Uneven running while decelerating

Uneven running while decelerating

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Discussion

lancelin

Original Poster:

238 posts

120 months

Monday 10th July 2017
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Hello, I’ve recently had my TVR Griffith converted to use the canems ecu. The car runs really well during acceleration and general cruising but suffers from some uneven running when letting the car slow down with the gear. This effect makes driving in slow traffic and slow B roads annoying. The effect is like applying the breaks on and off very lightly during deceleration. It’s very subtle and probably wouldn’t be noticed by most!

I’ve checked the plug leads and spark plugs and all appears well. I’m thinking it’s not the plug leads as this would be noticeable at cruising and acceleration. I was thinking transmission slack but surely this would show up at cruising speeds and the transmission should be under constant load when decelerating.

Just wondering if anyone else has experienced this with the standard car or with canems?

The car is so close to perfect that it hurts! I’d return it to the installer again but they will charge for a rolling road diagnostic test and its bloody miles away! Lesson learnt there.

Any help or advice really appreciated.

N7GTX

7,823 posts

142 months

Monday 10th July 2017
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Perhaps a vacuum leak on the intake side. Possibly a faulty fuel pressure regulator. Those would be my first checks.

lancelin

Original Poster:

238 posts

120 months

Monday 10th July 2017
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Thanks Ian, got any tips for finding vacuum leaks? I guess soapy water can work but it evaporates so fast.

Classic Chim

12,424 posts

148 months

Monday 10th July 2017
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Stepper motor. Check air leaks at pipe connections etc as I'm sure the ones Lloyds use are robust. Bosch I assume. How long has your Canams been installed?

lancelin

Original Poster:

238 posts

120 months

Monday 10th July 2017
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Canems has been installed about 6 months. It's all under manufacturers warranty. I'm really hoping it's just a vacuum leak. Stepper motor has been removed for the canems conversion. Stepper motor Hole has been plugged. Some mechanics use smoke to detect the vacuum leak!

Edited by lancelin on Monday 10th July 22:05

Classic Chim

12,424 posts

148 months

Tuesday 11th July 2017
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So you shouldn't have to pay if something is wrong that's related to the Canams system.
I'm assuming you still use a stepper motor that's externally plumbed in, usually sits on the r/h side rocker cover and is made by Bosch? Or have they done away with the stepper operation on yours similar to MBE.
I was assured by Powers that the first year any faults or anomilies would be taken care of without cost to me. Luckily I'm very close to them so travelling isn't an issue and I have had it checked out once or twice since install.
This re mapping,,, 6 months, your engine surely hasn't changed character in that time so it shouldn't need re mapping.
2 years for me now with no re mapping and over 10,000 miles use. Still seems excellent so I don't get this. It could be a lead or something off of which it isn't a fault of the system. Get a decent mechanic ( if your not that way inclined ) to confirm everything's working as it should before going any further I'd say. Good luck, probably something simple.

lancelin

Original Poster:

238 posts

120 months

Tuesday 11th July 2017
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Thanks Alun. So was it powersperformance that did your canems conversion? They are closer to home for me.

Out of interest is your car smooth even when cold? The uneven running is considerably worse when cold. Have you had any erratic cooling fan switching? sorry for all the questions.

N7GTX

7,823 posts

142 months

Tuesday 11th July 2017
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Al has got MBE like me, not Canems. I use brake cleaner or carb cleaner to check for vacuum leaks. When you spray it against joints and around components, if there is a leak the engine revs will either rise by 2 or 3 hundred revs or drop by the same for a couple of seconds. Be careful using it on very hot surfaces so don't use on exhausts!
If you can't find a fault then I would give Lloyds a call and ask them for guidance on what to to try before going all the way to see them (assuming they did this conversion?). Agree with Al, you should not be paying for anything as any new part has a minimum 12 month warranty. Lloyds seem a good place to do business with so I'm sure they will help you.

Classic Chim

12,424 posts

148 months

Tuesday 11th July 2017
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lancelin said:
Thanks Alun. So was it powersperformance that did your canems conversion? They are closer to home for me.

Out of interest is your car smooth even when cold? The uneven running is considerably worse when cold. Have you had any erratic cooling fan switching? sorry for all the questions.
Sorry for any confusion. I have Mbe as sold and installed by Powers Performance as N7GTX kindly points out which doesn't use a stepper motor.
A friend home installed Canams so I'm aware of the new stepper arrangement your Canams uses.
I think we got crossed wires over removal of the original stepper motor which is something we both share yippee smile

Hopefully LLoyds will be able to help but it's clearly a good idea to get it checked out locally to discount something mundane which surely is the case.
I spoke with the mapper at Powers (Jason) earlier today regards checking the map on mine as I'm getting paranoid smile unless something fundamental has changed with the engine or ive changed parts, which I haven't there's no need. Fuel returns are good etc so go drive it hehe
Oh my car was mapped on the rolling road and then a number of road sessions to fine tune 1200-1700 shunting with a standard catted Y piece. I've gone de cat Clive Y piece since and Jason didn't need to effect the map then either. Runs great. smile
So something's obviously not right with yours or something else is causing the hiccup.
Throttle pot sensor maybe, complete guess though!
As these ECU are rare on our cars and not many of us mention them please do come back and tell us what the issue is as it's a steep learning curve for many including me.
Here's hoping it's a wire or lead off.

Classic Chim

12,424 posts

148 months

Tuesday 11th July 2017
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And in answer to your question
cold starts or warm or vey hot,,, just fires instantly and idles, cold it will need slight throttle application after firing to hold a steady 1000 revs for about 5-10 seconds then will idle at 850 revs without issue. It doesn't have a stepper to help raise idle when extremely cold but it does cleverly and quickly advance the timing to help ease the pistons over rather than add more air and fuel, it can be Slightly groggy first couple of seconds after start up even in summer cold mornings but it's more a nasty fuel mix or something like oil as the firing sequence doesn't miss a beat.
I think once in what must be thousands of starts by now it turned over a revelation longer before firing. Very odd. It basically turns over for about 2 seconds and fires every time exactly the same way, even with 6 inches of snow allover the car and -5 degrees. Only started it to find out how well it worked. Exactly the same as any other day was the answer. It would fire in -15 I'm confident of that. Iridium plugs can't be underestimated here as it starts better on these plugs And has less grogginess for those first few seconds since using them. Slightly crisper feel when accelerating and they do give a big fat spark.
Again I asked at Powers re the plugs as the car had been mapped on 7 grade standard plugs and I wanted to go to the slightly hotter running 6 grade and with iridium tip and Jason said it wouldn't be a problem.
So this suggests you can do one or two things within reason and no re mapping or changes are required. Hop some of that helps smile

carsy

3,018 posts

164 months

Wednesday 12th July 2017
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Id say its probably a mapping issue. Having said that it is probably only needing a slight adjustment over a few cells where its shunting. This is where a bit of road driving mapping really helps in this respect.

Have you got a wideband afr guage so you can see whats happening when it starts playing up.

lancelin

Original Poster:

238 posts

120 months

Wednesday 12th July 2017
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Thanks everyone for the suggestions. Thats my weekend sorted! I'll report back with any findings. I'm a big fan of closing out problems and reporting back with the fix. I have no clue about engine mapping so might leave that to the experts. This car has been one hell of a journey for me.The car has so much sentimental value I cant let it go! I just want a smooth ride.

Classic Chim

12,424 posts

148 months

Friday 14th July 2017
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In your original post you say the installer will charge to re map it. If this car was mapped as part of the install and only six months ago and it is indeed the map that needs tweaking why should you be paying anything. Surely if no parimeters have changed in your engine since install, how many miles have you completed in that time?
It seems a bit rich to think things can go so out of spec in such a short time as to require re mapping on the rolling road. Surely it's more road mapping that you might need to fine tune your map.
CUX chips and set maps get installed and work effectively for years without really needing re mapping so why should the Canams now.
Powers had my car running for over a week before letting me have it, this allows a few cold starts and a number of road sessions as well as a rolling road session.
And it went back again after I'd had the car a couple of weeks to fine tune 12-1800 Rev shunting. The mapping time is vital to the success it seems.
Goodluck with it. smile

ChimpOnGas

9,637 posts

178 months

Friday 14th July 2017
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It does seem any Rover V8 running an idle air control valve be it the 14CUX with it's stepper motor or the Canems with it's far superior Bosch version can be susceptible to the condition described by the OP. I'd be surprised if this wasn't the driving force behind the decision by Powers Performance to completely omit an idle valve from their MBE RV8 installations, I'm assuming MBE idle management is exclusively taken care of with ignition timing 'Scatter Spark'?

Its fair to say there are benefits and negatives to both idle management systems so it's not like there's a right or wrong, in theory the Canems use of an idle valve gives a greater range of adjustment, control and flexibility over a broader mix of conditions. On the other hand as any idle air control system is just an air bleed valve it is in effect just another managed vacuum leak, and it was always drummed into me all vacuum leaks managed or otherwise are the enemy of smooth engine operation.

I'm running closed loop idle with my Canems system which works well to save stalls when maneuvering the car slowly like reverse parking especially in full lock with a power steering equipped car, it also offers a decay rate feature that can hang the throttle momentarily which does a great job of bridging and so smoothing gear changes. For these reasons alone I wouldn't want to lose my Bosch idle air control valve, and I've actually discovered a number of things that can be done to improve smoothness on deceleration while still keeping it.

For the last year I've been systematically experimenting with a myriad of little tweaks and calibrations to enhance deceleration smoothness, idle quality, and that moment you transition from idle to pulling away or when you snap return to the throttle following a gear change.

1. One thing I've learned with idle air control valves is on this engine the less it interferes during deceleration the better, and the Canems system offers a number of ways to configure it's calibration to achieve this

2. The other area I had success with was to put a PCV valve in the crankcase ventilation system as no such valve was fitted as standard

3. Finally by expanding the fuel and ignition scaling then adding both fuel and ignition advance at the bottom of the tables further benefits can be achieved, lean overruns with retarded timing numbers do not make for smooth deceleration events on my car so going the completely opposite way proved very beneficial, but you do need the increased scaling low down the tables to take advantage of this strategy

Combine all three and get the calibration elements right and the car decelerates with such smoothness it's uncanny, add to this to an increase in idle timing figure, screwing the base idle screw fully home and then bringing the idle speed back to 1050rpm using adjustment of the throttle butterfly instead and you can achieve a wonderfully smooth idle too. With all the above sorted reinstate the idle air control valve 'less is more' settings, activate closed loop idle control and the whole setup comes together as a cohesive and best of all worlds package.

Please be aware none of the above especially advancing the ignition timing at idle will do much to help you pass the emissions test at MoT time, but I didn't buy a TVR to save the world, I much favor that big bubble of low down torque, super smooth pull aways and lovely stable idle quality over saving a dolphin or two.

Finally I have to say even with all this implemented and while my Chimaera is as smooth as can be on liquid petrol, it's still considerably smoother on LPG especially a slow piston speeds (ie idle), but that's just the slower more complete burn properties of a gaseous fuel that mixes way better with air...

Because as we all know air is just another gas wink

lancelin

Original Poster:

238 posts

120 months

Sunday 16th July 2017
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Thanks for all the information. I've completed all the basic checks outlined in the post. I still have uneven running on the overrun! The strange thing is it gets a bit worse when the cab heater and lights are on! I'm starting to think its electrical interference. I also have New ceramic plug leads which DONT use the plug extenders. I have a new alternator and battery and the earth connections measure ok. I'm at the point of returning it. I don't want to mention who did the work. I'm tempted to try the suggested canems ecu map changes but don't want to invalidate the warranty.

Using an oscilloscope, I have observed switching noise on the ecu 12V supply. Perhaps this is interfering with the canems Operation. Interestingly, switching the cab heater on near the cooling fan switching point influences when it switches. All this makes me think the ecu is not immune to switching transients. If the warranty wasn't an issue I would put a 12v noise filter on the 12v supply to the ecu. This filter is basically a low noise 12V linear regulator and a bunch of inductors and capacitors to filter out nasty electrical transients upsetting the ecu. I could use an otter switch to eliminate the fan switching problem but the ecu should be capable of doing this and the problem has inadvertently highlighted the fact that the ecu is not immune to switching transients. This is a fact and it's happened eversince the car was converted. they didn't do enough testing.


QBee

20,904 posts

143 months

Sunday 16th July 2017
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Experts - reading the OP's last post, is there a possibility that the OP has completely deleted all resistive elements from the igniition?
OP, what plugs to you have in the car? The standard B7ECS?

I was told that you must have at least one resistive element. Chimpo and I both have resistive BPR6EIX iridium plugs, which by the way do make the car run better.

Comments from someone who DOES have a clue?

ETA, from what I have heard of the Lloyds fellas, they are good guys and will most likely be more than keen to resolve what is probably an obvious and minor issue free of charge. It's hardly as if they get repeat business from a small customer base - they are dependent upon people like you and Dave recommending their product and services for people like me to buy.
Your experience is why I went Emerald, rather than CANEMS or MBE. Nowt wrong with any of the products, but I live 38 miles from Jools' workshop. When I had a hot re-start and idling issue with mine soon after installation, I called Jools and he came straight over to my gaff the next morning with his laptop and tweaked the maps to dial in more fuel low down and 999 turns on something or other (shows my ignorance). One of the most important considerations with any new ECU is where does the mapper live.

Edited by QBee on Sunday 16th July 12:13

Classic Chim

12,424 posts

148 months

Sunday 16th July 2017
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You need some form of resistance on the plug lines.
I use resistive plugs as I too have removed extenders.
I know ceramic leads are not easy to remove but id try some resistive ones or change plugs before going further.

lancelin

Original Poster:

238 posts

120 months

Sunday 16th July 2017
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Interesting comment on spark plugs, I'll check. I'm hoping they check the system free of charge. The car may have left their workshop perfect but it shouldn't be playing up within a few weeks of being delivered. I'll stand corrected if it's not a problem with the canems system. The erratic fan switching is definitely a canems issue. The guys that did the work are very knowledgable.

I'd love to drive a smooth TVR. Perhaps they don't exist. :-).

QBee

20,904 posts

143 months

Sunday 16th July 2017
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Classi Chim MBE and me Emerald both have smooth running cars

Pull one plug - a resistive plug will have an "R" in the descriptive name.
For all we know your leads may be resistive.

lancelin

Original Poster:

238 posts

120 months

Sunday 16th July 2017
quotequote all
Interesting comment on spark plugs, I'll check. I'm hoping they check the system free of charge. The car may have left their workshop perfect but it shouldn't be playing up within a few weeks of being delivered. I'll stand corrected if it's not a problem with the canems system. The erratic fan switching is definitely a canems issue. The guys that did the work are very knowledgable.

I'd love to drive a smooth TVR. Perhaps they don't exist. :-).