I maxed out RPM (8k) in my Mazda3 automatic

[JEDI]

today, i had a long crank to start my car.

when that happened b4, i guess it was because of fouled spark plugs because when i red lined the engine, the long cranking went away. then was when i was driving and gunned the gas after i paid at the toll booth.

well today i tried it again, except i was in park this time. i thought engine would stop racing once it hit the red line (6k rpm). nope, it went all the way to 8k. i immediately let go of the gas when i saw that.

what would happened if i left the pedal to the metal and let it go to max for 1+ min?

 

[jagec]

When the engine was COLD?:shocked:

Never, never, never redline a cold engine. It is not fully lubricated, and the metal has not expanded to its intended tolerances. You're causing SEVERE wear, if not outright damage, when you do that.

When the engine is fully warmed up, you can redline it, but it's really better to do it in gear if you want to burn off carbon deposits, and letting it sit at redline isn't a really great idea for a number of reasons, including unnecessary wear, overtaxing your cooling system (not usually a problem when moving, but in Park it might be), overheating a component of the engine that is not overengineered enough to take constant redline operation, and so on.

Next time you want to do an "italian tuneup", follow the procedure listed below.
1)Make sure your engine is in good mechanical condition. No oil leaking/burning, no knocking, no CEL, no worn-out or nearly worn-out components.
2)Start the car, drive around without pushing it hard until the engine is FULLY warmed up (like, the temperature needle is in the middle of its range and no longer moving).
3)Go to a freeway onramp, CHECK FOR TRAFFIC AND COPS, then gun it and let the engine hit redline a few times. Once on the freeway, you can also downshift manually to let the engine sit at a high RPM for a half-minute or so, then shift back. Maybe add some spirited driving on the way back.

But really, if your carbon deposits are that bad, just use Seafoam.

 

[JEDI]

Originally posted by: jagec
When the engine was COLD?:shocked:

Never, never, never redline a cold engine. It is not fully lubricated, and the metal has not expanded to its intended tolerances. You're causing SEVERE wear, if not outright damage, when you do that.

When the engine is fully warmed up, you can redline it, but it's really better to do it in gear if you want to burn off carbon deposits, and letting it sit at redline isn't a really great idea for a number of reasons, including unnecessary wear, overtaxing your cooling system (not usually a problem when moving, but in Park it might be), overheating a component of the engine that is not overengineered enough to take constant redline operation, and so on.

Next time you want to do an "italian tuneup", follow the procedure listed below.
1)Make sure your engine is in good mechanical condition. No oil leaking/burning, no knocking, no CEL, no worn-out or nearly worn-out components.
2)Start the car, drive around without pushing it hard until the engine is FULLY warmed up (like, the temperature needle is in the middle of its range and no longer moving).
3)Go to a freeway onramp, CHECK FOR TRAFFIC AND COPS, then gun it and let the engine hit redline a few times. Once on the freeway, you can also downshift manually to let the engine sit at a high RPM for a half-minute or so, then shift back. Maybe add some spirited driving on the way back.

But really, if your carbon deposits are that bad, just use Seafoam.

oh man.. never thought of temps. yeah, ice cold as in sitting in the rain for 4hrs

RPM went from 1k to 8k in about a couple of sec, at which time i immediately let go of the gas. hopefully no dmg. anyway i can easily check?

thx for the tip to shifting to manual mode for high rpm.

carbon deposits probably from all the short driving (ie: less than 5 mile trips multiple times a day) cause of the holiday shopping/returns/refills at Starbucks.

whats seafoam, and how do i administer it?

 

[BUTCH1]

Maybe a new set of plugs and wires might make a difference..What type of car is this?

 

[Zenmervolt]

Wait, so redline is at 6,000 RPM and it went past that to 8,000 RPM? That's pretty strongly not good. If the engine is running fine right now, you got lucky. 2,000 RPM above redline is just asking to swallow a valve or bend one due to valve float.

Carbon deposits are not a huge problem with modern engine management, they would take quite a long time to build up unless something external to driving habits was causing them. That said, I still think it's a good idea to run the engine hard while in gear and driving to keep it happy. Revving an engine in neutral (or park, which is functionally identical to neutral as far as the transmission's true guts are concerned) won't put a load on it and won't be any real benefit to cleaning anything up. As you discovered, most rev limiters also do not function unless there is a load on the engine.

ZV

 

[imported_Truenofan]

well, i know my car redlines at 7, but it'll rev to 8. same with the model of mine that redlines higher, it'll go all the way up to 9k out of gear which is never good for any engine. good point though zv, it is good to redline your engine while in gear occasionally when its warmed up and all lubed up properly to break carbon deposits lose and get them out of your engine.

 

[jagec]

Originally posted by: JEDI

RPM went from 1k to 8k in about a couple of sec, at which time i immediately let go of the gas. hopefully no dmg. anyway i can easily check?

thx for the tip to shifting to manual mode for high rpm.

carbon deposits probably from all the short driving (ie: less than 5 mile trips multiple times a day) cause of the holiday shopping/returns/refills at Starbucks.

whats seafoam, and how do i administer it?

Unfortunately there's no really great way to check...but it doesn't really matter, because the sort of damage that overrevving a cold engine would do is the sort of damage that leads to a new engine, whether or not you know its exact nature. No one bothers to replace valves, hone cylinders, replace bearings, and remachine heads for economy cars, not when it would be cheaper just to do an engine swap or buy a whole new car.

For now, just keep driving it, and if nothing crops up count your lucky stars. If the car had actually been driven those 4 hrs ago (vs. sitting overnight), that would help, since it's more likely oil was distributed throughout the engine at the time of the overrev. You have two main concerns here: lack of lubrication due to high RPM operation on a cold engine, and potential mechanical damage due to exceeding the redline. I suppose the chances of permanent damage would be lower if you have a non-interference engine, but I don't know off the top of my head what they put in the mazda3's. If it's running fine now, chances are you didn't do any serious damage (things like bending the valves should be pretty immediately obvious, scraping the cylinder wall with dry piston rings less so).

Seafoam is a cleaning product for car engines. You get it at Napa, pour half of it in your oil, half in your gas tank (more if full), and the remaining half gets sucked up a vacuum hose, like the one going to your brake booster. This is done on a warm engine. Then you drive recklessly around the block until you're no longer outputting massive clouds of smoke, change your oil a few days/weeks later, and call it good. I think of it as a "once-every-few-years" sort of thing.

If you're doing lots of short trips, and having trouble cranking due to partly fouled spark plugs, the easiest solution is just to get hotter plugs. Those will be able to burn off deposits even during the short trips. Pull the plugs and check the color to confirm...are they kind of blackened and sooty? Hotter might be a good idea. If they are white, cooler is the way to go. They should be light tan under "normal" conditions.

 

[HannibalX]

SeaFoam is frikking great. Love the stuff.

I have been using it for years. I use a straw and let it suck about half a can in via the PCV until the engine stalls. Let it sit for about 30 mins to an hour, come back and rev the heck out of it. I generally take it on the interstate and open it up.

Change your oil and filter and at the same time dump a can of SeaForm into the oil. Drive around for a week and then change the oil and filter again. You will be amazed. My 150k mile 4.6 V8 runs like it did when it was brand new.

I usually do a SeaFoam treatment once a year along with tranny flush, spark plug change, cooling system change, rear end fluid change and other misc things like check the refridgerent level.

High milage cars can be very reliable if you look after them right.

 

[andylawcc]

i once downshifted from 4th to 2nd and it bounced to 8k rpm when the redline is barey 6k rpm (toyota 1.8L 7AFE). I shifted to neutral immediately. It scared me, but thought, hey, maybe I can push my car further. :evil:

anyways, the car ran fine afterwards. no problem for that one incident. the car never can go pass 6k rpm, and if it ever does, the ECU will cut the gas.

 

[ayabe]

I can't believe you did that with a cold engine, that's just a terrible, terrible thing to do.

That's like this guy at work who redlines out of the parking lot everyday in his Audi. Makes me sad for humanity.

 

[Zenmervolt]

Originally posted by: Truenofan
well, i know my car redlines at 7, but it'll rev to 8. same with the model of mine that redlines higher, it'll go all the way up to 9k out of gear which is never good for any engine. good point though zv, it is good to redline your engine while in gear occasionally when its warmed up and all lubed up properly to break carbon deposits lose and get them out of your engine.

Rotaries tolerate over-rev a lot better than piston engines though. No valvetrain to get screwed up. Apologies if you were talking about a different car than your RX-7.

ZV

 

[thomsbrain]

I rented a 2.0 Mazda3 for a week or so, with the manumatic transmission. It would hold a gear for about 1K past redline and wouldn't force an upshift, just bounced off the limiter. I made ample use of the headroom.

 

[MiataNC]

You can't go past the rev limiter on a modern automatic (you can do it with a stick if you down shift too far at speed). You will bounce off fuel cut. So you are looking at either tach error, or the red portion of the tach is a red line "zone".

If you are going to readline on a cold engine, you are SEVERELY limiting the life of that engine. Don't do it.

 

[DougK62]

I can't believe there are people who don't know to not beat on a cold engine. lol

 

[Zenmervolt]

Originally posted by: MiataNC
You can't go past the rev limiter on a modern automatic (you can do it with a stick if you down shift too far at speed). You will bounce off fuel cut. So you are looking at either tach error, or the red portion of the tach is a red line "zone".

If you are going to readline on a cold engine, you are SEVERELY limiting the life of that engine. Don't do it.

Not necessarily.

Most rev limiters are designed to operate when the engine is under load. If you rev the engine in neutral, it is most certainly possible to over-rev an engine in many modern cars.

Even if the fuel cut-out did stop the engine from over-rev, it is still very stressful on an engine to bounce it off the rev-limiter and doing so should be avoided if at all possible.

ZV

 

[Sluggo]

Originally posted by: jagec
Seafoam is a cleaning product for car engines. You get it at Napa, pour half of it in your oil, half in your gas tank (more if full), and the remaining half gets sucked up a vacuum hose, like the one going to your brake booster.

Hey, thats 3 halves. :frown: