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| Home > Help Needed / General Tech Chat > Anopther misfiring problem, Megajolt | |||||||
 1060 Posts Member #: 588 Post Whore Delaware, USA |
26th Apr, 2008 at 11:36:09pm
I finally got the engine started again today after 6 months waiting for parts. All went well and it started first time. It idles fine and runs OK but when driving It gets into a bad misfire...
website:- http://www.terryhunt.co.uk
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 4559 Posts Member #: 786 Post Whore Bermingum |
26th Apr, 2008 at 11:39:54pm
Hi,
VEMs Authorised Installer / Re-seller. K head kits now available!
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1060 Posts Member #: 588 Post Whore Delaware, USA |
27th Apr, 2008 at 01:18:27am
I just let it heat up at idle for a while until the fan came on, and i am not getting any missfire free revving at all..It takes a few mins driving to make it miss.. I would expect a sticky valve to show itself at least once when I am at home!! website:- http://www.terryhunt.co.uk
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 6753 Posts Member #: 828 Post Whore uranus |
27th Apr, 2008 at 01:50:58am
could it be a lean backfire tel? do you still have the bimetalic strip holding the jet ? Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM |
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1060 Posts Member #: 588 Post Whore Delaware, USA |
27th Apr, 2008 at 04:24:55am
On 27th Apr, 2008 robert said:
could it be a lean backfire tel? do you still have the bimetalic strip holding the jet ? I do but its been OK for all of last year even in real high ambients. Just did some googling and the lean misfire point is at AFR 16-17 Mine is nowhere near that when it starts. missfiring, when it starts the afr is normal and then slowly works its way to 15 or so, Apparently any missfire will give false lean readings because of unburned fuel and I suspect thats what I am seeing. Therefore I am not convinced its a fuelling problem.. That leaves ignition and compression.. I eliminated all ignition parts I could and it still could be ignition but on the compression side, standard sized manganese bronze guides were opened out by the machine shop and I'm worried that he did not open them enough and when I put any heat stress into them they start sticking. Now I think of it the missfire only comes in after I have hit boost couple of times, It sticks around for a minute or so then clears and I can hit boost again and it will start to miss again.. I know that could also be fuel starvation but I should see lean AFR's as well..and I am not. website:- http://www.terryhunt.co.uk
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 47 Posts Member #: 2547 Careful - I'm a sensitive little poppet Sydney Australia |
27th Apr, 2008 at 06:20:39am
Could be fouled plugs. Try going to a hotter plug. Try shutting the engine down straight away while its missing and look at the plugs. This should give you a better indication of what it is doing? Maybe try closing the plug gap a little. :) Adriano
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 4641 Posts Member #: 20 My sister is so fit I won't show anyone her picture Lake District |
27th Apr, 2008 at 09:35:48am
On 27th Apr, 2008 apalazz1275 said:
Could be fouled plugs. Try going to a hotter plug. Try shutting the engine down straight away while its missing and look at the plugs. This should give you a better indication of what it is doing? Maybe try closing the plug gap a little. :) This is a possibility. Mine is a tad rich low down + very low intake temps, and if you have just driven through town only using very small throttle openings when you come to use full throttle it often gives a few big misfires. The lambda still shows rich when this happens. A minute or two of progressively more throttle & the plugs have cleaned up, full throttle can be used and it doesn't misfire at all. |
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1060 Posts Member #: 588 Post Whore Delaware, USA |
27th Apr, 2008 at 02:50:16pm
On 27th Apr, 2008 apalazz1275 said:
Could be fouled plugs. Try going to a hotter plug. Try shutting the engine down straight away while its missing and look at the plugs. This should give you a better indication of what it is doing? Maybe try closing the plug gap a little. :) Brand new plugs and they look fine, I also closed ip the gap to .030 and reinstalled the old ones, no difference. Thinking back I do remember some louder valvetrain noises at times, This is really starting to look like a sticky valve so Im not keen on running the engine!! But I may do one more run without letting it get into boost. if it does not get into a misfire that should tell me that heat may be causing the guides to bind. I think I'll try take a peek into the chamber and look for any marks on the pistons, otherwise I recon the head will have to come off for my piece of mind.. But before I do that I will talk to the Machine shop. Not having much luck with machine shops... Terry Edited by Turbo Tel on 27th Apr, 2008. website:- http://www.terryhunt.co.uk
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4559 Posts Member #: 786 Post Whore Bermingum |
27th Apr, 2008 at 03:07:46pm
Hi,
VEMs Authorised Installer / Re-seller. K head kits now available!
|
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4641 Posts Member #: 20 My sister is so fit I won't show anyone her picture Lake District |
27th Apr, 2008 at 03:25:36pm
I just run a 9/32 reamer through the guides on my heads. |
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1060 Posts Member #: 588 Post Whore Delaware, USA |
27th Apr, 2008 at 05:08:21pm
On 27th Apr, 2008 Bat said:
Hi, Ask Benross what clearance he puts on his guides. I've not heard of any problems with his heads so that should give you an idea about whether you've got enough. Cheers, Gavin :) I asked Benross that exact question and gave his reply to the machine shop... Wonder if they read it!! -- 9/32 and 8mm if I remember correctly. Whats worrying me is that as an excuse for not having it ready the guy said something about needing new "stones" for his guide reamer.. I'm wondering if he just reamed them till they loosened and didnt give enough clearance, hence me wanting to talk to him Monday.. Edited by Turbo Tel on 27th Apr, 2008. website:- http://www.terryhunt.co.uk
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4641 Posts Member #: 20 My sister is so fit I won't show anyone her picture Lake District |
27th Apr, 2008 at 05:23:28pm
Stones for his reamer ? What kind of guide reamer's that then ? |
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1060 Posts Member #: 588 Post Whore Delaware, USA |
27th Apr, 2008 at 10:33:08pm
On 27th Apr, 2008 Turbo Phil said:
Stones for his reamer ? What kind of guide reamer's that then ? EXACTLY Phil!! Anyway I dont know why I didn't think of this earlier but over the long winter of waiting I made an electronic stethoscope from a cheap radioshack listening box thing http://www.turbominis.co.uk/forums/index.p...&tid=2563&fr=25 I drove the car . Its stereo and I had one channel on the front bolt for the valve cover the other on the back bolt Just as the misfire starts the valvetrain sounds increased considerably, in fact I could hear something going on before I even was aware of a misfire. Sometimes the extra noise was in my right ear sometimes the left and sometimes in the middle so they are all sticking, if it got real bad it scared me and I backed off.. That bit of kit has already paid for itself.. Im now pretty sure the valves are sticking...Offf with its head!! Edited by Turbo Tel on 28th Apr, 2008. website:- http://www.terryhunt.co.uk
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 7265 Posts Member #: 1268 The Boom Boom speaker Police! Essex |
28th Apr, 2008 at 09:28:42am
Well done for diagnosing it before something catastrophic happened.
In the 13's at last!.. Just |
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1060 Posts Member #: 588 Post Whore Delaware, USA |
28th Apr, 2008 at 02:56:06pm
I just talked to the machine shop.
website:- http://www.terryhunt.co.uk
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1060 Posts Member #: 588 Post Whore Delaware, USA |
28th Apr, 2008 at 05:38:35pm
I'm telling you, If TM ever puts together a world championship engine stripping team, put me down for Captain.. I'm getting real good at this!!
Edited by Turbo Tel on 28th Apr, 2008. website:- http://www.terryhunt.co.uk
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4559 Posts Member #: 786 Post Whore Bermingum |
28th Apr, 2008 at 06:11:05pm
Hi,
VEMs Authorised Installer / Re-seller. K head kits now available!
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6753 Posts Member #: 828 Post Whore uranus |
30th Apr, 2008 at 04:14:49pm
tel in case it helps , i ran a slightly worn reamer through the guides ,and think it was poss a bit tight when i had it on the dyno ,and ,at 6500,flat out against a slowly accelerating load , it went onto 3 or even 2 cylinders for 3 seconds ,then cleared , its been fine on the rd though . do you feel certain you have enough spring pressure for the cam profile ? id look for 90 on the seat and 185 to 195 on the nose to be sure of 7k rpm . Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM |
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1060 Posts Member #: 588 Post Whore Delaware, USA |
1st May, 2008 at 02:50:29am
I don't plan to go up to 7k and its only a Kent 266 so nothing wild. Plus the springs were checked and were OK in the last 2 builds!!
Edited by Turbo Tel on 1st May, 2008. website:- http://www.terryhunt.co.uk
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1641 Posts Member #: 178 Post Whore stowmaket suffolk |
1st May, 2008 at 06:55:17am
defo exhaust guides sticking, i use a 9/32 reamer and has always been fine.
always looking for them bigger bunches of bannanas |
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1060 Posts Member #: 588 Post Whore Delaware, USA |
2nd May, 2008 at 09:58:31pm
OK took it for a couple of runs today, no misfire all is well...
website:- http://www.terryhunt.co.uk
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 52 Posts Member #: 75 Advanced Member |
4th Jul, 2008 at 12:52:13pm
I also have a misfire problem with my megajolt, I can see on the computer thath suddenly the rpm readout goes crazy, I have tried different types of wires from the last one looks to me like it should do the job. can it be something else ? What kind of wires do you use; do they have to be individually shielded? |
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 8297 Posts Member #: 408 Turbo Love Palace Fool Aylesbury |
4th Jul, 2008 at 01:59:42pm
Are the wires the right was round (continuity)? What size gap do you have between your sensor and wheel? Have you checked the voltage at the point of the misfire, as the VR sensors are very sensitive to low voltage.
Edited by matty on 4th Jul, 2008. https://www.facebook.com/pages/Fusion-Fabri..._homepage_panel
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4559 Posts Member #: 786 Post Whore Bermingum |
4th Jul, 2008 at 06:41:40pm
Hi,
VEMs Authorised Installer / Re-seller. K head kits now available!
|
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 1105 Posts Member #: 1504 Post Whore Westbury, Wiltshire |
4th Jul, 2008 at 07:28:31pm
Petterb.
Minivanless, but reluctantly happy living with the decision. There'll be another one day.
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