Hey guys, for over a year now while driving 40-59 mph the rpms will surge 100-200 rpm. It will happen while giving steady throttle, it will not happen when accelerating. While driving at highway speeds and tapping the brakes the TC will lock or unlock w/e it is.

Ive searched the forum and a few other sites, gathered information and took the truck to a tranny shop nearby. From reading around I have come to the conclusion that its the TCC solenoid, relayed this information to the trans guy and he says that before I lay down cash to replace the TCC solenoid that I should look into updating or flashing the computer.

My questions are, will this help anything? Have I done damage to the TC by driving it this long? Anyone got other suggestions to why this is happening? lol

The guy sounds knowledgeable and this 'surging' is slowly driving me insane.

And fwiw im a long time blazerforum reader so I feel like I know most of you, I appreciate everything you guys do

 

When did you change your TPS? Any time/event correlation?

How about in Cruise? does it happen then?
It's also correlated to VSS. Any speedo misreads or Cruise control problems?

If it were the Solenoid, I'd expect the lockup/unlock to be slow and gradual rpm change.

So if there's no other indicators, I'd be inclined to agree with the shop tech. Could still be a wiring fault.

 

I changed the TPS when it first started happening, as it was cheap and easy to do.

Yes while in cruise control between those speeds it will surge.

Once when I first got the truck, while driving out of the driveway on a cold morning the speedo needle went haywire for a minute. Hasnt happend since.

Wiring fault? As in a bad ground or cut wire?

Thank you for the suggestions

Edit: Dunno if it matters but my speedo has always been off according to a local Highway patrol radar sign.

 

99 Jimmy RPM surge - YouTube

Video I took taking my fiance to work, cruise control on 55.

 

Mine is doing the same thing. It does it worse when i put my blazer under a load! So if anyone has any ideas on what it could be i would appreciate it. I have replaced my throttle position sensor and did a full tune up on it including plugs, wires, cap, rotor, fuel filter, ignition coil, and ran fuel system cleaner through it. still does it! talked to a chevy dealer and they said possibly a 4x4 actuater???!!!

 

My 98 blazer is doing the same thing. Surging while driving. I notice its having a slight problem shifting into the last gear when its cold out. It will finally do a final shift when i reach 55 then it will start to surge while driving. Just like that youtube video on this page. Has anyone found anything out about why ? Mileage is 170k

(As i start to read through all the problems on this site, i wonder if my blazer will start to do some of things i have read. So far, the windshield wipers stopped, the Heater actuator has went bad, The 4x4 lights up but only two back wheels are in 4wd, the heater core has plugged up. the cruise control stopped working. The gas pump had to be replaced. I know all cars have issues but geish.... ) all those problems but i still love my blazer. LOL

UPDATE: I changed the Transfer Case Switch and took it for a test drive. It still surged going down the road at around 55. I needed to get my oil changed and when i did, I told them to replace the fuel filter. It was really bad, almost rusted through he said. After getting it changed, I drove it down the highway and then home. It didnt surge once. I tested it out on my way to work and home from work on the interstate, it didnt surge at all. I guess that is where the problem was. Thanks for everyones help. It was 40 bux for them to put it on.

 

Surging is most often open vac line somewhere. When you say T case will lock and unlock, leads me to believe you may have a problem with the three hose actuator "switch" on top of the T case. Good Luck!

 

In the video, the ABS light is on... could be a problem with the VSS, but more than likely it's the Torque Converter Clutch solenoid. Drop the transmission oil pan, change the fluid, filter, gasket and the TCC solenoid. Extremely doubtful, borderline impossible, that the axle actuator is engaging the front axle. The transfer case would have to be making mode shifts so damn fast that you'd have lights on the dash blinking like a railroad crossing from 2WD to 4WD!

 

mine does the samething...i chalked it up to the 33's on there messing with the sensors....guessing not now.
i have changed tranny fluid and filter...did nothing for it.
i have no codes either...abs or other wise.
i have noticed just lately that letting off throttle at highway speeds my hvac dampers will go to vent while accel then when i let off they go back to def and floor.
so with that in mind i am planning a vac line hunting expedition this weekend.

 

The HVAC doors switching is without a doubt, a vacuum problem. Maybe the vacuum line came off the vacuum reservoir, or possibly a line leaking or the check valve is is stuck open:



It's usually hanging out right next to the master cylinder. Most auto parts stores have them in stock, maybe $5.