Heavy stuttering and loss of power under heavy throttle.

[the_traveller]

The car hasn't been running right for a week or so, I've got a new lambda sensor that I'm fitting this weekend that I know is shot, and when it start cold its like its running on two cylinders for the first minute. knowing this I still put my foot down fairly hard on the bypass then I lost all power at 60mph, odd whistling noise then a huge boom and a big cloud of black smoke out of the exhaust. ever since it runs fine, will easily do 90, but I can't accelerate hard without loosing all power and having the engine stutter and jerk, I'ts a bit like the turbo is boosting too much and its having fuel starvation.

[aardvarkash10]

which model, which engine, which fuel/ignition system?

[Laird Scooby]

Firstly, what Ash said ^^^^^

Secondly, it sounds as if you have a compound problem there, in other words not just one thing causing all of the problems.
My guess, purely on the information given above is there was a blockage in the exhaust and it's over-fueling because of the dead Lambda, compounded with a blocked fuel filter.
Also a probability the air filter needs replacing.

As stated - that is a guess and can be no more until you let us know the info Ash asked for.

[the_traveller]

Sorry thought i put that.... It’s a B230et pretty sure it’s the bosch motronic

[Laird Scooby]

First thing to do is change the Lambda sensor as you know it's dodgy. That alone could cause the over-fueling.

Also invest a few quid in a can of this stuff or similar :

https://www.ebay.co.uk/itm/CarPlan-C...wAAOSwyYFaAH-P

Disconnect the MAF on the engine side (usually a large convoluted rubber hose) and spray into the MAF, reconnect ensuring the hose is fitted correctly all the way round and the Jubilee clip is tight. While you're about it, also check all other hoses on the inlet side for security, condition etc.
Now disconnect the air filter side of the MAF, start the engine and spray the carb cleaner into the end of the MAF - the engine should splutter a bit and you'll get a lot of foul smelling smoke out the exhaust.

Reconnect the air cleaner to MAF hose as above. Now take it for a test drive - with luck all should be well.

If it's still holding back under hard acceleration or climbing steep hills in high gear, the chances are the fuel filter needs renewing.

Nearly forgot - at some convenient point during the above, check the air filter element - if it's dirty, renew it.

If all is good on the test drive, when you get back check the inside of your tail pipe for remains of burnt potato - it sounds almost as if someone has played the old practical joke of a spud up your tailpipe.

However, if it's not playing the game, do a hot compression test - fuel pumps disabled (remove the fuses, start the engine and let it die), all plugs out, throttle held wide open during cranking. They should all be in the order of about 140-160psi give or take. Looking more for consistency across all 4 rather than a high figure, it's turbo'd so possibly a little lower than i've quoted.
If the compression test is ok, check all the spark plug gaps, should be 0.65-0.7mm and all should be in good condition. Also check all your HT leads, the dizzy cap (don't forget the carbon brush inside) and the rotor arm.

Somewhere along those lines you should either find something amiss or fix the fault.

PS - don't do it all at once, you won't know which item cured the fault if you do!

[aardvarkash10]

Dave has covered a lot of ground, I'd only add that a fuel pressure check would be useful if you have access to the right gear and will save some guesswork.

The Big Bang you experienced is the result of unburnt fuel getting to a hot turbocharger. Eventually it ignites/explodes. Sounds like it cleared a slight exhaust blockage too - bonus!

[Laird Scooby]

I was thinking more that the cat was partially blocked Ash and was causing the misfire - when he lost all power and heard the whistling noise i suspect what happened was the turbo was still spinning, pumping air and unburnt fuel into the cat, the engine once again "caught" and a hot/still burning exhaust charge went through the turbo to the cat and ignited the unburnt fuel in the cat, clearing the blockage, creating the cloud of black smoke and the "KA-BOOM"!

Our theories are both pretty close on this, the actual place of the explosion is probably academic, i did consider it might be our old friend the crank position sensor but so far all the evidence is pointing to a blocked cat causing a misfire and eventually the explosion that cleared the blockage.

I wonder if the OP crawled underneath and tapped the cat if it would rattle.....

[the_traveller]

I didn’t get try anything yesterday as she wouldn’t start.... if i kept cranking the starter the engine would run, then she started but ran like hell when i actually tried driving, the exhaust is in a bad state anyway and I’m sure there’s an air leak, I’m going to change the lambda now the snows stopped and look into the other stuff, thanks for all the suggestions also ordered. New fuel filter because the engines getting fuel but sometimes acts like a fuel issue

[Casheye]

I had a problem like this which turned out to be a combination of a misfire from a broken plug (which ended up pitting the head and possibly resulted in the headgasket failure) and where the King Lead was coming into contact with the engine block and shorting out. As soon as i'd tied the lead out of the way, things instantly improved.

Check your HT leads for good flexibility. It takes a few seconds and won't cost money :P

[hichamaziz]

thank you for post