erratic acceleration

[cayvman]

I have a '94 j30 with ~155k miles. Have had the complete service done at 130K (timing belts, plugs, water pump, etc). What's happening is when driving the there is this temporary erratic acceleration occuring, typically around 50 mph and 2k rpm. The rpm's will go up to around 3k for a moment and then back down to the 2k level. This will happen intermittently while driving. I've had my mechanic check it out and cannot seem to find anything wrong on the scan. He's going to replace the ngk platinum plugs that he put in at 130k service and see if that cures it. Anyone out there with a similar occurence and or experience at resolving this. Thanks.

[bcole002]

I am having similar issues as you describe and, like you, I had the car checked out. The Infiniti folks cannot determine any probs with my '96 J30. They said that there's a computer hooked up to the J30's transmission and by accessing the computer they could easily see if there were any issues (it cost me $100 and no real answers to find that one out). Occassionally, the car will decide to downshift at 60 mph and shift back to the right gear. Some days it happens, other days it doesn't. Have you had any luch figuring out what the deal is?

burton.cole@us.pwc.com

[cayvman]

Did you say that the dealer did a diagnosis on the transmission and came up with nothing?
The new plugs didn't resolve issue. Did a transmission flush. Same result, problem is stll there.
Like yours, mine will do it on occasion. And typically between 50 and 60 mph and 2k rpm.

[apensity]

Could it be vapor lock? During these heat waves (in CA at least) if your gas tank is below 1/4 tank or so, it will create such a vaccuum that the fuel will not pump out of the tank. Crack open the gas cap and listen for a loud "hiss". If it does happen, fill the tank and then drive again and see if it still happens with a fresh tank of gas. Happened to me and saved me a lot of money trying to diagnose.

[cayvman]

Thanks. but I don't think it has anything to do with the engine. The more I analyze it and research it in this and other forums, I'm inclined to think it has something to do with the transmission. The trans is shifting for some unknown reason. Either a temp sensor, a revolution sensor or solenoid is bad. Appreciate the thought.

[cayvman]

Took it to the dealer. Turned out to be the Turbine Sensor. $$$ but the problem is gone, for now.

[bcole002]

I will likely have to do this. I have a '96 J30 with 50K miles and the car is definitely a keeper. Out of curiosity, how much did this cost you at your local dealership?

[cayvman]

$600. However, that was for the sensor as well as de-carbonizing the air intake. Parts totalled $200+, balance in labor and tax.

[bcole002]

Was de-carbonizing the air intake part of the solution to correcting the erratic acceleration?

[cayvman]

Yes, that's what the service rep told me. I'm not totally convinced, I think it was a way out for them in the event that the sensor didn't entirely fix the problem. That aside, the car does seem to accelerate much better and actually seems quicker. So, the long and short of it is that I think it was work the $100+ for this service.

[cayvman]

Update. Had to have the temp sensor replaced. Even though the turbine sensor corrected 90% of the shifting problem, there was still some odd stuff going on. Took it back to the dealer, tech almost gave up, then decided to let the car warm up before testing it. Voila!!! Temp sensor was bad, too. So far, everything seems perfect.

[halfbyte]

Originally Posted by cayvman

Yes, that's what the service rep told me. I'm not totally convinced, I think it was a way out for them in the event that the sensor didn't entirely fix the problem. That aside, the car does seem to accelerate much better and actually seems quicker. So, the long and short of it is that I think it was work the $100+ for this service.

Did they remove tranny to replace the turbine sensor?

[cayvman]

I don't believe so. But it's still running great, knock on wood.