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PostPosted: Mon Nov 12, 2018 1:52 pm 
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Full Pressure Turbo
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Car Model: '98 9000 cse (aero) Lpg
I'm chasing what I think/thought might be vacuum issues, but now I'm not so sure.

Long story short, is I have postive fuel trims at idle, indicating a lean condition.
I've checked all my vac pipework and it's all still good, having already been replaced with silicone a while back.

I reset my ECU and watched the trims from scratch. With the LTFT reset to Zero, the STFT is sitting at around +6%. So I'm losing either 6% fuel somewhere or gaining 6% air somewhere.

As an experiment, I disconnected my FPR and plugged the vac line......low and behold....by STFT went to approx zero.

So what's happening here?
Is there too much vac pressure? Causing ECU to overcompensate for it? Or a weak FPR diaphragm?

It's a new bosch FPR that I fitted whilst chasing a now fixed fueling issue (has had new fuel pump, fuel filter & fuel pump relay. Relay was the culprit).

So I know it's got sufficient fuel pressure when required, but this is boost referenced through the FPR.

I'm thinking possibly faulty FPR?

Or are there other issues that could cause this.
Do things like exhuast manifold leaks play into this? I know that I need to retighten my manifold studs, but I cant feel or hear a leak here. And if anything I figured that's just an O2 sensor confuser, rather than a vacuum issue, and thus not relevant in this case. As that wouldn't explain the normal reading when disconnected from vacuum.

I'm confused.

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PostPosted: Mon Nov 12, 2018 2:11 pm 
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Car Model: 96 V4 & 9-3 Turbo-X
What size hose did you use? Could it be that the FPR is designed for 3mm, and you've fitted 4mm?

Do you have a hose clip (or cable tie) on the FPR hose?

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PostPosted: Mon Nov 12, 2018 3:19 pm 
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Car Model: '98 9000 cse (aero) Lpg
beardydave wrote:
What size hose did you use? Could it be that the FPR is designed for 3mm, and you've fitted 4mm?

Do you have a hose clip (or cable tie) on the FPR hose?
Interesting idea.
Its 3mm hose and it's a nice tight fit.
So I doubt that's it.
If it were pressure I might consider a clamp, but its vacuum. And if anything it pulls itself tighter under vac.

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PostPosted: Mon Nov 12, 2018 3:42 pm 
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Location: Portsmouth
Car Model: 96 V4 & 9-3 Turbo-X
Whats the fuel trim like on boost? if it's trimming the opposite way on boost then it's indicative of a leak.

The idle adaption in the software exists to allow for variences in quality of parts. The FPR is backing off the fuel pressure when the manifold is under vacuum (they are designed to do this) but it's doing it a little bit more than Saab allowed for in the idle fuel map. So it's adapting to bring it back to target idle AFR.


If nothing else is being affected (ie, you don't have poor idling) then why worry?
Or if you can't help but worry, increase your mapped idle fueling by about 6% to offset.

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PostPosted: Mon Nov 12, 2018 4:05 pm 
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Car Model: '98 9000 cse (aero) Lpg
I've not gone into it here yet, but I also run LPG.
So my main issue is around ensuring the petrol mapping is as close to 100% accurate as it can be so that I can then map the LPG accurately. As the LPG is a piggyback ECU system which uses the petrol injector pulses and crank sensor etc to runs it's own injectors.

So if the engine itself has any issues, this may throw the LPG system off by a factor larger than just the petrol system.

I am discounting that system at this point, as i have switched it off for diagnosis of the engine.
If it ends up sat at a steady 6% LTFT with no other issues, then that would be fine.

But I've seen it running with combinations of 6 plus 10 at idle before and i dont know what's causing it other than vac leaks..

I've run the car under so many tests and conditions at this point that it's all become a blur, but I am beginning to measure it all again from today. That 6% is my initial reading and I will watch as it adapts further.

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PostPosted: Tue Nov 13, 2018 10:36 pm 
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Joined: Fri Nov 23, 2007 6:13 pm
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Location: Maidstone
Car Model: 9-5 Aero
Given the recent works to the fuelling side, lean on idle is probably a leak somewhere in the intake. The MAP sensor or the FPR may not be seeing the correct pressure value for the manifold pressure.

A leak on the exhaust manifold or downpipe would likely present as running rich.

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PostPosted: Tue Nov 13, 2018 10:41 pm 
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Car Model: '98 9000 cse (aero) Lpg
Thanks.

Now the car has settled into LTFT following the reset, its sat at 6.5% LTFT, with a fairly large swing on the STFT.

I'm thinking intake leak more and more despite the irregularity of how it presents.
I can see a positive trim at idle and a negative one under light throttle but under load. So that suggests vacuum. That said, I have a solid 19in/hg once warm, a little less when cold.

I have a spare MAP on the way to swap out just to be sure. But otherwise, I'm going to be hunting vac leaks.

Best method going to be spraying brake cleaner or similar around the intake manifold etc with engine running and listening for rev changes?

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PostPosted: Thu Jan 31, 2019 5:54 pm 
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Car Model: '98 9000 cse (aero) Lpg
So it's happening still, but worse......
LTFT is now settled at 15.5%....I have no idea what's causing it.

I've replaced the o2 sensor and map sensor...no change.
I've checked all vac I can find.

Could it possibly be a faulty intake air temp sensor? As it uses that combined with MAP to define air mass?

I'm going to fit a 3" exhaust and get a stage 3 remap in the very near future. I'm kind of hoping that solves it, but in reality I feel like it's just going to show it up more.

I'm frustrated as I cant think why it would be happening. It's either getting too much air, too little fuel, or the car thinks either of those things is happening and it isnt actually, eg sensors.

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PostPosted: Thu Jan 31, 2019 7:32 pm 
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Location: Saabshire
Car Model: Merc A200d AMG 7sp DCT
My little trick for hunting induction leaks.
Go buy a car of "Starter spray". and spray around each section of the intake one small area at a time.
If the Revs suddenly go up, you have found it.

Dont forget all the boost pipes and intercooler connections, as they are the most likely.

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PostPosted: Thu Jan 31, 2019 8:51 pm 
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Joined: Fri Sep 09, 2016 7:19 pm
Posts: 28
Location: Reigate, Surrey
Car Model: '95 9K V6 and '97 9K CS Anniv
Sorry for going off-topic but does resetting an ECU return it to it's base map if it's been tuned with T5suite?


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PostPosted: Thu Jan 31, 2019 8:51 pm 
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Location: Reigate, Surrey
Car Model: '95 9K V6 and '97 9K CS Anniv
Sorry for going off-topic but does resetting an ECU return it to it's base map if it's been tuned with T5suite?


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PostPosted: Thu Jan 31, 2019 8:57 pm 
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Car Model: '98 9000 cse (aero) Lpg
Level wrote:
Sorry for going off-topic but does resetting an ECU return it to it's base map if it's been tuned with T5suite?
If by resetting you mean a battery disconnect, then no.

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PostPosted: Thu Jan 31, 2019 9:25 pm 
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Location: Saabshire
Car Model: Merc A200d AMG 7sp DCT
Level wrote:
Sorry for going off-topic but does resetting an ECU return it to it's base map if it's been tuned with T5suite?


No, it simply clears any Adaptions that have been learned.
When i worked at Saab we used to reset all cars ECU's after a Service. Hence why some people thought their cars were faster after visiting the dealer.

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97 9000 Aero 2.3T
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PostPosted: Fri May 17, 2019 3:29 pm 
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Car Model: '98 9000 cse (aero) Lpg
This is still proving a problem for me.

I've had a new ECU, JT 3" full Exhaust system and 3 bar map sensor fitted (for more power, but also in the hope it might help cure these issues).
It did cure a small exhaust leak at the turbo to down pipe connection, but not much else.

Fuel trims are still showing a long term correction of about +10-15%. So not enough to trigger a code right now, but it's periodically been higher and i have had lean codes in the last few months.
I know it's getting plenty of fuel, and i've done my best to check for vacuum leaks, including soaking it in starter fluid around the intake manifold and relevant connections. No identifiable issues.

The one thing i can't confirm functionality on is the EVAP purge valve/solenoid.
I initially disconnected the hose form the back of the intake and plugged the manifold nipple (not the evap line). This seemed to show a difference, so i took the arch liner out and pulled the charcoal canister and valve out for inspection.
I unplugged the valve and tested operation, initially just blowing through it one way (towards the engine) when switched off led me to think this was the leak.
However as soon as it was plugged in, it shut and i couldn't blow through it anymore....so no leak.

I started the engine then however, and the solenoid switches on and off at a set rate, like it's dosing the intake with vapour.
I have no idea if this thing is supposed to be shut? and then open a fixed amount of time, or rapidly opening and closing like i witnessed.
It's also a little hard for me to see what it does in other scenarios.
Although, the only time it's running lean is light throttle and idle conditions. Under boost, the fuel trims show it correcting properly to near zero.

Does anyone know what it's supposed to operate like?
If i can just replace that and have it fixed that would be great....but as usual, it's likely to never be that simple.


Last edited by Blinkinink on Fri May 17, 2019 3:38 pm, edited 1 time in total.

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PostPosted: Fri May 17, 2019 3:35 pm 
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Car Model: '98 9000 cse (aero) Lpg
Also,

In messing with fitting the 3 bar Map sensor, i noted that which vacuum hose the MAP sensor was connected to had a big influence on fuel trims.
The original silicone hose connects to the nearest vacuum take off on the end of the manifold.
I tried running it to the longer hose which T's off to the dash boost display and the blow off valve, this made it run like rubbish and somewhat leaner. ( and looped the shorter hose back to the other intake nipple to seal the vac leaks).

What is the correct length/diameter/placement of the original hose, as it wouldn't surprise me if something this fickle was messing with the ECU's interpretation of the readings.


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PostPosted: Fri May 17, 2019 5:29 pm 
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Joined: Mon Feb 19, 2007 4:12 pm
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Location: Portsmouth
Car Model: 96 V4 & 9-3 Turbo-X
Have you tried a new fuel pressure regulator?

Sounds like it isn't supplying enough pressure at vacuum on the manifold, but once theres boost its ok.

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'09 9-3 Turbo-X Wagon No. 38
B204 Haynes Roadster Project


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PostPosted: Fri May 17, 2019 5:31 pm 
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Car Model: '98 9000 cse (aero) Lpg
Yes, it didnt make a difference.
Fitted a Bosch replacement and swapped them back again since with no change.

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