mx5cartalk.com

My se when hot is struggling to start, it fires a little bit then fails to run, If it’s left to cool down for 15/20 min, fires up ok.
It has a stage 2 kit, recently replaced cam angle and crank angle sensors. Has anybody had this issue, would love too have any input if you can help. Billyr

Does the car have an aftermarket ecu? My SE did this when the standalone ecu went in. I think the tuner disconnected the vtcs solenoid on the front of the intake manifold, underneath the throttle body. That solved the problem for me. I’m unsure if they changed any settings in the ecu, sorry.


Sent from my iPhone using Tapatalk

If it's got an aftermarket ECU it's likely intake temp sensor heat soak (where is the sensor? It should be in the cold side end tank of the intercooler, not in the engine bay), or injector heat soak.

Either way, you're running lean on the initial start until things cool down. There are strategies to minimise the issue, running longer After Start Enrichment is a popular one, but you still need to be gentle when moving off after a hot restart.

Thanks for your input fellas, it does have an after market ecu, has been reasonably ok,but there has been the occasional time when it doesn’t fire up as it should. the intake temp sensor might be the issue I need to look at. I will see if I can move it to where you suggested to maniaclachy. Haven’t considered that but your thought line is a good one. Will keep you posted
Cheers billyr

It's pretty common with after market ECU's. Give it a bit of throttle after it starts and has oil pressure. The IAT should get cooled pretty quickly by the cool air flow and the hot fuel in the injectors will be replaced by new cool fuel.

I usually keep the throttle cracked just a little bit to keep the revs above 1000rpm when I do a hot restart, and just feather the clutch to move about. Usually this is in a parking lot at the shops, by the time I'm back on the street I'm all good.

Do you know what ECU you're using?

Hopefully I’ve solved my hot not starting problem with my se. Recently I fitted a new aftermarket radiator hose, when fitted it was touching the inlet elbow before the inlet manifold, being a thinner hose it was transferring heat to the metal elbow which has a rubber tube coming off it that houses the air temp sender, that extra heat was giving an incorrect reading I fitted the original hose which has a 20mm gap to the elbow and it seems to be starting better. Ran it in the shed for a while and got it hot, stopped it and it fired up ok. Haven’t taken it for a hard drive yet but looks promising. Is it advisable to move the sender unit down closer to the intercooler, if I do that would it need to go back on the Dyno for another tune. It has a adaptronic ecu. It seems there is a lot of sh*t I don’t know about this stuff.

Billyr wrote:Is it advisable to move the sender unit down closer to the intercooler, if I do that would it need to go back on the Dyno for another tune. It has a adaptronic ecu.

Yes - the fix is to weld a bung to the cold end of the intercooler so the sensor is effectively no longer inside the engine bay. You will not need another tune.

See how you go. My test is always going to the shops on the way home from work, that 10-15 minutes while I'm picking up groceries and dinner. It's enough to the heat soak and properly affect the sensor, then the car park crawl makes it hard to hide as you need to go slow and dip the clutch often, which is what leads to the stall/dip.

But the best place for it is in the cold side end tank, exposed to fresh air. Agree, you won't need a re-tune, you're not altering airflow.

Thanks for the input fellas, think I might need to down the moving of the sender path. Dang it, I had the intercooler out not long ago when I did the cam belt. Should be a bit quicker at it next time at least. Will let u know how it goes. Thanks again great site for excellent advice.

I have seen suggestions that it is possible to simply drill and tap the IC for the sensor. This is dependent on the thickness of the aluminium end tank on the IC, and would best be done by removing it anyway, as I for one would not be happy with the prospect of chips or filings finding their way through the engine.

ManiacLachy wrote:I usually keep the throttle cracked just a little bit to keep the revs above 1000rpm when I do a hot restart, and just feather the clutch to move about. Usually this is in a parking lot at the shops, by the time I'm back on the street I'm all good.

Really depends on the ECU

My adaptronic (a sh*t ECU) would flood and hydrolock if you touched the throttle at all.
Except if you had it flat to the floor, when the ECU would then trigger flood clear mode and would cut all the fuel and allow the POS to start.

hks_kansei wrote:Really depends on the ECU

My adaptronic (a sh*t ECU) would flood and hydrolock if you touched the throttle at all.
Except if you had it flat to the floor, when the ECU would then trigger flood clear mode and would cut all the fuel and allow the POS to start.

I keep hearing such great things about the Adaptronic I may have gripes about the MS from time to time, but you keep reminding me how much worse it could be!

Actually, I meant after turning over the motor I keep the throttle cracked, as in when moving in gear, not the actual turn of the key. With ASE settings I have no issues with the actual start.

I've never had hot re-start issues with my Adaptronic select E440 in the SE and neither does my sister in law who also has the same (temp sensor in factory spot). Assume it's all to do with tuning (and possibly tuning around the issue?). My sister in laws ID1000 injector dead times vs voltage looks crazy compared to the Wari preset but obviously it works. I'm no expert so I can't provide much help for those with this issue though other than I know if you load the Eugene MX-5 base map in Eugene on an E440 there is a huge list of injector dead time presets available and other options previously not there with an original Wari map in Eugene or Wari.
Agree Adaptronic could be better with support and documentation and I hoped their amalgamation with Haltech would have shown some changes for the better by now but nothing obvious seems to have changed in the last year (bring back the forums!!). Wonder what the newer Modular ECU's are like. I know heaps of tuners have manually worked out exact dead times for a huge range of different injectors and provided this to Adaptronic and Eugene now has a big list of presets to choose from plus other idle settings, but like I said, I'm no expert.
The RX crowd still seem to be gaga over them.