Strange running issue
Turbo Mini Forums

Right guys, been running my new engine in over last couple of days (1293 MED turbo) and had a strange issue yesterday and another today.

Engine had been running superb for about 70 miles, mainly on A roads not achieving constant speeds. Yesterday on the motorway running between 3500 to 4000 rpm constantly, the car starts to stutter and feels like its running on 3 cylinders. I back off the throttle for a few seconds and let the car coast, then put my foot back down and it goes off like a rocket again and runs fine.

Now today I took it for a spin to get some more miles on it, and stupidly got stuck in the school run traffic, so wasn't able to keep the car running at a constant speed or really get any speed up at all for a while. Getting closer to home, the car started kicking and bucking and cut out as I set off from a roundabout. I managed to start the car again and set off but the car was kicking for a little while, and then ran ok. Came to another roundabout and had to stop for traffic. Went to set off, engine revved fine, but once there was load applied it cut out. I could restart the car no problem, but it kept cutting out when I tried to move away. We pushed the car round the corner to a pub and I let it sit for 30 seconds or so. Started the car again and let it idle for a minute or 2 and then set off no problem. Managed to get most of the way home with the car running perfectly fine, but closer to home it bucked and kicked a couple of times.

Oil temperature was running around 70 to 75 degree's C and water temperature was perfectly normal. There are no fluid leaks, fuel pressure seems fine etc...

Anyone got any idea's on this? I've done a search, but I've not found anything like my actual symptoms, especially the odd motorway running.

could be an ignition problem... any backfiring at all??

dizzy module? bad coil? maybe playing up when it gets hot esp after running slowly for a while..

My mates E-type did exactly that as we took it into a show.. Bloody embarrasing pushing it the last 1/4 mile with all the sarky comments from the hundreds of peeps watching. It ended up being the coil, he had used the original 1961 coil because it was "correct" for the judges!!

Edited by Turbo Tel on 21st Mar, 2008.

website:- http://www.terryhunt.co.uk

Hi,
Carb icing
Cheers,
Gavin :)

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carb icing or clogged fuel filter I would say

goosed pump/blocked fuel filter caused these sorts of problems for me a couple of times

I had this and a combination of replacing the fuel tank pick-up, fuel pump and replacing the metal fuel line that runs the length of the car with a rubber one cured it. Another thing to check, when i rebuilt my carb, i had exactly the same problem, i took the carb apart again and noticed the the new main jet sleeve (bit with the plastic bit on) was a slightly different length to the old one, put the old one back in and it was perfect.

But it does sound like a fuel starvation problem, maybe worth draining the tank just incase you have picked up some duff fuel.

Mine did this when the part throttle lean off pipe was leaking.

In the 13's at last!.. Just

Cheers for the responses guys. We've been looking over the car today and had the carb off and cleaned it all out. I've also replaced the part throttle lean off pipe with a new one and we've got the car running smoother. Gonna have another bash at it tomorrow, see if we can get it perfect or as near as ready for Sunday!

Car running well now - no problems with cutting out or anything. However, its still doing the same thing on the motorway with the stuttering - only happens above 4000 rpm and only if the car is held there for a while and power is restored if I back off the throttle for a while. Oh, and it only happens in 4th - tried to replicate the problem in 3rd on a long section of road and it doesn't do it, so I'm thinking something to do with cold air coming into the engine bay at speed.

Carb icing is a possibility I'm thinking as has been mentioned - when I get home after driving on the motorway, especially after its done the hesitating, the carb is absolutely freezing to the touch - like touching ice. I've blocked off the Era style bonnet vent to try to stop the flow of air over the carb, but its still getting as cold. Short of blocking air flow at the grille, is there anything else I can do to prevent this problem?

Have you got the water heating to the inlet manifold plumbed in?

I dont think its normally caused by air around the carb, more the temperature of the intake air. Surprising that the turbo doesn't prevent icing..though I think people have reported icing even on a turbo. In a normal car you use warm air from around the manifold when its cold
Does it have an intercooler? if so try partially blocking it in the winter?

Terry

Edited by Turbo Tel on 22nd Mar, 2008.

website:- http://www.terryhunt.co.uk

No I've not got the water heating plumbed in on the manifold - I cut the pipes off! The manifold itself is getting plenty hot, just the carb isn't getting any of the heat.

My air filter is right next to the radiator so its not like its getting really cold air, and I've no intercooler on the car yet. The plenum is warmer than the carb. I really don't understand it.

If you only stutter after lifting off Another thought is it leaning off, tried a thicker dashpot oil? 4th gear puts a bigger demand on the engine so its possible that a slight lean condition would show up there first..

Edited by Turbo Tel on 22nd Mar, 2008.

website:- http://www.terryhunt.co.uk

No it doesn't stutter after lifting off - it stutters when driving constantly, without varying speed etc... power is restored by backing off the throttle for a little while and then back on.

I see,
but it could still be little lean, do you have a wideband? can you tell? When you get to a constant speed the mixture is a little rich because of the oil. it takes 10-20 secs before it fully settles down same thing if you lift off and reapply the throttle it will get a bit rich again.

I'm only theorising here!!

Temporarily enrichening the mixture screw would maybe give you a clue, if it was lean the stuttering would get a bit better and a bit worse again when its leaned off.


But be careful!!

Edited by Turbo Tel on 23rd Mar, 2008.

website:- http://www.terryhunt.co.uk

Yeah, could be that - the car should be getting set up properly next week on the rollers so we'll find out then.

have you checked that the fuelpump is constantly working not cutting on and off? is your carb blowing on a gasket somwhere? has the car been setup properly? does it start poping when it start running badly? do you have a split in a fuel line? crap in your tank? does it happen after a curtain amount of time??

p

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All sorted. As someone had mentioned, it was the ignitor module breaking down - went completely this morning on the way to York Raceway. Luckilly the AA man just happened to have one, but by that time we were too disheartened to carry on, so we went home.

Good job we did as well as about 3 miles from home my turbo oil feed pipe cracked and sprayed oil everywhere, and had to get the AA out again to take the car home.

Right, I'm getting really anoyed with this car now.

Tonight I was out and about in the car, and decided to give it a bit of stick (on a private road of course) - took it upto 100mph in one swoop, full throttle and then backed off and when I went back on the throttle it was running on three cylinders. Strange thing is though, if I kept it above 3500rpm it ran like a dream and went like stink, if I let it drop below 3500 rpm, started running on 3 again.

Surely this can't be another faulty ignitor module. Looking at the plugs, they are very black suggesting way too much fuel - could it be fuel flooding the carb at high revs on full boost, then the spark not being able to ignite it properly at lower revs? It doesn't do it at all if I drive the car normally, and only does this if I've held it at full boost in 4th gear for a while. I can go through 1st to 3rd at full throttle to 6000rpm and it doesn't do it - only once its holding full boost in 4th.

Any ideas?

Has it been on a rolling road yet?

Yeah, Rob at Minisport set it up - I'm gonna ring him tomorrow as I'm not happy at all with it. After I'd got it running nice before, my plugs were a nice browny colour as they should be, after having it setup, they're black as anything and I've had to replace them within 2 weeks of having the car setup.

Funnily enough this seems to be the same issue as im suffering with at the moment

Im thinking:-
Running lean
Dodgy plugs (i had to make up a second hand set)
Or an air leak somewhere

Im going to investigate further tomorrow now im back in one piece again

I can't see it running lean to be honest - my plugs are black as night when I remove them. And on the rollers, it was reading cautiously rich throughout the rev range, but we left it at that to be safe rather than sorry.

Right, well I've replaced practically every part of the ignition system today - ignitor module, dizzy cap, rotor arm, coil, leads, plugs etc... and the car is still doing the same. In fact, if anything its got a little worse.

Just waiting on a mate to arrive with his compression tester to confirm the worst - I'm pretty certain cylinder 2 has gone.

Oh well, a nice ornament I'll have sat in my garage then.