I reply to every thread Posted October 9, 2008 Share Posted October 9, 2008 VX HPC on Jenvey Tapers. MBE 956. For 2 years now I have had an intermittant problem. The car imposes a rev limit on itself of 5200 on occasions. It runs absolutely fine until 5200 but then hits a wall that it will rev through if pushed hard but with nothing like usual performance. I initially thought it was a fuel octane problem (it's a Swindon 235 spec). I thought this because on three occasions draining and refilling the tank "cured" it. Then plug leads were suspected as it was noticed after an incident that the Magnecor leads were not fully seated - after they were it ran fine. Then after its winter inactivity it did it again. A tank of fuel cured it. I took it to Classic LM with no issues (other than a small fire 😳 & a lost D/S tank cap ❗) over 800 miles. Then last week it did it again. Fuel didn't cure it and I'm now sure that it isn't fuel because after 2 minutes of hopefull HT lead waggling it ran fine. Coincidence 🤔 I've never waggled the leads to cure it before - as it isn't fuel the cure previously must have been passage of time (even just time spent in a petrol station. My crank sensor lead runs through the plug cover - could it be interference? Do coil packs fail intermittantly? Any know issues with MBE 956's - I think earlier MBE's had an issue but this led to a consistant misfire on 2 cylinders. Mine runs perfectly until 5200 (exactly every time). Link to comment Share on other sites More sharing options...
I reply to every thread Posted October 9, 2008 Author Share Posted October 9, 2008 Forgot to mention - The problem never appears whilst driving. It either has it from when I push it out the garage or not. Link to comment Share on other sites More sharing options...
Dickie Normuss Posted October 9, 2008 Share Posted October 9, 2008 I can't help much but do the recommendation was not to run the crank sensor lead under the cover with the HT leads, given the problem is intermittent though I'm not convinced it's that. Coincidentally I have a similar problem with my HPC but it's the other way around, slow pick up until about 5k when it then goes mental. So far I've replaced most of the sensors/leads etc. VX HPC - Loud and proud here Adding power makes you faster on the straights. Subtracting weight makes you faster everywhere Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 9, 2008 Share Posted October 9, 2008 Hi Matthew It does sound like an ECU/electrical related problem. I've never had a problem with my crank sensor cable routed under the plug lead cover but others have so it would be worth trying. Be careful not to let it get too close to the exhaust manifold (I wonder what makes me say that!) It could also be the sensor itself so if you can borrow one it might be worth swapping over to see what happens. They have been known to fail and also can respond to a clean apparently. Other suggestions, some related to the possibility that a mechanical resonance at 5200 is making something shake about a bit - check plug connection to ECU - pull out and spray with switch cleaner, working it in and out a few times 😬 - similarly ecu and fuel pump relays in their sockets and, indeed any other electrical connection. More likely to be ignition than fuel related by the sound of it unless its fuel starvation. When the problem is present, does it rev freely off load? If it does it might be fuel starvation - Check fuel pressure - pump or regulator could be shot - Change/clean fuel filters. If you have a submerged pump that's been in the tank for a long time its possible that its bag filter is clogged and, when you fill up, the fuel inrush washes it clean for a while (a bit fantastical I know but might be worth having a look). From your description it doesn't sound like a misfire, just loss of oomph, so I would have thought coil unlikely. Is it a standard coil and dizzy set up or wasted spark? If the latter, check the connection from the loom. Sorry, random thinking-out-loud going on Hope it helps. Let us know if you find the problem Paul Link to comment Share on other sites More sharing options...
Paul McKenzie Posted October 9, 2008 Share Posted October 9, 2008 Aves, I've found the plug leads onto the coil pack work loose over a period of time, although this has never given my VX a problem, I'm a bit surprised it hasn't . I've bodged it by pulling them off and nipping the contacts tighter with long-nose pliers. Give them a wiggle and see if one (or more) feels loose. If they are it seems to me to be more a problem of worn contacts on the coilpack, and it might be worth replacing that first rather than the leads. Paul Paul Edited by - Paul McKenzie on 9 Oct 2008 13:36:30 Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 9, 2008 Share Posted October 9, 2008 Paul, I've had the self same problem with my coil pack. I tried nipping up the lead connectors but I think, over time, the ridges on the coil pins have smoothed off so there is no longer anything for the leads to hold on to. I currently hold my leads in place with a large tie-wrap around the coil and plug leads, Its solves the problem but isn't very elegant and I'm thinking of making a perspex plate/lid that will hold them in place. I did get a new set of leads a while ago and they were ok for a while but the old problem returned after a short time. I would have thought that, if this is Aves' problem, it could manifest itself at any time rather than above specific revs. However, vibration can cause strange behaviour. Paul Link to comment Share on other sites More sharing options...
ECR Posted October 9, 2008 Share Posted October 9, 2008 I suffered from a random mystery rev limit for some time and discovered that because of the way I had routed the crank sender wire, any water/condensation that was about was retained in the plug on the end of the sender wire and shorted out the signal causing the problem. The socket into which the sender wire plugs has chanels to allow moisture to escape and this should always be the lowest part of the joint. If you look at the joint it will become clear ... If you have routed the sender wire under the plug cover the joint should be the right way up though (I think) Worth a look . Following through with this line of thought, any shorting between the wires of the crank sender will cause the same misfire so can you swap out the crank sender? If you need one to try I have a spare you can borrow. Link to comment Share on other sites More sharing options...
I reply to every thread Posted October 9, 2008 Author Share Posted October 9, 2008 Thanks for all these suggestions - plenty to be looking at - No doubt the Honda Lotus mentioned in my other thread will be so reliable that I can devote my resources to the 7 Link to comment Share on other sites More sharing options...
Anthony Posted October 10, 2008 Share Posted October 10, 2008 Aves, I have just the Long Term Swindon solution for you, which includes 8 injectors :-) Link to comment Share on other sites More sharing options...
Mike Biddle Posted October 10, 2008 Share Posted October 10, 2008 AVES, I had a similar problem with the same set up. I replaced all kinds of bits untill I discovered the real problem, it was a cracked inlet manifold. Now that should not produce intermittent problems but it did! Link to comment Share on other sites More sharing options...
TIM 5O Posted October 10, 2008 Share Posted October 10, 2008 Go on Aves take Anthony up on his kind offer and I may even help by taking those Jenveys off your hands 😬 Link to comment Share on other sites More sharing options...
I reply to every thread Posted October 10, 2008 Author Share Posted October 10, 2008 A cracked inlet manifold ❗ ❗ 🤔 🤔 I'd love to take Ant up on his offer but I am £10K light on a Honda type R conversion to my elise at the mo & Mrs Aves isn't best pleased. Link to comment Share on other sites More sharing options...
Mike Biddle Posted October 11, 2008 Share Posted October 11, 2008 Yes I know, weird but true, it ran perfectly after I fitted a new one. Link to comment Share on other sites More sharing options...
Don Cook Posted October 13, 2008 Share Posted October 13, 2008 I had a similar problem. Turned out that the voltage produced by the crank sensor was higher than the ECU was designed for. The output voltage from a VX sensor increases with revs and well exceeds 100v at 7000 rpm. This was overwhelming the signal conditioning chip. On cold days it would run fine for a while then start misbehaving as everything warmed up. Link to comment Share on other sites More sharing options...
Swiss_Tony Posted October 13, 2008 Share Posted October 13, 2008 Mr Aves Just reading this and unless i have missed something have you changed the crank sensor? They can do really odd things sometimes! If you have not got it the Bosch metal one tend to works better imo as I have had all sorts of problems with the plastic ones. If you have not tried it I have got a good bosch one you can try and see how it goes. James Su77on Se7ens Link to comment Share on other sites More sharing options...
F355GTS Posted October 13, 2008 Share Posted October 13, 2008 I'd second James's post re the CPS, a change to the metal Bosch item cured all Mark Link to comment Share on other sites More sharing options...
Dickie Normuss Posted October 13, 2008 Share Posted October 13, 2008 Maybe I should try the spare James lent me I just (maybe foolishly?) that a CPS either works or doesn't, can they work partially? VX HPC - Loud and proud here Adding power makes you faster on the straights. Subtracting weight makes you faster everywhere Link to comment Share on other sites More sharing options...
Swiss_Tony Posted October 14, 2008 Share Posted October 14, 2008 ric Have you not tried it? I assumed that you had! Well worth a go as they can cause wierd problems. Silly question but have you got it Old age is getting the better of me and I cant remember where it is James Su77on Se7ens Link to comment Share on other sites More sharing options...
Dickie Normuss Posted October 14, 2008 Share Posted October 14, 2008 Yes I have as well as loads of other things I've replaced VX HPC - Loud and proud here Adding power makes you faster on the straights. Subtracting weight makes you faster everywhere Link to comment Share on other sites More sharing options...
F355GTS Posted October 14, 2008 Share Posted October 14, 2008 Matt They can certainly partially work particularly when the get hot, they start to lose count of the teeth creating a misfire because it has to find TDC and start counting again. Mark Link to comment Share on other sites More sharing options...
Swiss_Tony Posted October 14, 2008 Share Posted October 14, 2008 ric I was not entirely sure where it was for a bit 😳 You plonker 😳 As soon as you get home get it on the car and give it a drive 😬 James Su77on Se7ens Link to comment Share on other sites More sharing options...
Dickie Normuss Posted October 14, 2008 Share Posted October 14, 2008 Yes boss 😬 VX HPC - Loud and proud here Adding power makes you faster on the straights. Subtracting weight makes you faster everywhere Link to comment Share on other sites More sharing options...
Dickie Normuss Posted October 14, 2008 Share Posted October 14, 2008 Changed the Crank sensor and went for a blat. 😬 😬 😬 with added 😬 I can't be 100% sure just yet but it looks like that was the issue. Just need to sort out the other issues. Aves, sorry for the hijack but may be worth trying the crank sensor. VX HPC - Loud and proud here Adding power makes you faster on the straights. Subtracting weight makes you faster everywhere Link to comment Share on other sites More sharing options...
Swiss_Tony Posted October 15, 2008 Share Posted October 15, 2008 ric Thats good news 😬 Just need to sort out the other issues I am not entirely sure that a new crank sensor will sort out your other issues ric I have no personal experience in this field but my recommendation would be to start wearing mens clothes again and maybe it will feel right after a little while. Hope that helps James Su77on Se7ens Link to comment Share on other sites More sharing options...
Dickie Normuss Posted October 15, 2008 Share Posted October 15, 2008 Get a bloody job James ❗ Still going to come round to your Vx clinic to look as the rest VX HPC - Loud and proud here Adding power makes you faster on the straights. Subtracting weight makes you faster everywhere Link to comment Share on other sites More sharing options...
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