Bentley Continental GT misfire on full boost
#33
05-25-2018, 03:55 PM
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Join Date: Jul 2016
Location: Saint George, UT
Age: 65
Posts: 163
Rep Power: 14 
The part number they gave me is 07C 905 715 A. Its called a zuendspule which I assume is German for ignition coil.
It is a VW Group part. I believe it fits several VW, Audi, Seat, Skoda vehicles.
Keep in mind this was for my 2008 GT Speed. You may need something else.
It is a VW Group part. I believe it fits several VW, Audi, Seat, Skoda vehicles.
Keep in mind this was for my 2008 GT Speed. You may need something else.
Last edited by MrVette; 05-25-2018 at 03:58 PM.
#34
06-09-2018, 05:25 AM
Check for vac leaks
I know this is a little different than the normal misfire advise, but go with me for a second. I learned this from my Audi ownership and it applies to the Bentley’s too. My 06 Gt had a vac issue even though this is the “updated” vac line routing.” 05 and below had more vac lines and valves mounted on top of the tranny.”
Simple easy first test for a fairly major vac leak that will Not throw a light or code!!!! Mine and at least 2 other Bentley gt’s I have looked at and repaired did this BTW
Cold start the car car in the AM. Let it idle do not touch the brake or gas pedal. After approx 20-45 seconds the car computer will come out of cold start mapping and the idle should settle in around 900 RPM give or take. Let it idle for a few minutes it May “stumble” or vary in rpm like it’s searching for a stable idle... if it does this gently press the brake pedal. If the idle smooths out and you hear the vac pump run in the drivers fender you Most likely have a dreaded vac leak on the firewall. I did and the 2 other GT’s did also verified by smoke test and repaired. See the electric vac pump in these Bentley’s is strong enough to overcome Some vac leaks so they go unnoticed while driving.... For example you have you foot on the brake at a stop light and the vac reading is sufficient with the pump running for the computer so no light, no idle issues, and you Think it runs perfect... Again Mine did this.
But. Now that I intimately know the vac routing and issues on these Bentley’s it makes total sense.
This isn’t a golden end all be all test. Smoke testing is a better. And may show smaller leaks than this rough test. But this is the easy obvious way to see if you have a common problem. If your car does this you can bet $ you have a vac leak
Now your missfire. The 2 main vac lines that feed the engine go up behind the manifold in the center. These are common failure points in my limited experience and others, your turbos are controlled by vaccum, so if there is more of a vac leak on one which is Very possible in this daisy chained vac system, it will cause one bank to get a earlier and more aggressive boost. Causing a lean issue on that bank, Causing a misfire since that bank came on earlier, had more boos all the way through acceleration. Which can burn plugs and all kind of other bad things.
Also another side side note oddball possibility that I Haven’t explored much. but originally thought it might be a issue is a possible lazy cam adjuster might also cause a similar issue to yours. Bad cam timing can cause all kind of issues I Again only know from the Audi world...
A smoke test is easy and cheap to do. And on these cars after 8 years old I it should be a tool we use to help find less than obvious issues.
Hope it helps you or someone. We owners love to keep these cars running their best!
you can search my vac thread on here if it helps you. Feel free to message me if you have any question .
Simple easy first test for a fairly major vac leak that will Not throw a light or code!!!! Mine and at least 2 other Bentley gt’s I have looked at and repaired did this BTW
Cold start the car car in the AM. Let it idle do not touch the brake or gas pedal. After approx 20-45 seconds the car computer will come out of cold start mapping and the idle should settle in around 900 RPM give or take. Let it idle for a few minutes it May “stumble” or vary in rpm like it’s searching for a stable idle... if it does this gently press the brake pedal. If the idle smooths out and you hear the vac pump run in the drivers fender you Most likely have a dreaded vac leak on the firewall. I did and the 2 other GT’s did also verified by smoke test and repaired. See the electric vac pump in these Bentley’s is strong enough to overcome Some vac leaks so they go unnoticed while driving.... For example you have you foot on the brake at a stop light and the vac reading is sufficient with the pump running for the computer so no light, no idle issues, and you Think it runs perfect... Again Mine did this.
But. Now that I intimately know the vac routing and issues on these Bentley’s it makes total sense.
This isn’t a golden end all be all test. Smoke testing is a better. And may show smaller leaks than this rough test. But this is the easy obvious way to see if you have a common problem. If your car does this you can bet $ you have a vac leak
Now your missfire. The 2 main vac lines that feed the engine go up behind the manifold in the center. These are common failure points in my limited experience and others, your turbos are controlled by vaccum, so if there is more of a vac leak on one which is Very possible in this daisy chained vac system, it will cause one bank to get a earlier and more aggressive boost. Causing a lean issue on that bank, Causing a misfire since that bank came on earlier, had more boos all the way through acceleration. Which can burn plugs and all kind of other bad things.
Also another side side note oddball possibility that I Haven’t explored much. but originally thought it might be a issue is a possible lazy cam adjuster might also cause a similar issue to yours. Bad cam timing can cause all kind of issues I Again only know from the Audi world...
A smoke test is easy and cheap to do. And on these cars after 8 years old I it should be a tool we use to help find less than obvious issues.
Hope it helps you or someone. We owners love to keep these cars running their best!
you can search my vac thread on here if it helps you. Feel free to message me if you have any question .
#35
06-09-2018, 10:27 AM
Adrenalinejunkey hit the nail on the head. My 2005 exhibits the stated description given. The previous owner had the vacuum lines above the transmission fixed albeit by cutting the plastic lines and inserting rubber tubing fastened with standard worm clamps. Regrettably, there still is a leak. Under hard acceleration the misfire DTC codes on the right bank appear. Also, a pending code for a vacuum leak. I am hoping one of the feeder lines from the intake manifold. That way steering rack removal could be the remedy. I sprayed a shot of starter fluid above the transmission while engine was running and RPMs increased, vacuum leak confirmed. Time to do a smoke test.
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