Revving and Squealing?

[sparky11]

To follow on from my earlier thread about new coils, during the shenanigans I reset the ECU - since plugging it back in I seem to have acquired the following problems (i'm back on the old coil now BTW, which - previously - ran with no problems)

Both these problems do not appear when cold but happen withhin about 3 miles or so and then carry on when the engine is warm.

Revving - Whenever the clutch is depressed, she will keep 'revving' herself up to about 2000RPM. Usually about 4/5 times but i've counted as many as 10. After this, once the idle settles she will tickover fine. Until you move off, come to a stop and the whole thing starts again. I've also noticed that sometimes I can come off the throttle whilst driving and she'll keep driving along at 2000rpm then slow down gradually - almost like the above but whilst moving, if that makes any sense!
I've checked the throttle cable for snagging (none) and the stepper was cleaned about 6 months ago - this was all fine before unplugging the ECU.

Squealing - We seem to have developed an annoying squeal, its almost like a belt squeal and the pitch will rise and fall with the engine note - on sticking my head in the engine yeaterday, though, it appears to be coming from the resovoir for the PAS and nowhere near the belts at all! Tapping the bottle seems to make change the sound. I have no ideas what could be causing this. I've checked the fluid and the pipe unions and both are fine. Am I going mad?

I think the squealing may be a coincidence, but certainly I think resetting the ECU must have broken something, anyone have any ideas?


As usual, all help is mucho appreciated - the squealing is detracting from the burble!


Mark

[jonathant]

Hi Mark,

When my Chim was doing a similar revving thing (also with random cutting out of engine) it turned out the ECU contacts were corroded/dirty. The garage gave them a good clean and it's been fine since (touch wood!).

[sparky11]

Yeah, i'd thought of that - they 'look' pretty good though.

Any idea what they cleaned them with?

[jonathant]

sadly not a clue - I can ask.....

[petros]

might not be the same problem but mine used to rev like that, Pulled off the vacuum advance pipe, blew through it, cleaned the ends and bingo, problem solved. Hope that's all your problem is

[tahiti450]

sparky11 said:

1)... Revving - Whenever the clutch is depressed, she will keep 'revving' herself up to about 2000RPM. Usually about 4/5 times but i've counted as many as 10. After this, once the idle settles she will tickover fine. Until you move off, come to a stop and the whole thing starts again. I've also noticed that sometimes I can come off the throttle whilst driving and she'll keep driving along at 2000rpm then slow down gradually - almost like the above but whilst moving, if that makes any sense! I've checked the throttle cable for snagging (none) and the stepper was cleaned about 6 months ago - this was all fine before unplugging the ECU. 2)....Squealing - We seem to have developed an annoying squeal, its almost like a belt squeal and the pitch will rise and fall with the engine note - on sticking my head in the engine yeaterday, though, it appears to be coming from the resovoir for the PAS and nowhere near the belts at all! Tapping the bottle seems to make change the sound. I have no ideas what could be causing this. I've checked the fluid and the pipe unions and both are fine. Am I going mad? Mark

Just thinking out-loud...

1), sounds like a stepper motor problem, either a problem with the stepper motor (probably not as it is obviously working other wise it wouldnt settle at all), or more likely the control circuitry, ... ECU itself, Speedo signal to ECU (so that the ECU knows whether the car is moving or stationery), Engine (water)temperature sender. Is the speedo working correctly? it wouldnt hurt to tale the stepper motor ouyt and clean it anyway and check the gasket is intact and not allowing any air bleed.

2).... HEY JUST THOUGHT OF SOMETHING>>>> is the bolt that secures the PAS reservoir to the plenum chamber loose???
I'm not absolutely sure, but I think the threaded bore might communicate with the plenum chamber, if it were loose it would cause a fast idle and possibly a shreaking next to the PAS reservoir which would change in pitch with throttle postion and when moving (tapping) the PAS reservoir as air is being sucked past the bolt !!!!

I found mine was loose recently, though i dont think it was causing a leak but clearly it can work loose.

Go check it out!

[tahiti450]

Mark,
tried to e-mail you also but had it returned as "user-unknown" . Just to let you know.
Cheers
Alan

[sparky11]

Tahiti - Sorry about the email, I hadn't updated it. If you try now it should be OK.

That is a VERY interesting note about the resovoir bolt. I stopped today on the way to work (it was screaming!) and had a good listen to the PAS resovoir - even to the point of taking the cap off. It doesn't seem to be coming from there but from the plenum itself! Maybe you're right! I can't think of anything else around that area that would make that sort of sound.
I've also noticed that as soon as you shut the engine down - it stops. I would have thought if it was something 'pressure' related it would carry on leaking as the pressure released?

What you're saying would make sense as the vacuum in the plenum would stop as soon as the engine does. Does that sound right?

As for the stepper, it was working fine before the ECU reset, but the problem above would seem to be connected. Maybe its just a coincidence that I reset the ECU and that actually has nothing to do with it?

I'll have a look at the plenum later and see what transpires.

Cheers for that!!

Mark

[parrot of doom]

Sparky mine is making an air-gap related noise at the moment while I wait for a new stepper motor chamber to arrive. Mine sounds like an empty milk bottle though - I'm guessing yours is more like wind howling through trees?

Try checking all the pipes around the plenum, make sure they're all in good condition and with good seals. Also check the seal around the plenum, and that the hex bolts are all nice and tight. If you need to get the top of the plenum off, you'll have to bend the drilled piece of decorative metal at the base of the windscreen quite visciously, but don't worry it won't break

>> Edited by parrot of doom on Wednesday 17th August 11:02

[sparky11]

Cheers POD,

I've been spending this morning trawling through the net and have found that a lot of guys on a Cobra forum run Rover V8's and that a few of them have had 'whistling' thats been due to crankcase breathers?

If one of these is blocked is that likely to inrease pressure in the inlet system somewhere?

Anyone got a copy of the Bible at hand to see how these work? I really should start bringing mine to work!

Needless to say, once i'm home i'll check the resovoir connection to the plenum and all these other bits and pieces.

Cheers

Mark

[tahiti450]

Just checked re the reservoir bolt, yes indeed it is basically a redundant manifold tapping and as such will allow air too bleed into the manifold if it is loose. Also there are 2 further ports on that side ahead of the reservoir at the bottom of the plemun chamber, one feeding the brake servo and the other... well haven't a clue really, but either feeds a vacuum reservoir for vacuum controls or possibly a coolant pipe??? Anyway if these are both vacuum tappings then check these for sealing and the pipes for splits (possibly underneath where you cant see it). i cant see anything else there that would cause a squealing sound. Worn rockers / shafts can cause a rhythmic squeaking from the top end but thats rather different.
When the engine is turned off the vacuum in the manifold will decay almost instantly (the throttle / stepper motor being open at idle settings) so you would expect the sound to stop as virtually soon as the engine stops turning.
Good luck!

[tahiti450]

One other thing, i assume that the PAS fluid is up to level. The PAS will make a whining sound if there is air in the fluid, but it will be obvious that it changes with turning the wheels. Either low fluid or a pipe leak on the return side will aerate the fluid and cause this. PAS leaks are common, on Chims and in general. Had a friend recently with this problem - not on a TVR - and was told they needed a new steering rack...(£500) , had a look and all it was was a slightly loose banjo bolt on the suction side of the pump which was alowing a weep of fluid and also allowing air into the fluid. Nipped that up and problem solved. Aerated fluid looks opaque (or even frothy) in the reservoir due to tiny air bubbles.

>> Edited by tahiti450 on Wednesday 17th August 13:12

[sparky11]

Cheers for that - hopefully that may be the problem!

Re: the PAS fluid - its topped up and doesn't appear to be leaking anywhere (at least no more than usual...) it does look a little 'opaque' but its always looked like that in the year i've had the car!

I don't very often have to top it up, I suppose a little squirt every 2/3 months, which I figure comes out of the 'standard' leak I have from the unions under the pas pump!

It sounds more likely the bolt in the plenum - i'm tempted to skive off work and have a look now, actually....



Mark

[Ribol]

If you are saying your problems only started after resetting the ECU I presume you mean you unplugged it? The first thing I would check is the ECU plug, check all the pins are at exactly the same height and one has not got pushed back in to the plug and not making contact properly.

[sparky11]

Hokay.....

I couldn't restrain myself any longer and popped out to have a look.

The bolt into the plenum WAS a little loose and it looked like the bracket for the resovoir wasn't exactly 'flush' - not a gap, mind you, but I guess it doesn't take much.

I managed to do it up probably a 1/2 turn or so, so now its 'tight'. I didn't want to go too overboard as the plenum looks to be a soft casting and I don't want to strip the threads on that!

Going home tonight will tell......


Mark

[chimalsu]

dont know iff its the same thing but i had a reving problem on my 944 every time it came to rest ie at a junctuon it would rev and drop below tickover then rev again as though it was searching sometimes it would cut out but it would always start again turned out to be the air mass meter sticking

[glynlucas]

There is a tendancy on mine to not settle to idle once the ECU is reset. However, I find that this sorts itself out once the ECU default mappings have updated themselves. This only happens once the engine reaches at least 90 degrees apparantly! The other possible cause for this is the ECU coolant temperature sensor located on top of the engine near the Plenum. This is a £14.00 part from a motorfactor (Lucas part SNB802) But make sure they supply the right one...as there are two varients under the unipart ref. It's the one with the smaller thread!

[sparky11]

OK - Panic over!

Very odd this, basically it was about a litre and a half down on water.

I just noticed the other day that while idling in traffic that the temp was slightly higher than normal (she usually sticks solid around 90, regardless of where you are), checked the coolant level and I ended up having to put about a 1.5L in.

Now, its absolutely fine. Seems to have cured the tickover problem as well.

Would an airlock have caused the whistling from the heater matrix? Thats the only coolant pipe I can see around that area of the engine.

The only worry is where the coolant has gone - admittedly I havent checked it for quite a while (I know, slapped wrists ) but, as the temp guage never moved I assumed everything was OK. Theres a lesson there I feel!

I'm going to bleed the whole system through the next free weekend I get, and also keep a VERY close eye on the water levels, but since I topped it up (2 days ago) it hasnt moved.

Thanks for all the ideas guys - I was kinda tearing my hair out there for a while!


Cheers

Mark