Rev's keep dropping

[Dave]

I have a 1.4sx S reg, and occasionally when i come to braking after keeping the rev's high for a while, the rev's seem to drop to about 200rpm and the car just chugs away and seems like it is going to stall. This happens when im turning corners aswell so the power steering becomes heavy cos there isnt enough power. Nearly written off my car afew times cos of this, but cant seem to find out the problem. It doesnt happen all the time, but its happening often enough. I have an ecotek vakve on my car, which i thought may have been the problem, but i closed it off for a while and it made no difference. The problem was still there.
Has anyone else had this problem?

 

[Tom]

This seems to be a common prob on 1.4's but no-one has managed to locate the source.

My guess would be that one of the sensors on the inlet manifold is dodgey and the ECU is cutting the fuel for too long. Have you got a haynes manual? It might be worth just sticking your head under the bonnet and removing and replugging all the electical connections around the throttle body just to make sure they are all seated correctly.

Its not the lambda as some people like to suggest, that could not have that sort of effect on a car.. it would just make your MPG worse.

 

[Dave]

Thanks

Cheers Tom. I have got a haynes manual so i will have look into what you said. The car is going in for a service next week, so they may find something, but i will look anyway.

Thanks

 

[christian]

Re: Thanks

i thought these bravos were ment to be reliable ?

 

[SchumaniaC]

Re: Re: Thanks

I think its the Lambda sensor. Have it checked.

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The Bravo...different day, different sh!t

 

[mj]

Have the very same problem on a 2001 Brava 1,6 Selespeed (automatic). Often comes out with turning on the airconditioning and actually first notice was 10k kms after mounting the aftermarket twin exhaust pipe. My understanding is the lambda may be out of service. Possibly, I can try to disconnect the battery for a few hours to reset ECU and see what happens. Finally, I'll turn 45k kms and the car will go to the dealer for regular check so will keep you informed.

 

[Tom]

Re: Re: Rev's keep dropping

It *WON'T* be the lambda!!!

If your revs drop when the aircon comes on, that is normal. Its always possible you have a sticky idle control valve which is why it can't keep the revs up. It will not be the lambda sensor.

 

[mj]

To be honest, the nature of changing the REVs after turning ON the AC has changed siginificantly since the car turned 15k on odometer. It has 40 something now and it used to drop to 1,000 from 900 but now it goes up from 900 to 1,800 or even 2,500. Also, this sometimes happens if severe breaking is applied and then even if the AC is off, the revs keep oscilating 1,500 through 3,000. Very annoying.

 

[Tom]

Re: Re: Rev's keep dropping

Sticky idle control valve and possibly a slightly gummed up throttle.

Time to take it apart and clean it.

 

[mj]

Re: Re: Re: Rev's keep dropping

Thanks a million Tom, is there any place on the web explaining how to do the 'cleaning' job on my 1,6 Brava? That would help as I'm quite technically skilled at least for motorcycle engines etc.

 

[Tom]

Re: Re: Re: Re: Rev's keep dropping

Mk1 or Mk2 (1.6 or 100?)

 

[mj]

Re: Re: Re: Re: Re: Rev's keep dropping

I drive a 2001 Brava 100 16v (1,6) Selecta (automatic) if it helps.

 

[Tom]

Re: Re: Re: Re: Re: Re: Rev's keep dropping

Its a Mk2. If it was a Mk1 I'd be able to tell you what to do but not on a Mk2, sorry.

With any luck I'll get to see a Mk2 this weekend.

 

[mj]

Re: Re: Re: Re: Re: Re: Re: Rev's keep dropping

Tom, is this the problem we are talking about? (taken of http://www.bravo-guide.co.uk/)

Idle Air Control Valve

If you tap the idle air control valve (electro valve) and the revs drop back that the faulty piece is the smaller of the 2 little cylinders (2 pin electical connector). Fiat don't sell that part on it's own so you have to buy complete new unit at £140.

Or you can try taking apart the old one and cleaning all the metal pins, especially near the spring and re-trying it.
(We will try and get a bit more detail on this including a pic or two to explain this)

 

[Tom]

Re: Re: Re: Re: Re: Re: Re: Re: Rev's keep dropping

Thats the bit, the prob is that its different on every engine type and they changed the design from Mk1 to Mk2 1.6 as well. On the Mk1 its a 10min job to clean it but no-one has tried on a Mk2.

 

[mj]

Re: Re: Re: Re: Re: Re: Re: Re: Re: Rev's keep dropping

Tom please check the MK2 over the weekend as mentioned and possibly let me know. Thaks again, very helpful. Do you think I should try to cut off the battery overnight? would that be of any help?

 

[Tom]

Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Rev's keep dropping

I hope a Mk2 turns up, if one does I'll take some piccies.

Disconnecting the battery won't help as its a mechanical issue. The valve gets bunged up with gunk from the engine breather pipe.

 

[mj]

Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Rev's keep dropping

Tom, I did quite a lot of driving in Eastern Europe (over 900 kms in two days) and the engine runs with absolutely no problem. What a hell does this mean? Did the ECU return back to normal functioning or??? Your input please.

 

[Tom]

Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Rev's keep dropping

It really does sound like the idle valve. They get bunged up with sticky oil deposits and sometimes jam open or closed and then the next time it runs fine.

My car did it once, then went fine for a week and did it again. Its just one of those things

 

[mj]

Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Rev's keep dropping

Hi Tom, as mentioned, I did over 700 kms with no problem and yesterday, the revs got jumping between 1,500 and 2,500 on idle. I decided to reset the ECU and cut off the battery for 3 hours. Consequently, I made a 40 min drive. Today, the revs started to jump from 1,000 to 2,000 again and then kept on 1,300 as idle. At a moment i noticed a red light blinking at the left bottom side of the dashboard, under the fuel gauge. This drives me mad and I wonder if there is an advice or just take a car to a dealer. Please comment.