check engine goes on and off

[Ravins]

My check engine light has been coming on and off. It only goes on when above 15mph and goes off when under 15mph. Sometimes it does not even come on and then sometimes its on for long period of times. Does anyone know what this could be? Thanks Ravins

 

[Mbrooks420]

Have an autozone or similar place scan it for free. With several hundred causes it's very hard to make any good guess as to what it could be.

 

[Alanslinky]

Try changing your oil. When I bought mine the previous owner said that they'd just changed the oil less then 200 miles beforehand. It was doing the same thing your describing, so I got it checked out by autozone and they determined it was the MAF sensor. Not having the money to fix that at the time I just kept driving it. After a while i figured it was time to change the oil, so I did, and the check engine light hasn't been on since.

 

[colindo94]

mine was o2 sensors

 

[Tony H]

This happens to my '91. Not exactly like yours If I drive a long run and then get caught in traffic, it comes on, after getting back up to speed it eventually turns off.

 

[Bwana Bob]

Could be dirty MAF or bad O2 sensor, but might also be "bad gas". Try running a bottle of fuel system cleaner, like Chevron Techron in the tank.

Bob

 

[mikeinri]

OH MY GOD, STOP THE MADNESS!!!!

OK, now that I got that out of my system... Have the codes read. There's a reason the CEL came on, and even if it's currently off, it's stored in the memory.

Otherwise, you can buy new gas, change your oil, change my oil, get some magic dust, rub a bottle and wait for a genie to pop out, or sacrifice a chicken. You're still better far off getting your codes read and fix this correctly. Long-term, there are no acceptable substitutes...

Mike

 

[Glacier991]

Thank you Mike. I was turning blue from holding my breath.

FOLKS... that light has a computer that is turning it on. AND, that computer is just WAITING to tell you why it did. Give it a chance. Stop the roulette.

 

[Jason94sport]

I don't know...I had intermittent check engine lights & each time there were no codes stored. I read that these types of codes do not get stored long term. Only with each engine cycle. In my case it was a faulty DPFE thing(EGR system)

 

[Tony H]

Yup...no codes.

Tried that.
First thing I did was clean the MAF after reading that is can be problematic.

My guess is a lazy O2 sensor.

 

[bam_bam1ca]

If your not seeing codes, then drive it with the code reader attached and scanning to see if it will catch the code. Since it's a 94 you will have the EECIV OBDI system (poor you).

Like it has been said before, the computer is trying to tell you what is wrong, listen to it instead of guessing. There are a LOT of conditions that could cause the light to come on under those conditions. I can think of a few right off the top that are EGR, Vacuum or O2 related..... but you could spend hours of testing and investigating each circuit for each possible fault.

 

[Jason94sport]

Since the connector is in the engine bay you going to have to rig something. Can't drive with the hood up.

 

[UKExploder]

My '94 did that when the pipe that goes to the exhaust manifold and back to the fuel injector broke in two. It also started to make a slight exhaust noise, I got to looking around the engine & found that little pipe had worn into. I had the manifold plugged, the noise quit, the mechanic said that has to have the right amount of heat going to the fuel injectors or the light will come on. See if that may be your problem.

 

[bam_bam1ca]

Lol.... hook up the scan tool, close the hood.... go for a drive. The scan tool has MEMORY and will store the code faults in order. When you get back from your drive, open the hood and retreive the code reader.

 

[UKExploder]

You and your code readers

 

[mikeinri]

Ravins,

Have you had the codes read yet? If not, do that first. All these posts are circling around the idea that you don't have a stored code, which you haven't posted is the case. Until you try to read them, you don't know if they're in memory.

There are some codes on some vehicles that are not stored in memory, but the vast majority of them ARE.

Start with having the codes read (make sure you haven't disconnected the battery since the last time the CEL was on, or it will erase them). If you don't have stored codes, the you can resort to the Ouija board...

BTW, I speak from experience, NEVER ignore a CEL that comes and goes, that gets very expensive later...

Mike

 

[firewolfm]

Or you can do like I did when I found out how many possibilities there are to this light (CEL) going on. When my engine temp. reaches operating range the light goes on, somewhere there is a code memory stored, I repeat somewhere, If it's not broken don't try to fix it. Why do you think they call them IDIOT lights! If you have examined the obvious and your truck is running,shifting,starting,stopping wait for the problem to reveal itself. As with mine it has not as yet caused a problem, so I just enjoy the extra light at night when I'm driving....

 

[Mbrooks420]

They call them idiot lights because some people are too stupid to realize they should occasionally check their gauges. I don't consider the Check Engine light an idiot light since the computer senses an error. An idiot light is the one that tells you to check your gauges. A CEL might tell you about an out of range sensor that may lead to a mpg drop. If it is only minimal you may not notice. It's worth looking into since it may say you a larger problem in the future.