Hi everyone, Im going thru a bit of trouble with my 2005 Bentley Continental GT and was wondering if anyone had some insight. It has 109k miles, has been running good so far had vacuum lines replaced a while back, but anyways it started idling weak and sputtering when accelerating, the check engine light is also on and my mechanic ran the code and it came back for the catalytic converter. So I bought some catalytic converter cleaner from auto zone and did the cycle and the check engine turned off and it started running perfect again but when I went to smog it the mechanic said it need to be driven more the air portion failed, then a day later the car started sputtering again and the check engine light came back on. I did a second and third cycle with the cleaner but hasn't gotten any better. Should I just replace the cat or can it be anything else like sensor or something? Any thoughts? Has anyone had this issue?

 

Hi amanbal510,

Sorry to read your dilemma.

Let's start over with processing the analysis.

(1) Please make sure your batteries are fully functional. Ask one of the auto parts stores to do a dynamic load test on both batteries.

(2) Post the original trouble codes and indicate what tool was used to produce the trouble codes.

(3) Delete old trouble codes and drive the car under your normal driving conditions. Than rescan. Than please post those codes.

There are four catalytic converters on an 05. Two primary catalytic converters or pre cats. Then two secondaries. Your query is not clear which catalytic converter(s) is possibly restricted.

Another way to assess catalytic converter restriction is to drive the car put it up on a lift. Then immediately take a laser thermometer and read the temperature of each catalytic converter. Usually the guilty party is quite a bit hotter than the others.

Following the above procedure will greatly aid the forum's assessment. Depending which catalytic converter is ( possibly) bad could result in engine out. Historically on this forum catalytic converter problems have been far and few. However the "vacuum pipe issue" can cause misfires which can ruin catalytic converters. As stated your model has had the metal line conversion a while ago.

Please come back and let us know what you find out.

 

Hey thanks for the reply, so I was able to get the voltage checked on the batteries and the starter battery is kinda low, at 12, and the other one seems to be okay. I will be charging it tonight.. I was also able to run the codes for the check engine light. The codes were P0305 cylinder 5 misfire, P0430 catalyst system efficiency below threshold back 2, P0300 Random- Multiple misfire detected. The tool he used was the OTC 9450 OBD ll Scan Tool.

 

[QUOTE=amanbal510;4902549]Hey thanks for the reply, so I was able to get the voltage checked on the batteries and the starter battery is kinda low, at 12, and the other one seems to be okay.

Reply:
The load test is different than using a voltmeter. We need to establish that the batterys' function after being loaded (high amperage load) are still at an adequate voltage. The load test requires a special piece of equipment that car part stores have and can perform at no cost. This might not be the root cause of the problem however it can get in the way if the batteries are not up to the task. Many discussions regarding batteries on this forum.




Quote:
The codes were P0305 cylinder 5 misfire, P0430 catalyst system efficiency below threshold back 2, P0300 Random- Multiple misfire detected. The tool he used was the OTC 9450 OBD ll Scan Tool.


Reply:
The list of trouble codes are a good start. One of the codes indicates one of the catalytic converters on bank 2 is not heating up sufficiently to be efficient. Consider purchasing the: Ross Tech VCDS diagnostic tool. RT VCDS is the preferred diagnostic tool for the Bentley which will scan more modules then the above tool. Ross Tech has an internet sale site.

The misfire on cylinder 05 might be a bad coil or plug. When was the last time the car was tuned up? Additionally leaking engine oil in the spark plug cavities can lead to misfires. Might be time to change spark plugs, investigate the coils and make sure there isn't oil saturation in the spark plug cavities.

 

Sorry for the late reply, I was having some log in issues, Im going to start with the spark plug and coils, would you know where I can could purchase them for cheap, I know the spark plugs are the same for the vw phantom not sure about the coils..

 

I’ve run into bad fuel and the car did that shuddering intermittently. (Costco, Marathon…locally anyway)
avoid last place you fueled when it happens. Resolved after fueling up somewhere different.