.

[treeroy]

aside from checking for air induction leaks , maybe something got disturbed fitting the manny. Check the MAF O ring for wear/splits or if the MAF housing has come loose.

Nothing obvious.

Not sure what you mean by O ring.

[Gaz mr-s]

When the car is cold start it & check around the the manifold/cat joint for an air leak with your hand. What kind of gasket did you use at that joint?

If it is leaking & you get someone to rev it you should be able to hear the telltale noise.

The maf has a thin o-ring that seals between it & tube.

But I doubt either of those are rough-idle causing. Unlikely to be plugs either....they more likely misfire at higher revs.  Do you have a code reader...any codes?

[treeroy]

And sure enough, 10 miles later I've got an engine light. I don't have a code reader so will take it to the garage later and get them to plug the reader in.

Also - I'm pretty sure the engine is misfiring persistently. There's a fair bit of vibration at higher speed that wasn't there before.

[Gaz mr-s]

You should either get a bluetooth unit to work with your phone or a reader.  Diagnose & help from here you'll be able to fix most things.  What type of gasket was usewd between manifold & cat?  Come to think of it...which gasket was used against the head, original or a perforated type that came with it?

Misfire....check down the coilpack recesses for moisture, & inspect the coilpacks for any cracks.

Also..... idle.... check your coolant level when the system is cold, - is the level where it usually sits?

[treeroy]

You should either get a bluetooth unit to work with your phone or a reader.  Diagnose & help from here you'll be able to fix most things.  What type of gasket was usewd between manifold & cat?  Come to think of it...which gasket was used against the head, original or a perforated type that came with it?

Misfire....check down the coilpack recesses for moisture, & inspect the coilpacks for any cracks.

The manifold came with two gaskets. I've never used one before so have no point of reference for comparison.

The material looked like this:

[Gaz mr-s]

Your garage doesn't know the  1zz engine. If they did they would have re-used the o/e manifold gasket, - it's common practice to do so. If you can I'd get it back from them.

That type used in the cat joint won't last long.  I tried using one & it lasted hours only.  Look up 'crush rings' & if you still have the o/e manifold you'll see the recesses that the crush rings sit into. The type you pictured is designed to work between two flat faces with no recesses.

So you're now thinking 'shouldn't Toyo supply a proper gasket?'  Yes......

[treeroy]

Engine code is P0420. Cat efficiency too low.

Suppose it could be caused by any number of things. A leak like you suggest Gaz. Or the O2 sensor failed. Or the cat is knackered and the pre-cats were holding up the car's emissions.

Not sure what the best way around this is.

[Gaz mr-s]

The O2 sensors are easily damaged when removing....I've not read an explanation, but it's oft-stated.

Or it could be the man/cat gasket has failed.  I think I did less than 100 miles before mine started to go.
As said above, feel around the joint on start-up.

Crush rings.... https://www.ebay.co.uk/itm/Genuine-AJUSA-OEM-Replacement-Exhaust-Pipe-Gasket-Seal-19003400/232899021405?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

Some will say they won't work with recesses only on one part (your cat). But they can successfully work. I've seen the suggestion of using exhaust paste surrounding them.

The alternative is to buy a sheet of material & cut your own gasket. I can't advise on that.     

Don't spend £60+ on a new O2 without getting opinion on here first.

[Call the midlife!]

Manifold gasket leaking and pulling air in, possibly.
Can't really fault the garage for fitting the parts as supplied if they're not familiar with the problem associated with them, as Gary says the fault really lies with the supplier.

[treeroy]

Nope I don't fault the garage. I bought a manifold and gave it to them to fit, which they did.

It has been a lot more expensive than I wanted though. The manifold had poor quality welding and the O2 sockets had a lot of welding on the inner, so the sensors wouldn't fit. Mechanic had to file down the welding and overall it took 2 hours labour.

Looks like I will be spending money again on it.

Mechanic looked at it today, reset the ECU, I'm guessing this won't do anything and it will still run rough, but maybe as it's reset, it will adjust sufficiently to whatever the new problem is. Think I'm being a bit optimistic with that.

He also suggested mapping it out, which wouldn't take too much effort and would hide the problem. I don't really give a rat's arse what emissions it puts out, but I know that if it stays with the fault on, then it will use 30-40% more fuel, and it won't take very long for the fuel cost to go higher than the cost of fixing!

[Gaz mr-s]

If by 'mapping it out' you mean re-mapping the ECU, - it can't be done on these.

You've got pretty simple issues, (probably) stuff that has been covered by many. Work through what's been said & see how it goes. 

[Call the midlife!]

The old adage of buy cheap, buy twice comes to mind sadly but you're certainly not the first.
I remember seeing the manifold in question and thinking you were setting yourself up for a fall, it's a shame the Toyos came back on offer straight after you'd sourced the one you ended up with.
If it's looking like the cat then BM cats are around £90 on ebay at the moment on a Black Friday type deal.

[treeroy]

The old adage of buy cheap, buy twice comes to mind sadly but you're certainly not the first.
I remember seeing the manifold in question and thinking you were setting yourself up for a fall, it's a shame the Toyos came back on offer straight after you'd sourced the one you ended up with.
If it's looking like the cat then BM cats are around £90 on ebay at the moment on a Black Friday type deal.

The old adage of buy cheap, buy twice comes to mind sadly but you're certainly not the first.
I remember seeing the manifold in question and thinking you were setting yourself up for a fall, it's a shame the Toyos came back on offer straight after you'd sourced the one you ended up with.
If it's looking like the cat then BM cats are around £90 on ebay at the moment on a Black Friday type deal.

Yeah it's a shame. I had assumed all the ebay ones would be more or less the same.

It is frustrating as the only reason I got the manifold was for  my peace of mind that the engine would not blow up, as I have heard so many horror stories of the pre-cats. I thought "£90, that's reasonable price to remove the risk of engine blowing up."

£90 has already turned into £300 and the car is still not running properly.  Could have bought a engine for the cost of this fu*king manifold.

I only bought it with the intention of having for 6 months while I save for something else. Wanted to run it cheaply.
I am hesitant to spend much on it; every £100 I spend now on the car is £100 less budget that I can spend on my next car in march or whenever.


Above, @Gaz mr-s  you suggested that if the gaskets have failed, there will be a whistling noise? I was listening to the engine bay as the mechanic revved the car, and all sounded normal. No whistling.

I would have thought if the manifold was leaking air then the exhaust noise would be very loud?

As for your point about ecu, is the ecu locked and not mappable at all?

Thanks both of you for your help.

[Gaz mr-s]

I don't know the technical term, but but the ecu is 'locked'

If it was leaking the mechanic would have heard it. The info to check is above.

[Carolyn]

Manifold gasket leaking and pulling air in, possibly.
Can't really fault the garage for fitting the parts as supplied if they're not familiar with the problem associated with them, as Gary says the fault really lies with the supplier.

Gaz is correct - the ECU is impenetrable.

Exhaust paste up stream of the cat is a no-no (very bad for the cat).  Crush rings are the way to go - preferably OEM ones. Nowt wrong with the composite gasket on the cylinder head end of an after market manifold.

I've seen cheapo poor manifolds with a flange that warped in the welding process.

Has it had a basic tune-up?  Plugs, air filter, MAF clean....?

Sometimes one can be chasing something 'obvious' when fate has dealt you a coincidental other problem - like a coil-pack dying.

A code reader costs very little and it's a basic tool for any car with an ECU.

Many members download 'Torque Pro' for a fiver an buy a cheap dongle off Ebay and it all works fine.  sometimes pending a bit more on a quality 'dongle' pays off with greater reliability.

Anyway - before leaping to conclusions- it usually best to read the error codes.

[1979scotte]

Engine code is P0420. Cat efficiency too low.

Suppose it could be caused by any number of things. A leak like you suggest Gaz. Or the O2 sensor failed. Or the cat is knackered and the pre-cats were holding up the car's emissions.

Not sure what the best way around this is.

Pre cats do very little once the main cat is up to temp.

Those gaskets are known to be pants.

[treeroy]

Manifold gasket leaking and pulling air in, possibly.
Can't really fault the garage for fitting the parts as supplied if they're not familiar with the problem associated with them, as Gary says the fault really lies with the supplier.

Gaz is correct - the ECU is impenetrable.

Exhaust paste up stream of the cat is a no-no (very bad for the cat).  Crush rings are the way to go - preferably OEM ones. Nowt wrong with the composite gasket on the cylinder head end of an after market manifold.

I've seen cheapo poor manifolds with a flange that warped in the welding process.

Has it had a basic tune-up?  Plugs, air filter, MAF clean....?

Sometimes one can be chasing something 'obvious' when fate has dealt you a coincidental other problem - like a coil-pack dying.

A code reader costs very little and it's a basic tool for any car with an ECU.

Many members download 'Torque Pro' for a fiver an buy a cheap dongle off Ebay and it all works fine.  sometimes pending a bit more on a quality 'dongle' pays off with greater reliability.

Anyway - before leaping to conclusions- it usually best to read the error codes.

Yeah i used to have a code reader but don't have one atm.

The code is P0420 which is Catalyst Efficiency Too Low

I am very much a novice with mechanical stuff but can't see how spark plugs or air filter etc would cause an emissions fault to display?

[Carolyn]

Manifold gasket leaking and pulling air in, possibly.
Can't really fault the garage for fitting the parts as supplied if they're not familiar with the problem associated with them, as Gary says the fault really lies with the supplier.

Gaz is correct - the ECU is impenetrable.

Exhaust paste up stream of the cat is a no-no (very bad for the cat).  Crush rings are the way to go - preferably OEM ones. Nowt wrong with the composite gasket on the cylinder head end of an after market manifold.

I've seen cheapo poor manifolds with a flange that warped in the welding process.

Has it had a basic tune-up?  Plugs, air filter, MAF clean....?

Sometimes one can be chasing something 'obvious' when fate has dealt you a coincidental other problem - like a coil-pack dying.

A code reader costs very little and it's a basic tool for any car with an ECU.

Many members download 'Torque Pro' for a fiver an buy a cheap dongle off Ebay and it all works fine.  sometimes pending a bit more on a quality 'dongle' pays off with greater reliability.

Anyway - before leaping to conclusions- it usually best to read the error codes.

Yeah i used to have a code reader but don't have one atm.

The code is P0420 which is Catalyst Efficiency Too Low

I am very much a novice with mechanical stuff but can't see how spark plugs or air filter etc would cause an emissions fault to display?

no -but it could explain a misfire.... just covering the basics. A bad coil-pack would usually generate a code.  The Maf doesn't tend to generate codes.

The misfire and cat problem may have nothing to do with one another, is what I was clumsily trying to say.

Cat efficiency issue could well be an exhaust leak. It could be exhaust paste in the cat (if it was used) 0r the post-cat sensor is not happy.  A bit of tissue taped to the end of something long and thin (so it can flap about) and then held close to the joints, is an excellent way to track down a leak.

[Joesson]

@Carolyn your comment:
"A bit of tissue taped to the end of something long and thin (so it can flap about) and then held close to the joints, is an excellent way to track down a leak".

Reminded me of an old post where I "introduced" the sticky stick and @Enjay introduced his "sucky stick".

Perhaps we could name your invention a "flappy stick".

https://www.mr2roc.org/forum/index.php?msg=765455

PS
I would remind the reader that the Poor Man's Patent is still in force!

[Ac1962]

IF it were my car,after checking myself all pipes nuts n bolts on the exhaust and intake were properly tight,  i would carefully clean the MAF and replace the MAF O ring { £3 part } i would run some Cataclean through the system { £13 amazon }, take it for a good hard run to get the cat hot. I would disconnect the battery for 20 minutes, this will reset the ECU - i would check the plugs were clean, check the air filter was clean, run it hard for 20 mins or so up the motorway, get a £7 code reader from fleabayamazon , reset any codes, disconnect battery again for 20 mins and see whats what.
pennies spent to hopefully fix it.

[Call the midlife!]

Good old Italian tune up, make sure it's got plenty of quality fuel in it, get it up to temperature and then redline every gear change down the slip road onto a quiet stretch of motorway and keep the cat hot for as long as possible.

[treeroy]

ECU was reset on Monday, i've since driven 40 miles and no warning light has come on. I thought it would be back on pretty soon. Yesterday I would have said that it was still rough on idle and not staying still on revs, but it's fine today. I'll keep driving it and see what happens.

Thanks for all the advice and I'll report back soon!

[Call the midlife!]

ECU was reset on Monday, i've since driven 40 miles and no warning light has come on. I thought it would be back on pretty soon. Yesterday I would have said that it was still rough on idle and not staying still on revs, but it's fine today. I'll keep driving it and see what happens.

Thanks for all the advice and I'll report back soon!

Was that just one trip of 40 miles? Generally it'll take two or more trips for the ECU to convince itself there's a problem and throw a code.

Fingers crossed though.