Missfire... any ideas? 05/01 UPDATE

Hi all,

as some of you know since the conversion it's slightly missing. I did have a water leak day before so it's not because of the conversion itself.

Took my loads of bits off tonight as trying to solve this missfire mystery out (if you own a TT you don't know how lucky you are without that overhead intake manifold!!!!)

Ryan suggested checking resistance on the leads, so here are the resistance values I've NO idea if these are correct, he did comment and say you need some resistance but didn't say how much. Are these values what I should be reading, are any super high possibly causing the miss?

1. 10.22k

2. 7.18k

3. 10.29k

4. 9.47k

5. 12.03k

6. 13.94k

Though I haven't seen the values when it was running, chamber 6 has twice the resistance of chamber 2, that can't be right, can it?

I will try and get a set of 2nd hand leads and see if that makes a difference (grasping at straws), after that should I try the ignitor or should I try the dizzy end and maybe get a new rotor arm?

Thanks

Hi mate I have an NA supra and mine was missfireing, after replacing HT LEADS, dizzy, rotor arm, new pugs and gapping them correct. It turned out to be my coil it was breaking down under load!

Hope this helps :-)

Yea Ryan said about that, I was thinking about trying that as well. Thing is, I get the miss even at tick over.

It could be totally done for then mate! Has it just started happening or have messed about thing anything?

I can't comment on the resistance of the leads but from working on alot of honda's and MR2's with missfires it has usually been the ignitor/ ignition coil that caused it. I'm guessing you have fitted a 4runner cap to gain some clearance for your intake pipe?, I would recommend getting a new rotor arm for good measure and go from there..

I had a leak from the throttle body after I changed the plugs and it's not run right. I say leak, it was more like a flood. But sorted that out and it just hasn't run right since. Almost like water still in one of the chambers and the plugs aren't sparking right.

Yea using a 4 runner mate. I shall make some enquiries to new bits, what a PITA I'm so close to 400 I can smell it

I see AGB says you could have a 4 runner? Then yeah check them leads I put mine on wrong twice before lol

I had a leak from the throttle body after I changed the plugs and it's not run right. I say leak, it was more like a flood. But sorted that out and it just hasn't run right since. Almost like water still in one of the chambers and the plugs aren't sparking right.

 

Yea using a 4 runner mate. I shall make some enquiries to new bits, what a PITA I'm so close to 400 I can smell it

Ahh ok, was the Distributor cap wet after the leak? If it has only been doing it since the leak then i'd see about trying another set of leads... If the leak was so bad that the lead/plug ends were immersed then the leads could still be damp inside which could have a bad effect...

Get the engine up to full working temp. Take ALL the plugs out, either renew them with decent platinum or better ones, or have them blast cleaned. Turn the engine on the starter with the plgs still out to clear any water that's go into the bores. DO NO drop anything down the open plug holes. By the time you have done this the heat of the engine should have dried the valley and plug wells out. Refit the new or at least properly blast cleaned plugs and hope. if not get advice as to a suitable coil upgrade that won't fry the igniter, or convert to a Bosch igniter and use a Bosch Motorsports blue coil. I can do this conversion. The lead resistances seem fine, they VERY rarely give trouble. Get it on a diagnostic tester while under load on the dyno, if you have HT and LT ignition traces on a scope you can tell immediately what's happening.

Sure its not an igniter or coil issue?

I had a temperamental and inconsistent miss fire when I first finished mine. Turned out to be a bad coil.

Its been fine until I had a leak from the throttle body, I always assumed it would be lead or spark related.

I will change the leads and clean the plugs up, I'm using Spark Plugs: BKR7E's (6097) should I still be using 1.1mm gap as recommended for NA or should I reduce the gap?

I'll try and change the coil Martin if these ideas don't work. Then I'll try the rotor arm.

Put some proper platinum or iridium tipped plugs in it. I bet you find a load of condensation in the plug wells, or even standing water.

Paul dried the chambers out pretty well to be fair, I can't find any visual water lying around anywhere.

With a large amount of water in the plug well, is there a possibility the water surrounding the contact between the lead and the plug could of damaged the plug or the inside of the lead?

Just get the plugs out and have a proper look.

I'll take them out tonight and keep you posted

its surprising how water gets in .we once sunk our petrol shogun on the beach while trying to tow the dory full of nets and bass out.the jeep was running under the water until it died.long story short we got it pulled out and left it to the next day .took out plugs new battery turned it over to force all the water out ,put plugs back in and drove 50 miles home.

Guys,

I think 1.1mm gap is maybe too big as preset before, I read somewhere it should be 0.032" so might try this.

Also, looking at the plugs the first 3 chambers (from the front) have white tips. I'll upload some pics later. Theres no build up around the base, the last 3 chambers are a light brown colour (which is normal).

Would the tips be white due to not firing correctly? The throttle body being located at the front of the engine is this just conindence the leak would of affected the first three chambers first being closest to the leak?

if the leads dont sort i then to save you buying loads of bits best thing would be to try everything i have here,coil plugs dizzy igniter ect.just try them one by one .

On another note doesnt white tips mean that its running lean

my old man said due to no build up around the plugs he wouldnt think it was running lean when i asked him last night, i always thought a white tip indicated it wasn't combusting properly.

thanks for letting me swap stuff over mate if i cant get it running right il pop down after Xmas on one of my days off and grab the bumper as the same time.

ok mate fingers crossed its sorted.

STILL missfiring!!!

NEW plugs, NEW leads (or at least functioning leads), NO water in the well, NO leak, guys what the hell is going on here.

I seem to have found some clues to this problem though. When changing the leads I noticed that chamber 4 was hot and I was surprised, BUT I shouldn't of been surprising as this is normal due to engine heat. Then is suddenly came to me, the first three chambers had COLD ht leads on the plug end? Chamber 4 was hot for aaaaaaaaaaages and I checked chamber 3 and it was stone cold.

As previously stated, the first three chambers had a slight white colour to them.

So the question to solve this issue, is why are my first 3 cylinders not firing correctly, I think the ignitor must be working correctly as this would affect all the cylinders. Water has caused this problem, but only with the first three chambers.

Any ideas guys I'm starting to run out of ideas on this one...

was the water issue noticed before the build.if so was the car run before the conversion was started.Only saying as if it wasnt then you cant say for sure it was the water issue and not something that has been done during the build.Could some part of what you have fitted be at fault here.

Just start with the basics, but without proper test gear you will find it hard going. Start with a compression test. Then you need to see which cylinder(s) are missing, for which you really need an oscilloscope and test probes. I could quickly probably tell you what's wrong with it without any dismantling, using the correct gear, but without it you need to start from scratch if it's not water in the wells. If 3 cylinders were missing badly it would hardly even start, and run like a total dog. It'll be cheaper and better for your sanity to get someone with the right gear to diagnose it for you.

It was missing.becuz of water but not at idle. is there anyway different injectors could cause it.

I.'m not sure what you mean, it has been mapped on the setup it's running now, hasn't it?