Sagaris engine problem - Can't seem to find the cause

Sagaris engine problem - Can't seem to find the cause

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Discussion

Tom74TVR

Original Poster:

169 posts

156 months

Wednesday 23rd April 2014
quotequote all
Hello,

to get straight to the point, when I put my foot down in any gear except first my engine starts stumbling and shuttering like it is drowning in too much fuel. It takes a few seconds before the engine finds his breath again and starts accelerating.

I have had the car looked at and what we can see is that there is a big difference between the data from the lambda sensors and trottle possition sensors on the two banks. But we cannot find the reason for this.

Also in the adaptives file of the ECU you can see that one bank fluctuates a lot more than the other bank.
Same thing with the throttle position sensors... the one at the front fluctuates all the time while th eother is stable. Same for the lambda readouts... one stable, another not.

I do not get any sensor errors and we have tried to change the lambda sensors but nothing worked. I am not sure if this is correct but for me a sensor works or it doesn't work.
I also had the mass checked out and put in some other extra cables but this is not the issue either.

Does anybody have an idea how I can best tackle this issue?
Thanks a lot.
Tom

EvoOlli

605 posts

162 months

Wednesday 23rd April 2014
quotequote all
Hi Tom,
you said you have erratic readings with the throttle potentiometers. Is only one 'out of bounds' or both ? If it's only one you could remove the plug from it, the engine/ECU runs fine with only one of them.
Or you could do the following (with both Pots connected):
Use my MBETool, turn on ignition and deactivate the immobilizer, dont' start the car,
Then open the Scope Window and enable only both Pots. Press down the accelerator slowly and look at the graph on the screen. Do both pots show the same values ? There should be a steady increase from 15% to the max.
Now you know if both throttle pots work. If not, replace them. It's very easy to do.


Edited by EvoOlli on Wednesday 23 April 11:51

phoenixz

439 posts

165 months

Wednesday 23rd April 2014
quotequote all
Not an expert, but it sounds like ur throttle pots need re-aligned

phoenixz

439 posts

165 months

Wednesday 23rd April 2014
quotequote all
What he said....

tongue out

chris watton

22,477 posts

259 months

Wednesday 23rd April 2014
quotequote all
I had the same symptoms on my then 3 year old and less that 20k mile Tamora - it was the throttle pots, a Ford part, IIRC.

Quite a common problem, it seems.

SagarisChris

28 posts

138 months

Wednesday 23rd April 2014
quotequote all
I had the same symptoms about 3 weeks ago; putting foot down and the engine making lots of noise but not accelerating. Took it to the garage and ending up being the coil pack that needed replacing,

shep1001

4,599 posts

188 months

Wednesday 23rd April 2014
quotequote all

Could be the coil pack/HT Leads/Lambdas or the throttle pots or any combination of them!. The throttle pot (position) readings should move smoothly between about 15% at idle & 95% fully open, they should move together and stay within about 1-2% of each other. Lambda's should switch rapidly. The coil trace on the diagnostics should be smooth with no spikes running at idle.

Momentary hesitation under load as you accelerate usually points to HT leads and or coil pack starting to fail.

Whitenoise1

197 posts

138 months

Saturday 26th April 2014
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Does it do it at all temps? Mine struggles at cold temps but absolutely fine at high temps. I have heard that replacing rubbers on throttle bodies and getting throttle body spindles rebushed can help. http://www.tvrpower.co.uk/machining/

Andy

Whitenoise1

197 posts

138 months

Saturday 26th April 2014
quotequote all
Does it do it at all temps? Mine struggles at cold temps but absolutely fine at high temps. I have heard that replacing rubbers on throttle bodies and getting throttle body spindles rebushed can help. http://www.tvrpower.co.uk/machining/

Andy

Tom74TVR

Original Poster:

169 posts

156 months

Saturday 26th April 2014
quotequote all
Hi,

It seems my issues are caused by the lambda sensors. We could see when we measured the exhaust gas that the CO2 levels were much to high. At some point the lambda sensors would work and CO2 levels would drop but only for a few minutes.

We had a look at the sensors and it seems they were very badly installed. We had to use a lot of heat to get them out but as they were positioned incorrectly in the factory we could not get any new ones in....

We also put in a etra mass cable from the lambdas to the engine block.

We hope to have the car back together later today to see if it fixed.

Thanks for all the suggestions.
Tom.

Tom74TVR

Original Poster:

169 posts

156 months

Saturday 26th April 2014
quotequote all
With both lambda sensors replaced it drivers again as it should.
Thanks again for the tips
Tom.

BuzzBillsberry

1,306 posts

230 months

Sunday 27th April 2014
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That's great to hear Tom...happy motoring

Buzz