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350matt, Engineer
Category: Hyundai
Satisfied Customers: 21715
Experience:  Mechanical Engineer BEng Hons 22 years experience in car engine industry, 10 years in formula 1
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JA: . What is your issue regarding? Customer: I

Customer Question

JA: Hello. What is your issue regarding?
Customer: I have a 2004 Hyundai Santa Fe 2.0 petrol, with a P0172 code and power los throughout the speed range, need some help diagnosing the problem.
JA: Sometimes things that you think will be really complicated end up being easy to fix with a Hyundai. The Hyundai Mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so he can help you best.
Customer: Suspected MAP sensor giving incorrect readings. I hooked a vacuum gauge up to the fel pressure regulator hose and im reading 21 inches hg at idle, however on the scantool it is reporting back 71 inches hg. However it is accurately reporting back barometric pressure in Ireland of 102 Kpa. Backprobed the signal wire of the sensor and at idle the reading was approx 1.5 Volt, increasing with endine load to maxing ot at 4 V WOT. Do you know what the voltage readings should be for this engine?
JA: Are you hoping to fix this yourself?
Customer: Yes
JA: Great! What have you tried so far?
Customer: As above
JA: Is there anything else important you think the Hyundai Mechanic should know about your Hyundai?
Customer: Timing is good. Coolant sensor accurate. Code P0172 System too rich recorded, and was logged according to freeze frame data at about 3000 rpm, at which point Long term fuel trim was -17.5%. Also at idle the reported load is about 34%, this seems igh and as i underatmd it is calculated by MAP and other engine critical sensors, any direction would be appreicated
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Hyundai Mechanic about your situation and then connect you two.
Submitted: 1 year ago.
Category: Hyundai
Expert:  350matt replied 1 year ago.
Hello typically the sensor range is 0.5 to 4.5V and is a ratio metric between the 0.2 bar absolute and 1.5 bar abs ( if its a non turbo engine) so if its going full scale then I'd agree that its very likely to be faulty and should be replaced
Customer: replied 1 year ago.
So the 1.5 V at idle speed for this MAP sensor on a Hyundai Santa e 2.0 petrol is incorrect according to you?
Customer: replied 1 year ago.
I have 0.34 bar pressure at idle speed, increasing to 0.96 at WOT, do these figures look correct. Just to clarify it is normally aspirated engine.
Expert:  350matt replied 1 year ago.
hello those pressure figures don't sound too bad but the high load figure and high voltages don't stack up so its possible that the wiring is faulty and offsetting the signalCheck for exhaust leaks before the O2 sensor as if this has been experiencing an exhaust leak then it will have been running very rich as the sensor will see the extra air pulled in as fresh / lean fuelling and be adding fuel to compensate. this can lead to catalyst failure as the extra fuel can re-light inside and melt the catalyst The best way to find an exhaust leak is to run the engine from cold and feel around the exhaust joints with your bare hands - you'll have about 30 seconds before it all gets too hot and you should feel any escaping gas blowing over your fingers
Expert:  350matt replied 1 year ago.
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