My first post to this board (about 5 months ago) was about my experience with an unintended or uncontrolled accleration incident that I traced (so I thought) to my cruise control. This is where my car took off by itself as I was backing into a space at low speed.

Ever since then, my cruise has been disconnected and I have had no further incidents

That is, until the other day.

I was making a quick U-turn and when I completed my turn, I accelerated to avoid oncoming traffic. I sl,owed down rather quickly when I came to a stoplight. When the car came to a stop, suddenly, the engine started racing uncontrollably.

I flicked my gear lever into Neutral, and the engine was still racing. I gave a stab at the gad pedal, and the racing stopped.

Now, I woulde chalk that up to a stuck throttle plate, if it were not for the fact that the engine was winding down as I braked for the light. There was a second between the time the car came to a complete stop with my foot on the brake, and when the engine started racing on its own.

Now, that sounds more like a bad IACV.

Thoughts?

 

I'd suggest. . .

Check the throttle plate again
Check throttle cables.
Clean out TB,IACV.
Check tps sensor
Check for codes.

 

My 300zx did that at one point, and it ended up being the stop that sits behind the pedal. It had rotted away and when the pedal was allowed to go all the way to the firewall it started sticking. Just a suggestion

 

ITS A MIRACLE! a noob posting something useful to get to 15! kudos to you man. But yeah, check your pedal, if it wasnt the pedal, it might have been iacv, how long was it racing like that? around what RPM did it start?

 

Hope you can figure it out. I remember I was driving our Chevy Blazer after I had just got my liscence and it started doing that. I was freaking out because it was accelerating itself up a huge hill on the highway!

 

The good news is that, as much as I tried, I could not reproduce the problem...which could also be bad news if it happens again.

If the pedal had stuck then the RPMs never would have dropped down to 1,000...which it did...and right below that is when it kicked in.

My brake pedal had been feeling wierd before then...like the further I pushed it, the harder it felt...almost like I was pushing against a dead pedal instead.

Ever happen to you?

 

That same thing happen to me when I put my shortram intake. I had taken off the sensor that conects to the snorkel part of the stock intake and forgotten to put it back in. So when I had the sensor off, the accelerator was going half way smooth than real hard the other half and it would stick and the pedal wouldn't come back up. I figgured out that I didn't have the sensor back in so I put it back and reset my ECU, problem was gone.

 

that definately sounds like something IACV or Vacuum related... If our cars were drive by wire, I would be concerned about the pedal, controller, and/or wiring... but they're not. It couldn't really be the TB plate or a stuck pedal, if it was, the RPMs wouldn't have dropped before it exhibited the racing RPMs, check and double check your IACV, Vacuum parts, check any associated sensors you can think of, heck, check the MAF even.

 

If you have an aftermarket intake, make sure that you didnt install the coupler ring so that it gets caught by the throttle body. Meaning the screw end of the ring is catching your throttle plate.

 

Good advice from all. Thanks. I suspect either a sticky IACV, or a vacuum leak. I'm going to check the lines with a vacuum gauge, and also hook up my OBD II scanner (to see what I find).

I happen to have a totally stock intake, except for a K&N filter.

One thing I noticed -- perhaps unrelated -- is what happened when I experimented with running a tank of Chevron Regular (87 octane).

I got caught up into the octane debate on another thread, and with me believing that my car would not run well on anything lower than 91, I had to prove it to myself and others on the thread.

My car was running great up until the octane switch. After putting in regular, the car seem to run fine without knocking, but it felt like I was towing a boat behind me; i.e., the car took a big hit in terms of performance.

Also, it took longer to start in the morning, and my auto tranny had a lot more hesitation in downshifting, probably caused by the ignition timing having been retarded to deal with the lower octane.

After finally using up the regular and permanently switching back to Chevron 93 premium, my car has yet to get back to where it was before the switch -- which was more than four weeks ago.

Many of the other members did not believe me when I told them that regular gas affected my car in this way, but I know my car better than I know myself, especially when it is not running the way I know it can.

I understand that lower octane, by itself, should not cause these problems, but whatever came out of the Regular pump that day and into my tank was bad enough to screw up my car's sophisticated engine management system.

I've heard reports of "dirty gas" or gas that had water in it. We blindly assume that the gas stations keep their tanks free from any external contaminants. We also assume that their tanks are filled to capacity instead of the more likely scenario of them being nearly empty.

When gas prices were hitting all-time highs, that is when people started flocking to whomever had the lowest price on regular. Following Katrina and Rita, there were major gas shortages in this region. So, the likelihood of a gas station selling low-priced regular having their tanks close to empty is probably pretty high.

In other words, I may have picked the wrong day to give up premium.

After I do my checks, I'm going to take my car in for a thorough fuel system cleaning, including cleaning the TB and IACV.

Maybe then my ride will b e back to its old, happy self.

 

Hey Guys! Im a new memeber and cant post a new thread but I am having the same problem and it has really been a nightmare for my friend. I'm really tring to help him figure out the cause of this. So Im sorry if Im thread jacking. Were just desperate for help because it has become extremely dangerous to drive it this way.

When he has the Air COnditioning activated, his car will sometimes just start racing UNCONRTOLLABLY and stick at certain RPMS and sometimes rapidly start increasing on its own after wards. The only thing that stops it when it does this is to shut off the AC or Shut down the car!

The vehicle was previously involved in a front end collision that had only done cosmetic damage (Or so it seemed). When taken to the Nissan Dealership, they tested the wiring harness (And not the computer) and said that this might be a wiring Harness issue? Would that be the case and if so, what would our options be at this point?

And I wanted to ask the OT if he had noticed this problem in his case. Do you remember if YOUR A/C was on when it happened in your situation also?

Thanks in advance for any help guys! Sorry if I broke your rules!

Uhm, its a 2000 Nissan V6. Thats all the info I have on it at this time.

 

Hello, and welcome to the forums. We hope you enjoy your stay.

First, we need just a bit more information than just "Nissan V6". That description includes nearly all the cars in the Nissan Portfolio.

Second, as you said, it happens only when the AC is on, so it probably is safe to assume that the wiring harness is at fault. Our AC system is virtually isolated from all the other engine components except at the compressor (compressor clutch, accessory belt powered, etc etc).
On my car, the engine automatically increases it's RPMs very slightly to compensate for the power draw of the AC compressor. A bad harness or error in the ECU could cause the ECU to tell the engine to increase power infinitely.

 

Check to see if your throttle body has anything that the throttle can get stuck on. Even if the car started to dump enough gas, the fact that the throttle plate in blocking it will limit the rpms.

I've had stuck thottle on 2 occations. One in a 200x Ford Expedition when I mashed it, the throttle got stuck on the rug. I turned into the center lane and lift the pedal with my foot. The other is in my i30. I had messed with a sensor that isn't mounted near my throttle body.

When the gas was fully pressed, the throttle body connection got trapped around some wires. I was making a left turn and after letting off it kept accellerating. I quickly tried to lift the pedal but it fell back down. I then tried brakes and nothing so I put it into neutral and turned the engine off making sure not to lock the steering. I turned it into a drive-way. I had to use both legs to slow down the car and lots of force to turn the wheel to cruise into the driveway.

 

Actually, when the AC is on, the IACV sends more air to the engine. I would check that first.

 

 

You sure your not in a toyota? Had a 300zx do that just at a stop light took the gas peddal apart and thers like a rubber kinda gaunlet underneath it and it rotted out from i gusse heat from the engine and it got if pussed down just right and some times comeing back up it would connect and go but this mite be diffrent from yours since your on the break (sounds likes a toyota) ha

 

Is it enough air to cause that much acceleration?