Loss of/lack of power when pulling off

[Artair]

Hi,

A few days ago after pulling away from a set of lights, I suddenly lost power few a second or two - almost as if I had taken my foot off the accelerator. It's happened a few more times since, and its usually when pulling away or trying to go up hill. It seems to be more prominent when the engine is warm.

It feels like fuel starvation, like I'm running out of petrol. I've read various posts that suggest a range of different problems but all seem to point to fuel starvation as the likely cause. I am confident in tackling any work on my car providing I have the tools, but diagnosing problems isn't my strong suit. I have an OBD2 reader and some OBD2 software (on a trial) on my laptop - I successfully connected it to and got readings from the car, but no reported faults.

Does anyone have any ideas? I'm at a loss on where to start. I don't want to go replacing everything I've read it could be as I don't want to be wasting money. It's a 1.6l petrol '08 model.

It may or may not be related, but I have been having a cold starting issue for a few weeks where the car would start and then immediately stall, or would turn over for a while before starting. In both cases, touching the accelerator a little would help it start and I would not have any further problems whilst driving.

Thanks for any help you can give me.

[triumph2.5man]

Hello there. Yes your problem could be fuel starvtion or a host of problems. I can however offer one suggestion but this is only a possibility.
My daughter suffered this problem on and off for years. I described it as "holding back briefly" but never stalling. It would come and go and resisted all attempts at solving.
It was found to be the brake light switch would you believe. It sounds incredulous and I was cynical but the problem was permanently cured. I jest not!
Think about it. You applied the brakes at traffic lights. Then when you pulled away, your car held back briefly.
The brake switch is a fiendishly clever device consisting of two sets of contacts in one small unit. You apply the brakes, the switch releases and the brake lights come on as one set of contacts close. At the same time, another set of contacts opens and this alerts the UCH to the fact your are stopping. However the contacts sometimes play up and while you are trying to pull away, the UCH thinks you still have the brakes on! It does not like this!
I removed my switch ( It's on the left side - look under and behind the glove box or remove the box which is quite easy), dismantled it and cleaned the contacts. I could not see owt wrong but the problem was solved. I could not believe it! The actuating rod is another fiendish device which is on a ratchet. Pull it out to its fullest extent and when you refit the switch, the rod will find its own position to take account of the small gap between the rod tip and the switch bracket.
The switch is easy to take apart and springs do not fly everywhere (one's biggest dread....). You could even use some switch cleaner although I did not bother.
Other owners have had this problem and it is thanks to Vroom, Vroom, Clonk Clonk for the resolution. (Yes, that's his Forum name!)
Most cars use a similar system to tell the ECU about braking (ECU then amends the amount of fuel injected for a smoother transition.) My everyday car for example (Mondeo TDCI 130 - 161,000 miles up!) uses two separate switches for this process.
This could be the cause of your starting problems. When you stopped you applied the brake. In attempting to start up the UCH thinks the brakes are still on, or neither on nor off - "indeterminate". The system is not programmed to handle this situation and stumbles for briefly!
Regarding OBD reader, you are finding, as I did, that most of the stuff on sale is useless. The one I bought could not contact the injection computer and could not even see the MIL was on when clearly it was. ELM 327 interface on a laptop was also disappointingly useless. You need to shell out a lot of money to get a decent machine which can access the many computes in our Meganes. How much? I recently borrowed a friends Snap on machine. It worked but all it could do was read and delete codes - nothing else. This was a cheap machine at a special price - around a grand!! It did not even give P codes!
Try the above work before you do anything else. Take an hour max.
Mike

[Artair]

Hi, thanks for this suggestion. I've taken the switch off and given it a clean (it looked pretty clean already) but its not made any improvement.

I've also now noticed a very loud gurgling noise coming from the petrol tank (whilst sat in the car, though it can also be heard from outside) which I can only describe as the sound you get when trying to suck up that last bit of juice from the bottom of a glass with a straw; almost like the pump is sucking up air. I've lifted the rear seat and removed the access plate and it is definitely coming from the tank.

I know there is bound to be some noise coming from the tank as the pump sucks up the fuel, but I've never noticed it before and it only seems to start when I've been driving for 5 minutes or so, which is when my problems begin. For those first few minutes, the fuel pump is fairly quiet.

Could it be that the fuel pump/regulator/filter (I think its all one assembly, right?) is on its way out?

Thanks again.

[rfman]

I had that problem when I bought my Megane and finally tracked it to an incorrectly set-up timing belt. Previously the de-phaser had been replaced by a cowboy who hadn't set it up correctly and damaged the inlet cam in the process. The car drives fine now that everything is set correctly.

[gareyt]

Hi im not too familiar with the petrol models but I would suggest that you go with your gut feeling.

It seems entirely plausible that the fuel pump at your fuel tank is faulty some how. I think you should take it out and inspect it.

I have a diesel and when I first bought it, it seemed to lack power a bit like you described but it turned out to be the boost pressure sensor thing. I got a 2nd hand one, fitted it and hey presto , power restored. So simple.