Thought I would ask if anybody else has run into this issue.

Driving down road my 07 V8 Vantage will suddenly loose throttle and a half second later throttle comes back. It might do it every second for several seconds or once in 5 minutes. It does not matter what speed I'm going, what gear I'm in, the temperature of the engine nor RPM. If I'm sitting at a stop light when it decides to act up the car will die.

It's also strange that when it looses throttle it's not like taking your foot off the gas pedal. It's somewhat violent and instant how quickly it jerks as if you hit the brake. Likewise the half second later the throttle kicks back in and you get whiplash the other direction.

Another oddity is that it started one day as soon as I filled up the gas tank. So, I thought it was just bad gas. As my gas tank got lower it acted up less and less. The last quarter of a tank had no issues. Then I just filled the tank back up (it had 30 miles to empty). As soon as I pulled out of the gas station it was back to acting up as violently as it was with the previous full tank. I went to a different gas station with this fill up and a different brand of gas.

The check engine light does not come on and when my local repair place hooked it up to the computer there were no error messages...even when it was sitting there acting up.

Called the AM dealership and over the phone they are at a loss as to what it might be. Problem is they're 3 hours away from me.

So, anybody have any experience with this issue or any random thoughts?

 

Try resetting the ECU. Easiest way is to disconnect the battery overnight.

 

If that concern always is happening when you fill up fuel(other times to like driving and corning left more than right)..sounds like your in fuel tank rubber hoses for the purge system are frade and coming apart..with the hose being frade and coming apart, fuel is being sucked through the purge hose line in tank, when purge opens to test line, vent canister and test cap after fueling was done..raw fuel instead of vapour is sucked into engine..fuel is uncalculated thus engine runs rich but and your concern ocurs ..to test pull of purge and dmtl lines, check for raw fuel, raw fuel should not be present in these locations

If this does not always happen when/after refueling to mid/full..can be another concern I'm aware of..

 

engine adaptation/settings will not be cleared by a hard reset..

 

This is the give away here. The purge line that irish07 is talking bout is at the top inside the tank. Weird I have never seen this on a V8, only DB9's. Same concern DB9 customer will have too, then again it is pretty much the same tank.

Be glad it's a V8 and not a DB9 cause the tank access port is a pain to get too on Coupe's

 

I have the exact same issues, however it seems to act up the most at a cold start, up a hill, and from a stop. I have had my purge valve replaced, and they might have replaced the lines at the same time (I'm not exactly aware of what they did). The problem still exists, however my car backfires much less. Yes, that was another issue; which I assumed was related.

I want to note I have the Automatic Transmission and the Roadster, if that adds anymore complexity to the issue.

One final issue is that if you are not careful, the fuel cap can be screwed on in a way where it is actually loose (where you can smell fuel). I wasn't as careful about my fuel cap before I discovered this problem. Just assumed when I filled it up that it would small like fuel.

 

You have more on DB9's??..to be honest, only seen V8V's with this concern..coupe and volante..have not had the concern on a DB9 yet..hehe wait, next season bet that's all I'm gonna get ..lol

 

Is the fuel cap plunger loose or just the cap..sometimes the retaining plastic grey surround ring can crack and the cap is not secured correctly to the plunger (bottom white section of the fuel cap).. To smell fuel when filling is normal..but not when your cap is closed and your away from the fueling station..if you haven't spilled and fuel, there should be zero fuel smell..has the check engine light come on since the time your garage changed the purge valve??

 

Yes, as soon as I discovered that the wire holding the cap to the car can easily get caught under the cap and prevent it from closing all the way; I've been closing it fully with no odor at all.

I have no check engine light. The valve was changed within the last 3 months.

I will say the throttle reset does help a ton. I.E. if I start my car and perform the throttle reset, when I drive out of my garage and up the hill I will not feel the hesitation to accelerate issues.

 

Ok the cable..I getcha..cable does get in the way at time, i just use 1 hand to hold the cable away from binding near the cap seal..

By "Throttle Reset"..do you mean "Clutch Relearn"? Cause the throttle resets and calibrates itself everytime the vehicle is cycled on without any request from user..Clutch Relearns are not calibrated everytime cycled on unless correct guide lines are met..

 

Here is what I do.

With A/C off, power car on; keeping foot on break. After 15 seconds you hear a click.

Not sure if all of that is necessary; but it does wonders.

 

"Clutch Relearn"...normally your supposed to select neutral also...

"With a Cold Engine" ..Start vehicle, select neutral..let idle for 10 seconds..you will hear a click beneith vehicle..clutch relearn has completed. if heavey use has been done on clutch since last shut down (track racing..etc then engine was shut off) ..up to 3 relearns can be required, to do so ignition will need to be cycled off between each relearn..

Yes it will do wonders on driving and on clutch operations/feel..also will help minimize the slippage of the clutch which will prolong clutch life (clutch life also depends on driving behavior)..

 

Wow, that is weird. Only DB9's here. But now that I say that I'm going to get a V8.

 

It is amazing the difference. I'd wish the clutch wouldn't forget in the first place! I have the automatic, so it's in Park/Neutral on start-up anyhow. It's strange but if I turn the A/C on, it will not work.

 

I'm glad you're all so smart. I just picked up my car from the local repair shop and I gave them the comments you all posted. Sure enough, the purge valve in the vapor line was the issue. So, for now they've unplugged and capped the vapor line as they can't find the ball that's supposed to keep the gas out of the line.

They said it's bound to cause a check engine light but I can at least personally take it to the dealership now vs paying to have it towed.

My local shop didn't want to try to find/fix the ball as there's a lot of things going on between the engine and the gas tank they're not experienced with.

Thank you for helping me solve the mystery.