V8V Cough / Misfire on Acceleration

[Baron Von Alders]

Tried the useless search and not found anything, however I'm probably asking about something that's been posted before.

A few times now when accelerating back after slowing down, using the torque of the engine rather than changing down a gear, the engine has briefly coughed / missed and then carried on as normal.

No problems have occurred when accelerating through the gears, just when gently accelerating in perhaps a too high a gear when for example you've backed off for a car to turn off in front of you then accelerated back again without changing gear.

Seems like it's either flooded as the coast down has pumped in fuel that it's not used or the throttle hasn't responded properly and given the right fuel / air mix.

Runs fine after the hiccup and no warnings / faults on the dash.

Is this something that the throttle body clean described in the wiki may fix or anyone else encountered this and found a different fix?

Ta in advance for any help.

[ds2000]

Very very daft question but what fuel are you using? Mine has had a tiny splutter once or twice on the none premium variants of go juice. On better fuel its perfect..... so that was my solution

[Baron Von Alders]

Running Esso standard unleaded as just been pootling about.

[peterr96]

Had something that sounds similar on our alfa. Only misfired from 1500 to 2000rpm. Otherwise it was fine.
Ended up being a coil pack. You'll need to get some diags read to confirm that. Does it pop on the engine light after?

Otherwise it could be an errant cough that I and other V8V owners have had. For me about 5 times in 6.5 years. Rumour has it that early cars suffered from an issue with fuel tanks that was diagnosed as the issue. I seriously don't buy that as the fuel is pumped from the tank and injected under pressure. Quite how a fuel tank can give rise to a cough defeats me.

[v8woollie]

I've had it now and then. No pattern - had it three times in 15 months.

[shunt]

I've had this a few times too, throttle body clean mostly fixed it. I cannot remember the last time it happened, but used to be quite regular when I first bought it.

Hey, I'm no expert just my experience!

[mikey k]

shunt said:

I've had this a few times too, throttle body clean mostly fixed it. I cannot remember the last time it happened, but used to be quite regular when I first bought it.

Hey, I'm no expert just my experience!

Worth a try and easy enough to do

[RIB27]

Kris did a nice tutorial on cleaning the throttle body - http://www.pistonheads.com/gassing/topic.asp?t=112...

[robgt]

You own a fabulous car! Would you take your Missus to Macdonalds? Give your Aston the bestest fuel, then no problems. Go to Switzerland, they have 100 octane fuel, your Astonwill love it . 10 BHP gain apparently.

[yeti]

robgt said:

Would you take your Missus to Macdonalds?

Definitely. She doesn't like KFC though

[mjk1]

Had this problem with my 06 V8V about 5 times per year. Mentioned it to Stratstone Derby when it was in for the 6 year service last year and they updated the ecu software. Not had the problem in the 10 months since. The engine is also a whole lot smoother especially when it starts and picks up from the starter motor. Forget about the fuel tank and dirty throttle body being the problem, it's an ecu software glitch for which there is a fix available from AM.

Edited by mjk1 on Thursday 18th April 23:08

[peterr96]

mjk1 said:

Had this problem with my 06 V8V about 5 times per year. Mentioned it to Stratstone Derby when it was in for the 6 year service last year and they updated the ecu software. Not had the problem in the 10 months since. The engine is also a whole lot smoother especially when it starts and picks up from the starter motor. Forget about the fuel tank and dirty throttle body being the problem, it's an ecu software glitch for which there is a fix available from AM.

Edited by mjk1 on Thursday 18th April 23:08

Does this do anything to improve low speed pick up? One thing that I hate about the V8 is mooching in slow traffic. Transition to/from light throttle to no throttle is lurchy. Given that Tim at Trinity has noticed the same behaviour on his V8V I know it's not unique to mine.

[mjk1]

I know what you mean about the slight throttle lag. There is a small time delay between the pedal being pressed and the throttle valve moving which makes smooth driving in stop start traffic and hill starts quite difficult. Unfortunately the ecu software update did nothing to improve this.

[JohnG1]

peterr96 said:

Otherwise it could be an errant cough that I and other V8V owners have had. For me about 5 times in 6.5 years. Rumour has it that early cars suffered from an issue with fuel tanks that was diagnosed as the issue. I seriously don't buy that as the fuel is pumped from the tank and injected under pressure. Quite how a fuel tank can give rise to a cough defeats me.

Peter.

Feel free not to "don't buy".But you'll be wrong.

Early V8V have a flawed design of fuel tank breather and present a clear risk of engine shut down when driving under certain loads.

This issue is known to AML - they replaced the fuel tank on my V8V. They also replaced the tanks of another few Pistonheads folks. The issue is not the tank itself, it's the breather system that vents the air in the tank into the inlet manifold. Under certain conditions it floods the engine and causes a misfire as the spark is retarded OR can cause the ECU to cease all fuel to the engine to prevent catalyst failure. It's a terrible piece of design.

Feel free to look on the Bamford Rose thread where this has been discussed in great detail.

[mjk1]

John,

I think we are talking about different problems here. My engine certainly wasn't 'shutting down'. It was literally a momentary cough that lasted a fraction of a second. Afterwards it was as if nothing had happened. The new ecu software has sorted it because whereas I had it happen about once every couple of months beforehand, it has not happened once in the 10 months since.