Check engine light

[mehedgec]

I was driving earlier and I felt a bit of a kick, and glanced down to see the check engine light. I was moving at about 35mph and it felt like when the car drops into gear when stationary.

I turned it off, and cranked it back up, and the light was not on. The car ran fine, but after a couple of seconds, it began to idle a bit rough, and every now and then would try to cut out.

Any ideas on what the problem could be?

This is a 93 explorer btw.

 

[MrShorty]

Start by pulling codes from the computer to see what kind of problem the computer saw.

 

[marragtop]

Most autozones will pull the codes for free. Call ahead to verify. Also, remember even if the CEL is off, there may be codes stored.

 

[mehedgec]

I actually did that, it came up with a MAF low voltage code.

I got some MAF cleaner and an air filter while I was at it since it was nasty. The MAF cleaner seems to have worked, its idling smooth when I cranked it. so I hope its over. I haven't gone driving around to see if it worked yet, so we'll see tomorrow if it indeed was the problem.

Are there any other things that could trigger that code?

 

[MrShorty]

So many other possible causes. In theory, most anything involved in fuel management (which is a lot) could also cause that code. IMO, clear the code from memory (if you haven't already) and wait to see if it resurfaces.

 

[mehedgec]

So many other possible causes. In theory, most anything involved in fuel management (which is a lot) could also cause that code. IMO, clear the code from memory (if you haven't already) and wait to see if it resurfaces.

It seems to have taken care of the problem. Runs nice and smooth. No check engine light so far.

 

[mehedgec]

Well nevermind, the light came back on and it continued to stumble off the line like before.

It didn't happen any this morning on the way to work, but after sitting all day in the sun it happened almost immediately. Does anyone think the fact that the air is so hot in the afternoon would cause this?

 

[MrShorty]

Is it the same MAF code as before or something else?

 

[mehedgec]

Is it the same MAF code as before or something else?

Same

It didn't do it earlier when the engine was cold. only seems to happen when its warm.

 

[MrShorty]

Code 157 or 159 or ?? KOEO, KOER, and/or CM code? Did it pass (111) any of the above tests? Wiring/connections between MAF and PCM good? Fuel pressure correct?

 

[mehedgec]

Code 157 or 159 or ?? KOEO, KOER, and/or CM code? Did it pass (111) any of the above tests? Wiring/connections between MAF and PCM good? Fuel pressure correct?

I got a 157 memory code. And a 111. All harnesses seem good. Voltage at the MAF was around 0.2 14 6 and 0 for the ground.

It didn't do it this morning as I expected. It does it in the afternoon when it gets hot. So I think it might have to do with the heat. Not the engine heat, but the hot air. Does this maybe narrow it down?

 

[mehedgec]

Does anyone know if air temperature can affect a bad MAF? I don't have any problems in the morning with the cool air, but do in the afternoon in the hot air.

 

[Alaskanredneck]

Myguess would be a bad air charge temp sensor
motorcraft part number dy674 good luck

 

[mehedgec]

Now its happening no matter what the air temp is.

 

[Alan_V]

Does anyone know if air temperature can affect a bad MAF? I don't have any problems in the morning with the cool air, but do in the afternoon in the hot air.

Yes and no. Intake air temp is an input to the PCM on all MFI vehicles. But it is unlikely to have as much an effect as coolant temp.

By your description (it comes and goes, right), it sounds like mine did a few months ago. Checked for ref voltage and ground at the maf. Also backprobed the signal voltage and it was out. Replaced the MAF with one I got at Autozone (it was a BENDIX part, as the original), Problem resolved.

 

[mehedgec]

Yes and no. Intake air temp is an input to the PCM on all MFI vehicles. But it is unlikely to have as much an effect as coolant temp.

By your description (it comes and goes, right), it sounds like mine did a few months ago. Checked for ref voltage and ground at the maf. Also backprobed the signal voltage and it was out. Replaced the MAF with one I got at Autozone (it was a BENDIX part, as the original), Problem resolved.

It really isn't a come and go thing anymore, seems pretty consistent now. Rough idle, no power when taking off from a stop, but once I get above 1600 or so RPM it acts as it normally should. Also, I've noticed the smelly exhaust. What do you mean ref voltage? Can you explain in a little more detail what you did? Thanks.

 

[Alan_V]

It really isn't a come and go thing anymore, seems pretty consistent now. Rough idle, no power when taking off from a stop, but once I get above 1600 or so RPM it acts as it normally should. Also, I've noticed the smelly exhaust. What do you mean ref voltage? Can you explain in a little more detail what you did? Thanks.

It's been a number of months. Let me go home tonight and look a the truck. Then I can tell you what to probe and what values to expect.

 

[mehedgec]

It's been a number of months. Let me go home tonight and look a the truck. Then I can tell you what to probe and what values to expect.

Sweet thanks.

Also, on the way home from work just now, The light and symptoms decided to go on and off a few times...This is ridiculous.

 

[Alaskanredneck]

Can you describe the smelly exhaust does it smell like fuel or like coolant or what? does it only smell funny when its acting up or all the time?

 

[mehedgec]

Can you describe the smelly exhaust does it smell like fuel or like coolant or what? does it only smell funny when its acting up or all the time?

Smells like unburnt fuel. Only when I'm sitting there idling, like when its having trouble idling smooth.

Its obviously running rich.