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Discussion Starter #1
Hello All

This is my first post so be gentle. Have owned Saab's for the past few years but have rarely had a problem which I couldn't sort.

The car is a 1989 900i 8v and it starts first time everytime but after about 1 min of running at idle as normal she will start to run rough to the extent that I believe she is missing on a cylinder. The engine will start to surge and die vibrating quite a bit until finally she konks out.

I initially suspected an ignition problem as I have had problems before with moisture in the dizzy cap but I have checked all of Spark plugs, leads etc and all seems well.

Have started to suspect that its maybe something to do with the cold start sensor but don't want to just start buying parts in a hope that I stumble across the cure.

Also When the engine has been running for a fair distance problem dissappears. Also If you apply the accelarator engine runs sweet.

Thanks in Advance
Here a pic of the car in question
Gordon
 

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it maybe that the sensor is wearing out?? and it works for a little time but once any temp increase is detected it is knocking it off, so you are running without 5th injector(choke) as you say it runs ok when warm. does it start and run ok if been left 1/2 hr etc or is it only on cold start up, as it does appear like your missing fuel as you say once warmed up its ok and it runs. sounds like temp sensor though for cold start is on way out and it will struggle.
I had the wires come of one of the connecters under rubber sheath took me ages to find, as the connector was sited on sensor but wire had come off GGGRRRRR, I had to keep blipping the throttle quickly to flood it a bit and then run a bit until it got warm once warm no problem:cheesy:
 

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Remove and clean (lots of carb cleaner) your aux air valve - really simple to do - it may be gummed and carboned up and not closing - leaning out your mixture just as your cold start (5th injector) cuts out -
 

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Discussion Starter #4
Thanks for the replies so far!!!.

Right removed and cleaned the Aux Air Valve and all pipes associated with it. To be honest it was all very clean and wasn't surpised when their was no change.

Completely forgot to check the connectors on the Temp sensor but will do that tonight. Just a pity my other Saab 1986 900 carb doesn't have the cold start otherwise I could swap it over to check.

Seems most likely to be the cold start thermo time switch. Is it worth buying one just on the chance of that being the offending item??? I have emailed a Saab breaker in the UK to try and get second hand Cold start valve and the thermo switch. That way if I can find out what bit is not working I can buy a brand new replacement part for it.
 

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You're lucky (or perhaps not) - when I checked mine it was all gummed up -

check the resistance across the poles on the AAV - if there's no resistance then the little heat coil that closes the valve won't work and you'll be over-lean. Actually you could test for this by plugging the AAV and running the car - if it runs well then chances are you're either not getting voltage to the AAV (easy to check for - you should be getting 12V so long as the car is turned on) or the valve is shot.

You can also check the thermotime switch for output - both while cold and when warm - or just check the resistance across the switch - don't know the spec off the top of my head - but a Bentley or similar book would have it -

Best of luck -

Steve
 

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Beanbaggz said:
Hello All

This is my first post so be gentle. Have owned Saab's for the past few years but have rarely had a problem which I couldn't sort.

The car is a 1989 900i 8v and it starts first time everytime but after about 1 min of running at idle as normal she will start to run rough to the extent that I believe she is missing on a cylinder. The engine will start to surge and die vibrating quite a bit until finally she konks out.

I initially suspected an ignition problem as I have had problems before with moisture in the dizzy cap but I have checked all of Spark plugs, leads etc and all seems well.

Have started to suspect that its maybe something to do with the cold start sensor but don't want to just start buying parts in a hope that I stumble across the cure.

Also When the engine has been running for a fair distance problem dissappears. Also If you apply the accelarator engine runs sweet.


hello Gordon that's a very nice looking Saab you have there! My 1981 8v turbo sometimes behaves the way you described when starting - it'll crank and fire but act like it's only running on 3 cylinders until I push the throttle a bit more which seems to make the engine settle into a normal idle without the tell-tale vibration caused by not all cylinders firing properly.

I suspect but am not sure it could either be an injector not opening (remembering that the K-jet injectors are fully-mechanical) or a blocked fuel filter resulting in the fuel line pressure into the fuel distributor not being high enough for the first 10 to 15 seconds after the ignition key is moved into the 'run' position in preparation to crank the engine.

The engine runs fine otherwise so it's probably not the filter, but they're a cheap item to buy new.

I intend to get some injector cleaner and put that in the next fuel fill to see if it makes any difference. The fuel filter in the car is the same one that was in it when I bought the car back in May, so it could be due for replacement.

The cold-start valve/injector is controlled via the thermo-time switch but even if the thermo-time switch is not working, the engine will still start although it might take a bit longer since there won't be any pre-injection of fuel vapour into the intake manifold.

My 83 900S has a dud thermo-time switch that causes the starter auxilliary relay to stick on and keep the starter engaged after letting go of the key so I just left it disconnected, and the engine starts every time after about 3 to 5 seconds. I'll get a replacement for it eventually.

If you want to check out the ignition side more, try measuring the resistance of the ignition leads and of the coil windings. The Bentley manual has the specifications for these items. Also you may want to remove each spark plug in turn and check that the electrode gap is correct (between 0.6 and 0.7 mm). If the gap is larger on one that could prevent it firing initially when the engine is cold.

Craig.
 

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Beanbaggz said:
The car is a 1989 900i 8v and it starts first time everytime but after about 1 min of running at idle as normal she will start to run rough to the extent that I believe she is missing on a cylinder. The engine will start to surge and die vibrating quite a bit until finally she konks out.
I doubt the problem is the cold start valve or thermo time switch as the car starts and runs for a minute.

Try the troulble shooting procedures in Bentley. The fault is either ignition/electrical or fuel related.
 

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A fellow Saaber had his car over this week to try and sort out a similar problem. Its been my experience that most 8v I've had get this way and I've never quite run the problem down - and I've tested and inspected everything! Of course now my car is really dogging it on the damp cold starts.

I've always suspected it was a common ignition fault, not cold start, just by the symptoms of not quite running on all cylinders.
 

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jetman said:
Its been my experience that most 8v I've had get this way and I've never quite run the problem down - and I've tested and inspected everything!

I've always suspected it was a common ignition fault, not cold start, just by the symptoms of not quite running on all cylinders.
Hmmm.
In over 17 years of owning an 8v C900 I have never had this problem.
If an engine stalls there is a fault causing that. You just have to search to find the cause. :cheesy:
 

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Discussion Starter #10
Hi Guys Thanks for the subsequent posts.


Right Did a bit more investigating on the car. I take it when you speak about Bentleys you mean the US equivalent of our British Haynes Car Manual?

I Checked the Auxiliary Air Valve as per the manual and it appears to be in good working condition as is the cold start Valve. After much searching I found that the thermo switch has been removed but as it has always been removed this isn't likely to be the problem. I also checked all air pipes associate with Air valve.

I have already checked the Ht leads and Spark plugs plus dizzy and contacts rotor arm etc but all are fine. Swapped most of these parts around from my other Saab with no visible effect on either car.

This leads me to Suspect like a few of you have advised that the problem is more likely to be due to the fuelling side. Might be worth trying to fire through some injector cleaner with the next refuel. If I have time tommorrow I will test the Fuel injectors as per Haynes.

Anyway Thanks all will keep trying
Gordon
 

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Is this problem from cold starts only, worse with cold starts, or problematic with all starts? I wonder if you have a good power supply to the WUR. You should see at least 12V at the WUR under all circumstances.

I had a bad ground on mine once, which allowed me to fire up, drive about 50 yards and then it misfired and ran badly until it had warmed up. If I revved it, it was okay. If I drove it, under load, it behaved badly.

The thing about the CIS system is that there are a number of bi-metallic strips inside the devices which when cold need to warm up. When warm may need a little current to warm up. The WUR or the AIC are the main culprits, usually and the wiring is almost always the problem.

HTH.
 

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The Bentley manual is an abridged version of the Saab factory manuals - published in US - but available in UK. Try Amazon. Get a Bentley manual - the best use for a Haynes is as a door stop.

You should have a thermo time switch.

As Orca says, a faulty warm up regulator could cause your symptoms. The Bentley manual has detailed troubleshooting guide. You need to follow to ascertain the fault. It could be caused by a number of things.
 

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Discussion Starter #13
Right Didn't have much time today as I was transplanting a 2000cc Triumph Vitesse Engine into a Triumph Herald but that is for a Triumph Forum.

Firstly checked the voltage going to the WUR as per Haynes which came up as 11.8v which seems about right. Then disconnected the WUR completely and started her up. She ran for about 20 mins with absolutely no problems so seems that the cause of the problem is definately the WUR.

The electrics to the WUR Seems to be ok and during cold start for at least 1 min there is fuel going in and out of the WUR. Does this suggest the internals of the WUR are the culprits or could there be another reason???

Also I have already ordered a Thermo switch for the car. Where is the best place to find a replacement WUR (New or recon) I plan to check my local Bosch supplier tommorrow as buying one from the states will cost $150 and with the present strikes on the UK postal system could take quite a time to recieve one.
 

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have you a pic of wur might have one.
straight 6 vitesse in a herald, well that's a vitesse anyway just different bonnet and panel round no plate on boot.(used to work there till closure) a friend of mine once got one with a 2500 pi engine in, said it scared him stiff, and he used to do sidecar racing?(he was the hanger out) your trying to make a saab eater are you:nono; :cheesy:
 

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A new WUR from Saab in UK is about £200+VAT. Try Bosch dealer if you want new, otherwise get 2nd hand from breaker.

I think the only way to test whether a WUR is working OK is doing fuel pressure tests.
 

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Discussion Starter #16


Here is the offending item. Bit on the left is the thermostat housing and the right side is the WUR. Got prices from local Bosch Dealer and Saab Dealer. The prices they qouted were almost twice the price I paid for the car so have ordered a recon unit from the States
 

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16saabs said:
your trying to make a saab eater are you:nono; :cheesy:
Might be a Saab Eater as long as you don't have to go around a corner. The biggest problem is the design of the rear suspension. Have Installed a Swing spring suspension kit to uprate the rear suspension to Vitesse standard
 

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Beanbaggz said:


Here is the offending item. Bit on the left is the thermostat housing and the right side is the WUR. Got prices from local Bosch Dealer and Saab Dealer. The prices they qouted were almost twice the price I paid for the car so have ordered a recon unit from the States
My 85 900i (8V) has a broken +12 volt feed to the warm-up regulator and auxilliary air valve so at start up the car is really rough and idles at about 500 rpm until it starts to warm up. I don't think that would be a problem with other years as the 85's apparently had bad wiring harnesses, but it's worth checking that each of the key devices in the K-jet system are getting their power feeds properly.

Craig.
 

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Beanbaggz said:
Right Didn't have much time today as I was transplanting a 2000cc Triumph Vitesse Engine into a Triumph Herald
heh ... I owned a RHD Herald - can't imagine what it'd be like to drive one that could move!!!:cheesy:
 
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