[SOLVED] No Start (Heat Soaked?)

Jaaren

Jaaren

Greenie N00B Member
Hey everybody!

New to the forums, and just recently picked up a 2008 MS3. Performed basic maintenance, and overall car is great... except for it won't start after have recently driven it. Each and every time the solution has been to let the car cool off for ~30 minutes, and it fires right back up. Here are the scenarios, followed by a list of mods and other details:

No Start #1 and 2: Drove in traffic for ~30 minutes, then waited idle in my car for 10 until my wife arrived. We had a doctor's appointment for about ~45 minutes. After we were done it wouldn't start. Propped hood open and looked around. Car was able to start after about 30 minutes.

No Start #3: Yesterday's SCCA autocross. After my 5th lap it died in the staging area. Same as before I was able to let it cool off for about 30 minutes, and it fired right back up. I drove home normally.

Mileage: 110K
Mods: Cobb intake/BOV, Catback Exhaust
Recent service: Oil/Trans fluid, spark plugs (NGK Iridium gapped to .026")

No engine codes. I log the OBD2 port and I do know IATs get high (~140-160F range) when idling for a while. I also know the vent has a duct to the battery compartment. My theory is that perhaps there's some integrated circuit (ECU, immobilizer, or similar) that could be overheating? I also thought coil packs, but it seems like I'd get a rough idle in the transients vs. the ON/OFF behavior.

Has anybody experienced something similar, or have any ideas how to trouble shoot it?

Thanks!

Colin
 
Hey welcome to mso! That's an odd one makes me think something is overheating, alternator? Coil packs? Bad fuel pump (in tank or hpfp), bad electrical connection somewhere. I'm simply spitballing here. Any immobilizer light? Take it no codes since you didn't mention them

Found a post online from a different vehicle having similar issues this was one of the responses "It’s curious that you don’t seem to have a code in the ECM. Usually if you have a malfunction that prevents the car from starting, there will be a code resulting. That being said, it sounds like you may have an issue with a crank position sensor or an ignition control module. Both of these have a history of failing when they are hot and coming back to life again when they are cold. A bad crank sensor will almost certainly result in a code, but an ignition module might not"
https://www.yourmechanic.com/questi...n-before-i-can-start-the-engine-again-by-alen
 
OP what method are you using to pull codes? I'm assuming the AP? If you want more detailed data I suggest getting FORSCAN on your phone and getting a compatible ELM Bluetooth adapter.

FORSCAN will let you see DTCs and developing DTCs it will also give you the ability to look at snapshot data from any triggered DTCs.

Not sure if any of that would help but the more detailed information may give you a better idea.

https://forscan.org/faq.html#licensing
 
Awafrican said:
Hey welcome to mso! That's an odd one makes me think something is overheating, alternator? Coil packs? Bad fuel pump (in tank or hpfp), bad electrical connection somewhere. I'm simply spitballing here. Any immobilizer light? Take it no codes since you didn't mention them

Found a post online from a different vehicle having similar issues this was one of the responses "It’s curious that you don’t seem to have a code in the ECM. Usually if you have a malfunction that prevents the car from starting, there will be a code resulting. That being said, it sounds like you may have an issue with a crank position sensor or an ignition control module. Both of these have a history of failing when they are hot and coming back to life again when they are cold. A bad crank sensor will almost certainly result in a code, but an ignition module might not"
https://www.yourmechanic.com/questi...n-before-i-can-start-the-engine-again-by-alen
Click to expand...

Thanks for the welcome! I swapped out the coil packs and still no dice. I can hear the rear most fuel pump activating when I turn the key, and I'm getting ~1000 psi during crank when monitoring using a Bluetooth OBD2 adapter and "Car Scanner" app. From what I can see in wiring diagrams, spark is basically ECU --> Coil Packs. Either the ECU, Coils or perhaps a ground could be another issue. Thanks for your help; I'll keep digging!

Mtnbker3531 said:
OP what method are you using to pull codes? I'm assuming the AP? If you want more detailed data I suggest getting FORSCAN on your phone and getting a compatible ELM Bluetooth adapter.

FORSCAN will let you see DTCs and developing DTCs it will also give you the ability to look at snapshot data from any triggered DTCs.

Not sure if any of that would help but the more detailed information may give you a better idea.

https://forscan.org/faq.html#licensing
Click to expand...

I'm using an OBD2 Bluetooth adapter and "Car Scanner" app. I do not have an access port. I tried to download FORSCAN but it wouldn't couple with my adapter. Would I get more functionality vs my Car Scanner app?

There's no check engine or active DTCs, but I do have a pending DTC for U2064 (control unit 728) that is showing up. That's been on the car since I bought it a few months ago, and since I have an airbag light I assume it's something with that module.

Really appreciate your help! I'll let you know what I find out.
 
Last edited by a moderator:
Jaaren said:
Just to close the thread - turns out there was a broken wire in the coil sub harness, making intermittent contact. Fixed the wire, started right up and no more “heat soak” issue.
Click to expand...
Glad to hear you got it fixed, thanks for the update
 
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