Running Rich and idle problems

[M.Dub]

Hi all,

I'm new to the club hoping for some assistance please.

Iv recently purchased a mk3 2000 that has had an engine rebuild at some point.

I'm having issues with both banks apparently running rich according to the OBD. Iv already replaced the 3 x 02s with Densos also replaced the MAF with a Denso as it was a cheap one installed. replaced plugs also

My short term fuel trims are -20 at idle on both banks.long term also massive -

Also maybe a unrelated problem is that the car idles fine but if I give it a Rev and then let it drop the car really struggles to find it's idle point again and it shakes for a few seconds until it does.

Any ideas would be very much appreciated.

Thank you

[jonbill]

can you see what colour injectors it has? they're at the top of the engine, by the bulkhead

[Carolyn]

You've done the obvious stuff.  Have you put in a new air filter?

After all that, it might be time to clean the idle air control valve and the throttle body.

A quick search of the 'how to' section will help you with that.

[shnazzle]

Hi all,

I'm new to the club hoping for some assistance please.

Iv recently purchased a mk3 2000 that has had an engine rebuild at some point.

I'm having issues with both banks apparently running rich according to the OBD. Iv already replaced the 3 x 02s with Densos also replaced the MAF with a Denso as it was a cheap one installed. replaced plugs also

My short term fuel trims are -20 at idle on both banks.long term also massive -

Also maybe a unrelated problem is that the car idles fine but if I give it a Rev and then let it drop the car really struggles to find it's idle point again and it shakes for a few seconds until it does.

Any ideas would be very much appreciated.

Thank you

@M.Dub
It does sound like your idle air control valve is a bit gummed up. Unfortunately not an easy fix as the throttle body has to come off.

You could try a couple of cans of EGR cleaner down the intake (after the air filter) while running to try to free it up.
Two small cans of Wynns EGR cleaner.
It's a bit tricky as the engine will undoubtedly stall a few times as you spray it but you start to get the hang of how much you can spray and how much to rev (by twisting the lever on the throttle body) without it stalling.

If that fails; throttle body off. This involves taking off two small coolant hoses that are connected to the idle air control valve which is a hoot.
Once off you can carefully remove and open the idle air valve and clean its insides, relubricate and refit.
It has to be refitted EXACTLY how it was. To the millimeter.
Best way is to use permanent marker and basically draw around the fitting where the IACV mounts to the throttle body.

I might do a little video on this as I've got a spare throttle body..

[Gaz mr-s]

Both issues might be caused by an air leak after the maf. Did you lube the maf sensor 'o' ring?  They can get damaged, but when fitting go in with a real 'plop'.

A common problem of fluctuating idle is the Idle air control valve fitted onto the throttle body. Sometimes it's influenced by the car not being used for some time.  See this - https://www.mr2roc.org/forum/index.php?topic=60448.0

However, if you think it is the IACV, before you attempt the job, try bleeding the radiator at least twice. Vent screw is top left corner LOOKING at the car. Undo some of the frunk clips - only press down 2 or 3mm maximum. If pressed 4mm, guaranteed breakage.....but they are susceptible to age-hardening anyway.  Get the coolant properly hot. Also, when the engine is cold, keep an eye on the coolant level....if it's dropping you may have a leak (front left bottom corner of radiator is most common) & the air in the coolant will mess with the idle.

[Dev]

A car pulling fuel like that is either a restrictive intake, restrictive exhaust or a bad fuel pressure regulator.

Based on the history that the engine was rebuilt it could have been due to pre-cat failure. If so then there is a possibility the main cat is clogged from the previous pre cat material. This has been a likely scenario in the past where the owner or the shop doesn't replace the main cat. 

[Ardent]

All of the above.

Big fan of starting at the easy cheap end of possibilities.

What condition is the air filter in?

[M.Dub]

Thank you all for the reply's

The injectors installed are green aftermarkets. I was thinking maybe change theses as the may be over fuelling?

Iv also considered the fuel pressure regulator so Iv ordered a replacement because I thought it might be running too high pressure.

Iv but a stock air filter system back on the car as it had a cheap aftermarket previously. I thought that may have been causing the problems. Iv installed a new panel filter.

The car had the original exhaust system on when I got it and the pre cats looked good and it doesn't use any oil. Iv now put a full stainless steel system on.


I'll try cleaning the idle control valve, is it worth me swapping the injectors or should maybe do everything else first?

I really want to get this car running right but don't want to keep throwing parts at it. With it having both banks rich that would indicate a common problem?

Thanks

[Carolyn]

As you have had the intake in bits, then checking that it's airtight would be a good one.  It's highly unlikely to be injectors as it's rich on both banks (more than one would have to be dodgy), so it's more likely to be something that affects all cylinders.

Pressure regulator failures are not at all common, but it can happen.

[M.Dub]

Yea I thought the same on the injectors but I'm honestly running out of ideas now.

I'll re check the air intake when I try to clean the idle valve.

I did check my short fuel trims with the maf unplugged and one bank stayed negative and the other went +20 so that confused me?

You think is more chance of being restricted air flow some point after the maf? 

Would a vacuum leak give me a lean condition?

Sorry for so many questions I'm just happy to have someone else input.

Thanks

[jonbill]

what voltage are your b1s1 and b2s1 o2 sensors reporting? just wondering how rich it is.

[M.Dub]

Very rich, both are around 0.88v to 0.90v

Thanks for any help

[jonbill]

what value is the maf reading at idle?
what values do you have for inlet air temp and coolant temp?

[M.Dub]

This idle is after a 50min drive sat on the drive afterwards

MAF - 26 g/sec
Intake temp - 37oC
Coolant temp - 91oC

I'd post screen shots but don't know how on my I phone

Thanks

[M.Dub]

Screen shots

[jonbill]

That MAF value sounds very high to me, I'd expect 3-5 at idle.

[Ardent]

Just thinking out load.

Is there any benefit to be had in disconnecting the battery for 20 mins to reset the ecu and monitoring what happens.

Has the maf been cleaned?
O ring sitting correctly?

[M.Dub]

Sorry think I missed a decimals point out on the MAF.

It's a new Denso MAF only been insane a week.

I'm seriously confused.

I'm thinking either fuel pressure is high or maybe a bunch of e bay injectors gone wrong??

[Carolyn]

looks like its running hot.

[M.Dub]

Installed lol sorry for the typo!

Honestly thank you for helping out, it's driving me mad! I bought this car banking on it having a solid engine but Iv only done 200miles and 100 of them was getting it home lol

[M.Dub]

looks like its running hot.

You mean coolant hot?

[M.Dub]

This is her,

Not sure if the previous owner was a member, think he sort advice from here on the rebuild.

[shnazzle]

This is her,

Not sure if the previous owner was a member, think he sort advice from here on the rebuild.

Don't recognise the car. Did see it on Facebook I think. 


When yoy said 26g/s for MAF did you mean 2.6g/s? Because that's the value I often see. 

Air leak after MAF before TB = unmetered air = run lean = add fuel (pos trim). So that's not it. 

Air blockage = not enough air = rich condition = reduce fuel (neg trim). You said you've replaced it all.

Exhaust leak manifold = fresh air making o2 read lean = add fuel. You're not seeing it add fuel. 

Air leak after TB?.. That would start to make sense. It pulls in X air, it reads X air, determined fueling, X air makes it past the throttle body... And then is lost? = overfuel.
Engine rebuild lead to leaky intake manifold?

If history is any kind of teacher.. It's going to be something very simple.

Try disconnecting a few things in sequence.
A) o2 sensors. Just unplug them
B) maf
C) throttle position sensor

[Ardent]

Don't like seeing folks with issues.

But love seeing the team come together to help resolve it.

[Ardent]

Is this an occasion when trying to find a vac leak, a squib of egr cleaner or similar, near, around the throttle or intake manifold would cause the revs to rise. Helping to pin down where the leak is?