s300 cuts spark and fuel when VTEC...

[JoseMiguel_100]

Hello there

Im having a VERY strange issue with an Hondata S300 in a B18 integra. Car has worked fine for quite a few time, but some weeks ago, for no reason at all, the ecu completely cuts off the injectors and the spark (you can see the 0.0ms) at the point where the VTEC comes in. The ECU does not power off, because I can continue seeing all the parameters, but you can see spark and fuel cut (like when the fuel cuts on overrun). If you let off the throttle, the ECU returns the fuel and spark and you can continue accelerating normally (and VTEC works well)...

This happens always when I floor the car from low RPM (like on a dynorun) and it is very annoying. Im not getting any codes whatsoever. Im only getting a code related to the air temp sensor which I have been unable to solve.

I have changed practically all the hardware involved. At first I thought it was a faulty TPS, then I tried with a new MAP sensor, new VTEC solenoid. I even bough a new S300 and the problem persists. From what it looks on the computer, there is some setting im missing somewhere that is cutting everything, I dont know why, but like a "failsafe". I have tried all the possible settings one can think of, without luck. I have read the manuals like 3 times, but I have been unable to find the problem. I already had a few experimented tuners in town to take a look at it and they are clueless...

Im attaching the latest ECU file and a few datalogs. In the latest datalog you can see that as soon as I let off the throttle, fuel comes back...

One more thing. If I completely disable VTEC in the settings, the car works great, no breakups, but of course, without VTEC

Thanks for your help

[Spunkster]

First you need to resolve the IAT error which could be a wiring fault, or a damaged ECU.

Second you need to look at your grounds as it sounds like it is grounding through the VTEC solenoid and that is why it fails when VTEC activates.

[JoseMiguel_100]

First you need to resolve the IAT error which could be a wiring fault, or a damaged ECU.

Second you need to look at your grounds as it sounds like it is grounding through the VTEC solenoid and that is why it fails when VTEC activates.

thanks for the quick answer...

I highly doubt there is a damaged ECU. The first ECU was a S300V1 and it worked great for many months. I thought it was a faulty ECU so I tried a S300V2 from another car that works great and I get exactly the same error. I was completely lost with this so I bough a brand-new S300V3, and exactly the same issue. The original S300V1 from this car is in another car and works perfectly.

I have looked at the grounds quite a few times and found nothing abnormal. Im well aware that the thermostat ground causes many problems, but it has been double checked. Is there a specific ground you think I should take a closer look at?

One more thing. It looks like the cut also happens if the car is already on boost. To explain myself. I didnt knew why if I accelerate the car hard on 1st gear, it would work flawlessly, and sometimes in 2nd gear. Then I realized that on those gears, the car was hardly generating any boost at all. I tried lowering the VTEC RPM and it works if I put it somewhere where the car is not making boost, or making very low boost (something like 3000 RPM, consider this is a big turbo)...

[Spunkster]

in 2 of the datalogs you also have a knock sensor error even though the calibration shows you have this error disabled, which to me indicates this is not the calibration these datalogs were made with.

You will need to resolve both of these errors before doing anything else.

[JoseMiguel_100]

in 2 of the datalogs you also have a knock sensor error even though the calibration shows you have this error disabled, which to me indicates this is not the calibration these datalogs were made with.

You will need to resolve both of these errors before doing anything else.

You are right on the datalogs, the first two were made with another calibration I was testing to find the problem with no luck. No matter what calibration I use I still get the error.

The knock sensor error has been solved, but the intake air temp has not. What seems strange to me is that the car has always had this problem ever since we installed the first hondata and it worked flawlessly. Is it possible now that this error is causing the breakup error I am having right now?

[Spunkster]

Try your ECU/s300 in a known working car and see if the AIT error persists, if it does then it is most likely a faulty ECU. Start there and once you have eliminated the error code see if that resolves the other issues you are having.

[JoseMiguel_100]

Try your ECU/s300 in a known working car and see if the AIT error persists, if it does then it is most likely a faulty ECU. Start there and once you have eliminated the error code see if that resolves the other issues you are having.

Been there done that, no errors in other cars, and as I said before, this is the third ECU im trying in this car and this one is a brand new ecu from a reputable shop in the country. This car has had this error like forever, but it did not seem to cause problems in the past. I would like to know if you guys think that for some reason this is related to the problem im having right now.

[Spunkster]

It could be. Resolve the IAT error and go from there.

Post pictures of all the engine bay grounds.

[nevil]

i got a similar problem i have a s300 v1. and im having error code 10. ait. tried to repace the sensor and i still got the same. the fault appears as i rev the car within 8800 rpm. less it doesnt appear at all .dont know where to start.in my opinion the wires are good other wise it will show up the fault before i reace certain revs.

[Spunkster]

You may have a wiring problem or have the wrong sensors plugged into the wrong connectors.