SC running poorly

[BMR2L]

My SC was running poorly today. At times it struggled to rev over 4k and felt a bit like the rev limiter was cutting in. Other times it felt close to normal.

Strange thing is the SC light on the dash doesn't come on at all but I thought I could hear the SC humming at the right times when it was pulling more normally.

Shorting the diagnostic terminals doesn't show any fault codes, just the check engine flashing steadily about 2 times a second which I gather is normal.

I changed the gearbox oil yesterday and whilst I was underneath also had a go at loosening off the exhaust heat shield to get ready to put my stainless system on. As part of that I had unplugged the oxygen sensor but I would have expected a fault code if there was a problem with that. I also had the battery out to give me more room to get the filler plug on the top the gearbox off. There's no special procedure for reconnecting the battery is there?

First time I've had any sort of problem with it, its always run very sweetly for me the last 2 years. Any pointers much appreciated.

-AL

[JMR_AW11]

Strange thing is the SC light on the dash doesn't come on at all but I thought I could hear the SC humming at the right times when it was pulling more normally.

The SC light on the dash has nothing to do with the SC status. I know that sounds a bit weird but the SC light is driven by the ECU and it will light the SC light if it thinks there is a lot of air going into the cylinders.

It calculates the amount of air as a function of engine rpm and the AFM reading.


So if your SC light isn't coming on then either:

1/ The light is faulty

2/ Your engine isn't able to pump enough air to make the light come on due to a SC problem (you would feel a big drop in performance as well?)

3/ The AFM is misreporting the true airflow into the engine. This could be due to a faulty AFM or an air leak or a poor electrical connection from the AFM to the ECU. The engine would run badly as well. This is because the ECU would be miscalculating the ignition timing and fuelling because of the misreporting AFM.

Have you checked for air leaks?

[BMR2L]

Makes sense as I took the intercooler off to get at the gearbox filler underneath it. I've just tried taking it off and redoing jubilee clips again several times without any great luck. I even tried swapping with another intercooler in case the rubber joints were cracked but it was exactly the same.

Accelerating moderately hard up to about 3.5k rpm in 1st everything is perfectly normal then it just sort of hits a wall and won't speed up any more. Thats about the time you'd expect the green light to come on and start to hear the hum of the SC (I know they're not exactly related). So sounds plausible that the SC is engaging and the extra pressure is finding a leak somewhere.

Anyway off to bed now, need to get up early enough tomorrow to get the train to work. Once I get some more time I'll investigate the rest of the pipework to see if anything got knocked loose. Is there any way to find a leak when its at idle? Fairy liquid on the joints and watch for bubbles?

[BMR2L]

Got this sorted. Took the IC off, cleaned up all the gunk around the joints and put it back together with the jubilee clips done up good and tight. Now its pulling normally and the little green light is back again .

Thanks JMR_AW11 for suggesting an air leak.

-Alan

[JMR_AW11]

[BMR2L]

Got this sorted. Took the IC off, cleaned up all the gunk around the joints and put it back together with the jubilee clips done up good and tight. Now its pulling normally and the little green light is back again .

Well the problem is back again. I haven't used the car much since I thought it was fixed. Mostly same symptoms - moderate acceleration is mostly ok, accelerate harder it bogs down and doesn't want to go past 3k rpm. SC light (almost) never comes on although whilst test driving it this afternoon it pulled normally in second and the light came on, but that was just the once.

For some reason seems to be worse when cold - as the engine warms up the engine speed at which it will bog down gets a bit higher and it runs normally below that speed.

I just tried disconnected the SC relay to verify the theory about an air leak and it revs much cleaner but way down in power so that seems to suggest something amiss when the SC engages.

Bit stumped on this, I've undone and re-done the hose clamps so many times. I did notice whilst poking around today that someone had hacked around the vacuum pipes on the ABV VSV so I've put that back to standard but it didn't make any difference (car seems to have had a big pulley in a previous life judging by this and the timing pointer mod).

Anything else I could check, particularly that could explain why it gets a bit better as it warms up?

Its due for its bi-annual government inspection (shaken) this week so timing-wise this isn't ideal. I don't really want the garage that does the inspection preparation also spending time (and money) sorting this for me.

Thanks, Alan

[Lauren]

Have a look at the dizzy cap and rotor arm for tracking.

[BMR2L]

Sorted (again)! Seems to have been the hose on the supercharger outlet. All the wiggling of the intercooler from above must have knocked it a bit loose. Pulling like a train now.

Thanks, Alan

[BMR2L]

Aaargggh! Its gone again

I'm beginning to think I have 2 problems.

1. When its cold it just doesn't want to rev past 3k. Gradually gets smoother as it warms up and revs normally enough once its warmed up except...

2. Not pulling like it should and no green light (does come on when you turn the ignition on so the light does work). Its not completely gutless like when the SC relay is disconnected but its not the expected shove in the back either.

I've done another round of hose clamp loosening, re-seating and tightening today and all seems properly lined up and as tight as it will go.

Wondering if maybe the ABV isn't closing fully?? Next thing I'll be trying is to swap that with the one on the spare engine since mine has been mucked about with in the past.

Suggestions on anything else to check or try much appreciated.

Btw, what is the can shaped thing and piping bolted onto the top of the SC for? There's a vacuum line comes from the throttle body and various rubber and metal pipes running into different parts of the SC body. Is it a pump to circulate the SC oil?

[Lauren]

Wondering if maybe the ABV isn't closing fully?? Next thing I'll be trying is to swap that with the one on the spare engine since mine has been mucked about with in the past.

Suggestions on anything else to check or try much appreciated.

Btw, what is the can shaped thing and piping bolted onto the top of the SC for? There's a vacuum line comes from the throttle body and various rubber and metal pipes running into different parts of the SC body. Is it a pump to circulate the SC oil?

Much better option is to blank off the ABV completely. I doubt that's your issue though.

As I said before check dizzy cap for tracking.

[cartledge_uk]

Are the hoses to the ABV unblocked and in good condition (not leaking)?

You can bypass the ABV using the hoses alone to check the charger is working first.

[nosfera2]

Might be worth a look at the knock sensor, if it's gone bad then it will run like a dog.

[MartG]

Btw, what is the can shaped thing and piping bolted onto the top of the SC for? There's a vacuum line comes from the throttle body and various rubber and metal pipes running into different parts of the SC body. Is it a pump to circulate the SC oil?

IIRC the pipes on top of the SC are connected to a VSV operated by the ECU, and are meant to smooth the onset of boost pressure by equalising pressure across the SC ( or something like that )

[BMR2L]

Last night on a hunch I swapped the engine computer ... and ... it started and ran perfectly from cold and the green light is back again

Not the first time its tricked me into thinking its fixed so I'll give it a few days to see if it continues to behave itself.

Thanks everyone for the suggestions. If nothing else I'm a lot more familiar with the contents of my engine bay now.

[BMR2L]

Well, its gradually been getting worse again. Same symptoms, won't rev when cold, gradually revs better as it warms up, but most of the time its down on power. Hardly ever see the green light or get normal acceleration. No diagnostic code when shorting E1 and T.

Since last post I've changed distributor cap, leads and coil from the spare engine without any difference. I've also changed the engine computer back and forth and also no difference so think that was just a coincidence before.

Last weekend I replaced the exhaust gas temperature sensor on the cat which I knew had a dodgy connector and found that actually both wires were broken. It ran a bit better after that, in fact was perfect for one trip, until....

Today it was worse than ever. It just wouldn't pull past 2k, not even after it warmed up. Even sitting in neutral it wouldn't rev past about 3k most of the time.

Blipping the throttle I noticed that the supercharger pulley started turning. Even at idle it would sometimes turn slowly. Same thing with the supercharger relay disconnected. I'm guessing this shouldn't happen, so could this be the source of my problem? If this is normal what else could I look at?

Thanks again.

[cartledge_uk]

How are the earths?

It maybe worth adding a few more as they are very important on the 4agze.


The supercharger does turn on its own with the engine sometimes.

[Paul in the Port]

I guess the SC runs a MAP sensor? Have you checked that at all?? It does sound very much like the ECU isn't being fed the right engine parameters to run properly

[JMR_AW11]

How are the earths?

It maybe worth adding a few more as they are very important on the 4agze.


The supercharger does turn on its own with the engine sometimes.

Sorry to hear this is still causing an issue

It's definitely worth checking the earths

However, please be careful about adding extra earths in the wrong places.

I got into an argument about this before on here but you can make things worse for the ECU if extra earth wires are added to some of the ECU connections. However, the degradation you would get from adding earths in the wrong places is nowhere near the same ballpark as the horrible symptoms that are currently being experienced.

BTW, it might be worth trying a known working AFM unit.

Rest of post edited away to keep the mods happy and avoid confusion.