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9-3 not firing on cylinder one

10K views 12 replies 3 participants last post by  russell31 
#1 ·
Hi all i have picked up a saab 9-3 convertible for cheap but has a bad misfire. ok lets gt to the problem, i have worked out that its No.1 not firing i have pulled the HT leads one at a time to check, the spark seems ok as can hear it "popping" when near the plug, i also dont think its fuel related as the car has been fitted with LPG and wether running on lpg or petrol it still does not fire.

ok thats that any help would be very much appreciated, a few extra things you may need to know is, its a 1999 non turbo, with the early engine, and a manual, thanks in advance chris
 
#2 ·
Hi Chris,

Hopefully it is something simple. Likely candidates from what you describe are:
Plug leads, dist cap and/or rotor arm. on that age of car i would replace them all. If one plug lead is failing then it is likely the other three/four are not to far behind. to test this try swapping this lead with another on the dist cap and plug/cylinder (swap no's 1&2 around), if the missing then moves then it is very likely the plug lead at fault, if not then rotor arm and dist cap. You can try cleaning the electrodes with wire wool or fine emery cloth to see if this improves things - also look for fine cracks in the cap as this can lead to shorting out. otherwise it could be a shagged distributor or worse still valves/head issue.


if it is no1 which is missing then i would replace the plug lead, they are normally sold in sets and if one is failing then
 
#3 ·
Thanks for the reply, just tried swapping 1+2 and it made no difference, if i pull the lead from the dist cap while its running there is a lovely big spark that can bee seen, i do think it is going to be a head job/no compression the head gaskets on these ok to do or a pain in the butt?
 
#4 · (Edited)
ahh, i see what you are saying, you have a spark at no1 but it is still not firing or appears not to be firing. Pull the plugs first, check the colour of no1 compared to the others, it should be a light brown/grey colour you will notice the difference between it and the other three if the plug is faulty. Try swapping the pugs around to see if the misfire moves, if not then suggest a compression test. Is the coolant clean? any signs of oil/contamination and likewise the oil, any mayo build-up in the cap, if the car has been stood or doing short runs there may be a little mayo due to condensation.

Compression testers are relatively cheap, around £20.00 or so. It may be worth investing in one. Remember to get the car warm before testing.

http://www.google.co.uk/products/ca...a=X&ei=84iJT4X7CsyIhQf7x5DRCQ&ved=0CGMQ8wIwAA

http://www.screwfix.com/p/engine-compression-tester/16856#
 
#5 ·
To add, if it is the valves you might want to look at the LPG system and also the petrol fuel injection to check the mixture/fuelling is correct. 110k miles is not a lot on a modern engine these days.
 
#6 ·
thanks, ok just got a compression tester on ebay fo £11 so should help me out a little, looking up parts a headgasket kit is only £60 plus £28 for bolts so not too bad i suppose, i will update on my findings. is there a way to check fueling mixtures? surely what its putting in No.1 the same will be going in the other 3?
 
#9 ·
Best done by an auto electrician or local indie/garage with the right kit to test the functionality and fault find the problem(s). It should show up on the diagnostic kit. swapping the injectors/maf is relatively straight forward, it is the isolating of the problem(s).
 
#10 ·
Be wary of a compression test as I'm not sure under what conditions you need to test a Saab engine.
When I changed my BMW 320 engine for a 2.5 unit I tested the compressions although I knew the engine was fine and only two showed up any compression.
I later found out that that particular engine can only be compression tested when it is at operating temperature.
Silly I know as when you have low compression normally you can't start the car.
 
#11 ·
compression tests should only be done with the car at normal operating temperature. Re the car running with low/no compression if you have no compression at all across the cylinders then no it will not start. if a couple of cylinders are low or no compression at all then it will run - but roughly. dependant on the year of your bm some engines can shut down individual cylinders so save fuel - the ecu controls this and opens the exhaust valves slighly on the shut down cylinders so they are not compressing the cylinder.
 
#12 ·
ok cool, well the car starts and drives ok so can get it up to temp easy, disaster struck today, driving it down the road changed gear but she didnt :( gear linkage snapped in half not good, ah well changed her to first by hand an limped home, a load of epoxy putty, mix glue and fibre glass later seems to be stronger tha a new part :). so still just waiting on that tester kit.
 
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