All,

I have a Weekend 1.6 Auto and over the last few months I have noticed intermittent power loss after about 45 minutes of driving, It feels as though it's holding back on acceleration then suddenly it will surge back to full power. As I only travel these distances maybe once a month I haven't bothered too much but I'm going to be doing 300 miles in a weekend soon and I'm worried that it will play up.

Now I had problems in the past with high tick over (2000rpm) on wet days after about 10 minutes of driving, this has not happened for a few months. Recently the car has had lumpy tick over when hot sometimes cutting out, this sometimes goes hand in hand with the power loss but not always.

I've had a diagnostic check which showed no faults, I've removed and cleaned the throttle body to de-carbon the idle valve which looked ok and felt free.

No oil in water / water in oil etc all checked.

I did have a new exhaust fitted a few months back and it's never sounded right, maybe something in the exhaust, well I plan to fit a new Walker this weekend and whilst I'm at it service the car, (oil plugs filters etc), I have had a fuel filter in the past but never managed to find it to replace on the Weekend model.

When ok power feels normal, sometimes when it's "holding back" and I accelerate hard it sounds like a bang from the exhaust and then it gives good power until next time i ease off the throttle.

Also following traffic at 2000rpm it seems to surge slightly.

Anyway any ideas why the power loss etc and why no faults shown on diagnostic?

Thanks

Jim

check resistance of all injectors, there are plenty of guides in the bravo/a section if you do a search.

also try replacing the lambda sensor.

Hi Jug, thanks for the reply.

OK I just checked the injectors resistance by unplugging the multiplug that feeds the injectors and going from centre pin of the flat 5 pin plug to each injector pin in the plug, these all measure 16.6 ohms each, or if I put the meter across any 2 of the injector pins (2 in series) I get 33.2 ohms. So going by the info in the Bravo/a forum that states they should be above 13 ohms these are OK. test were carried out with the engine warm but not hot.

As for the lambda sensor, when it was on the diagnostics it showed 2 lambda sensors, and upper and a lower. I guess the upper is the one in the top of the exhaust manifold and the lower must be on or near the CAT? dark here so I couldn't get under and have a look, any ideas and would I need to replace both.

Also I thought Lambda's played up once upto temperature which is usually within 5 minutes of running? please correct me if i assume wrong.

For information it's current spark plugs have bee in for around 12k and will be changed this weekend.

Car has done 43k

Thanks

Jim

OK Update time.
Serviced the car last weekend and fitted a new exhaust, Purchased new Lamdba (NGK which I hope will work) but couldn't fit. Took the car for a run this weekend and it's getting worse.

So today I ran over to my local auto electrician making sure the car was playing up when I got to him, we plugged in the diagnostics and the error was a Fuel Mixture Problem.

We looked the the Upper and Lower Lambda sensor mV readings whilst the engine was running and the upper was in the 1100mv (Lean) and the lower in the 30mv (Rich) range.

We stopped the car for about 5 minutes and restarted the engine and retested, the car now running smooth had upper and lower Lamda readings in the 600 mV range. So we diagnosed that one of the sensors was faulty, we ran the car on tickover for 10 minutes watching both live readings from the Lambda's when suddenly the upper became erratic going from 60 to 600 mV very quickly.

This was good enough for me to decide it's the upper sensor at fault.

On the way home the car started to hesitate and become erratic with uneven idle again so i pulled over and unplugged the upper lambda, as soon as I did this the engine idle was fine so I drove it for about 3 miles with the sensor unplugged and the car felt fine.

I've booked the car in to get the sensor changed as we went to do it when we serviced the car but cannot get it to budge, using a lamda removing tool and a jubilee clip to stop it spreading a large nuckle bar and even a pneumatic knocker gun. I'm slightly peeved because this will cost me money I don't like to spend but I really don't have the tools if it goes wrong and I wring the sensor off or pull the threads out of the manifold.

Anyone else had a problem getting the upper Lambda out?

Thanks

Jim

well done identifying the problem. a lazy lambda is often the cause of these types of problems. for future reference it will always be the first lambda in the exhaust system because the second downstream lambda is only there to check the operation of the cat, it does not affect fueling.

heat and rust can almost weld the lambda in place. it can help if you try to remove it when it is very hot because the exhaust expands more than the lambda due to the different types of metal.