Hi Everyone
I'm new to this forum and seek advice. I bought a 2000 vintage 406 coupe 2ltr automatic (100 000 miles) a few months ago and have been generally satisfied with this vehicle barring one minor - but irritating - problem.
This problem occurs when the engine is cold, irrespective of the ambient air temperature. The engine fires immediately when started and idles reasonably smoothly in Park and in Drive at about 700-800 rpm. But when you try to pull away, the engine splutters and burps and hesitates and all but dies in the rev range 800-1300rpm. I discovered a user-workaround is to first rev it sharply but briefly to somewhere above 3000 while it's still in Park. Then when it idles again it can be put in Drive and it will pull off fine as if nothing bad ever happened.
I took it to the agents who followed a computer diagnosis and replaced an engine speed sensor. They also replaced the plugs with a set of multi-electrode ones. I had my doubts on the logic in this and predictably it made no difference; if anything it's slightly worse. I'm reluctant to let the agents tinker further, because I don't want to get into a fruitless and expensive loop of guess-replace-charge.
I decided I might investigate this problem myself, because intuitively I think it may be mixture-related or timing related. I have good mechanical skills and experience with cars of the 1970's and 1980's. Of today's generation of cars I know very little, but I am a hands-on electronics engineer, have access to scopes, function generators, frequency counters etc. and know how to use them. As a start I've ordered a Haynes manual.
Can anyone give me some advice on this problem? Does it ring any bells?
Cheers
John
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