My wife drove the 98 to work this morning. After 5-10 minutes into the commute the engine started to race ....like a Toyota Camry on steroids. She said the pedal went to the floor and it took off like the cruise controls was on. She rode the brake, it didn't stop and she rode it to a stop and I think she said it killed the motor - or it was chugging real bad. Regardless, it was trying to race out of control she said like it was floored. She then started it up in Park and it would immediately race up to 4k-5k RPM or so, she didn't let it top out. She called me in a tizzy and I suggested the throttle cable could possibly be broke, spring broke, pedel stuck, etc and she said the pedal action was good (not running). We had freezing rain a couple nights before, I suggested frozen water in the cable, but she checked and said the action felt good.

I drove out there and checked it out and the throttle action was fine so was the cruise control actuator. It was dry as a bone under the hood. I held the throttle lever closed and she started it up and would race up into the 4k range till she shut it off. Did this a couple times and each time I closely inspected it. I did not see anything unusual that would cause it.

I put it in N and turned the key on (but did not try to start it), then did the same for D. Then I put it back in Park and it started fine, no racing, although the idle was hovering around the 1,800 rpm mark. I drove it to work and the idle stayed at 1800 for a time, then worked down to about 1,200. When I went to lunch the idle had climbed to about 1,500 rpm. I did not disconnect the battery to reset the computer yet. I was hoping to see if I could repeat the engine racing scenario.

Any thoughts/suggestions on what it might be?

Thanks,

 

Throttle position sensor perhaps...are you getting any codes?

 

It was probably the floor mats (like Toyota tried to explain their problem).

No seriously, did you get a check engine light? Any codes?

I would suspect TPS or possibly an ECU issue if the linkages and all did not account for it.

It is wierd that the gas pedal physically moved without being pushed. Does it mormally move when the cruise control maintains a set speed?

 

Man I was hoping for a by-passed throttle body heater so I could shove this in the DII guys faces.

 

Now I know why some of em think you're not impartial... lol

If the pedal movement could be explained away like Danny's Toyota scenario then your problem is pretty much solved.

Probably not that easy... I'd suggest starting with something other than the ECU. Lets take the Cruise Control for instance... It is physically impossible for the CC diaphram to remain in an open throttle position (suction) once the brake pedal is pressed. Once the brake pedal vacuum switch is opened there is NO vacuum in the circuit to hold that diaphram. It could not have been the CC system / ECU.

The only physical components that directly affect idle without user input are the IACV, the fuel pressure regulator, vehicle speed sensor, MAF... to name a few. I lean toward the IACV only because it is capable of the most drastic rise in idle, nearing the values your wife experienced, if it is stuck open. Your Gems ECU may need to be replaced also but that is the LAST resort. start cheap and work your way up.

 

I'm not partial, I'm all the way...

 

No codes, but I'm almost sure I fugured out the problem. It continues to idle about 1200 rpm so I shut it off and looked at it some more with a flashlight. There on the idle stop was part of an acorn, partly crushed. My theory is that it's fall, I haven't driven it in a week or so, and the vehicle has been sitting outside. We have a lot of oak trees around. Some rodent carried acorns on the motor (there are a collection of them sitting on top of the intake. One must have been sitting on top of the intake and rolled off as my wife was driving and got wedged between the throttle idle positioner and the idle stop land. So when my wife took her foot off the gas as she was coming up to the stop sign it kept going ...may have seemed like it was surging but it probably wasn't.

When I arrived at the scene the nut was probably still there,at least part of it at first. I remember sitting in the vehicle and I blipped the throttle several times quickly (kind of like you would to take a carbureted car off fast-idle ...for those that remember those days). I did that when it wasn't running before I put it in N and D. That action crushed the acorn. The acorn parts were still there. I removed them and not it idles perfectly. We get little creatures that carry nuts onto engines from time to time where we live but nothing severe. If you look at where the idle stop is, there is a cavity that a nut could easily fing its way into and get wedged there.

I'll drive it around for a few days and see how it goes, but I'm sure that was the problem.

Geeez, Toyota never thought of that one!

 

I sincerely hope that all of you realize my floor mat comment was in jest. I am glad that your wife was not injured and your Rover also survived without harm. So it just turned out to be a loose nut, damn them rodents.

If they are climbing up on your engine, they may also take to chewing ou your wiring and other goodies under there as well. A fellow local Rover club member left his Discovery in a barn for a long period while he had started a head gasket repair. Unfortunately he ran into some issues and it was two years before he got it running again. Between teens breaking in and messing with it, rats chewing up some wiring and nesting under the hood, he had a hell of a time getting it back together.

Happy to hear that it all worked out well.

 

Hey I had a mouse build a nest in the engine bay last winter. He was even nice enough to use some insulation from the underhood mat. Almost started a fire.

 

I remember those carbureted days...and I mis them.