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CarDoc, Auto Mechanic
Category: Car
Satisfied Customers: 530
Experience:  IMI L3 Motor Vehicle Mechanic
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I have a 2004 Suzuki Grand Vitara. Sport. Automatic-

Customer Question

Hi. I have a 2004 Suzuki Grand Vitara. Sport. Automatic- convertible. 3 Door. 1600cc. And has done 70.000 miles. It has always been serviced as required. And is in great nick, for its age. At the last service in January this year, I had new top quality plugs. new HT leads and new coil pack. It was running just great up until about 3 months ago. When I noticed that it was struggling uphill and not changing down in gears like it should do. It would just stay in the same gear and slowly loose power. Over the weeks it is also doing it on the flat now. It then just suddenly changes gear, then spurts off. I have put a new crankshaft sensor in and I have also bought a Mass air flow spray cleaner and done that. There was a slight improvement. My mechanic is baffled, but he is not an expert on Suzuki's. The only regular reading we get on the Scanner is P0420. Catalyst System Efficiency ?. about once a month, the warning light was coming on. But it went straight through the MOT test last month, no problems. And I had told the tester the problem. Any idea's please. I spoke to a gear box specialist. He was happy with the smell and the oil temperature and gear movement. And said it might be the Mass air flow Sensor. Is it worth me trying a new Mass air flow sensor, as they are a lot of money. And still not be the problem. Cheers. Mick D.
JA: How old is the transmission? Have you checked the brake switch?
Customer: The transmission is the same age as the jeep. No have not checked the break switch. I am sure its not that.
JA: Are you fixing your Grand Vitara yourself? What have you tried so far?
Customer: I am trying to do some things. As I am a retired person and money is a bit tight.
JA: Anything else you want the Mechanic to know before I connect you?
Customer: I think I have covered everything.
Submitted: 8 months ago.
Category: Car
Expert:  CarDoc replied 8 months ago.

Thank you for using JA. I'm Baz, one of the automotive experts, I try to be available in the afternoon on weekdays and in the evenings on the weekend. I apologise if I do not respond to your question promptly, I can assure you that I will respond as soon as I can. Thank you

Expert:  CarDoc replied 8 months ago.

This fault code is more related to the o2 sensor but you can't rule out the MAF sensor because it is part of the system that maintains the air:fuel ratio which is 14.7:1.

I would suggest getting the garage to look at the live data (whilst the engine is running) for the upstream and downstream o2 sensors, you could have a bad/clogged CAT converter or possibly an o2 sensor that's gone bad.