Hi all the title says it all.
I’ve been battling for a while with this one. It makes no difference cold or hot, sometimes it starts on the turn of the key, more often there is extensive cranking then a cough and a start.
The first thing I found wrong was that one of my two fuel pumps was dead - I changed both, disconnecting the fuel lines from the tank was a ***** fixing that made little difference.
I have fitted all new plugs, checked the compression, changed the fuel filter, swapped the canister purge valve.

I’m trying to decide whether to buy a smoke tester and look for air leaks, but I’m clutching at straws a little.

any ideas would be greatly appreciated

 

Have you checked for any codes? Have you physically checked the fuel pressure at the Schrader valve on the fuel line at the front of the engine?

I would spend money on diagnostic tools if you don't have them (including a code reader that can give you live data), before spending any more money on parts.

 

^^ Excellent advice....

 

I agree good advice

No codes, I have a mongoose connected to IDS/SDD running in a VM

I did check the fuel pressure before replacing the pumps and it was within tolerance and very stable - I will recheck as I have the required tools (I maybe rashly) assumed after changing the pumps I had eliminated any issue in that area .

I changed the plugs last week as they were one of the areas I’d not previously looked at and it was not clear from any of the history when they had last been changed and the car Is 0n 135K.

 

While the car is running check fuel trims and importantly check out the amount of air that the MAF sensor is reporting coming into the engine.

At both, Park and Drive - idling - the numbers should be as low or lower than 5.3g/s (I think), I've seen as low as 4.6, 4.9... If it's just a few grams off, even tenths, it can make a big difference. If there is an issue trims can be pretty wild and the ECU can get confused as hell because,,, well, you know, nothing is jiving, and STILL it won't throw a light or code,,, just keep trying to compensate. I'm sure that the confusion even kinda spreads to trans function shift points etc

It can be stuck at a higher than normal number (say 6.3 or whatever) to a dirty or shot MAF, a bad connection, increases resistance somewhere and immediately the ECU begins firing the injectors and mixing air for those values.

More than that, if the bad readings are intermittent, on those good start or running days, the ECU is dealing with that old bad information,,, trying to figure out what's going on and correcting.

Not that long ago I had a chaffed wire in my MAF loom at the area it goes around the filter box. I replaced the entire plug, soldered wires in (I just may be getting better at this) and,,, things were much much better. Especially after a hard reset.

 

Also may want to trace the loom/wiring for the coolant temp sensor and replace the sensor all together... I'm sorry, I'm not smart enough to know the CORRECT CTS readings at different temperatures.

 

That’s really helpful - thanks Jay

 

Ok why is nothing straight forward.
I went out armed with my laptop yesterday and connected up to the XKR with the Mongoose and fired up SDD/IDS 130. This was a fairly recent install as my previous surface pro died a few months ago and I’d only installed the VMs a few weeks ago and tested SDD on my x350.

Anyway of course nothing worked as expected, SDD informs you the car is too old and tries to fire up legacy IDS which fails to work. The IDS 125 vm connects but is hugely unstable and hangs and crashes. I vaguely remember spending quite a lot of time getting IDS to work acceptably with my mongoose so I will have to try to remember what I did!

So I grabbed my iCarsoft and gave that a go At capturing some info- I spent more time formatting it in excel than capturing it! (Must write some macros for next time) I thought I’d share the data…bearing mind it’s taken on the drive in park with mainly at idle with a few throttle changes.
sadly nothing labelled as MAF data
any comments?

 

..and with the data sorted by RPM which may help more

 

You dont need a smoke tester ...take out the air filter ..bung up the air inlet and put a smoke bomb in the airbox from a plumbers merchant....
For a petrol engine you need air / fuel (check the injectors are clicking with a stethoscope ) and spark. So which are you missing.

 

To date, my one experience with a plumbers smoke bomb was in about 1979 (I was about 16) when my mate said the best way to get rid of a huge wasps nest from my parents loft was to use a smoke bomb…….

Many stings and an unnecessary fire engine visit later - plus weeks of grief from my mum and dad….

 

Lolololololol 🤣🤣🤣
I can see it now.

Get the torque pro plug in OBD on Amazon and download the app... Best 20 something x2 I've ever spent...

 

I think your MAF is reading high for this RPM...?
But at the same time I don't think the car was up ta temp...?

Looking again at 2500+ RPMs (without load I presume) the MAF is reading just 9g...

I want to hear what other folks think...

My car was warmer/hotter with these numbers (just read).

No load - in P foot on gas.
2000rmps
MAF just under 13g (yours is 2500rmps - 9g)

I think you might clean the MAF or replace

 

Thanks Jay, I will aim to get it properly warmed up and maybe record some whole range figures

 

No worries...
Looking at your fuel trims,,,they look good/normal...
I THINK,,, usually when there is a MAF misreporting volumes trims can be irradic and all over... I'm confused

 

ok developments.....

I connected up my reader and had a blat up the road to Tesco it actually started on the first turn (unusual) and drove ok.
After shopping it took a bit of cranking to start and then fired up giving me an EML -which was also unusual

On returning home I checked the code which was P1646 - supercharger fuel pump relay. No spare relays so I've ordered some and in the meantime dropped the heated rear window relay in as a temporary fix (although its the same) Not sure how long the fuse has been playing up but it hasn't thrown a code before.

I've taken off and given the MAF a good spray and will try again to get some good telemetry tomorrow

 

Good STUFF, I say...

Careful... I think p1646 is telling you about an O2 sensor. Oh shoot, maybe a fuel pump issue? One of the 2?

Google the year, make and model of your car and (p1646), believe it or not, you will find volumes of info on this very forum. Depending on the year of the car, it could be fuel pump OR O2 sensors so,,, git ready, lol...

I think you are getting close to learning one of your fuel pumps ain't happy. I'm typing on my phone and after I hit reply I'll go back and look at your model year in your profile details.

 

Lol,,, this will make you happy - if you're a GOOD sport,

OMG. These CARS!
​​​​​

 

Thanks for the links Jay but believe that the code p1646 changed mid way through 2000 from o2 sensor to supercharger relay and my A2xxx chassis number fits with this theory and, the supercharger relay is definitely nerfed.

however, this does not account for the poor starting, but it’s one more issue removed.

I did notice last night that sometimes with ignition on the throttle body buzzes as if it’s trying to do something. I you press the throttle it seems to move smoothly enough and then when close may or may not stop buzzing

more investigation required

 

Interesting. I didn't know. Can you link me, or point me in a direction, so I can read a bit more about the code and the SC relay for p1646? I've never heard of it