Mk1 Gs. Misfire On Acceleration.

[randyreindeer]

This is driving me mad now. I have had my GS for nearly 3 Years now and never had any issues with it at all. Recently, it has been hesitant when accelerating. It seems to lose all power for a split second every time you boot it. Not just for one split second but several times during hard acceleration. Its as if its not getting enough fuel or a spark is not being delivered. Difficult to tell which one it is.

So far I have, replaced plugs, Dizzy cap, rotor arm, fuel filter, oxygen sensors and HT leads. All with new items. I have compression tested it and its fine and I have tried a different Airflow Sensor as well. The whole intake tract has been removed and cleaned out and put back and double checked for air leaks. The vacuum pipes are on the right way around and don't leak and the EGR valve is working. TPS is ok.

The car starts from cold and settles down to a nice smooth idle and drives perfect when pottering around the streets but just misfires or hesitates when you want to overtake. Once you get to your speed its fine.

Has anyone had any similar issues and if so would you like to share the cure?

[88b]

Sounds like a classic case of HT leads but you changed them. If you ease off the throttle under acceleration does it stop ? I'm wondering about an injector, have you tried some injector cleaner ?

[terry moore]

This is driving me mad now. I have had my GS for nearly 3 Years now and never had any issues with it at all. Recently, it has been hesitant when accelerating. It seems to lose all power for a split second every time you boot it. Not just for one split second but several times during hard acceleration. Its as if its not getting enough fuel or a spark is not being delivered. Difficult to tell which one it is.

So far I have, replaced plugs, Dizzy cap, rotor arm, fuel filter, oxygen sensors and HT leads. All with new items. I have compression tested it and its fine and I have tried a different Airflow Sensor as well. The whole intake tract has been removed and cleaned out and put back and double checked for air leaks. The vacuum pipes are on the right way around and don't leak and the EGR valve is working. TPS is ok.

The car starts from cold and settles down to a nice smooth idle and drives perfect when pottering around the streets but just misfires or hesitates when you want to overtake. Once you get to your speed its fine.

Has anyone had any similar issues and if so would you like to share the cure?

Hi Randy, try changing your fuel filter ,Merry Xmass. TERRY.

[randyreindeer]

I have changed the fuel filter twice and tried an injector cleaner. A friend of mine is gonna hook it up on his scope to do a few checks. When we worked on Triumphs together many years ago we had a philosophy that we still use to this day and it hasn't failed us yet. If I can't fix it then he can and vice versa. He rang me when he read this asking me when he can come over and fix it. Keep you posted.

[Tony9r]

I would be interested in the outcome, as mine hesitates every now and then under heavy acceleration...

[randyreindeer]

No worries Tony. I will post it on this very same thread. may take a while though. The car is currently only used to take my Mum shopping and lives its life on her driveway now.

[terry moore]

This is driving me mad now. I have had my GS for nearly 3 Years now and never had any issues with it at all. Recently, it has been hesitant when accelerating. It seems to lose all power for a split second every time you boot it. Not just for one split second but several times during hard acceleration. Its as if its not getting enough fuel or a spark is not being delivered. Difficult to tell which one it is.

So far I have, replaced plugs, Dizzy cap, rotor arm, fuel filter, oxygen sensors and HT leads. All with new items. I have compression tested it and its fine and I have tried a different Airflow Sensor as well. The whole intake tract has been removed and cleaned out and put back and double checked for air leaks. The vacuum pipes are on the right way around and don't leak and the EGR valve is working. TPS is ok.

The car starts from cold and settles down to a nice smooth idle and drives perfect when pottering around the streets but just misfires or hesitates when you want to overtake. Once you get to your speed its fine.

Has anyone had any similar issues and if so would you like to share the cure?

Hi Randy, it seems like a fuel problem, if u replaced the filter try checking your fuel pressures .I think your fuel pumps playing up. TERRY

[randyreindeer]

Thanks terry. Fuel pressure is my next port of call. I believe the voltage to the pump changes to up the pressure when the revs get to a certain point. I had a quick look at the Manual but I had my Uncle jack Daniels with me at the time so I found it hard to fully concentrate.

I'm gonna get it hooked up to the scope in the next 2 weeks.

[terry moore]

Thanks terry. Fuel pressure is my next port of call. I believe the voltage to the pump changes to up the pressure when the revs get to a certain point. I had a quick look at the Manual but I had my Uncle Jack Daniels with me at the time so I found it hard to fully concentrate.

I'm gonna get it hooked up to the scope in the next 2 weeks.

Hi, before u get to deep into it ,try checking the fuel pump inside the tank,because they have a fine filter.If thats blocked,it won't cost u. Hope u win.

[randyreindeer]

Thanks Terry.

I have just put the car back on the road. I will try and have a look inside the tank .

[Yakuza]

Spark plug gap?

[randyreindeer]

Sorry.

I didn't realise I had 2 threads running on this more or less the same.

To quote the title of a very early Spandau Ballet song, its all fixed and working and is still pulling strong.

It was the air flow Sensor. The one I replaced it with was faulty as well.

Check out the other post under, "Where is the Fuel Pump" for the full saga.