bx trd turbo: rough idle for a few seconds

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freek
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bx trd turbo: rough idle for a few seconds

Post by freek »

5 years ago I changed the engine of my bx for a A8A with a LucasCAV fuel pump. Since app. 2 years I noticed that when the temperature is below say 10 degrees C the engine idles a bit rough for a few seconds when the engine is cold. It starts instantly, and runs perfect for 2 seconds, than the rough idle begins for 2 or 3 seconds (with blue smoke) and after that it runs perfectly. With higher temperatures this does not occur.
Does anyone recognize this behaviour or knows what might be the cause? The engine is in quite good shape I think: less than 1 liter oil on 5000 km. I changed the heater plugs and the wax thermostat.
I my self think of:
a) the preheating system (however: the warning light burns for 7 seconds and the relais cuts out in app. 15 seconds),
b) the fuel filterhousing with hand pump (purflux filter; I heard that this can cause trouble as well because of air leaks,
c) injectors not 100% (leaking?)
d) compression not 100% which shows under these circumstances
What could be the most probable cause?
Furthermore: there is a hose from the intercooler to the overfuelling device. To this hose another hose is connected which goes to the left side of the car near the battery. There it ends with a relais or so. Does anyone know the meaning of this device? Is this for Bosch en Lucas CAV pumps the same?
I would be very grateful when anyone replies to my questions! Great idea this forum.
Freek Hofker (Holland)
louis1
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Post by louis1 »

Hi i have the same problem but without the blue smoke. I dont think that it is anything to worry about because when my head gasket went on it 10,000 miles ago i had a new head, head gasket, injectors and a full service and it still runs rough on cold mornings. It uses no oil or water and runs nice, but let me know if you find the problem.
tomsheppard
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Post by tomsheppard »

Thick, cold air and thick cold oil working together. Smoke may well be condensing more easily on a cold day. I think that you could spend a lot of time and money worrying about this and find that you cannot do anything about it. I am fairly sure that it is not a problem. I suppose that you always start the cold engine with the clutch down?
Dave Burns
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Post by Dave Burns »

Could be air getting in, as the temperature drops and objects contract even further its possible that a gap may open up somewhere.
Try pumping the hand primer for a few moments before cold starting, if it makes any difference that gives you somewhere to begine the search.
The pipe going down by the battery operates the turbo overboost light on the dash.
Dave
jeremy
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Post by jeremy »

On my 89 DTR Turbo the glowplug warning light glows for quite a while longer when the temperature drops to about 10C. The difference is quite noticeable but never having had to investigate I can't be much more precise than that. As long as I wait until it has extinguised it starts without problems and idles (a bit faster) smoothly. Are you getting the longer heat?
Blue smoke suggests lubricating oil?
jeremy
JohnD
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Post by JohnD »

I'm inclined to go along with Dave's theory. It sounds as though it's running roughly while it disposes of a few air bubbles.
oilyspanner
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Post by oilyspanner »

Mine used to do that, I changed the fuel filter body which did the trick, likely an air leak somewhere, also check the stiff fuel line from filter to pump.
Stewart
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