lumpy running on low rev aceleration

[JohnG]

Gents

I have fitted my refurbished metering unit and have fuel to 6 cylinders

UK spec 125 bhp PI

Starting is not smooth. Usually 4 pots, picking up to 6

When she is warm, she ticks over nicely on 6 cylinders with a pleasant rythmic sound rather than the smooth sound you would expect.

Blip the throttle and she misses and stutters

Pull away and with revs and work, she smooths out

The engine pulls well through the gears, but is erratic pulling away from a standstill.

The car is fitted with a luminition electronic conversion. Don't know how old.

Fuel?

Ignition?

Can anyone help?

 

Thanks

John

[Peter Cobbold]

John,

Cant tell form the symptoms if its fuel or spark. So check spark timing is optimal . Loosen the disy clamp unitl you can turn it a few mm to and fro until you get the fastest rpm at tick-over. Reclamp. If it pinks on sudden acceleration turn it a litte anticlockwise until the pinking is minimal. This method avoids doubts that the TDC marker on the crank pulley-damper has shifted with age.

Peter

[JohnG]

Peter

That's tomorrow afternoons job then.

It's so nice to be able to work on the mechanics of a car

 

I will report back

[Peter Cobbold]

Peter

That's tomorrow afternoons job then.

It's so nice to be able to work on the mechanics of a car

 

I will report back

Yes, mechanics and the electrics - which is why I prefer good old fashioned points to electrickery.

[Tim D.]

You could test if is underfueling. Pull the choke and see if it helps.

On my car I have weakened the mixture a little recently which makes it a little lump at low revs when cold without choke. Pull the choke and all hunky dory. Once warm I return the choke and alls lovely.

Tim

[JohnG]

Tim
Good morning

Pulling the choke out makes for lumpy running very very quickly, this is what makes me think that lack of fuel is not the issue

I plan to have a go at tweeking the timing this afternoon, if work doesn't get in the way

If this has no effect, I think i will look at changing the electronic ignition

I will put points back in, just as a check, but have a new powerspark set up that I can use if needed

 

John

[GT6M]

a few of things no mentionee,d above

 

1, check the throttle are all opening at the same time,

as if not, yer only running on 2, maybe 4, till throttle opens wider to get all six wuk,n

 

{ Actually looked at a TR at the weekend, and middle one was an 1/8 th oot, but still running

albeit with great fuel use,}

 

2, if not all throttles are opening, then it will run richer, cos its no getting the vac to lift the rollers

but running rich, it will still hesitate cos the throttles are no in sync

 

3, ye,ve got a plug,or a lead breaking doon

 

4, a cracket cap

 

5, a dodgey coil

 

6, MU actually set wrong

 

7, an air leak,

 

8, there is air in the injectors, if it starts on 4, the goes to 6, also clears when revs,or hard throttle, ye say. this a sure sign of air.

Ye got a bigg filter After the pump, ...nope,!!

 

9 , a loonnnng shot, but one I kem across, and it took some finding

the moving shuttle stop, the one that presses agenst the roller end in MU,

can stick v v slightly on v v light throttle, and not move when it should,

this gives a misfire symptom, as no fuel is getting in as to what engine needs,

 

this unlikely, as its a new MU, but weird things happen

 

M

Edited June 27, 2014 by GT6M

[JohnG]

All

Many thanks for the advice

Adjusted the timing, found that the distributor clamp bolt was u/s, threads stripped!

Done a temporary fix with a short piece of metric studding, and a couple of nuts & locking washers

The throttles opening in unison is something I think I should check and will have a go at this, before I rummage around in the electrics any further.

As always, I will report back

 

Thanks

John

[JohnG]

Evening all

I have managed to improve things on the lumpy running front

Managed to get hold of a synchro check b89 (good mates are a Godsend) and used this to balance the air input at each cylinder

Whilst doing the job we noticed that the ports were v grubby, so used carb cleaner to remove as much of the **** as possible

There is a new throttle cable, obviously fitted just before I got the car, but with no slack in it at all.

Made the adjustment here.

Noted that the air filter is grubby, so there is a new one on order

All in all a good start

 

Thunder storms and torrential rain stopped further work, so the change of ignition has been postponed a week or 2. Still, it will give me time to get some miles under the wheels and get a better feel for the new set up

[peejay4A]

There's a school of thought that cleaning around where the butterflies close is not a good idea as it can upset sealing at idle making a smooth idle difficult to achieve. Mind you I fitted refurbished bodies and didn't have a problem so maybe it's a myth.

 

Edit: just noticed you have a CR and the throttle linkage is different to the CP so perhaps the above won't apply anyway.

Edited July 8, 2014 by peejay4A

[BlueTR3A-5EKT]

No one has mentioned Nos 2 and 5 metering unit banjo bolts being possible culprits. History tells me the PI starting and running like a bag of poo on 4 or 5 cylinders then eventually finding all 6 was often down to the NRV that are integral to the banjo bolts holding the fuel pipes to the MU.

Used to sell a lot of these items to the PI car tuners like Matin's Fuel Injection, TR Workshop etc many years ago.

 

This is of course after all the basic stuff has been proved correct.

 

Peter W

Edited July 8, 2014 by BlueTR3A-5EKT

[JohnG]

All

Good morning

Cleaning around the butterflies was discussed over a cup of tea, prior to going ahead. We thought that clean was, overall, better than rank dirty.

Grubby, I can live with, but these were well beyong this.

I have to clean the throttle & choke linkages / springs / bearing surfaces as these are all gummed up with crud. I hope that doing this will improve the operation and feel.

I hope that the NRV's and associated springs are OK, Neil Ferguson has only just finished working his magic on the MU.

During reinstallation of the MU, I was careful to keep things clean, I fitted new hose assemblies to 2 & 5 cylinders and fitted new O rings all round

 

Anyway, if the weather relents over the weekend, I will take her out for a run to see what difference the work we have done, has made.

 

John