Jump to content
Click here if you are having website access problems ×

420R misfiring


J888PRB

Recommended Posts

Hi All

My 420r picked up a misfire this week. On inspection it is cylinder 1 (front).

I've popped in new plugs - no change

popped on new coils - no change

now left scratching my head. Has anyone any experience of similar. Any advice welcomed.

Car is a 2016 420r - 13000 miles.

Thanks 

Link to comment
Share on other sites

Yes, Friends 420R stopped firing one cylinder at a Trackday at the beginning of the year.  Swapped coil packs and plugs with no change in symptoms.   Loom connections all checked out ok.  Eventually diagnosed as the ECU coil pack driver.  MBE provided first class support, replaced the coil pack driver for a very reasonable charge. 

Link to comment
Share on other sites

I had exactly your problem on my 2008 R400D.  The cause was a fractured (brown) wire in the #1 COP connector.  It was difficult to spot at first as the fracture was partly obscured by the connector itself.  The cure was to fit the sub-loom (3AL080A).  I had to splice this into my main loom, but your 2016 loom may already come with a plug 'n' play Econoseal.

ETA: Some pics here.  And a bit of history here.

JV

Link to comment
Share on other sites

Spot on JV

the wire had sheared off in the connector. Bit of faff to isolate but great result that it was only this.

ordered the new loom (£44) and will fix the old one as a spare

as clearly yet another week link

 

im new to C7 ownership and can see already it will be a love-hate relationship.

 

Link to comment
Share on other sites

Pleased to hear you've confirmed the problem!  Do you already have the Econoseal connector in your main loom?

The upgraded coil loom has fatter, silicone-sheathed wires, and is much more resistant to engine vibration.  Re your old loom, I'd suggest that the best place for it is the bin.

While on the subject of Duratec engine vibration, another weak point is the TPS (Throttle Position Sensor) loom.  CC supply a "race" version, also fitted with silicone-sheathed wires.  You may already have this, of course.  If not (and if CC are out of stock), it's not difficult to make up your own.

JV

Link to comment
Share on other sites

Hi John

Old coil loom repaired - still misfires but all 4 cylinders are working so all a bit odd., no longer isolated to cylinder 1.

Rather frustrating.

will try new loom when it arrives Thursday before freaking out. 
 

will look at tps next but none in stock as you say and beyond me to make one.....supposed to be driving to Spa in 6 days

Better warm up the M3

 

Link to comment
Share on other sites

Yes indeed, it could well be the ECU.  Worth checking that the earth is sound.

As for the TPS race loom, making your own is straightforward.  This is the one I made up some years ago while waiting for CC stock to arrive:

Home-maseTPSsubloom_2.thumb.jpg.fe58b10851593fb63751990650c98a56.jpg Home-maseTPSsubloom_connectors.thumb.jpg.c2e582ed552f2427419f64038971eb43.jpg

The wiring is from domestic mains cable.  The LH connector (to the TPS) is the 3-way from the existing loom, and the RH one is a new Econoseal 3-way male (ESC3M).  I replaced the original 3-way connector with an Econoseal 3-way female (ESC3F).

If you do find that your TPS wiring is faulty and CC don't have the race sub-loom in stock, you're very welcome to borrow my homemade one in the interim.

JV

Link to comment
Share on other sites

Just been looking at my notes....

Back in May 2013, I was discussing TPS wiring problems with Tony in Parts, and he mentioned that "current" cars no longer used the race loom as the standard loom had been changed.  So maybe your wiring will prove to be ok!

JV

Link to comment
Share on other sites

  • Area Representative

Scott & JV - As mentioned a few threads ago a member in my area with a recently home built Duratec car had exactly the same snag, miss fire on number 1 cylinder. Three of us went around in circles swapping plugs, coil overs & finally replacing the sub loom to the coil over. This moved the miss fire around a few times but always came back to number 1 cylinder.

Due to the symptoms we suspected the ECU which was sent of to MBE via CC. The circuit(s) controlling number 1 ignition were faulty as was something else which is why the snag sort of moved a few times. We put this down to the 'corrective tap' the ECU was given a few times.

Can't beat percussive action on electronics to realign the internals !!

Also believe it or not another snag was the rev counter refusing to budge off 1000 rpm. Replaced it.

There is a theme here once again -  defective brand new components.

Link to comment
Share on other sites

Hi everyone - update - thanks for all your thoughts

 

and I am adding detail to help with all your thoughtful suggestions.

 

new TPS fitted with no change.

 

symptoms originally were cylinder 1 not firing at all - the  fixed wiring loom sorted that out  - all 4 cylinders now running 

 

the new symptoms are rough idle (not much worse than standard)

when gradually accelerating under load the car is cutting in and out hence thinking TPS

Doing a night drive tonight I also note that the gear shift light is dimly glowing and not going off after the stuttering which is odd

 

so wondering it could be related to the rev limiter?? Presume all of this is pointing back to the ECU as you all hinted at needing some work,  I was hoping not as supposed to be driving to Spa on Tuesday and can't get that done in time I don't imagine.

With the ecu - can that just be flashed and reinstalled or is it more involved than that?


the new coil loom arrives tomorrow I hope so i will update if that changes or improves the symptoms.. my next thought was a full wiring loom, but I'm clutching at straws. Would prefer to look at the ecu first. 
 

JV - your notes are correct - mine doesn't have  a connector for adding that loom you made - the wires track back into the main loom.

GB - I will look up MBE tonight and call them tomorrow 

 

thanks again for reading/advising chaps

 

 

Link to comment
Share on other sites

Thanks Chris

looking more like this could be the issue. Will speak to MBE 

on a separate note - great build blog. Quick question though - I followed your blog for checking the diff torque. My resistance was circa 45 lb ft - newly serviced Titan diff - but I was rotating clockwise on the passenger side not counter clockwise as per your write up.  little to no resistance in the counter clockwise direction. 

Any thoughts? 

Link to comment
Share on other sites

Re #18:

...mine doesn't have  a connector for adding that loom you made - the wires track back into the main loom.

AFAIK, CC didn't fit that Econoseal 3-way connector as standard, but it's required for the race sub-loom.  

Does your TPS wiring look like this thin, spindly stuff or is it more meaty?

FracturedTPSwiring.jpg.8a4abab67faeef8801baf6530833a62c.jpg

The photo shows the fracture in my original 2008 TPS wiring.

JV

 

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...