5 year unsolved engine problem

I_6_AstonFan

So ever since I owned my '07 I-6 DB7 it will "occasionally" only idle above 3,000 rpm's the engine quits if you take your foot off the accelerator. It will restart but you must keep the R's very high. It does not kick any codes. If you let it sit over night it starts and runs normally and my not do it again for months. When it does however there is nothing you can do except park it till it completely cools down. Been to the dealer twice - found nothing, been to local Aston guy.....can't find anything wrong. Love the car but don't trust it to get me from point A to B.

I_6_AstonFan

Sorry it's a 1997 not an 'o7

thecardoc3

Diagnostics have to be performed when the problem is occurring. Can you determine the conditions that make it happen? From there testing is first done to prove what you are losing as it stalls such as spark and/or injection pulse. Then the testing shifts to prove why.

I_6_AstonFan

It is almost impossible to get it tested during the problem, we use the car once or twice a month on the weekends and it may be fine for 3-5 months and then it acts up. So you tow it to the dealer or shop and they start it the next morning and tell us there is nothing wrong with it, because it runs fine once it cools off. Interesting Huh?

As far as conditions, it is almost always during a higher outside air temp, 80+. It does not seem to be electrical, it always has spark, so I'm guessing air or fuel. I can't tell however if it is fuel starved or flooded since I usually occurs in some place where parking is tough or I'm by myself and can't do anything but nurse it to the curb or roadside. I once let it sit for 5 hours thinking that would cool it enough.......but no. I had to Uber home and come back the next morning.

I was hoping to find someone that had experienced a similar problem and knew the cause & cure. There are just not a lot of these cars around.

Someone suggested disconnecting the battery when this happens for a few minutes and then reconnect and try to restart, I'm not sure what that would mean if it restarted and ran normally but it would be a good place to begin I suppose? Any thoughts?

thecardoc3

I_6_AstonFan said:

It is almost impossible to get it tested during the problem

Good thing you said "almost". I have solved hundreds of problems like this over the years.

I_6_AstonFan said:

, we use the car once or twice a month on the weekends and it may be fine for 3-5 months and then it acts up. So you tow it to the dealer or shop and they start it the next morning and tell us there is nothing wrong with it, because it runs fine once it cools off. Interesting Huh?

The event would likely occur a lot more if you used the vehicle more, the first thing that needs to be done is identify as many of the conditions as possible that have to be correct for it to happen.

I_6_AstonFan said:

As far as conditions, it is almost always during a higher outside air temp, 80+. It does not seem to be electrical, it always has spark, so I'm guessing air or fuel. I can't tell however if it is fuel starved or flooded since I usually occurs in some place where parking is tough or I'm by myself and can't do anything but nurse it to the curb or roadside. I once let it sit for 5 hours thinking that would cool it enough.......but no. I had to Uber home and come back the next morning.

That is plenty of time to prove what is wrong. According toyour previous post the car will run, just not below 3000rpm. So at that engine speed you do have both spark and fuel, the question is what is happening once you allow the engine to slow dow. How exactly have you confirmed spark when this is acting up, amd by that I mean nwhen you allow the engine to slow down? BTW you not only need sufficient spark, it has to occur at the right time. The same goes for fuel, you need to have fuel pressure and injection pulse, plus the injectors have to deliver the right amount of fuel. Lastly we have to consider the air which has to be both enough and the right amount of O2.

I_6_AstonFan said:

I was hoping to find someone that had experienced a similar problem and knew the cause & cure. There are just not a lot of these cars around.

A lot of people think that way, but that is not how its done. While there is a chance that someone has dealt with the symptom you described there are any number of plausible causes. Attempting to do this by "a silver bullet" is far more likely to be wrong and result in spending money without fixing the car. Plus if the attempted repair somehow is right and solves the problem you wont have any proof of that which really would leave you still not able to trust taking it anywhere.

What you need is an electronics/diagnostics specialist


Someone suggested disconnecting the battery when this happens for a few minutes and then reconnect and try to restart, I'm not sure what that would mean if it restarted and ran normally but it would be a good place to begin I suppose? Any thoughts?

I_6_AstonFan

Thanks cardoc3, I will call my local shop and see if I can get the mech to drive it for a week and maybe get it to dump on him. It's getting hot in FL now so maybe if driven regularly it will act up? Good Advice

thecardoc3

With the really tough ones I would often have the vehicle owner drive the car and do specified laps. That first of all allowed me to earn a living while I worked through a problem like this by keeping me busy in the shop.

One of the keys to this is I would preset (plan-out) the testing that I need to perform when the problem occurs. In some cases that could lead directly to the answer, but the expectation is to first identify the system involved in the failure and work from there. The main key here is I would keep myself ready to hit the road and get to the car the moment it acts up. By having the owner on a pre-planned route that usually meant five to ten minutes travel time. Once getting to the car I would perform all of the testing that could possibly be done out on the road.

I_6_AstonFan

I'll check it out with him and see what is possible.

Davercee

Definitely learning a lot in this thread alone. Thanks, fellas!