Hi i have a 89 TN Magna 2.6 Ltr (Carby Model), when we first start the car and until it warms up it blows thick black smoke, stall's and chugs. Once the car is at running temperature it is fine and runs nice, although is chewing the petrol a bit. Does anyone have any idea's as to the possible cause or causes?

Thanks in advance, Daz.

A very common problem on these is the auto choke, lift off your air cleaner cover, see where the choke is when cold, start and warm it up for a while, give a rev and see if teh choke plate backs off

You may have a broken spring or loss of power to the choke assy.

Black smoke is too much fuel and this is also told by your consumption

I am happy to look at it but I would need to have the car overnight so as to have the engine dead cold when tests are done

If i am standing at the front of the car leaning in toward the carby there seems to be two throats in the carby. the choke plate is the one that is closest to the windscreen isn't it? Actually note sure where the choke plate is.

Sorry another edit, i have the Gregory's workshop manual at home i will use this as a reference.

Madmagna, how close are you to Keysborough? Cheers Daz.

I have a similar problem on my EFI model TP, minus the black smoke. It runs really rough at first, and if its a cold morning it stalls and i need to rev it a bit to warm it up. I normally let it run for 30s-1min on a normal morning before putting it into gear and its fine from then on, but EFI shouldnt have these problems right? cos the choke setups completely different?

EFI doesn't have a choke as such. The ISC motor is told to give the engine more air by the computer, taking its input from air and water temperature sensors. The computer then feeds fuel in to give the right mixture as determined by the oxygen sensor. A high and smooth idle @1200 rpm approx results on cold start up. If the idle speed on cold start up is too low, suspect the ISC motor, temperature sensors or oxygen sensor.

The carb choke works differently. A wax pellet when cold pushes against a strong spring and partly closes the choke valve and opens the throttle a bit. As warm water flows past the wax, the wax shrinks and allows the spring to open the choke fully. Check the choke setting - its in the manual and involves removing the carburettor from the car - and the hoses that feed hot water to the carb. Also, the thermostat is involved here. If it is defective and not closed when cold, it takes much longer for warm water to reach the carb. On a properly functioning setup the hoses to the carb get warm after only 10 seconds after startup. More like 5 minutes if the thermostat is open when cold - the choke stays on and the engine loads up with excess fuel.

Good luck sorting this out!

Cheers, thanks for that i will check all of the hoses this morning for temp.
Might be easier just to go get me a s/hand job from the wrecker and swap them over! ;p

Daz.

Second hand carbs from the wreckers will be in the same or worse condition than yours! Been there done that! Better off doing the fault finding/tuning yourself.

EFI doesn't have a choke as such. The ISC motor is told to give the engine more air by the computer, taking its input from air and water temperature sensors. The computer then feeds fuel in to give the right mixture as determined by the oxygen sensor. A high and smooth idle @1200 rpm approx results on cold start up. If the idle speed on cold start up is too low, suspect the ISC motor, temperature sensors or oxygen sensor.

Hey thanks for that :)
When I start it up it ideles alot lower than 1200, maybe 600-800 depending. never any higher though. Maybe I'll have a look into replacing these parts all in one go as they are all fairly old I suppose and replacing them all at once will save me hassle in the future. any idea on how much these parts cost?

ta
-Matt.

Try raising the idle speed with your right foot to 1200-1500 on startup and see if it runs better. Sounds like the ISC motor - do the revs drop when the engine is warm and you turn on the air or lights? The ISC motor, if working, should up the idle speed. If the speed drops, it is definitely the ISC motor. They usually burn out one of the coils inside after 180,000km or more. I would test/swap this out first. ISC cost? Try eBay, that's where I got mine from. $60, but that was like 3 years ago.

Try raising the idle speed with your right foot to 1200-1500 on startup and see if it runs better. Sounds like the ISC motor - do the revs drop when the engine is warm and you turn on the air or lights? The ISC motor, if working, should up the idle speed. If the speed drops, it is definitely the ISC motor. They usually burn out one of the coils inside after 180,000km or more. I would test/swap this out first. ISC cost? Try eBay, that's where I got mine from. $60, but that was like 3 years ago.

yer I reckon youve hit the nail on the head. when i rev it to about that much it is much smoother. my engine mounts arent in greatest shape either which probab;e makes the problem worse. the car has done approx 165ks but this engines on about 140ks so yer ill look into it.

Thanks very much, appreciate your help mate,
-Matt.