Stumble when cold

[urq]

If the problem happens at a very consistent point in the warm up another 
possibility might be the OXS.  If the stumble occurs right after a cold 
start up the OXS is not the cause, but if the car runs well at first and 
then stumbles at some point during the warm up ... then works fine afterward 
... and you know the OXS has not been replaced lately ... you might want to 
consider this.  Once I got an aftermarket sensor that was not made by Bosch, 
and had a problem where the car would stumble in a very predictable way ... 
in fact it would be at almost the exact same point on the road!

Tony H's advice would be worthwhile following through with as well ... the 
Control Pressure/Warm Up Regulator is a mechanical device and can have 
issues after 20 years in service ...

Don't forget to check the ECU codes ... there may be a clue there ...

Steve B
San Jose, CA (USA)
>
> Lately I my 86 5kcsq has had a stumble when cold. It starts fine and idles
> fine. But any application of power, and it will stumble for a few seconds
> and then smooth out. This only happens when my engine is less the 75% 
> warmed
> up.
>
> Sometimes the stumble will be serious enough to cause a backfire. The
> problem goes away once the engine is warmed up. Any suggestions would be
> much appreciated, any extra information that would be helpful in 
> diagnosing
> this I would be more then happy to provide.