Powerloss, Spluttering And Misfires

[Aaamrit145QV 0]

Hello all.

 

As also posted on the 145.co.uk forum and am hoping for a little more info before giving in and taking to garage.

 

My phase 2 qv has suddenly started to play up with sudden power loss and jerking from 3k revs upwards underload. im getting the fuel starvation symptoms (ie. the bucking, jerking and loosing power) but yesterday it drove ok for around 15mins without any issues whilst getting up to temperature then suddenly started playing up when putting it under load. <-- Temp Sensor Faulty?

 

Suspected MAF / Lambda straight off as the car was running slighly lean during last Mot in June.

 

So plugged in to Multiecuscan - no errors logged

Ran the graphs on Lambda/MAF etc. shows occasional blips/voltage drops on idle and replaced both with genuine new Bosch ones

 

Check plugs etc. All good. Plugs were s nice golden brown on all 8, no soot & dry. Only done 20k.

Crank sensor is genuine and a month old.

Temp sensor is 2 months old.

Check BBOB (Fuses & Relays) - All good and where professionally rewired and sealed with heat shrink tubing last year - Never had any issues

No water or oil in wells.

Air filter 6 months old.

 

Reset ECU, took for a blast - all great, gave it a good blatt through full rev range and all the gears.

ICV Is a little twitchy and have cleaned throttle body + reset.

 

Done about 50/60 miles since and have noticed the slight hesitation, powerloss around the 3-4k rev range, almost like its starving of fuel and then just bucks and clears.

 

Cat is not rattlling or giving of any funny smells, havent checked exhaust for blockages yet but car drives fine except when on an incline or turning.

 

Next suspected coils so put another set in which I also know where working.

 

Again, same as before, revs fine through full rev range apart from the very slight twitch at idle, ran diagnostics again and no errors logged.

 

Suspecting either a wiring issue or an intermittent fuel pump failure or even both.

 

Found the pump but am asking whether it has a separate earth somewhere.

 

I put some Tesco regular unleaded in yesterday as I forgot to fill up by at my local Shell, Tesco fuel usually makes my car run really sluggish but never had anything like this.

 

Will check the exhaust inlet as this was taken off when I had my sub frame fitted in January. Cant hear any blowing at the moment but will check anyway.

 

Exhaust currently has a minor leak after the CAT which has been like that since June and has never really caused any problems but will be fixed in the coming days.

 

Questions:

 

Is there a separate earth for the fuel pump?

Am I missing something really obvious?

 

Any help appreciated.

 

Oh and if anyone needs a diag doing around Shropshire, give me a message as laptop is free most weekends.

[Smaky 73]

Your welcome to pop down and I'll have a look, it sounds like a MAF problem but it's the kind of thing you need to see first hand in this case.

[Aaamrit145QV 0]

Thanks smaky, where you based?

 

Im going disconnect everything today, clean & double check everything again.

 

MAF Is literally brand new as is the Lambda - both genuine bosch parts

 

Will let you know how it goes.

[Aaamrit145QV 0]

Quick update on this.

Rechecked and cleaned all electrical connetions, took for 5 mile drive and srill sputtered and jerked around 3000 revs.

 

I was running on reserve (tesco unleaded) - put £15 of Texaco unleaded and car seems to run fine again?!

 

Took for another 5 mile drive, no issues... so far anyway!

 

As said already, Tesco unleaded always makes my car run lumpy but never this bad!

 

Surely it cant be the fuel?

[Smaky 73]

It possibly coould be, and I'm near Oxford, an hour from Stafford.