Dieseling EFI engine

2002 HYUNDAI SANTA FE
375,000 MILES • 2.4L • 4 CYL • 4WD • MANUAL
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TSG333
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My vehicle does not switch off straight away and I have to stall the engine to turn it off. After I turn the key to off the engine does a slow lope until it is stall by me. I have no check engine light and an obd11 scanner finds no fault. The engine idles fast, 1250 rpm, uses a lot of fuel and shifts (manual) stiffly with revs staying very high between shifts.

At times I hear a loud bang and when I turn off the car I hear a crackling sound. I thought at first it was a hot muffler cooling after fuel catching but have since discovered massive vacuum in my fuel tank so much so it split the tank at the top! I have replaced the fuel cap but it has not changed. When I release the cap a great whooshing sound starts as air enters the tank.

At first I was told the dieseling was sensor related so all sensors have been replaced, IAC, TPS, MAF, new injectors, spark plugs, PCV valve, fuel regulator. Could this be an EVAP issue? Purge valve? Blocked carbon canister? Perhaps two separate issues? All mechanics I talk to say its impossible for an EFI engine to run on. But it does! After each 'fix' the car seems to run great for two to four days then goes back to its issues. Unleaded fuel seems to make it worse than e10.

Car has actually done 155,000 miles.

Please help. I am at my wits end!
Jul 11, 2017 at 6:25 AM
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STRAILER
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Hello,

One thing comes to mind on this one. It sounds like you have a large vacuum leak. Here is a guide to help you confirm:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

I do not think it is a EVAP issue.

Please run this test and get back to us we are interested to see what it is.

Cheers, Ken
Jul 11, 2017 at 4:01 PM
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TSG333
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The first thing we checked when this happened was vacuum. We have inspected all hoses and gaskets and sprayed carburetor cleaner around. We did not find any leaks. I will however do it again today just to be sure.
Jul 11, 2017 at 6:20 PM
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TSG333
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May or not be related but there is a high pitched ring sound when driving, like it has a turbo.
Jul 11, 2017 at 6:25 PM
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STRAILER
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Hmm, like the exhaust is plugged please try this test as well.

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

Please let us know what happens.

Cheers, Ken

Jul 11, 2017 at 7:34 PM
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TSG333
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I did the vacuum leak tests again and did not find anything. I did however discover that the high pitched noise is coming from the power steering pump. it has a leak too!
Jul 12, 2017 at 3:21 AM
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STRAILER
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That is one problem but I do not think it will effect the engine dieseling. I am wondering if the IAC motor is going bad.

Here is a guide to help you confirm:

https://www.2carpros.com/articles/how-to-replace-an-idle-speed-control-motor-iac

Please let us know what happens.

Cheers, Ken
Jul 12, 2017 at 11:43 AM
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TSG333
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I replaced the aic early on. I have rwad though that even new iac's can fail so I have. New one and will replace it again just in case. Thanks for help.
Jul 13, 2017 at 5:50 AM
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STRAILER
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Please let us know what happens.

Cheers, Ken
Jul 13, 2017 at 12:05 PM
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TSG333
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Hi Ken. I replaced the iac valve. No change. Still runs on.
Jul 14, 2017 at 8:02 PM
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TSG333
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My car isnt running on as much as it did. But still 1 in 8 times it does. Better than the every time it was doing. Would a faulty IAC cause the vacuum/pressure in the fuel tank?
Jul 20, 2017 at 4:58 PM
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STRAILER
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No it only adjusts the idle air inlet. Lets scan the car for codes again

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please let us know what happens.

Cheers, Ken
Jul 21, 2017 at 10:19 AM
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TSG333
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There is no check engine light on but a scan threw code: po335 camshaft position sensor.
This has appeared and disappeared once before. Could this explain the problem?
Thanks for persevering!
Jul 23, 2017 at 6:46 PM
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STRAILER
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Yes, that can cause the problem for sure. Here is a guide to show you what you are in for and some diagrams below to help you get the problem fixed.

https://www.2carpros.com/articles/camshaft-angle-sensor-replacement

Please let us know what happens.

Cheers, Ken
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Jul 24, 2017 at 3:35 PM
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TSG333
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Crumbs! P0335 is crankshaft not camshaft sensor. I wrote wrong one! I gather this can cause the problem too!
Jul 24, 2017 at 5:14 PM
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STRAILER
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No problem,

Here is a guide and the location of the sensor. The guide will give you an idea of what you are in for when doing the job.

https://www.2carpros.com/articles/crankshaft-angle-sensor-replacement

Please let us know what you find.

Cheers, Ken
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Jul 25, 2017 at 11:29 AM
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TSG333
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Would the crankshaft sensor cause these issues I am having or is it just another problem?

Jul 25, 2017 at 5:04 PM
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STRAILER
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Yes, it sure will.
Jul 25, 2017 at 8:15 PM
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TSG333
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I finally found the problem! (two months ago). The purge valve that connects after the carbon canister was stuck open. So the engine was drawing air and vapor constantly back from the tank through the carbon canister. This had the effect of creating a massive vacuum leak causing the tank to implode and the mixture to run rich. After disconnecting the hose to the intake manifold and clamping it closed the car ran like a dream. Tested valve and it was stuck open. Replaced purge valve. All good.
Feb 1, 2018 at 2:48 PM
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STRAILER
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That is a great find I will feature this post in our experts forum.

Use 2CarPros anytime, we are here to help. Please tell a friend.

Cheers, Ken
Feb 2, 2018 at 10:41 AM
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HMAC300
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I have run into a purge valve problem like that many times especially on obd1 cars.
Feb 2, 2018 at 11:58 AM
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CLEE01
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I have a similar dieseling problem on a RAV4 2003 model that has done 280,000km. I also have a 'hard to start' problem. I have changed worn spark plugs, used high octane fuel, replaced the fuel filter, clean the injectors, check battery and start motor. I am left with fuel pump and regulator. Could the pump and regulator contribute to dieseling?
Jul 23, 2019 at 6:59 AM
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STRAILER
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Not really, I would try cleaning the throttle bore first, also is there any codes here are two guides that will help us fix the problem.

https://www.2carpros.com/articles/throttle-actuator-service

and

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please run down these guides and report back.

Jul 23, 2019 at 1:06 PM
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CLEE01
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Hi Ken, I typed my respond in 'Was this answer helpful?'. Hope you can view it.
Jul 31, 2019 at 6:14 AM
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STRAILER
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Hmm, I don't see it. can you re-post in the correct reply box? That box is for visitors to the page that are not involved with the problem. We are making changed to clarify the issue.
Jul 31, 2019 at 11:57 AM