Frustrating acceleration problem!!!

Some of you may have seen my post on XWEB forum

xwebforums.org/showthread.php?t=24181

I need some advice regarding an on going problem with my 1300. The car seems to idle fine however when I accelerate the car starts to stutter slightly between 4000- 5500rpm unless I put my foot down on the accelerator pedal straight to the floor. It seems to run normal above the 5500rpm (very smooth).To me it seems to feel like a carb problem however I have cleaned the carb out three times with carb cleaner and compressed air. I'm convinced the car ran better on the third cleaning and to date I have readjusted the timing 5deg BTDC, replaced the dizzy cap, points, ignition leads, spark plugs, fuel hoses/ filter and accelerator pump diaphragm. The problem is getting really frustrating and I'm beginning to wonder whether I need to send the carb off to be ultrasonic cleaned or perhaps I should change the distributor? I'm assuming when the secondary venturi kicks in, this is when the car runs smooth however low down there is a slight hesitation. The previous owners states the fuel tank was replaced due to fuel contamination with rust however the fuel pump looks very old.

As mention the stutter on accelerating is only slight and Eurosport have suggested looking at the pump, condenser and adjust timing to 10deg btdc. Can someone confirm the 1300 has 5deg or 10deg BTDC as the timing? Also forgot to mention as far as I know the carb (32DMTR) has standard jetting and the car has a CSC full exhaust system. Could the jets be upgraded?

I look forward to some help and advice!!! Damon 07971923945 or reply by this forum

Hi Damon,

Lots of good ideas in the Xweb thread. There's not much to add really!

Depending on how you are operating the throttle, it sounds to me like you have a blockage in the primary main circuit or in the progression circuit of the secondary barrel. The DMTR/DATR carb is effectively two separate carbs with a staggered opening sequence. Hence both primary and secondary barrels have idle and main jets and calibrated progression holes in the chokes. These manage the fuelling as the throttle butterflies start to open.

One off-the-wall thing you could try is to disconnect the linkage between the two barrels so that you only run on the primary barrel, the secondary staying closed. If the car drives smoothly (albeit with limited power), the problem will be in the secondary barrel. If it is still bad the blockage is in the primary.

Rachael, that is a very good idea! I will try and do this tonight however I suppose it doesn't rule out ignition problems? Has anyone had to rejet the carb after fitting a CSC system? I know my other 1500 never needed to be rejetted and as I mentioned I'm not sure what the car was like with the standard exhaust as I bought the car like this.

Hi Damon - I've had the same problems as you before. 10 years ago I nearly sold my X because I was so fed up of breaking down and power loss. I cured it in the end though and the same with my Gran Finale last year.

Upgrade the primary and secondary jet - see eurosport's website
Replace the fuel pipe and add a filter just before the carb.

I think you will be suprised.

Did it a year ago on the Gran Finale and not a hint of a blocked jet since. It was a right pig before.

you could always fit a 1500 carb

Rob, thanks for your response. I have replaced all fuel lines and placed an in line filter before the fuel pump. This evening I cleaned out the integral gauze filter from the fuel pump which looked pretty clean. Perhaps some sediment at the base of the pump internal bowl.

I've also looked at the jets in the carb (weber 32dmtr) and compared these with the sizes in the X1/9 owners club technical data handbook. The only ones that are different are:

Primary air correction jet is 2.20- book says 2.10
Secondary idle jet is 0.50- book says 0.70

Seeing as I have a donor car, I compared these jets on the other car and they are the same so I'm a bit confused why the data manual is saying different when both carbs have the same jet sizes?

I've also checked the dwell angle and this seems to be about 30deg when should be 55deg. I took the distributor out and found a little bit of play in the rotor shaft so I'm going to swap the dizzy with the one off the donor car.

Any other help would be appreciated!!

Pete, is the 1500 carb a straight swap or would I have to rejet it? I presume all had auto chokes which could be removed for a manual one?

A 1500 carb won't be far off for the 1300. At least it might help to show there is a fault in your 1300 carb. I have a couple of 1500 carbs about the place if you want to try one. Of course I can't guarantee them!

Thanks Rachael, I think at this stage I'll keep to the 32DMTR otherwise I might end up having a bigger problem to deal with. If I change my mind I'll let you know.

No worries, you're welcome.

Looking at the jet sizes, that would lean out the top end of the primary circuit and lean out the early part of the secondary circuit, which sort of ties in with your symptoms. Interesting. Maybe try jetting as per the book. But then again, have you had this issue since you got the car or has it come on recently?

It's been like this since I owned the car in August 2013. I spoke to the original owner and he was a little vague. He said possible the CSC system did effect it however he used it so little he couldn't really remember. I may get a 1.20 main jet.

Right, well a freer flowing exhaust will change the volumetric efficiency of the engine and may well warrant a re-jetting.

I'm surprised nobody else on this forum can comment if they have had similar problems with the CSC system as there must be others with this exhaust fitted?

Well, apart from the obvious comment that many owners just don't post on here, it may be that the exhaust doesn't make a noticeable difference to most people.

Fiat generally jet the engines to run as lean as possible to give good economy figures. Most cars' performance can be improved by running a tad richer, if you don't mind paying with reduced economy.

So if I'm to order some jets tonight via Eurosport shall I order main or idle jets?