R400 k series misfire

[pandjack]

Following recent posts of woes (R400 bad to worse/MBE ECU) eventually remedied via a full fettle (new plugs/leads/dizzy cap, RBTB's re-balanced, TPS re-set, injectors cleaned & full re-map, the car has been running perfectly for 2-300 miles but is now misbehaving - again!!

 

It starts/idles & pulls through the lower to mid revs on a gradually opening throttle all OK, but when flooring the throttle from low/mid-revs (from which it normally takes off like the proverbial scalded cat) it initially feels like someone's hit the kill switch before stuttering upwardly through the revs & then again in the next gear.

 

It started at the weekend about 60 miles into a blat through the Yorkshire Dales, at which point I stopped for the mandatory fish & chips in Hawes, had a quick poke around the engine for anything untoward then continued on another 70-80 miles back home running OK.

 

Went out last night for a quick 20 miler & exactly the same - only this time it didn't clear.

 

Any thoughts appreciated

 

 

 

Edited by - pandjack on 19 Jun 2013 12:32:08

[prangerman]

I've had a similar issue with my K Series R300 and been on the same technical journey as you.

 

I've done all that you have done and got it back to OMG performance (and had the ECU and Lambda operation tested, and RBs and TPS settings confirmed), only for the engine to revert to less smooth running after 200 miles or so, but not as bad as yours seems to be.

 

A recheck of the TPS showed the resistance had dropped off after 200 miles or so from what I had set it at. As the TPS seems to have been the cause of the original issue I'm thinking of replacing it. I'm told that they do wear out, although mine has only done 18,500 miles ☹️. I can't think what else might be causung the issue.

 

(Dave Andrews pointed me in the direction of the TPS as the likely culprit with the problem originally. )

 

Peter

 

Edited by - prangerman on 19 Jun 2013 13:42:12

 

Edited by - prangerman on 19 Jun 2013 13:48:19

[James.S]

Had the same thing with my R400K.

 

'Twas the Throttle Potentiometer - £100 or so from CC.

[Stationary M25 Traveller]

Look at the markings on it ..... try Googling ...... lots of cheaper sources out there.

[Stationary M25 Traveller]

Also .... try unplugging lead on lambda sensor. If that cures it ..... get searching on line for the part number on the sensor.

[Racingshoe]

A few of us have also found the wiring from the throttle pot to the ECU to be suspect. Take a look at the 3 wires running back from the throttle pot before buying a new sensor.

 

Running new wires cured a very similar & persistent problem for me.

[prangerman]

How did you isolate the problem and identify the wiring as the issue?

 

Peter (automotive electrical numpty )

 

Edited by - prangerman on 19 Jun 2013 15:30:26

[Paul Deslandes]

what type of air intake/air filter arrangement do you have? If you have the multi-hose intake that sits below the radiator and the air filter fitted into the trunking, take it apart and clean it out and replace the filter. A local guy had a problem with his simply not making power and it was all due to a totally choked airfilter. It was only discovered after at least two engine rebuilds and a 'service' (so-called) by CC.

This arrangement allows all the sh*t and corruption off the road to be sucked in and totally blocks the filter. Even if yours isn't like this, either replace or try it without the air filter to be sure its not the problem. They are often overlooked.

 

Edited to add, although the syptoms don't sound quite the same, check that your fuel tank breather is clear and the fuel pump isn't trying to suck fuel through against a vacuum. Immediately after a longish run, remove the fuel filler cap and see if there's an inrush of air. If so, you need to clear the blockage.

 

Edited by - Paul Deslandes on 19 Jun 2013 15:40:27

[pandjack]

Many thanks for the prompt responses guys

 

Re the TPS, I already have a brand new one which I bought as a potential replacement when I had the original issues - but didn't fit it as the diag's didn't highlight it as being 'faulty' - merely out of adjustment. I'll obviously now try try this as a matter of course (although I'm not sure how to set it up in Easimap - so any help/advice on this would also be appreciated)

 

Re the air filter, I'm running the standard R400 Pipercross foam one (CC ref 73433) directly mounted to the RBTB's (which is actually quite oily but I'm told that's how it should be....?)

 

The other thing that's been mentioned is contaminated fuel, & rather ominously I did actually fuel up at a garage (albeit reputable 'Inner space station') I hadn't used before on the day the problems started - hmmmmm - tank purge & refill coming up.

 

Re the lambda sensor, I'll try disconnecting this also. One thing at a time.....

[pandjack]

Oh, & Paul - yes I do get the inrush of air you describe, but always have done - even before the problems started.....?

[Paul Deslandes]

I'm not convinced that this is your problem but you could eliminate it by loosening the cap to let air in and then see if the symptoms are still there. Unless full, there should be enough air in the tank to delay the vacuum problem for a while so you could lock the cap. If the symptoms have gone for a while and then creep back, it could be the problem, however, if the problem is there immediately, I would say unlikely. Worth a try and easy to do. I think I'd have a look at this or some other loss of fuel pressure before looking deeper. Can you measure the fuel pressure?

[pandjack]

Not sure how to measure the fuel pressure but when spinning the engine over with the fuel line removed from the end of the fuel rail the flow is good & consistent. I also dismantled/cleaned the fuel pressure regulator as part of the original investigations (prior to everything being sorted & re-mapped) & all seemed OK as far as I could see - I've covered 2-300 miles since then with no issues.

[Paul Deslandes]

Looking at your list of items replaced, it doesn't look as though you changed the crank sensor. Might be worth a look.

 

You can check the TPS setting using Easimap. The 'standard' idle setting is 360mV which should increase smoothly to roughly 4.5V as you open the throttle. Others can advise whether the idle voltage setting is the same for the R400. If the voltage is wrong you can adjust as below. If the progression is rough and 'noisy' with the voltage jumping around, change the TPS. Even a new one could go bad after a few miles but it would be pretty unusual.

 

TPS setting

 

Assuming the engine runs, get it warmed up first.

 

To set the TPS, switch on the ignition with Easimap running on your pc so you can see the TPS voltage. Don't start the engine yet.

 

Slacken off the two TPS locking bolts so you can rotate the body, and adjust to about 250mV or less. Lightly tighten the clamp bolts. (This low initial setting puts the voltage firmly in load site 0 and means that any adjustment of the throttle bodies to set the idle speed won't push the ECU into a higher site which will affect fuelling and ignition advance and change the idle speed.)

 

Start the engine and adjust the throttle body idle screw for your desired idle speed.

 

Cut the engine and then switch the ignition back on.

 

Slacken the TPS bolts again and carefully rotate the body of the TPS so that the voltage is 360mV (or as specified if different). This adjustment is quite fiddly as the voltage is very sensitive to the slightest movement of the TPS body. The voltage doesn't have to be exact but should be more than 355mV and not exceed 365mV.

 

Gently tighten the clamping bolts, enough to stop the body moving but not overtightened. You'll probably find that tightening the bolts affects the voltage so you may have to have a few goes at it. I've been doing this for years and it still takes ages

 

Hope some of this helps and you get to the bottom of your problem. Blatmail me if you need help with Easimap.

 

Paul

[skeetsy]

Quoting prangerman: 

How did you isolate the problem and identify the wiring as the issue?

 

Peter (automotive electrical numpty )

 

Edited by - prangerman on 19 Jun 2013 15:30:26

 

I had the issue of a broken wire at the plug which connects to the TPS and the problems I had were hunting revs at idle and a general tendency to stall when coming off the throttle (i.e. when approaching a junction)

 

I have a copy of the build manual so I just used a multimeter to check the continuity between the corresponding connectors on the big plug which attaches onto the ecu and the various small plugs which attach to the various sensors.

 

All the best

 

Richard

[pandjack]

I've worked my way through all of the above to no avail. Latest observations during yet another 'diagnostics blat' however (with performance varying from normal R400 woo-hooooo!! under all conditions, to absolute dog on sudden throttle inputs) were : wildly fluctuating battery voltage on the Stack (13.0 - 17.1v from cold, eventually dropping to 11.2v & 'low batt' warning after 20 miles or so), fluctuating indicator beeper tone when stationary at junctions etc, corresponding change in idle speed & 'unusual' idle sound (not rough or mis-firing - just 'different' from normal).

 

I'm now thinking - alternator goosed & this actually makes a lot of sense as it was badly contaminated with oil/cleaned with copius amounts of electrical contact cleaner after the initial oil leak!

 

Could this be the answer to my prayers......??.

 

 

[Paul Deslandes]

Defo the place to start. Get the alternator checked out/refurbed.

[MereCat]

Sounds like the problems I recently had. Before you condemn the alternator check the circuit from the starter motor to the alternator. If this is intermittent ( loose) wire it will give these symptoms. It would appear that the wiring to the starter motor can get cooked and whilst not show any sign at first glance can bake hard and work loose from the crimped connectors which connect to the starter and thus complete the circuit to the alternator.

 

This would explain different readings from alternator and give differing experience when applying throttle or differing amounts of throttle.

 

Hope that helps and makes some sort of sense...?

 

Cheers

Paul

[pandjack]

New alternator fitted & the battery indicator on the Stack is showing 12.5v with the engine idling on a re-charged battery (not the usual 14-14.5v), this then gradually drops over a 20-30 min blat to 11.9v, &....return of misfire on sudden throttle inputs. Thinking the previously spikey alternator outputs have fried the battery I then invest in a brand new battery & the same thing happens - after a 20-30 min blat the voltage drops off & the misfire returns!!!

 

I've checked the integrity of the thick cable from alternator to starter solenoid & all OK, also fitted an extra earth cable from the battery negative to the chassis & still no improvement.

 

Scraped through Harewood at the weekend (actually managed a PB!!) by charging/swapping batteries between runs but I really need to get to the bottom of what's stopping the alternator from charging the battery at the normal 14-14.5v.

 

Any further pointers (or recommendations of a good auto-electrician in the York area in lieu of my numpty understanding of the black art!!) would be VERY much appreciated........

[Paul Deslandes]

That's really bad news and sorry to hear that you've laid out on a new alternator and battery, only to have the same symptoms. ☹️

 

It would appear that the alternator is not charging the battery and the engine is running on the battery until the voltage drops below an acceptable level. So, why?

 

You've checked the main cables

Do you have an isolator switch, if so are all the connections tight? Is this a new switch and has the problem just occurred since it was fitted?

How many individual wires go to the alternator and to how many terminals, 3 or 4?

Are there any alternator terminals without wires connected, especially a single terminal, separated from the others?

Is there a brown/yellow wire connected to the alternator or floating nearby with no home to go to?

The reason for the above questions is that OE alternators have a separate terminal that senses the battery voltage and tells the alternator how many volts to put out. If this is disconnected, it won't give anything out and the battery will go flat. This wire should go between the alternator and the battery but if a cut out switch has been fitted its easy for it to be left unconnected.

 

I can't help with an auto electrician in York but I suspect you really need a 7 specialist. See how we go with the above and I'm sure we'll get there.

 

BTW, congrats on the PB at Harewood.

 

Paul

 

 

 

Edited by - Paul Deslandes on 8 Jul 2013 20:44:22