Car stop suddenly whilst driving

Hi !

I have a odd problem. My car has been tuned by a professional tuner (with very good reputation). This was done with HP Tuners. However, after this was done the car stops (not possible to start) suddenly whilst driving. This has happen several times.
The only thing that tells me that something is wrong is that after the car has stopped the priming time for the fuel pump when cranking is very short. Normally the fuel pump should prime the fuel pump for 2-3 seconds, now it is only doing it for less than 0.5 sek. The fuel pump does not run when cranking and therefore not starting.

If I read and down load the file from the PCM, switch off the ignition for 15 seconds as you should according to the instruction, the engine runs again .....
What I understand, the only thing that happens when reading a tune file from the PCM is some kind of reset of the PCM when disconnecting the computer/interface.

What could be wrong ? Any clue were to start to search ?
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Hi Saltsjoqvarn !

Do you know if there are any non-factory devices connected to the CAN bus, for example an alarm?

Does the problem happen if you are driving with FlashScan connected to the bus?

Fuel pump prime less than 2 seconds indicates that the ECM is not seeing all the conditions necessary to prime, I'll have to consult the service manual.

What year/model...?

Hi Joecar

Maybe I should add some more information. My car is a -68 Firebird with a engine swap to a 2002 LQ9 engine. The PCM is a LS1B, 512 kb unit. The main things that was done during the tuning were update of VE-table, spark-table and some changes in around the idle parameters. The tuner observed that the MAF-sensor was placed to close to a 90 degree turn so it did not work well. Therefore it was turned off by him.

There are no alarm connected and I have not tested what happens when the flash scan unit is connected. I can test this.

My headline is some what misleading, all four time when the car has stopped the ca was standing still, no speed. It has happen in traffic jam, at the stop sign or when the car was warming up in the garage.
It feels like it is some kind of fuel cut-off parameter that kicks in.

Thanks in advance and I appreciate any information that helps my where to start searching.

Magnus

Hi Joecar,

some update from this evening (in Sweden). My plan was to take the car for a drive and se if I could get the car to shut off again and sure I could. Rolling out of the garage and jumped out to close the doors to the garage and the engine stopped.

This time the scan tool was on so I have a file. Also, when cranking the fuel pump does not run. However, if I force the pump to run with the DVT output control on for the pump the car does not start. So it is not the pump that is the problem.
I also read the DTC from the PCM and I got several.

P1514, P0106, P0103, so I think it has to be something with MAF/MAP. May the the turn off of the MAF-sensor. Do you know how I should proceed to find the actual reason for the malfunction.