Loss of power

[DaveB]

Don't know if anyone can shed any light on this.
When our FL is up to temperature it suddenly loses power. Revs won't go above about 2500k, and gradually drop if you try to hold it there. Sit and let it cool for a while and it then goes fine again.
It almost feels like it's being starved of oxygen or fuel.
The only error codes being thrown up are lamda sensor related, but all 3 were new this year when we replaced the manifold with a catless one.
I put it into the garage before going on holiday, and they've come up blank as well, other than seeing that it's running a bit rich.
Could one of the new lamda sensors just be dodgy?

[Ardent]

We always like to start at the cheap easy basic end of fault diagnosis.

What's the condition of the air filter?
What's your fuel consumption like?
Any recent changes?

We will leave things like a blocked cat for later.

Do you have a elm/obd type dongle and an app? you could see if the sensors are working. Is the voltage flat or dancing. What is the voltage. Looking for +/ - 0.5v

[Call the midlife!]

Have you checked the condition of the crank position sensor earth? At the bottom of the timing chain cover area, it's prone to corrosion and can lead to bad signals to the ECU without necessarily throwing a code.

[Topdownman]

Sounds like something that happened to @shnazzle a few years ago on the Holy Island run if my memory serves me right?

[shnazzle]

Sounds like something that happened to @shnazzle a few years ago on the Holy Island run if my memory serves me right?

Bit different. That was because I had fecked about wiht my piggyback so much that it wouldn't run on 95 fuel LOL

[DaveB]

We always like to start at the cheap easy basic end of fault diagnosis.

What's the condition of the air filter?
What's your fuel consumption like?
Any recent changes?

We will leave things like a blocked cat for later.

Do you have a elm/obd type dongle and an app? you could see if the sendirs sre doing anything.

Ta

All the normal stuff like air filters seem good.
Fuel consumption is maybe a bit higher than normal, though I wouldn't swear on that.
Recent changes, a new non-cat manifold, & new middle bit with cat, plus 3 new lamdas, & it's run fine/lovely since. Although it has thrown a sensor error occasionally.

[DaveB]

Have you checked the condition of the crank position sensor earth? At the bottom of the timing chain cover area, it's prone to corrosion and can lead to bad signals to the ECU without necessarily throwing a code.

The garage has suggested replacing the crank sensor to see if that helps. Not that it's showing an error, just as something to try. No idea about the condition of the earth, but I'll mention that to them.

[Gibla]

The garage has suggested replacing the crank sensor to see if that helps. Not that it's showing an error, just as something to try. No idea about the condition of the earth, but I'll mention that to them.

If you need a crank sensor I bought one in error a year/two ago .....would let it go cheaply

[Topdownman]

Bit different. That was because I had fecked about wiht my piggyback so much that it wouldn't run on 95 fuel LOL

Ah, I thought it was something to do with your iac, ignore me!

[Carolyn]

Have you cleaned the MAF lately? 

[Ardent]

The garage has suggested replacing the crank sensor to see if that helps. Not that it's showing an error, just as something to try. No idea about the condition of the earth, but I'll mention that to them.

Typical garage. Lets spend your money just to see if it helps. So no diagnosis then.
As suggested. Check it is
Secure.
Even if it is. As suggested undo the connection. Bit of a rub with some emery paper or similar. Just to ensure a good clean connection.

[shnazzle]

Ah, I thought it was something to do with your iac, ignore me!

Oh you mean when we went in Helen's old pile of shite?

That had all sorts of reasons for its issues. Some to do with the IAC.
Unlikely what this user is experiencing.

The errors codes on the o2 sensors, what are they?
If they're heater circuit then not so much a problem for now, but if they're for the sensors themselves then it might cause this behaviour. 

[Ardent]

Have a good feel, look listen for any vacuum leaks.

[DaveB]

Excellent, thanks all, a few things to be going on with

[Ardent]

Let us know what you find.

[Gaz mr-s]

Like Carolyn, my thinking's maf.  Do you you know about cleaning it?

The crank sensor earth is an easy thing to check. Happened to me once, - it just needed the earth bolt tightened. But it usually affects higher up the range, & has no bearing on the O2 sensor codes. The maf will though.

[Iain]

Got to go with the obvious for me and look at the work thats recently been done. If its throwing o2 sensor codes up thats where id be starting.

The o2 sensors - are they a proper brand like denso or bosch? If they are a cheap or non branded one that could well be the problem. They can be easy to damage if installed without care.

[DaveB]

Thanks again. Nope, never looked at the MAF, or at least not yet. And yes, the sensors are all Denso, but it could be one is dodgy I suppose.

[shnazzle]

MAF can cause the o2 sensor codes as well BTW. 
So, start with MAF. 

[Carolyn]

You can start by cleaning the MAF with carb cleaner.  Take the O ring off first as the carb cleaner eats O rings.  A thorough spray soaking, a couple of times should suffice. That may, or may not, do the trick.  Mafs, themselves, don't throw codes (faulty Maf codes, that is).

If there's no result, the only way to know for sure is replace it with a known good one.  If the car has never had a new one, it's probably time.

[Petrus]

If the car has never had a new one, it's probably time.

Good one that.
If it has neven been replaced, or you don´t know it has so must assume it has not, the 17 to 22 year old sensitive yet crucial sensor is best replaced.
Just ordered one for stupid cheap. Hope it is not too stupid cheap but I can always put the current one back in which I will keep as a spare anyway.
Will be a nice proof of the new pudding between a functioning, problably 20 y.o. and half a dozen times cleaned one and a fresh example.

[DaveB]

Well, this took some time, but fingers crossed it now seems to be OK.
Had the earth on the crank sensor redone, and cleaned the Maf. That got it running again, but very thirstily. So changed the Maf for a new Denso one and all seems good now for a couple of weeks.
Probably jinxed it now.