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Discussion Starter #1
Here's the info:

MY93 900SE body, added T16S engine (and running gear). All work done by an independant Saab specialist.

The story
Car starts and runs fine except an intermittent cough. It can be under light throttle or full throttle at various revs. The cough is like a drop in power as if there is no throttle. It can be a single one or a splutter of two or three. I cannot make it happen at will and its always such a suprise I don't have time to see what the boost guage is doing. Oh it also packed up on me and was diagnosed as failed fuel pump. Nice trip in an RAC truck after 2.5 hours at -5C waiting with no engine. The fuel pump was replaced - still coughing It does it from cold or when warm.


I've tried.
Plugs were the corret NGK, but I put new ones in anyway (7mm gap). Ouch said the autofactor when he was charging me!
I changed to super unleaded and thought the cough was not so severe (it had felt like whiplash on ordinary unleaded). Still there in frequency though.
I went to Shell Optimax and it was a noticeable softer cough, more an ahem, but still similar frequency.
The end of my mechanical tinkering...

The garage have:
Replaced fuel pump
New fuel filter
Adjusted air mass meter (was rich)
Replaced FPR with 3 bar one from 900i
New Distributor cap
Changed injectors
Changed coil
Boost Control valve appears OK

It still coughs, but it took 33.8 miles to do it after I left the garage, then did it about 15 times in the next 60 miles. The car feels really smooth and responsive with plenty of whoosh
except for this cough which tends to make me nervous about overtaking. I appreciate why their road test didn't find it!


Additional
I am not boosting into the red with fall back only about 3/4 through the orange. Garage has suggested staying away from optimising boost till we sort the problem.

Any ideas please? I've had the car a month and its incredibly frustrating and time consuming to keep taking it to the garage. They are incidentally being very understanding.
 

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Can't think of anything right now except to ask if the specialist has tried pulling any fault codes from the fuel injection ECU (I'm assuming it's a Bosch LH). That the problem diminishes with higher octane fuel also implies there could be something not right with the timing. But that's just a passing thought really.
 

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Discussion Starter #3
Thanks for the lead. I had a look under the bonnet, can't see the fuel suply lines like on my old 8 valve, its all wrapped in a big loom, but there is a thingy with wires that seem to go to the injectors (looking from the front of the car it is just infront of the injector rail) and it is stamped Lucas and Saab. I can't see any big box saying Bosch as in the 8 valve - is there any other way of telling which injection system it is? A brief glance at the Haynes says it should be Lucas - does this capture fault codes? I will mention timing too - it goes back on Wednesday.
 

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Depends on what year the T16 donor car was from. If it would still be running the original N/A fuel injection, it'd be wonder the car's not running properly...


The fuel injection computer is located in the right side kick panel (footwell area) - you will have to remove the door weatherstrip (partly) and the carpet retaining strip (three screws). Then you peel back the carpet to find the ECU.
 

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Discussion Starter #5
Thanks Eric - the donor car was a 1993 900 SE. I will get them to check. What should it be running - Bosch LH or the Lucas and which one? I assume its not just a matter of switching the box..

I would have thought that they would have married the fuel injection to the engine - but you never know - roll on Wednesday
 

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If the donor T16 was the same year as your recipient 900 SE('93), it should have the Lucas CU14 fuel management system. Look for a Bosch 3.0 bar fuel pressure regulator on the fuel rail (not a surefire method as 3.0 bar has been also used by the Bosch systems on normally aspirated 16v models and is a popular fuel upgrade for Bosch systesm on T16s, but conversely if it's 2.5 or 2.8 bar chances are the fuel system is an older Bosch LH 2.2 or 2.4).

Just realized there's a better way of looking what kind of fuel system you have: the orientation of the air mass meter (first thing after the air filter box). If it's horizontally mounted (i.e. in line with the turbo intake pipe) it's a Bosch system, if it sits vertically it's Lucas (right, fellows?)...
 

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Discussion Starter #7
Hello again Eric,

I found the air filter and there is a block shaped gubbins coming off it vertically in line before the pipe shoots off at a right angle and under the pipe from the intercooler towards the Turbo. Attached to the this block thing is a flat rectangular box oriented thin side vertically with "LUCAS 5AM 73350A 1991" on the side.

There is a brass coloured device that could be the FPR labelled made in Germany and 3.0 bar on it at the bulk head end of the injector rail. They put this on last week as part of the try all avenues approach - see list in original post. Not sure what the old one was (I think 2.8).

Does it look like I have a mixed injection system?

What now?

Jan
 

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That's all correct for this specific engine and year.

If the former fpr was indeed a 2.8 bar, you have swapped an incorrect part for a correct one. Shouldn't hurt.
 

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Discussion Starter #9
well thats
getting there slowly.

So we are left with checking the timing and error codes from the FI?

Yesterday I noticed that the exhaust was blowing a little at the junction of the Turbo outlet and down pipe - could that be it.

Also the symptom does seem to occur more under hard acceleration and also up hill.....
 

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Sorry,

Only just got around to reading this post.

It's sounding very much like my old C900 Carly which would do exactly that, and sometimes for 2-3 minutes!

That was finally tracked down (after many many trips to the garage!) to being faulty earths.

After all the earth points were cleaned up it ran much better.

The main earth points are at the end of the injection rail near the thermostat, and by the bottom of the radiator by the battery tray.

I also had a faulty EGR valve on the underside of the inlet manifold which would mess up the fuel setting at idle when tuning so it ran wrong when revving...

Andrew
 

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Discussion Starter #12
Seems the garage do earthing as the first thing when fitting the FI.

No fault codes available from the Lucas FI - apparently it only activates the CHECK ENGINE warning light.

The engine and associated systems came from a car that was running great!

Ignition timing rechecked. OK

They are starting from the beginning again and going through everything as no ideas left. They and I are a tad frustrated. Whilst a E 900i is wheels and dry I do miss my
 

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An intermittent fault like this is really hard to pin down
I would seem that it is an electrical contact that is usually ok but sometimes is broken
hence the coughing

To find it you need to either find it when it is dodgy (unlikely ) or work through the ignition system/fuel system with a fine tooth comb
checking connections /checking earths/checking wiring looking for corrosion util you get the problem
A real pita but there is no other way....

good luck
 

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QUOTE Jan95aero:

I changed to super unleaded and thought the cough was not so severe (it had felt like whiplash on ordinary unleaded).
End quote.

Have you checked the overboost cutout switch? Its behind the glove compartment and only requires that you tighten a screw or bridge the wiring. Maybe I've picked up your symptoms differenly but if you are thrown forward as if to nearly bite the steering wheel, then this could be the simple cure.

hth
 

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Discussion Starter #16
The Turbo gauge does not drop its boost pressure during the cough. So I guess that rules out the overboost.

Going to get the alarm and imobiliser disconnected today - just incase its drawing power and causing the issue.

Wonder how that affects the insurance - not to mention if it is the alarm people or me or who pick up the garages time costs....
 

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just a thought, but i had a similar-sounding problem with my 92 900T... though it felt more like the car was suffering a seizure than a 'cough'... it happened to be an intermittent problem with the throttle position sensor. checked the terminals for continuity with it bolted to the throttle body and found no faults. took it off the car and rechecked continuity at the terminals at closed, half open and full open positions and again while tapping the TPS... proved to be the faulty part.

i hope you get you get the problem figured out soon!
 

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Discussion Starter #18
The Car alarm people removed the connection to the coil (immobiliser circuit) last night and it has been fine since. Glad there were no cameras or cops around Dorchester for my testing session.

Theory is the alarm was creating a resistance.

Going to leave it off for a week and see how I get on.

Will post an update and details of the alarm if it is the culprit.

Many thanks for all your support.
 

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Did you ever get this sorted Jan?

You didn't mention whether you'd changed the plug leads - I had very similar symptoms on my old Rover 25 that replacement of HT leads cured.
 
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