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Discussion Starter #1
I am new here so hello all
My customer 2007 Grand Vitara has a terrible hesitation, especially from
cold startup, it idles perfectly and there is absolutely no codes but it will backfire and hesitate when accelerating,similar like an extreme retarded timing or lack of fuel. I change the fuel pump,tried a good air flow sensor and set of coil packs but it made no difference. I removed the intake manifold and found the knock sensor insulation all melted away I got a resistance of .577 mega ohms resitance it is the same as the toyotas and nissans I am not sure if it is correct on this vehicle.Can anyone tell me if the sensor can create this extreme problem, I have not purchase it yet I am from Trinidad and it is very expensive, want to know if anyone ever experience a similar problem.
 

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Have you looked for air leaks into the intake after the throttle valve, specifically from the EGR and PCV systems?
I don't think the knock sensor could affect this. It's likely a piezo type and will have high impedance.
 

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Discussion Starter #3
thanks for your response, I dont see any air leaks the egr is out I will try and clean it
it ,I am not sure I will have an egr problem at medium to high speed without having an idle problem especially at startup though,the pcv is good,when the engine is cold the vehicle will hardly rev out, the knock sensor though insulation is so burnt out you can see the internals in it. these parts here are in the thousand dollar range so I have to get it right
 

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Has your customer ever indicated that it's using, losing or otherwise burning away engine oil over a long period of time?
Having seen the engine running at operating temperature, I'd expect you'd notice any significant oil burning condition immediately under different throttle conditions?

In 20 years of working on G13/10 Suzuki engines, I've found that a simple, almost undetectable oil burn from just one cylinder will eventually cause massive carbon buildup in the EGR passage from the exhaust side to the intake side of the cylinder head.
It often doesn't show up as an OBD EGR fault code. I'd guess it depends on how severe the blockage is and under what conditions the engine is running.

Several times I've had to clear out built up carbon blockages in the head using skewers, picks and whatever else worked and sucked out the material with a vacuum.

if you have both manifolds off, I would suggest inspecting and probing the EGR head passage to rule out any EGR head blockage. Look for light at the end of the tunnel.
 

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Discussion Starter #5
Suzuki update, the water pump impeller and its housing was badly worned I realised the vehicle was working at a higher temp, changed it and pressured test the cooling system with a cylinder leak down tester and found the head gasket leaking a vacuum gauge testing also show me the dropping vacuum to low at continous off idle speeds with heavy backfiring when cold. I am in the process of the repairs.
thanks for the responses.
 
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