308 QV Rough idle/miss? intermittent | FerrariChat
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308 QV Rough idle/miss? intermittent

Discussion in 'Technical Q&A' started by marcro, Oct 26, 2007.

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  1. marcro

    marcro Karting

    Oct 25, 2007
    68
    Canada
    Full Name:
    Mark Cross
    #1 marcro, Oct 26, 2007
    Hi there! My first Ferrari (1985 US QV 308 GTS) has 30K and has been running awesome until last week. When I start the car cold, it runs right up to 2K on the tach then settles down to 1K. Usually I pull away and all is good.

    Every so often (2 out of 10 times) it will start to idle rough both cold and warm and will spit/stumble a bit as I rev it up to 2-3K. I can still pull away OK and it pulls strong under load with no hesitation at all. It seems to clear up and then half an hour later as I come off the highway and pull up to a stoplight it starts to idle a little rough again. It never dips below 1k but I can 'feel' its not 100% I rev it up and it seems to clear up. This only happens the odd time and I dont want to start throwing parts at it without nailing it down.

    I'm starting to loose sleep at night...............
     
  2. Iain

    Iain F1 Rookie

    Jan 21, 2005
    3,354
    UK
    #2 Iain, Oct 27, 2007
    Could be one of many things but essentially its likely to be either a fuelling issue or an ignition problem. The latter is much more likely. However its a good idea to run a bottle of F I cleaner through with a fresh tank of juice just to make sure all the injectors are clean anyway.

    On the ignition side get an inductive timing light & see if you can figure out which cylinder(s) are misfiring & then start at the plugs & work backwards. If you are losing only one or two cylinders then the problem has to be either the plug, the extender, the plug lead or where the plug lead meets the Dizzy cap (i.e. either the connection into the cap or the cap itself basically).

    If you are losing a whole bank (and you'd know this because the thing won't rev past about 4K under load with a bank down) then you need to look at the cap, the rotor arm, the coil to cap lead, the coil itself or the crank sensor(s). In this case you need to start swapping parts over between the banks till you figure out which one is the issue.

    Favourite problems for this kind of symptom are either simply a plug lead not seated properly or an extender burning through - take them out & examine for scorch marks/holes - not expensive to replace. Another simple one is the longest plug lead may have come out of its clip & might be hanging down onto the exhaust & is melting through.

    If you end up taking the caps & leads off then check all the leads for continuity, clean up the crud on the rotor arms & the brass pegs inside the caps & check the resistance level of the leads themselves.

    Good luck!
     
  3. marcro

    marcro Karting

    Oct 25, 2007
    68
    Canada
    Full Name:
    Mark Cross
    #3 marcro, Oct 28, 2007
    Many thanks and I will try that! Usually by the time I get it up to my shop the problem is gone. I am going to try the FI cleaner again as well. I'm hoping its just a wire/plug lead or extender. Now that I think about it the odd time my Model A Hotrod does the same thing, its a plug that fouls and then clears up so your comments make sense. For some reason I had convinced myself thet it was fuel related or electrical i.e relays etc. Reading past posts it seems that some parts in the CIS can cause some grief as well as quite a few electrical issues. Once the weather turns a bit nicer I'm going to check those wires. Any ideas out there on where I can buy a good quality wire set?

    Mark
     
  4. f355spider

    f355spider F1 World Champ
    Owner Rossa Subscribed

    May 29, 2001
    18,055
    USA
    #4 f355spider, Oct 28, 2007
    www.kingsborne.com

    Or if you want oem, call Daniel at Ricambi America (one of our sponsors).

    Check those pesky plug extenders, and if they are original, would not be a bad idea to just go ahead and replace them too after 22 years. ;)
     
  5. marcro

    marcro Karting

    Oct 25, 2007
    68
    Canada
    Full Name:
    Mark Cross
    #5 marcro, Oct 31, 2007
    Ok, so the extenders are all new, so I popped off the distributor caps. Low and behold some nice crud on the contacts and on the rotors. I gave each wire screw a tighten (they all easily turned 1/8 inch), put some fresh high test gas, some cleaner and not a miss/stumble! (however I did state that it was intermittent....). It also went right up to 2K cold, which is always used to do before this problem started. The front coil wire also popped off very easy so I spread the connector a bit. The rear cap bolts were also only finger tight. (Just had a 4K service less than 1K ago, hmmmm)

    Going for a long drive on Sunday, keeping my fingers crossed......
     
  6. Iain

    Iain F1 Rookie

    Jan 21, 2005
    3,354
    UK
    #6 Iain, Oct 31, 2007
    Sounds like a bunch of stuff that could account for your issues. Hopefully you will have sorted it, keep us posted. Just have a good feel as to how loose/tight the extender-sparkplug connection is. Sometimes they can be a bit loose & you need to mess round with the wire spring thing in the extender to make the connection tight.

    I.
     

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