Ok so I didn't know where to post this so I hope this works here since I'm new and I hope maybe someone could help me. I'm not good with explaining but here's my best. Ok so I have a 1999 blazer 4.3L and I have 157k miles on it and lately I've been noticing a problem with my tach and it's seems to rev up by it self when I'm driving at a steady speed between anywhere from 40 to 55 I've noticed and my rpms are usually at 1500 when this happens and they also seem to be stuck there when I try to accelerate slowly the tac kinda jumps up a bit by like 2 to 300 and yea I can't seem to figure out why I already replaced the tps and now I'm not sure what else it could be.

 

When the tach jumps, does the engine speed increase, or just the tach?


Is there a lack of power when engine speed increases?

 

Just the tac but I can hear the exhaust rev with it to but my speed does not jump around

 

If you hear the engine speed increase when the tach jumps up, the tach is probably indicating correctly. Is the check engine light illuminated while driving? Could be transmission slipping. Have you changed the transmission fluid, filter, & gasket lately, (within the past 50K miles)? These are great transmissions, but you can't neglect them, they need to be serviced regularly. Might want to have a transmission shop take a quick look at it.

 

Ok so you don't think this could be because of a vacuum leak? Because I haven't check on the tranny at all I've only had this truck for about 5 months and I haven't really be able to do much to it. I'm just a lil confused cuz this just started or at least I just noticed it I mean I do drive it ***** to the wall a lot so I really never noticed it before I don't usually go the speed limit

 

Very doubtful a vacuum leak is causing this issue. Is the check engine light illuminated while driving?

 

No it's not just my abs light

 

You need to get the codes retrieved for the ABS. Each time you turn the ignition off, certain codes are erased so the light might not be illuminated when you turn the ignition back on. The ABS performs a self test each time you start the vehicle and reach ~5mph. If a fault is detected, the light comes on and a code is set in memory. The light must be illuminated when the codes are retrieved. When the light comes on, do not turn the ignition off. Most auto parts stores will check the codes for free. When the light is on, have them retrieve the codes for you, then post them here.

 

Sounds like the TCC disengaging with increased engine load to me. Do you get the same tach jump if you tap the brake instead of accellerate?

 

No I don't get that rev when I brake but only when I drive calmly. It does kinda feel like when it revs up its changing gears and then dropping back down again