Missfire / Running Issues - One For The Uber-Techies

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System-G
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Missfire / Running Issues - One For The Uber-Techies

Post by System-G »

Right I'm at my wits end with an issue on our SC.

On Saturday Tom & I replaced the cambelt and the dizzy ( :wink: ) seal (outer O-ring). As I found a tiny hole in the cambelt and the dizzy was leaking a bit.

Everything went as well as one could expect.

Got it to TDC, replaced cambelt.
Removed dizzy replaced O-ring, refitted making sure it was all aligned etc...

Before removing the plugs to get it to TDC, I clean out the plug chanel - it had oil residue from a spill not long ago but a tiney bit of oil got into the holes. Attempted a blow out by cranking the engine without the plugs - nothing came out as expected (it wasn't much at all that went in)

Reassembeled everything. Car started after a bit of spluttering and set the dizzy to it's previous position as marked up before removing.

Car idled well and seemed to respond well off throttle.

Took it for a test drive to the shops (pick up much needed beer :mrgreen: ). On the way out there was one tiny stutter - nothing much. It felt like the SC belt slipped (I knew it needed nipping up).
On the way back there were a couple of bigger hesitations/missfires only when pegging the throttle (WOT). So took it gently all the way thinking I got the timing out.

Due to time and other commitments, didn't get chance to look at it until yesterday.

As the dizzy had been leaking oil over the altenator and associated connectors/wiring I clean them up thoroughly (each pin removed from the connectors etc...). Double checked everything. Put it all back together and the same thing...

Got the timing gun out and found that when timing is bang on any movement of the throttle, the engine just missfires/hesitates/stalls. The engine wont start when timed either. It idles fine.

Advance the timing by a bit, the engine starts fine and idles fine and runs OK with gentle increase of throttle, but under WOT the same symptoms occur...

Tom seams to think it's electrical, possible that the coil pack has gone faulty, but this would be a massive coincidence between cambelt change. Others on the SC forum reckon it may be the dizzy, but again none of the contacts have been touched.

All vacuum hoses, electrical connectors (related & not) etc... have been checked.

This is really doing my head in... I have access to a spare dizzy and coil pack from this evening and will try them.
The car ran perfectly before all this work so we just can't understand what/how/why :?

Any ideas? Anyone experienced similar before?

This topic is mainly aimed at Mr Woods, Kev & Kevin-in, but anyone else with actual definitive knowlege, your sugestions would be more than welcome. JAE beer tokens available :thumleft:

(The car is needed to get us to and around Spa this coming weekend... So we are kinda very desperate...)

TIA :thumleft:
85 MK1 MR2 Track N/Ail | 99 528i SE Touring | 01 Mandarin VX220
ligertigon
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Re: Missfire / Running Issues - One For The Uber-Techies

Post by ligertigon »

Problem can only be what you already touched.

Recheck valve timing, (could have slipped a notch)

And remove/ reinsert dizzy.

I take it you timed with t&e1 shorted?

bet 50p its something simple
System-G
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Re: Missfire / Running Issues - One For The Uber-Techies

Post by System-G »

Yup T&E1 bridged...

We have checked for tooth slippage 4 or 5 times between us at different stages. But will check again...
85 MK1 MR2 Track N/Ail | 99 528i SE Touring | 01 Mandarin VX220
PW@Woodsport
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Re: Missfire / Running Issues - One For The Uber-Techies

Post by PW@Woodsport »

A few questions....

1) Was everything A1 before work started? no misfire and everything ok?
2) I take it you have done the obvious and checked for fault codes?
3) Are you 100% sure the distributor and cambelt are timed properly?

Off the top of my head the problem is screaming High tension related to me,quite possibly a breaking down HT lead or one thats come adrift from its plug socket when pulled off a spark plug.

Id remove the spark plug cover,wait until its dark,fire the engine up.... ideally somewhere with zero light pollution,and induce the misfire by revving the engine....any sparks or shorting to ground on the HT side of things will be very clear,look around the coilpack area too.Ive done this many times and its amazing how a little spark can jump to ground that you will never see in daylight.

Hope that helps
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System-G
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Re: Missfire / Running Issues - One For The Uber-Techies

Post by System-G »

Thanks for looking/responding Paul :thumleft:

1] Yes - all perfect, except for tiney hole in cambelt and leaking dizzy...
2] Yes - checked for codes yesterday - all clear. Not one fault code. However... since fettling this evening code 14 has appeared (which is directly related to the ignitor/coil etc..)
3] Yes. Well. No. About 98% sure. Have rechecked things so many times now :lol:

This evenings update:
Went to MK1 Chris's and got hold of the dizzy, coilpack & ignitor. Got back and tried the coil pack on the car.
It didn't work. I tried my coild pack again - Nada. I then realised it needed to be grounded to the chassis. Voila engine starts.
However...
Still missfires when giving agressive throttle. And then spotted Diag Code 14 which relates to what I'm doing. One of the coil pack bolts sheered when trying (very carefully) to remove it so I hope this is not what's caused the code to apppear (I wouldn't have thought so though...)
By this time it's raining and I gave up... Dinner beckons

As it's pretty dark, I'll check for arching in a bit :thumleft:
85 MK1 MR2 Track N/Ail | 99 528i SE Touring | 01 Mandarin VX220
PW@Woodsport
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Re: Missfire / Running Issues - One For The Uber-Techies

Post by PW@Woodsport »

well the code 14 puts a new perspective on it,that would indicate a low tension issue as a HT issue wont throw a 14... id definately check continuity of all wires between the distributor and coilpack/amp and ecu,i have the relevant diagrams showing the ones you need to check but it should be simple to locate the colours on the ecu plugs and test all wiring to the distributor and amp are ok.

One thing that did cross my mind was the king lead,if that is shorting to the coilpack terminals it could possibly throw a 14 so still wouldnt rule out a HT issue.

You have got to be 100% sure the cam and ignition timing are perfect before any of this though or its pointless,keep us posted.
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System-G
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Re: Missfire / Running Issues - One For The Uber-Techies

Post by System-G »

Cranked the engine off ignition last night and got it to misfire. No sparks seen anywhere at any time.

Code 14 only appeared after messing about with it last night. No fault codes were present Saturday, Sunday & Monday.
But least it's something to work on in what we think is where the fault lies.
The code appeared after I hot-swapped the coil packs (i.e swapped them over with the battery still connected) so it's possible the ECU picked something up then. I'll reset the ECU and try again.

Someone else mentioned faulty oxy sensor could cause similar??? So I will check this out as well.

I also have a spare dizzy from Chris that I didn't have chance to try last night so will also try that tonight.
85 MK1 MR2 Track N/Ail | 99 528i SE Touring | 01 Mandarin VX220
mr2mk1chick
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Re: Missfire / Running Issues - One For The Uber-Techies

Post by mr2mk1chick »

PW@Woodsport wrote:One thing that did cross my mind was the king lead,if that is shorting to the coilpack terminals it could possibly throw a 14 so still wouldnt rule out a HT issue.
.


Tom apparently tested for faulty leads etc by taking them from his car and put them on ours during Monday - still the same prob, so prob not any of the leads.
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System-G
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Re: Missfire / Running Issues - One For The Uber-Techies

Post by System-G »

mr2mk1chick wrote:
PW@Woodsport wrote:One thing that did cross my mind was the king lead,if that is shorting to the coilpack terminals it could possibly throw a 14 so still wouldnt rule out a HT issue.
.


Tom apparently tested for faulty leads etc by taking them from his car and put them on ours during Monday - still the same prob, so prob not any of the leads.


Tom didn't swap all the leads to my knowledge - just the king.
85 MK1 MR2 Track N/Ail | 99 528i SE Touring | 01 Mandarin VX220
System-G
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Re: Missfire / Running Issues - One For The Uber-Techies

Post by System-G »

Update:

Last night put on the spare dizzy & coil/ignitor from chris. I reset the ECU and there are no fault codes appearing. The ECU must have issued the code during a hot-swap of the coil pack.
Started the engine & the symptoms were still there :(

I decided to take a massive step back and re-do everything and double check everything as I went along re-fitting it all. I got to re-fitting the altenator belt and found the cambelt retaining ring still on the ground - so everything had to come apart again ](*,) :evil:

By the time it was dark, everything was back on the car, all that was needed was to re-check the dizzy for alignment and re-fit leads. It was dark, I was hungry and had a beer thirst. So I will continue this evening. I am not confident though :(

Cams & crank are all aligned perfectly. TDC is 100% correct. I started thinking that perhaps we got the crank 180deg out of the cams, but this wasn't the case. Everything is tickety boo.

So basically I have established that timing was bang on. The missfiring must be caused by something else...
Deffo at a loss on this one :?

Will update later... :?
85 MK1 MR2 Track N/Ail | 99 528i SE Touring | 01 Mandarin VX220
PW@Woodsport
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Re: Missfire / Running Issues - One For The Uber-Techies

Post by PW@Woodsport »

my money's still on a HT issue,check the resistance of your leads,shouldn't be more than 25 kohms
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System-G
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Re: Missfire / Running Issues - One For The Uber-Techies

Post by System-G »

PW@Woodsport wrote:my money's still on a HT issue,check the resistance of your leads,shouldn't be more than 25 kohms


Will do :thumleft:
I was also going to run the car with the Magnecors from our N/A track car too (without the plug channel cover) to test as I know they are deffo working well :mrgreen:
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greglebon
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Re: Missfire / Running Issues - One For The Uber-Techies

Post by greglebon »

I'm with Paul on this one.......

Even though testing an HT lead with a multimeter doesnt REALLY prove too much: conductors and insulators behave totally differently when subjected to KV's.....

It could be igniter-related, too...but I doubt it'll be anything upstream of that.....

Does it misfire when you're on WOT, or when the revs are around 6-7k?

ie: if you floor it from idle, but lift off before the revs catch up, does it do it?

If it doesn't, then the leads are favourite by a mile.......

Assuming that the duration of the spark is the same (ie: a very short pulse), then the overall current through any lead is gonna be small.
However, at max revs, the interval between each spark is much less, so the overall flow can be quite high: this will expose weaknesses in conductor / insulator that will never be revealed with a multimeter.

The king lead obviously has the same problem, but x 4...!
(one of the benefits of wasted-spark and coil-on-plug! :thumleft: )
mr2mk1chick
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Re: Missfire / Running Issues - One For The Uber-Techies

Post by mr2mk1chick »

It just seems strange that the car was fine before the cam belt change and dizzy seal fix. No issue with leads then as i was using it as a daily runner to work.

I suppose these cars have a nasty habbit of throwing other faults up at random intervals, and this could be one. As the leads could have been accidentally damaged during the process i guess may be something to check. The are they extra thick red magnecors though.
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Lunarmatic
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Re: Missfire / Running Issues - One For The Uber-Techies

Post by Lunarmatic »

Does your tacho needle go crazy when it starts to misfire? I had a problem with my SC where it would misfire and then stop. The tacho needle would be swinging around all over the place! It threw a code 1-4. It turned out that some coolant had got into the big green connector for the ignitor. It wasn't obvious that the connector had coolant in it just by separating the two halves of the connector either, it only became apparent when I turned them both face down and coolant came out, so it was sort of trapped inside the connector where there is a white rubber bung thing.

It's a bit of an outside chance that this is your problem (as you've tried swapping ignitors already) but if you've topped the coolant up and maybe spilt some it could be the cause.

Andrew
System-G
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Re: Missfire / Running Issues - One For The Uber-Techies

Post by System-G »

Nope Tacho needle is fine :thumleft:
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PW@Woodsport
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Re: Missfire / Running Issues - One For The Uber-Techies

Post by PW@Woodsport »

thing is with HT leads is when they are pulled off a plug the connector up inside the lead can become dislodged from the lead itself,they can even feel like they clip in properly as well,but have a broken or high resistance right at the connector inside the lead.

This problem could be absolutely anything on the igntion circuit,it really could,but its got to be tied in to the work thats just been done,and presuming the dizzy and cam timing is perfect the only other thing thats been touched is the HT leads,thats why im favouring them,the symptoms of misfire also fit with faulty leads,but i could be totally wrong.

Process of elimination though,we can keep throwing tests and suggestions at you until its fixed :thumleft:
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System-G
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Re: Missfire / Running Issues - One For The Uber-Techies

Post by System-G »

](*,) ](*,) ](*,)

Gett right effed off with this now!

Tested the leads - they are all metering around 5 - 6kohms...

Used the Magnecors from the N/A anyway & Chris's coil/igniter. Set TDC put dizzy on. Car started first time.
But missfire is still there. Timed up with timing light, gave throttle and it missfires/stalls ](*,)

Put Chris's dizzy on and it won't start at all. Even after tripple-checking alignment etc... :?

Really headbutting a brick wall ](*,) ](*,)
85 MK1 MR2 Track N/Ail | 99 528i SE Touring | 01 Mandarin VX220
010on1986
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Re: Missfire / Running Issues - One For The Uber-Techies

Post by 010on1986 »

I found when putting the distributor back in......

it may seem aligned, but unless the cap is off and you can keep an eye on the rotor arm remaining where it should be, you can't tell that as the cog engages the cam shaft bevelled gear, it turns the distributor rotor arm out of alignment.

my tuppence worth of useless info.
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Re: Missfire / Running Issues - One For The Uber-Techies

Post by Mk1Chris »

G, seriously check for air leaks, and that the AFM/02 sensor are functioning according to the BGB.

Your symptoms sound similar to what I had when Geoff Bloor diagnosed an air leak, and prior to finding my faulty 02 sensor I replaced ALL of my ignition parts for new without improvement.

Including another AFM from japan at great cost :cry:
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