Hey So I've just recently completed a service and a few extra bits i was hoping would help solve a misfire problem I've been having but no luck still the same as it was before new 02 sensors, new spark plugs, new fuel filter,Detonation sensor installed (was not there before :/ ) and oil changed. also this is a 92 TT MT running 14psi on high flowed stockies, bigger SMIC, pod filter and JECs 740cc injectors with supposedly tuned ECU but no proof My problem i'm having is it always misfiring when reving (not under load) whether warm,cold, at idle rpm or holding anywhere throughout rev range the miss is not consistent like once or twice every second but intermittently. But when driving under load it is only noticeable up until boost kicks around 3k rpm then it clears up, it happens much more commonly and more noticably (like running on 5 or 4 cyl) when below operating temp) once warmed up it seems to go away firstly things I have checked tested so far spark - is there on all 6 cylinders, new s2 ptu 7,000km's ago all coilpacks are go, new plugs just installed NGK iridiums, connectors going to coilpacks are fine) fuel - injectors are JECS 740cc 7,000km's old and firing in sequence (checked only by listening for ticking not flow tested etc possible suspect), injector connectors are brand new as of 7,000km's ago and make a difference when pulled off and on so all good there, filter is new, fuel pump seems to be fine is stock and untouched,running standard fuel pressure reg but is linked up to pressure gauge (defi gauge) showing up to 85psi i thought the stock reg was meant to hold 43 psi? also found when looking at fuel system i dont have a fuel damper at all! (another possible suspect) all fuel lines are fine no petrol smell anywhere vacuum - 100% no vacuum leaks checked every single line, hose and clamp many times ECU - is one of the other possible suspects as I am unsure if the person who built my engine actually tuned it for the injectors or not also have done - compression check 130-135psi on all cylinders - timing check with a timing light and the crank pulley was lined up with the 20 deegree notch (not sure if thats advanced or the other way?) on the timing belt cover taking induction off cyl 1 - ecu talk fault code check - ecu talk is showing up code 34 det sensor but with 0 in the box that says how many times the code has been read since engine started? even though i have connected up the det sensor now? but already had this problem before detonation sensor was installed? - TPS is steady on 0.46
Hey Xave, I'm going to go with coilpacks/connectors/wiring, injector wiring, or perhaps you have a sticking valve? Hope you get to the bottom of it! Have you changed spark plugs?
For starters, the timing is normally set at fifteen degrees plus or minus two degrees, not twenty. However if the engine has been tuned, twenty could be the optimum setting. There comes a point where voltage, continuity checks & viewing spark at the plugs may not provide enough information. Could be time to analyse the injector & ignition waveforms.
when you changed the air filter did you check and clean the MAF connector? Have you checked and cleaned the CAS connector. like East coast says, 20 may be a bit too much, try it at 15 and see how it goes... either use the dr300zx software to see what is written on the eprom.. or an easy check is to remove the ecu, open it up and check to see if the eprom is removable... or has anything on it to indicate it's been mapped. if it's also running rich it might be worth checking the ecu temp sender unit.. good luck
No problem not having a fuel damper. Your issue sounds to me like bad O2 sensors, mostly because of when you said it clears. What brand are your replacements, how old are they? I had similar symptoms with bad O2's, 18 month old eBay spec units.
