brumster 135 1 Cars Posted June 12, 2007 Looking for some separate insight into this problem I have; have a couple more ideas but would value any additional thoughts. Who knows, if I'm lucky, someone else may have had the exact same problem. Started like this - car was running fine, running a beauty in fact, and on Stage 4 of a recent event we pulled up to the finish control to find her unwilling to idle. We managed to complete the event because, thankfully, once up above 2500-3000 revs or so she ran perfectly fine - just a real erratic idle. No biggy, I thought, just some part of the ignition system most likely... Got car back home and set about replacing ALL of the following, to no avail :- Coil (new) Ignition Amp ECU Throttle pos sensor Water temperature sensor Air flow meter Leads Plugs (new) Dizzy cap Dizzy arm (new) Dizzy itself Injectors (put another set on) After all of this and still no result, we suspected cam timing, so checked it and it seems okay (need to ring Skip Brown in a second to make sure there's nothing weird with it). Next was thinking a sticking valve, so checked compression - 190 across the board so no worries there (it's a Skip Brown Grp.N blueprinted engine from an ex-challenge car). During all the swap-outs it's got a little worse now, such that it is very rough on idle (it barely idles at all) with the occasional 'burst' up to revs. This doesn't last long before dieing again. Lots of popping, banging and farting back through the inlet manifold. Interestingly if I swing the dizzy (clockwise - advancing, therefore, I believe?) it gets 'better' (although still nowhere near good enough). All I'm left with thinking now is the fuel pump might be on it's way out, and the pressure poor? How much should it flow in good condition (please specify in multiples of coke bottle sizes ) within a given time? Any other thoughts? (Off to ring Skip B...) Share this post Link to post Share on other sites
Richie-Van-GTi 71 2 Cars Posted June 12, 2007 stick it on a co meter and check if its fueling correctly, assume youve checked for air leaks? If it were fuelpump I would expect it to be wors higher up revs, I know when mine failed it became impossible to rev over 3500rpm when under load. Theres was a thread in last day or so about flow rate of the pump, check XU engine forums, its on the 1st page anyway. May also be worth checking the wiring, it could just be a badconnection somewhere causing issues. One definatley worth checking is the ECU temp sensor as when either the sensor or wiring fails it will idle like a pig. Share this post Link to post Share on other sites
brumster 135 1 Cars Posted June 12, 2007 I'll drop the inlet manifold off tonight and give it a good looking over; certainly no obvious air leaks but I need to check that pipe on the underside of the manifold (I can just about see it's still on there, but can't physically reach it to check for sure). The wiring thing is the one that I dread, but suspect the most! Right - off to the garage, see you all laters! Share this post Link to post Share on other sites
brumster 135 1 Cars Posted June 12, 2007 Hmm, interesting. On closer inspection it turns out a manifold stud had sheared. On removal of manifold, the gasket was rather squishy and kinked/folded, and I'm not sure if it's just because of how I removed it or whether it was like that in-situ, and has been blocking the injector or air flow in general. It might even have introduced a little air (or, heaven forbid, water - although I think that's unlikely) into the inlet stream. Hard to tell really, but I'll get a new gasket tomorrow and re-fit and we'll see how it is... it's a long shot, but you never know... Share this post Link to post Share on other sites
brumster 135 1 Cars Posted June 13, 2007 Sorted it, thank goodness. It was indeed all down to the sheared inlet manifold stud. You wouldn't have guessed to look at, but I guess it was leaking in air or the gasket was part-blocking the injector as I refitted it all back up with a new stud and gasket, and she's back to her normal self. It all echoes to me to "believe in your first diagnosis" and chase that elusive reason rather than veering off onto other possible problems and just confusing yourself! Everything pointed to a weak mixture at low revs (shown by the amount of advance that the engine would take before it started to run semi-better) but I convinced myself that swapping every bit of the Jetronic was the way forward! Oh well; you live and learn. Right, back to some driving now... and time to stick this mi16 in it too Share this post Link to post Share on other sites
