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car starts to stutter

Posted: 08 Jul 2019 22:51
by stevie_a
On the road home from Gaydon always going well,sat between 55 and 60 miles per hour,as I had a long way to go and was towing a small trailer, I was sitting at 60 mph, started to overtake a lorry, car starts to stutter and pull back.
further down the road when road was quite i tried again and same thing happened

I went back to 55/60 and all recovered , my fuel tank was 3/4 full temp was good

what are your thoughts

Re: car starts to stutter

Posted: 09 Jul 2019 00:51
by Hasbeen
I have had this problem 4 times with different cars for different reasons.

1/ My dads Mitsubishi Galant. It would run nicely until asked to accelerate hard. I found the disposable in line fuel filter was 95% full of water. It probably had never been changed in his ownership. New filter fixed this. A similar effect would occur if you had a rusty [internally] fuel tank with the fine rust particles choking the filter.

2/ The TR7 was intermittently flooding on the front SU after fitting a new fuel pump. I kept adding extra cardboard gaskets between the pump & the block to reduce the fuel pressure. By the time I had cured the flooding, the thing would go flat/hesitant at about 3500 RPM, & not rev past 4000. I decided the problem was the much higher fuel level in the front carb, due to miserable Triumph bean counters not setting the float chamber horizontal to the carb throat on the 7, as they had on the old Vanguard 4 pot, & fixed that. No further problem with flooding at 2 PSI fuel pressure.

3/ Fitted free flow air filters to the 7. Accelerating through the gears, the engine would go flat at 3500 in third. Had to go up to BAL needles to fix this.

4/ Fitted a Morgan air filter to my new 1962 Morgan +4 [1991cc TR3A engine]. Due to the shape of the bonnet, this was a box, with a single filter at the rear end only. at 4250 RPM the engine went flat, & would not accelerate, due to the back 2 pots taking all the mixture the single filter could pass. I believe this could happen with a dirty or wet filter on the TR7 filter system, particularly with a tuned engine.


Re: car starts to stutter

Posted: 09 Jul 2019 14:59
by paul w
Hey Steve,
another possibilty is worn jets/needles, so that at certain revs,too much air/too little fuel is mixing through the venturi. Check the jets to see if the opening has become oval and the needles for wear. Also worth checking the carb mounts for leaks - smear some grease/oil on them and look for bubbling - again air flow could be affected. Probably worth a full strip down and service as it will only get worse over time.
Great to have meet you again on Sunday, I'll try not to make it another decade wait next time we meet !

Re: car starts to stutter

Posted: 09 Jul 2019 22:34
by Beans
Sounds like either not enough fuel/air or to much air reaching the engine;
Check for blockages (fuel/air), air leaks, faulty pump, heat soak (vapour lock)
Have you checked the spark plugs colours? Always a good starting point!

Re: car starts to stutter

Posted: 10 Jul 2019 21:30
by simps
I had vaguely similar symptoms in my sprint engines TR, the car ran fine at small throttle openings, was a little lumpy at idle but really missed when you put some load on to the point there was backfiring. Back off a little and it was all ok again.

Traced it to a stretched timing chain eventually.

Yours doesn’t sound the same but worth considering maybe??

Re: car starts to stutter

Posted: 13 Jul 2019 22:02
by sonscar
Points gap closed up?.Steve