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Discussion Starter · #1 ·
I have a tuned 9-5 it is highly modified to about 350bhp with Nordic software.

Recently I have had a problem.

Please note that there have been no hardware or software changes for over a year and suddenly I have a huge misfire under full throttle conditions.

I don't think its the software because the car was ok for 12 months, but now has a problem.

Under heavy load I get a huge misfire, Tech 2 codes 0300 and 1300 with the misfire across all cylinders.

We suspected the car was running lean under full throttle possibly caused by a weakening fuel pump.
  1. An up rated fuel pump (walbro 255) was fitted, as was a new fuel filter, but still the massive misfire under very heavy load.
  2. We changed the 3.5 bar FPR but no improvement, and the misfire is across all cylinders according to Tech 2 so its not an injector.
  3. We put in new spark plugs and a new DI, plus the MAF was changed, but still the same problem.
  4. We have also changed the forge dump valve and the boost control valve just in case.
So we can assume fuelling is fine and spark is fine, leaving......."air leak" perhaps?

At base boost it does not happen.

I haven't been able to get the A/F read yet ;oops:

All this points I guess to an air leak, but one that only appears under heavy load (full throttle), i.e. full boost, the rest of the time she is fine.

BUT....we (Wessy, Karl and I) cannot find any obvious leaks, all vac pipes look fine, all joints seem fine, the EVAP system is fine, the cobra pipe is properly fixed to the turbo etc.

So next I guess we have to start pressure testing things like the Abbott inter-cooler - unless you guys have any better ideas??

One idea though - the car runs a TD04HL-18T turbocharger - Could the waste gate actuator be the problem? (its a standard TD-04 one that came with the turbo some 18 months old now)



I could buy the Forge Waste gate Actuator if you think that this might be the problem.

http://www.partsforsaabs.com/product_info.php?products_id=2604

I'd appreciate any feedback, help or guidance.

Thanks Chris
 

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Discussion Starter · #3 ·
Kermit said:
Chris, if the pipe you blocked with a bolt is reconnected does the misfire still occur under WOT?
Yep, the effect is the same :confused:
 

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Discussion Starter · #5 ·
Al's Red Wagon said:
By air leak are you suggesting that maybe there's not enough O2? Maybe a recirc problem (as in too much)??
Hmm, you have spotted the "logic" flaw in this.......

My poorly educated brain thinks that if, air was released (leaked) then the car would run rich not lean, but the indicators are that its lean, so I assume that extra air is getting in somehow?

Its all Swedish to me :eek:

Al's Red Wagon said:
Also, weren't you fiddling around with the spring in your BPV lately? Different spring perhaps?
Nope, tried that :confused:

Keep chucking the ideas in guys, we will find it ;)
 

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Chris. Probably not a lot of help:- But

Don't discount the ECU, its a common problem with GM/Vauxhall, I know its rare for ECU problems with Saab but its also rare for you and wes to struggle.
Has wes got a spare to drop in and try?
Pete
 

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Discussion Starter · #7 ·
The problem is that no spare ECU will be mapped for the hardware configuration I have.......

Lets say a spare just lowers the boost, well we know that works cos on base boost the problem isnt there.............mind you neither is the power :confused:

But the straight answer is we dont have a spare with anything like the correct mapping on it :cry:
 

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I'm thinking out loud, so this may be garbage and I'm giving more questions than answers, but...........when a misfire for whatever reason is detected, which in most cases causes unburnt hydrocarbons to be emitted, the ECU normally intervenes and cuts fuel to that cylinder.

So, two things.....

1) at your last MOT how were the HC readings (the genuine ones;)). I was just thinking that if they were highish, that would give an indication that you were running rich?

2) you say the misfire is across all cylinders as shown by TechII, so your ECU thinks there is a misfire in all cylinders. Could the ECU be getting corrupted info? Would a short in the block that connects to the DI cause this?
 

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Discussion Starter · #9 ·
Andyaero said:
I'm thinking out loud, so this may be garbage and I'm giving more questions than answers, but...........when a misfire for whatever reason is detected, which in most cases causes unburnt hydrocarbons to be emitted, the ECU normally intervenes and cuts fuel to that cylinder.

So, two things.....

1) at your last MOT how were the HC readings (the genuine ones;)). I was just thinking that if they were highish, that would give an indication that you were running rich?

2) you say the misfire is across all cylinders as shown by TechII, so your ECU thinks there is a misfire in all cylinders. Could the ECU be getting corrupted info? Would a short in the block that connects to the DI cause this?
Makes sense but:

1. Cant remember, I'll try and find the papers ;oops:

2. I think its more that the misfire moves accross the cylinders suggesting a common problem rather than one linked to a specific plug / cylinder - but a good point that I will pass on ;)

I just went out and gave it a blast, its strange because if you load it up gently its fine, but, take say 2nd gear and stamp on the pedal, car lifts up, wheels spin, TCS's flashes and lift off............then at say 4500-5000 massive nose dive as it "mises", so violent is it that the seat belt hurts your neck when it happens.............back off and off you go again.........

It also gets worse when the engine is really really hot, say after a 2hr drive.......... :cry:
 

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Discussion Starter · #10 ·
MOT was in April 07 and:
  1. The HC's were 43ppm the max is 200
  2. CO was 0.11 max is 0.20
  3. Lambda was 1.01 - limits are 0.97 - 1.03
MOT in April 06 and:
  1. The HC's were 22ppm the max is 200
  2. CO was 0.12 max is 0.20
  3. Lambda was 1.00 - limits are 0.97 - 1.03
 

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Discussion Starter · #12 ·
Garrett said:
Possible oxygen sensor?????
Wouldnt that give specific fault codes :confused:

If a hose is split or the I/C it would surely happen all the time, certainly more constantly than WOT only?

We spent hours with carb cleaner and easy start trying to find a leak...........:confused:

Anyone got a box of matches :roll:
 

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Discussion Starter · #13 ·
Maybe a rolling road / dyno session would be a way to find out whats going on, but do they understand saabs?

Have Abbott Racing got dyno facilities?
 

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CPS? My 900 gave me the exact symptoms when my sensor had a bad connection. It really would only happen when sudden torque was delivered.


WHat are the symptoms of a bad TB?
 

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Discussion Starter · #15 ·
Rolf at Nordic mentioned CPS too :confused:

Gotta be worth a try!

TB is about 6 months old............
 

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Blocked exhuast/ semi melted Cat can also cause likewise problems.
Have you noted any change in exhaust noise?

Better is to test, i.e connect a pressure sensor (boost gauge will work) to DP's O2 hole and give it a go on WOT. Depending on the exhaust you may see values
0.1...0.5bar in the DP, if blocked the pressure will raise heavily and you cant miss interpret it.
 

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Discussion Starter · #17 ·
Vigge said:
Blocked exhuast/ semi melted Cat can also cause likewise problems.
Have you noted any change in exhaust noise?
Not noticed it, but thanks, I will have a go at that test.

The car has the Abbott racing race cat fitted.
 

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Sounds like a CPS to me too. Only way I could see you getting a misfire across all cylinders under load when the engine is hot. I believe the theory on this site is that when the CPS gets hot, it goes "blind." And if it goes blind, while under a high load, I'm thinking the ECU won't fire the spark at the right time, not correcting for the load and boost.
 
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