My 348 has recently started to give me the jitters when it first starts from cold. It will fire fine but for a few seconds will idle around 700 revs before jumping to the normal circa 1200 revs. It makes me initially feel that its going to cut out. Any thoughts, is something slow in cutting in. - What do auxilliary air valves do ? I am just curious in case matters take a turn for the worse and it won't start altogether. Thanks
Check your vacume hoses. Make sure that they are all hooked up properly, and that they aren't leaking.
It's been said over and over, but the first thing to try might just be to re-initialize the electrics on the car (numerous mentions in archives) and DON'T touch the throttle when you restart the car or the ECU will store faulty throttle position reading (if I understand correctly).
Thanks Guys, I had already done the 'system reboot' without success. I will check over the vacuum pipes John
I'll step out on a limb, and guess you've got some problem that is causing 1 fuel pump side to come up to pressure more slowly (or have a longer way to come up from a lower residual "off" pressure level -- i.e., the check valve function is not working) so the RPM transistion is going from running on 1 bank initally to 2 after the second side fuel pressure comes up. 1st question -- Are you saying that, in every other way, everything is PERFECT operationally. You never get some of the same behavior (even to a lesser degree) after a warm restart (like, say, after a couple~few hours sitting)? 2nd question -- Is it doing it at every cold start with repeatable time-from-light-off vs RPM behavior? AAVs are rather a "slow" thermo-mechanical mechanism so IMO it's unlikely that it/they can cause a repeatable, quick step function in RPM (but never say never )
91 tr, 1- yes, everything else appears normal. 2 - It only happens at cold start at its repeatable - but only after initially starting, if I start, then start again, everything is OK
Well, you haven't said anything that would allow a check valve function problem to be ruled out. Your report that an immediate 2nd cold restart is fine also points in that direction (i.e., your report that "few seconds off = no problem", "few hours off = no problem", but "overnight off = problem" indicates a fairly long time constant which is consistent with a slowly leaky check valve). Ideally, I'd ask: "if you run the fuel pumps manually (by bypassing the controls) with the engine off for 10~20 seconds before an initial cold restart is the problem eliminated?", but this probably needs the wiring diagram and/or WSM to accomplish (and isn't much less complicated than making a direct fuel supply pressure measurment on each side so you're getting to the point where you need someone with the Motronic/348 documents/tools to get involved) -- sorry I can't be more helpful.
