It runs the dBilas ABF kit, which uses standard management and sensors with a piggyback chip. It's all been balanced (and I've rechecked it since), so this side of things is ok. ------------ I've just realised something, though, and this may well suggest a vacuum issue: if I pinch the MAP sensor line at idle, it doesn't affect the idle much - I would have thought this would flood the engine and make it stall
Keep at it! There's nothing this motor wants more than to be in rude health and beating on the local ricers Now, just where is that vacuum leak! And, is it the only issue?
Ok, another update - I've just spent nearly four hours going over all the vacuum lines, coil wiring, rechecking compression and spark etc... and results: - There are definitely no vacuum leaks! - #1 still has very strong compression - spark is there consistently, but does appear to be weak - though, I need to check it with a proper spark tester, rather than sitting it on the strut tower brace, so this may make a difference - #1 still not firing at idle: you can even feel the 1st branch of the exhaust manifold is cold and only heats up after revving the engine - unplugging hall sensor makes no difference God knows what to check now Should I bite the bullet and try a dissy?! They are fecking expensive new, though
Distributor/ht leads/plug troubleshooting trick Glad vacuum has been eliminated Re the dissy, unbolt it and turn 90 degrees, retain in position with a custom cut piece of flatbar of the appropriate length with two 6mm clearance holes so one capscrew and another with nut prevent the distributor turning Now move the ht leads one hole around the cap, start and see - -
could you not bolt it on 180 degrees out instead? one thing, take the cap off but leave the arm on and crank it over, make sure the arm isnt all wobbly. as i say though, pull the plug off the hall sensor on dizzy and that will rule out the dizzy entirely. car will switch to batch fire and run pretty much the same, on mine with the dizzy unplugged its slightly more jerky on/off throttle and feels more 'raw' but runs just fine apart from that, still pulls to the rev limiter
Tried this and runs exactly the same I've also checked for wobbliness of the rotor and that's fine too... The new cap is also wearing evenly. It's very unlikely to be the dissy, I suppose, but I'll try anything to fix this minger!!!!!! Next step is to fit a 24v, I think
P.S. Should also add, I took it out for a longer drive last night (about 1.5hrs) to see how it goes long term and it starts to develop flat spots around 3-4k and also stammers a bit when cruising on the highway. Also, holding it at 4k causes some missing, then dumping full throttle occasionally gets a massive flat spot... How excellent! Still feels very flat in the top end too, when it should be the complete opposite, even when lugging a pig Mk3!!
Elusive combination - - Reviewing this thread, it does seem likely several weaknesses are combining to create intermittently unfavourable combustion chamber conditions[:^(] Tristan pre-empted my suggestion by asking whether you had rotated the dissy and re positioned the leads - - you responded by saying you'd swapped the leads; this does not test the dissy cap which, if so manufactured, may have an excessive gap between #1 conductor and #1 plug lead connector which one cannot measure because it's sealed WITHIN the cap material The resistance created by this air gap may be compared to the other three with an appropriately set multimeter He also questioned the injector, and you responded by saying they had tested ok - - were they checked whilst still attached to their fuel supply hoses, which can develop internal blockages? And what of the fuel distributor itself - - can you check by removing all injectors, reattaching the fuel lines, laying the assemblies out on a towel or similar, activating the starter and looking for symmetrical spray patterns, fire extinguisher at hand as previously? Have faith - - it's ALWAYS something simple - -
Have re-checked fuel delivery and all is ok here too The next theory I have: ...The head was recently rebuilt - could this be a lifter/valve problem due to poor re-assembly (the shop was pretty hopeless and even put the cams back in one tooth out!)? I'm starting to think it may well be something mechanical, especially given I've checked and replaced pretty much everything else. What's the best way to check for a sticky valve etc?
Time for another update! I've since bought a good spark tester and found that spark on #1 is blue and very strong (fuel delivery, pressure etc has also between triple checked) The issue persists with no firing at idle from #1 and occasional missing on this cylinder. I recently decided to remove the rocker cover to investigate further and found something interesting... As I rotate the engine and watch the intercam chain, its tension fluctuates a lot as if the cam sprockets are unevenly worn or the cams bent! It goes from being very tight to slack as I rotate the engine around and is surely meaning the cams are losing alignment by several degrees... Why this would affect #1 more than the other cylinders, I don't know (any ideas?), but I think I'm onto something. I can only assume that the guy who rebuilt my head screwed up the install and bent the cams?? I'm inclined to purchase some new cams and a fresh chain... Opinions? This has to be a mechanical issue now, as I've tested and/or replaced everything else!!! P.S. I should also add that you can hear some excessive noise from the top-end at idle. I really think this is a cam timing issue caused by the fluctuating chain tension... Especially because it is far worse at idle when the chain is carrying less velocity and is more likely to allow the cam timing to "float" in and out of alignment. The only question is why is #1 the worst affected cylinder...
I wonder if one (or more!) of the lifters on pot 1 has been left out accidentally during the rebuild? I can't help feeling you'd have noticed while you were looking at the chain though!
All the lifters are definitely in place! Whether they're working properly is another thing, though. When watching the valvetrain whilst turning the engine over by hand, everything seems to be working fine, but clearly it isn't. I'm actually considering replacing the lifters on #1 while I have the cams out. There has to be something wrong with the valve actuation, but exactly what I really don't know as the compression test is perfect, so I'm thinking there are no bent valves. If I ever fix this problem, there's going to be a huge celebration!!! Anyway, I've ordered a new intercam chain and have got hold of some different cams too. I'll fit them next week and report back on my findings...
Not by my reckoning. Don't have an ABF lifter to measure up, but I'm pretty confident that the minimum effective length will be significantly more than the maximum valve lift. Therefore it's a miss. Bit academic though, as the OP is sure they're all there.
Wrong car! This is my Mk3, which now sits in bits until I can be bothered stripping the engine down to find out what the hell is going on... So, no, still no solution, after replacing no end of parts and everyone from plebs to high-end Bosch engineers looking over it [:^(] It now looks something like this
aw shoot , love hearing how the tiny widget on the end of the doobry had a split seal and fixed it...
