No rev past 2500

[lt1nova]

I have developed an problem where I cannot rev past 2500. However this does not happen right away, when it does I've had luck disconnecting the battery to make the problem go away temporarily.

The problem started when I was at a stop sign, loaded the convertor and then took off. The following day I drove to the dragstrip (60 miles) without issue. On the launch of my second run it acted up. I disconnected the battery, got in a run awaited about 40 mins, got in another. I tried to hot lap it and it acted up again. The drive home the next day was fine.

I drove it yesterday about 3 miles one way and it worked fine revved up to 4500, on the return trip it acted up. This morning it ran fine on my drive for the first 5 minutes (once going past 5000) then it acted up again.

I am going to try to attach a datamaster file of this mornings drive. It started acting up around #4250.

Any help would be appreciated.
datamaster.zip

[95ImpySS]

Curious, will it rev up in neutral after the problem occurs? Is your Check Engine Light on? Can you tell if it is a problem when your car enters closed loop? Data Master should tell you when your in closed loop. Also, does the car pop and back fire when its having problems going above 2500RPM?

[lt1nova]

Yes it will it in neutral, well park actually. No the light is not on. I know it does it in closed loop, not sure about open but I think so as I've shut it off, checked somethings, started it and tried to rev and it did it, I don't know how quick it can go into closed loop. Yes it does pop/backfire when trying to rev past.

[Formula 350]

Ill not sure but it sounds like you may be having a problem with your throttle position sensor

[lt1nova]

I don't think it is the TPS as I looked at that info on the datamaster and it seemed to be responding fine.

Yesterday I disconnected the battery for a while, today I drove it about 40 miles without going over 2500, ran it up to about 3000 the parked it for ten minutes. When I when to drive it again it was missing again. I was thinking it was ignition related but that doesn't make sense if a disconnect fixes it temporarily. A friend suggested a limp home mode but I am not getting any codes to suggest that.

[lt1nova]

I am posting a much longer file than I had before. I didn't want to post something non relevant but I guess it may help. After looking at it a bit more I see that I was able to make it over 2500 a few times in closed loop.

Rec #'s around 1410, 1910 & 3075 show over 2500 with only 1410 being in open loop. around Rec #4300 is where it starts acting up. See screenshots or download the whole file.

Datamaster 7/17 long file

[firebird_1995]

whats the deal with the vss dtc? sensor not hooked up or something?

[lt1nova]

It's the output to the speedometer. It's a transplant, the car has a Dakota Digital speedo in it so it may not like that. I've had that code for years.

[lt1nova]

Guys,

Sorry for bringing up a dead post but I thought I'd let everyone know that I figured out the issue last night after 11 months. I had said it was running like it was on a rev limiter and it was. My MSD Digital 6 is acting up. I put a light up spark tester on a plug wire and could see the spark die around 2500 so I put it on the coil wire. Same issue so I knew it wasn't the opti. I set the rev limter to 1500 and the problem followed. I set it to 9500 and it now rev's past 5k. I'm getting a little breaking up around 15-2000 so I cranked up the two step also but haven't retested. It will be going back to MSD at some point to get checked out.

Thanks to everyone for their input, it's much appreciated.