P0402 & no start when hot

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P0402 & no start when hot - Miata 2000

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P0402 & no start when hot - Miata 2000 - 9/9/2007 3:37:02 PM

2000gal

Posts: 7
Joined: 9/1/2007
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Can someone help this girl please!

I am having problems with my 2000 Mazda Miata MX5.

Code: PO402 EGR Flow Excessive Detected. The engine light usually stays on for a day or two and then off the next, but never stays on continually. According to all the suggestions I found within this forum - I checked EGR boost sensor and boost sensor solenoid valve vacuum lines and the vacuum line from the EGR boost sensor to the manifold. All lines proved to have vacuum, EXCEPT the short vacuum line running from the solenoid valve to the EGR boost sensor. Is there supposed to be vacuum in this line while engine in idle status? I also pulled the EGR Valve – no carbon deposits at all, but went ahead and replaced gasket.

This TSB regarding the P0402 Code states to "remove EGR valve (for Protege), or Surge tank (for Miata)". Where (and what) is the surge tank? I cannot locate any info of a surge tank for a Miata.
http://www.mstore2000.com/PDF_Files/1060.pdf

And another issue - when I drive my car over a few miles, once it heats up, and I shut the car off - it will not start. The engine turns over but will not start until completely cooled down - 20-30 minutes later. Car runs great - smooth – no overheating – no indications of leaking oil, nothing – its runs great. Any suggestions of what the cause of this may be?

Thank you for any assistance anyone can give me on this.

< Message edited by 2000gal -- 9/11/2007 7:19:20 AM >

Post #: 1

RE: P0402 & no start when hot - Miata 2000 - 9/9/2007 5:26:07 PM

hixx

Posts: 451
Joined: 8/26/2007
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Sounds like the EGR ports are clogged as far as the P0402 code.You will need to clean more than the EGR valve itself. But a partially clogged converter will also set that code. You will have to physically remove the converter to look inside. A surge tank is used for fuel and air systems for more available air or fuel. It is just a small storage tank. Say if you floored the car from a stop the fuel/air available would be limited to what was in the line at that time. Add a surge tank and you increase the available air or fuel.

(in reply to 2000gal)

Post #: 2

RE: P0402 & no start when hot - Miata 2000 - 9/10/2007 7:22:47 AM

2000gal

Posts: 7
Joined: 9/1/2007
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Thank you hixx! When we removed the EGR valve we also checked the manifold ports and these were clean also. I will pass the converter info on to my brother (he's the one helping me in checking these items).
Also, after your explanation of the surge tank use for fuel and air systems - this could possibly be my problem with the car not starting when hot. (???)
Is this surge tank possibly referred to as the 'catch tank'? There is a cylinder shaped item that is noted on the hood diagram as a 'catch tank'. It has multiple vacuum lines running to it - but it didn't appear that you could access (get into) this tank. If not - do you know 'where' the surge tank is located on my car? Thank you again for your help!!!

(in reply to hixx)

Post #: 3

RE: P0402 & no start when hot - Miata 2000 - 9/10/2007 10:12:35 AM

hixx

Posts: 451
Joined: 8/26/2007
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The catch tank is used for fuel vapors. The fuel system is a closed system. Any excess pressure in the tank is vented to the catch tank and the purge valve dumps it into the intake to be burned. The hot nostart problem could be due to heat soak if your converter is partially clogged. When you shut an engine off it actually gets hotter because water is not circulating through the engine. If a converter is partially clogged it adds to it. If your converter is partially clogged then you will need to figure out why. A worn out coil could cause what you describe as well as a few other items like fuel pump/dirty injectors/ etc.

(in reply to 2000gal)

Post #: 4

RE: P0402 & no start when hot - Miata 2000 - 9/10/2007 11:10:24 AM

2000gal

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Joined: 9/1/2007
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Understanding more now, thank you. Is this the catalytic converter you are referring to when you say converter? Is this something that AutoZone can test to see if it registers as being bad or faulty? Will try checking this as the next step as suggested. If this doesn't work, we will continue on to the other possibilities you named. THANK YOU for your assistance.

< Message edited by 2000gal -- 9/10/2007 12:50:23 PM >

(in reply to hixx)

Post #: 5

RE: P0402 & no start when hot - Miata 2000 - 9/10/2007 2:04:09 PM

hixx

Posts: 451
Joined: 8/26/2007
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The converter is an exhaust component. It looks a bit like a muffler but is honeycombed inside. It gets very hot so that when unburned fuel hits the honeycomb it burns it up. If too much fuel hits it the honeycomb breaks up causing a restriction,or if the car is running too rich it will clog with carbon and restrict the flow. I normally remove them to check them though you can use a pressure gauge to check back pressure, it will not pinpoint the restriction however so i just remove them or at least remove the pipe in the front of it to look inside.

< Message edited by hixx -- 9/10/2007 2:06:44 PM >

(in reply to 2000gal)

Post #: 6

RE: P0402 & no start when hot - Miata 2000 - 9/11/2007 7:33:02 AM

2000gal

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Joined: 9/1/2007
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Thanks Hixx - we will remove the front pipe and I believe I can get my hands on a pressure gauge. Won't be until the weekend as my brother helps me - but I'll let you know the results. THANK YOU!
As a quick test, I read you can give the converter a good punch and you'll hear the honeycomb rattling around if its broken down - and since I could really use something to hit right now - maybe I'll give it a couple of punches.

(in reply to hixx)

Post #: 7

RE: P0402 & no start when hot - Miata 2000 - 9/11/2007 7:52:51 AM

hixx

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Joined: 8/26/2007
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Thats true if it has completely broken up but if it is just partially clogged with carbon a visual will be required.

(in reply to 2000gal)

Post #: 8

RE: P0402 & no start when hot - Miata 2000 - 9/14/2007 9:01:45 AM

2000gal

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Joined: 9/1/2007
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While waiting for the weekend and brother's help in checking manifold - I went to Advanced Auto and had them re-run OBD code check. Apparently we fixed something when checking the vacuum lines and cleaning the EGR Valve, as the P0402 code no longer exists....however....I am now getting a P1345 DTC CODE, (Print out reads: Manfacurer Contrl., Ignition System or Misfire). The guy running the code check stated it could be my COIL PACKS (coil and control module all one unit on the Miata-$250). He took off one of my spark wires and had me turn the key for a quick second...according to him, this confirmed the car was misfiring. He asked when last tune-up was, (August 07 by Mazda Dealership), that's when he suggested problem may be in the Coil. Wouldn't misfiring cause the car to run rough all the time? (as it doesn't). Could the coil be the cause of my car not starting when hot? He stated the dealership would be able to run a check on the car to get the exact area/part that was malfunctioning (is this true?). Any suggestions of what else may be causing this P1345 Code?

(in reply to hixx)

Post #: 9

RE: P0402 & no start when hot - Miata 2000 - 9/14/2007 11:47:07 AM

hixx

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Joined: 8/26/2007
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A coil can cause a no start condition hot as the hotter it gets the more resistance it has. That said you could have caused that code to set in your search for the problem and it could be meaningless. Erase the code and see if it comes back.

(in reply to 2000gal)

Post #: 10