Engine RPM all over the scale

[Cypress_1973]

Out of the blue just an hour ago, I went to start my car, and my car will not idle at a constant RPM. It's all over the scale. Goes from 800 RPM right up to1500 RPM and it's not gradual. it spikes. Then spikes back down. Spikes back up 200 RPM then back down. At no time am I touching the gas. I pressed the peddle slightly to get up to 2000 RPM and even keeping the pedal steady, the RPM drops and rises sharply on it's own. It will not stabilize.
I live on a quiet street so I put her in drive and went out and the car will accelerate then suddenly it'll surge fwd a bit then smooth out again. I go to slow down and the RPM will drop off and it's like the car applies the brakes sharply on it's own.
I've been driving all day with no issues at all. The car sat in the driveway for the last 2 hours and I had to make a quick run out and that's when it started suddenly.
Anybody else ever have this issue or hear of it? Any suggestions? Clearly the car is not safe to drive at the moment.

[ImStricken06]

MAF SENSOR MAYBE. YOU HAVE WARRANTY?

[Cypress_1973]

Quite possible ImStricken. Thanks. I'll check that. No warranty. Long gone. Have 180K on the car.

[Rogue One]

As first guesses go, InStricken may be on to something. I'd like to suggest running it over to some place like Autozone and have them run a check for error codes.

Of course you could try cleaning your throttle body with some intake cleaner, what with having 180k on the engine.

[Cypress_1973]

Hey Rogue One. I have an ODB II reader and had it hooked up. No error codes recorded. At no time did the engine light ever come on. I took the MAF sensor out after ImStricken mentioned that, and gently cleaned it and reinstalled. Started the car and she runs nice a smooth now. Went for a quick drive and no issues.
Hopefully that was it, some slight contamination. If it re-occurs I'll be going to my dealership.
Thanks for the input guys.
Cheers.

[ImStricken06]

glad that worked out for you! care to share how you cleaned it?

im not a fan of touching that sensitive pain in the but sensor, as just about anything can break it or send it wacky. but i hear great results and often no change from this spray available in every auto store:

[Rogue One]

Hey Rogue One. I have an ODB II reader and had it hooked up. No error codes recorded...
Thanks for the input guys.
Cheers.

Not surprised by that. Here's a synopsis of why you didn't find anything.

To minimize the occurrence of false Malfunction Indicator Lamp (MIL), the OBDII system is programmed so that the MIL lamp only comes on if a certain kind of fault has been detected twice under the same driving conditions. With other faults (those that typically cause an immediate and significant jump in emissions), the MIL light comes on after only a single occurrence. So to correctly diagnose a problem, it's important to know what type of code you're dealing with.

Type A diagnostic trouble codes are the most serious and will trigger the MIL lamp with only one occurrence. When a Type A code is set, the OBDII system also stores a history code, failure record and freeze frame data to help you diagnose the problem.

Type B codes are less serious emission problems and must occur at least once on two consecutive trips before the MIL lamp will come on. If a fault occurs on one trip but doesn't happen again on the next trip, the code won't "mature" and the light will remain off. When the conditions are met to turn on the MIL lamp, a history code, failure record and freeze frame data are stored the same as with Type A codes.

A drive cycle or trip, by the way, is not just an ignition cycle, but a warm-up cycle. It is defined as starting the engine and driving the vehicle long enough to raise the coolant temperature at least 40 degrees F (if the startup temperature is less than 160 degrees F).

Once a Type A or B code has been set, the MIL will come on and remain on until the component that failed passes a self-test on three consecutive trips. And if the fault involved something like a P0300 random misfire or a fuel balance problem, the light won't go out until the system passes a self-test under similar operating conditions (within 375 rpm and 10% of load) that originally caused it to fail. That's why the MIL lamp won't go out until the emissions problem has been repaired. Clearing the codes with your AutoTap scan tool or disconnecting the powertrain control module's power supply won't prevent the lamp from coming back on if the problem hasn't been fixed. It may take one or more driving cycles to reset the code, but sooner or later the MIL lamp will go back on if the problem is still there.

Likewise, the MIL won't necessarily go on if you intentionally disconnect a sensor. It depends on the priority ranking of the sensor (how it affects emissions), and how many driving cycles it takes for the OBDII diagnostics to pick up the fault and set a code.

As for Type C and D codes, these are non-emissions related. Type C codes can cause the MIL lamp to come on (or illuminate another warning lamp), but Type D codes do not cause the MIL lamp to come on. http://www.autotap.com/techlibrary/obdi ... future.asp

[ImStricken06]

my father's 2010 Lincoln towncar that he uses for his limo business, surges upon acceleration for months now, and its not always. sometimes every other stop-light and never a MIL light. i have learned to not rely upon that silly light. it only turns on when its dead obvious or when something minor happened and its a false reading.

[Cypress_1973]

Hey guys. I just removed the sensor and quickly sprayed it with CFC free electro contact cleaner. Made by LPS. I'm an aircraft maintenance engineer and we use it for cleaning Aircraft electronics/avionics connections. Fast evaporating and doesn't leave any residue behind. Just gave the sensor a couple quick bursts and that was it. Reinstalled it and good to go.
Thanks for the great info on why I didn't get any codes Rogue One. Very informative.

[stranger21ny]

My battery Died and the than i noticed my RPM especially at idle is all over the place. I cleaned the TB and the flow sensor but i tried the re learn process by my self many many times with no luck, i had to take it to a shop and paid $100 for a minute job with the computer which is a rippppppp off.

[rickrogue]

Hey guys. I just removed the sensor and quickly sprayed it with CFC free electro contact cleaner. Made by LPS. I'm an aircraft maintenance engineer and we use it for cleaning Aircraft electronics/avionics connections. Fast evaporating and doesn't leave any residue behind. Just gave the sensor a couple quick bursts and that was it. Reinstalled it and good to go.
Thanks for the great info on why I didn't get any codes Rogue One. Very informative.

Hahaha.. LPS FTW!!!