Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Is revving the engine equivalent to driving at high speeds?

I have a 95 Mercury Villager that didn’t pass inspection. I put SeaFoam in it before inspection to help clean the engine. Now I have been told that it may have caused gunk to loosen up and that I need to run out all of the gas in it and then fill it up and run it at high speeds for a period of time on the highway before I try to get it re-inspected. Since it didn’t pass inspection I couldn’t get it registered and it is technically not street legal at this point. I’m letting it run in the driveway to burn up the gas. Should I fill it completely when I get gas or should I put just a bit in and run it out a couple of times before I try to get it inspected again? Also, if I put it in park and rev it for 20 mins or so would that be equivalent to driving it on the highway? Any other suggestions?

If the car idles and revs OK, it’s doubtful you dislodged any gunk.

Reason for failure? HC…CO…NOx?

What state do you live in? You might be able to get a waiver to move the car to a test station, or get a temporary registration (a form of waiver) to give you a month or more to get it sorted out. Some of the usual posters know the regulations in their states and might be able to help you.

Once you have the issues sorted, drive the van for at least 20 minutes on the highway at highway speeds, then go immediately to the test facility. No stop and go on the highway, but continuous driving at highway speeds.

Please post the results of your smog test

We would like to see exactly what part was over the limit. Most important, we need to see “the numbers”

Then we will advise

How many miles on this 21 year old classic? At this point, it might take more than Sea-Foam…

I too would like to know the miles on the odometer and its maintenance history.
And, of course, the details of the emissions report. Exact numbers and your state’s specs please.

No, revving the engine without a load on it is not the same as driving it down the highway at high speeds.

Running the engine day and night for three days to consume a tank of fuel will test the neighbors.
You should obtain a temporary movement permit and take the vehicle to a shop for repair.

I would toss in as much junk as you can, find a steep hill, drive up with the ac on full blast. Then coast down in low gear with ac off. Rinse and repeat

That may take quite a few hills. If he lives in Illinois…he’s out of luck. he’ll have to go out of state to find a hill.


revving it up only heats the engine. It uses up gas too.

Revving in place could also overheat parts of the exhaust system due to lack of airflow.

I don’t know what state the OP is from, but in Wisconsin if you don’t pass you are given an extension so at least you can drive it so you can get it fixed. I think the first extension is for 30 days and at the end of that period if you fail the testing. you are then given a few days to get it fixed or get it off the road.
I don’t know how long the extension is for, but maybe the OP has already gone through the extension period.


That may take quite a few hills. If he lives in Illinois.....he's out of luck. he'll have to go out of state to find a hill.

No hills no problem, inertia can load an engine just as well as a hill. Accelerating from zero to 60 is like climbing a 120 foot tall hill. Surely there is a straight stretch of road that can be used as a drag strip, if not an actual drag racing track in the state. Grudge match night at the local drag strip, see what your car will do in the quarter mile and burn up that gas too, two birds with one stone.

No…no way.