Launch control activated when car is moving

soldave · Apr 1, 2009

Got a friend with an Evo III who's encountering a strange problem. He's currently using an Eeprom chip (I believe from DSM Chips) which has been made for the Evo III. As part of the chip's code, a launch control feature has been implemented at 5,700rpm. The launch control works great... in fact it works too well and seems to be activated even when the car is moving!

Whatever gear he is in, whether at WOT or gently raising the revs (and even in neutral), as soon as 5.700rpm is hit he gets an ignition cut from the launch control. It's consistent at this RPM and he can't power through it so we are pretty sure it's not a misfire. If he does put his foot down he can build up boost but will not pass 5,700rpm. Also, encountering no knock at that level either. The speedo is working fine and reporting the correct speed, and the wiring from speedo to ECU has been replaced. Indeed, the entire gauge cluster has been replaced in an attempt to troubleshoot, but with no luck.

We're almost out of ideas, other than to remove the turbo timer, which we're going to do today. Wondered if anyone out there had any other ideas of things we could try.

Cheers in advance for any ideas you may have.

evileclipse909 · Apr 1, 2009

Isnt the launch control suposed to work off the clutch switch.

DsMWookie · Apr 1, 2009

Im having the same problem with my 1990 awd, 2step coming on while driving. Iv also replaced the speedo and checked the wiring and its still doing it. So let me know if you figure it out. :banghead:

awd4g63turbo · Apr 1, 2009

I had the same problem with my 90 talon using dsmlink. My launch control was set at 4500 rpm and when I was going down the road and got to that rpm launch control would kick in and not go any higher. After looking on dsmlink forums I found out the launch control worked off the speed sensor. On 1g it is located in the gauge cluster, 2g on the tranny. After swapping out clusters with another one it started to work fine. I am not sure if there is a way to check your speed sensor but I would start with that. Also everything else worked on the cluster before I swapped it out to the one that had the working sensor(speedometer, tach, ect).

dsmwookie, try raising your launch control to @7k and see if you can get your rpms that high, if so your speed sensor is probably bad.

soldave · Apr 1, 2009

evileclipse909 said:
Isnt the launch control suposed to work off the clutch switch.

Have asked friend to double and triple check but he's adamant this launch control is based off the speed sensor and not a clutch switch (which the early Evos don't have anyway).

jrohner · Apr 1, 2009

It could use either the clutch switch or the speed sensor. Does the ECU show the vehicle speed or does it sit at 0?

Zack Huffman · Apr 1, 2009

Have you contacted the person who burned the chip?

It sounds like a programming bug or an ECU hardware issue.

soldave · Apr 1, 2009

jrohner said:
It could use either the clutch switch or the speed sensor. Does the ECU show the vehicle speed or does it sit at 0?

How would the ECU show the vehicle speed? If you're talking about the speedo, then as I said it's working fine, and he has tried 2 gauge clusters with it.

toofast82 · Apr 1, 2009

If you are using mmcd, the speed sensor is the vss reading.

soldave · Apr 2, 2009

Using Pocketlogger to log.

TurboAnything · Apr 2, 2009

If it is a DSMchips chip then they use the TMO clutch wire mod 89-94 Clutchwire Installation. I have a chip from PrecisionEcurepair.com that works off of speed when the car moves it disengages the launch rev limiter.

jrohner · Apr 2, 2009

soldave said:
How would the ECU show the vehicle speed? If you're talking about the speedo, then as I said it's working fine, and he has tried 2 gauge clusters with it.

People usually use vehicle speed to decide which rev limiter to use. If your ECU thinks you're not moving when you are, the (lower) launch rev limiter will be used. If not then the clutch switch is used, so check the clutch switch and it's wiring.

soldave · Apr 5, 2009

Right - an update on this one. We decided to rule out the ECU by throwing it into mine. ECU worked fine in mine and I could free-rev to redline when the car was moving, with launch control when I was stationary. Only thing I didn't try (and should have done) was put my ECU into his car. So that means we have tried replacing in his car:

ECU
ECU harness
Wiring from speed sensor to ECU harness
Spark plugs & wires
Coil pack
Ignitor
Cam angle sensor

Should note that when he was using aftermarket ignition boxes (MSD and ARC) he wasn't having the problem, but he has blown 2 ignition boxes so far. Interestingly (although possibly unrelated), when he changed cam angle sensor last night again he couldn't set timing for the car. When the wire that is tied to the firewall was grounded that needs to be, the car wouldn't stabilize and would just lose power.

->PrOjEcTGS<- · Apr 5, 2009

My bet is it's the speed sensor. I had the same problem on my car.

Most of the time the code for the launch control will check against the speed sensor. If the car is NOT moving you get the launch rev limit. If the car is moving you get whatever is programmed for your normal rev limit. Then, with the clutch depressed and the car is you will get a 6000rpm (or whatever is programmed) no lift to shift rev limit (if you have the clutch switch wired to the ecu.)

Therefore if you are always stuck at a 5700rpm rev limit, then it's never seeing any speed from the VSS. I would try and swap the gauge cluster with a KNOWN good one. I would always get a Vehicle Speed Sensor DTC through my logger. I replaced the VSS and have never had that code since.

soldave · Apr 5, 2009

->PrOjEcTGS<- said:
My bet is it's the speed sensor. I had the same problem on my car.

Most of the time the code for the launch control will check against the speed sensor. If the car is NOT moving you get the launch rev limit. If the car is moving you get whatever is programmed for your normal rev limit. Then, with the clutch depressed and the car is you will get a 6000rpm (or whatever is programmed) no lift to shift rev limit (if you have the clutch switch wired to the ecu.)

Therefore if you are always stuck at a 5700rpm rev limit, then it's never seeing any speed from the VSS. I would try and swap the gauge cluster with a KNOWN good one. I would always get a Vehicle Speed Sensor DTC through my logger. I replaced the VSS and have never had that code since.

soldave said:
Indeed, the entire gauge cluster has been replaced in an attempt to troubleshoot, but with no luck.

Already been done.

->PrOjEcTGS<- · Apr 5, 2009

soldave said:
Already been done.

Are you sure the one you swapped it out with was a good one? I would take the one out of your car and swap it into his. Since, obviously the ECU works fine in your car. Use yours to swap parts to his and figure this thing out.

soldave · Apr 5, 2009

99% sure it came out of a fully working cluster.

->PrOjEcTGS<- · Apr 5, 2009

soldave said:
99% sure it came out of a fully working cluster.

The cluster will still work even if the VSS is bad. You can separate the VSS from the speedometer by disassembling the cluster. On a 1g it's held in by two screws to the back of the speedometer. You can swap this out between the units if the cluster won't work in his car.

I'm not familiar with early Evos but if your cluster will work in his car, I would try that first. Since you know for a fact that his ECU worked in your car therefore all of your sensors are working properly enough for the Launch Control to work.

kraka · Apr 5, 2009

I had this problem in my old Talon. It only activated the permanent launch control when the logger was hooked up.

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Launch control activated when car is moving

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