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  1. #1
    Junior Member
    Generation
    3rd Gen
    Model
    Si 4ws
    Join Date
    Nov 2010
    Location
    Queensland
    Posts
    32

    Question 1989 Prelude hard cold start

    Hi folks, I have a 1989 Prelude (manual), for the last 2 months (notably after sitting mostly unused for several months with the same fuel) it's been hard to start on a cold start (I.e. engine has cooled back down, nothing to do with winter etc.) requiring about 10 seconds of solid cranking to properly kick over and run and then runs pretty rough for another 20 seconds or so. On a warm start it starts up pretty normally first time. Just about gone as far as I can with my own troubleshooting and now stuck so thought I'd reach out to the community in this late stage, things I've done:

    • Air filter (already had for service)
    • Fuel system/injector cleaner
    • Few tanks of fuel since we first started driving it again
    • Fuel filter (already had for service, put in after fuel system cleaner)
    • Spark plugs (old ones looked pretty normal, nothing that stood out against a spark plug chart)
    • Upper engine cleaner/foam (probably waste of money... ah well)
    • Cleaned IACV (idling a little better now)
    • Ignition leads were within spec for resistance according to the workshop manual
    • Injector resistor resistance was a tiny bit higher than spec according to manual (like 8.5ohm instead of max 7 etc.), they were all equal and not much mention of them in forums outside doing engine swaps so doesn't seem like the sort of thing that fails often
    • Main relay tested according to manual and all fine
    • Gave up and took to mechanic who suggested problem with injectors or further down in intake manifold or MAP sensor given no hydrocarbons in the exhaust on cranking, was also dying with any throttle while still running rough (mechanic stated as no throttle response) which would suggest no fuel/lean?, otherwise good fuel pressure and flow so effectively ruled out fuel pump or fuel pressure regulator??
    • New injectors after mechanic advice (in original Honda packaging for $80 off eBay!! cheaper than getting current ones cleaned).
    • No error codes flashing on ECU however has only had a day of driving since pulling the ECU/clock fuse a few days ago
    • Starter motor also now been swapped with one from wreckers (presumably brushes/commutator worn down last little bit after all of this hard starting)
    • Fast Idle Valve disassembled/cleaned/reassembled


    Notably after doing the injectors it's starting a lot better (and running better straight after start) but now requires 4-5 short cranking attempts/bursts before it starts instead of the 10 seconds of cranking, otherwise it just turns over a few times and dies. I haven't checked the MAP sensor properly, had a play kinking off vacuum hose to it and the engine responded so it's not completely dead if it is faulty at all. In amongst this I've been trying to swap the oxygen sensors (because figure ones in there are originals so why not, had them before this problem popped up)... they're still in the manifold but FUBAR from my attempts to remove them so are effectively out of action, as far as I know being the older non-heated sensors the ECU doesn't use them until everything is nice and warm so shouldn't be causing the starting problems.

    Any ideas? Would appreciate any advice, Cheers.
    Last edited by brodsta; 6th May 2016 at 12:39 AM.

  2. #2
    Junior Member
    Generation
    3rd Gen
    Model
    Si 4ws
    Join Date
    Nov 2010
    Location
    Queensland
    Posts
    32
    For anyone curious, it ended up being the coolant temp/ECT/TW sensor. Swapped new one in this afternoon and starts first crank now.

  3. #3
    PA Janitor Bob's Avatar
    Generation
    3rd Gen
    Model
    Si 4WS - B Spec
    Join Date
    Jan 2006
    Location
    Western Australia
    Posts
    11,091
    Cheers for coming back with your findings. It may just help someone someday.

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