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Warm Start Struggles


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Hi Guys,

I have quite an unusual problem with my car. Cold starts are perfect, the car fires up almost on the first crank.

Once the car is warm, if I turn it off and then start it up within a minute it will fire straight up. However, if I leave the car for 5 minutes, it will then struggle to start. It cranks for a few seconds then sputters a couple of times then jumps into life. I've tried increasing/decreasing both air and fuel but unsure what could be causing this. The only thing that makes sense to me is perhaps fuel pressure drops, but I let the pump prime before I crank the car, and cold starts are fine so this still doesn't quite make sense. I know it's hard to diagnose over the internet, but hopefully someone could advise what the likely problem is (ie not enough fuel).


On my map I don't believe the pre-crank prime is activating as it doesn't have the digital input.

Any suggestions on what to try would be greatly appreciated! Car is running on e85 for reference, but given I'm only having problems with warm starts I don't think this is the problem.


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It sounds like heat soak. Depending on the location of your IAT sensor, either your intake manifold and head soak up lots of heat from the engine but the IAT doesnt see it, or your IAT is in a spot where it picks up lots of warmth from the engine as it cools. One way or another, it means your IAT reading is quite different from the actual temperature of the air entering the engine.

It could also be fuel boiling in the lines/fuel rail depending on where the lines are in relation to heat sources. This is only really likely to be an issue in a returnless system and it would have to be really quite hot.

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Thanks cj. The fuel system returns to the tank and this happens when the engine is 60 degrees so I don't think fuel is boiling. 


When I'm cranking the engjne the charge temperature is 70 degrees so absolutely could be due to the AIT sensor reading hot. Any idea how I could try fix this? 

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I'll take some logs tonight. Unsure if AFRs are leaner as my afr gauge takes 30 seconds to give any feedback. I've tried adding fuel and air and nothing I did seemed to improve it which was really frustrating, and I don't know as to whether there was too much fuel / not enough fuel because changes either way did nothing. Its just very strange that if I turn off the car and start it straight away or within a minute it fires up fine, but if I wait 5 minutes it cranks for about 5 seconds then fires up. I did notice the charge temp was very high like 70 degrees but when I looked at the AIT corrections it didn't seem like it would impact anything in a meaningful way. 


I'm very eager to get home and try the map you posted above! I'll take some logs if that doesn't fix it

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11 hours ago, Ducie54 said:

Try this map. Ive added a extra row on the IAT table @1% and added fuel at high air temps.



warmstartstruggles test.pclr

I was warming the car up to see how it would go with this tune and the car was pouring out a fair bit of white smoke.

I really hope this is related to the tune and not something with the engine. White smoke would usually be too much fuel correct? Oil would be blue smoke right or could it also be white? Since I live in an apartment I'm going to let it clear from the carpark and then start it up again with 0 values for all IAT values at 0% throttle.


Car seemed to start okay but I haven't been able to really try given the smoke haha

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okay I think the smoke was related to the tune as that has now stopped thank god. Im unsure how the tune affected it as the snaketrail didn't show it hitting the extra fuel you added at 0% throttle so that really has me stumped.


Anyway, sadly this hasn't fixed the starting problem. I've attached a few logs of trying to start the car. The figure in the log name reflects the crank enrichment % I tried with the log. I didn't change any other values.




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Since I couldn't upload any more logs in this thread I had to upload them elsewhere:

Logs: the details in the log relate to the crank enrichment





Here is the map I used for the logs:


For each log I only changed the crank enrichment for 80 and 90 degrees. The log filename shows 80 degrees then the crank enrichment then 90 degrees and the crank enrichment.

There are little to no changes in each.

Really out of ideas :(

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Ducie thank you for your help so far. At first it seemed to have fixed it, but alas the problems continued. I'm wondering if it could be something non-tune related. As there is a heap of water in the exhaust lately from the e85, I'm wondering if perhaps this vapor fills cylinders so it takes a few revolutions to clear before it will fire up? I've uploaded 3 logs. The first two are after about a 5 minute break between starts and you can see it cranks for a while before it fires up. The third is when I turn it off and start the car immediately, and you can see that it has no problem starting under these circumstances. Happy to try any other theories though.

1 - https://ufile.io/0oqfc

2 - https://ufile.io/gjgnd

3 - https://ufile.io/s73ht

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I'm on shift so can't look at the logs but just check your trigger patterns and arming voltages from a good start and the longer ones.

Also once the wideband is up to temp hot wire it so you don't have a 30sec delay. 

Another to look at is fuel pressure between the two scenarios. Do you have a gauge inline?

Also when was the last time u had the injectors out. E85 can cause buildup on the ends.

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Not too sure what trigger patterns are sorry so I can't check those. The battery voltage is around 10 volts for both when cranking. If you mean Trig1 and Trig2 Arming they look to be the same both times.

Unfortunately with the gauge it takes 30 seconds to turn on it is inbuilt into the gauge and there doesn't seem anything I can do about it.

One interesting thing I noticed, the crank enrichment was different even though the tune was the same and the engine degrees was only about 1 degree off.

I haven't had the injectors out and I will try this next but as there are no other symptoms I would have thought this would show itself elsewhere. I may also buy a fuel pressure gauge, but I always let the car fuel pump prime from the ignition before I crank the car.

Given this e85 is a few months old now, and the amount of water vapour coming out of the exhaust I feel this must be somehow related. If the exhaust valves are open when the car is turned off, the cylinders could in theory fill from warm water vapour from the exhaust? That would explain why the car starts fine cold and it's only after I leave it for a while. Today I will go for a really good drive to clear all the water from the exhaust and get new e85 and see if that makes any difference.

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Well just went for an hour drive to clear any possible moisture and same problem so I don't think that is the cause. Fuel pressure could be a problem but since I let the pump fully prime before I try cranking the car, I don't think so. When I crank it does cough and try to fire a few times before it really goes. Would that indicate not enough fuel or air usually? 

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Two more logs with the corresponding maps - both started poorly tried different things. This is beyond frustrating! If anyone could let me know if the fuel temp is adjusting anything in the map that would be greatly appreciated as I believe that could be causing some problems for the starting. I've read a few threads about e85 not liking to start when it is warm so maybe this isn't software related


Log 1 https://ufile.io/r33bn

Map 1 https://ufile.io/wpjof

Log 2 https://ufile.io/ii6cc

Map 2 https://uploadfiles.io/7221q

1 minute ago, Ducie54 said:

Looking at those logs i noticed that the cranking enrichment has been reduced in the ones that are hard to start. Try adding more fuel. Also what model wide band kit are you using?

Crank enrichment table

80 DegC=22.5

90 DegC=18

100 DegC=12



Seems we posted at the same time - I will try these settings now cheers

okay I attempted this and sadly no luck - cranked for an extended period of time. I had values of 3 in the AIT correction at 0% throttle however, so I'll let the car sit for 5 minutes and try those crank enrich values again but without that 3% ait correction

Log - https://ufile.io/52b9q

Map - https://ufile.io/ebluc

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okay here is the log without the AIT compensation at 0% throttle. Cranks for quite a long time still :( https://ufile.io/2qbg3

I will try lower the values a little maybe?

80 - 18

90 - 12

100 - 10

AFR Gauge is innovate motorsports. The car also has the factory air fuel sensor wired in however I don't believe the ECU uses this


EDIT: attempted the enrichment numbers above

Okay it stuttered into life a little more here with the values above so I'm thinking to add some more air through the startup step table


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Okay so I tried a few other things. I tried your recommended crank enrichment values with more throttle body opening - https://ufile.io/7ehfz


I also tried less crank enrichment values with more throttle body opening - https://ufile.io/qk49s


I tried even less again and it seems to be getting better - https://ufile.io/ea5bw


I'll try even less again fingers crossed!

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