1995 mighty max - check engine light turns on and off while driving

[new95max]

Hey I just got a 1995 mighty max. I passed the California smog test the other day but now my check engine light turns on for a few miles than back off for a few miles. If I turn off the truck when the light is on, it's still on whenever I restart the truck. But, it will turn off after I drive a bit. It doesn't seem to come on when just idling. Any ideas about what might be happening? I don't have the manuals yet... hopefully today I'll get them and also a multimeter to check the ecu codes. Thanks yall.

[new95max]

oh yea, it's 4g64 2.4l

[royster]

Once you get the voltmeter and manual, the manual will tell you how to hook up to see what the ECU is bitching about. I'm gonna place my bet on the throttle position sensor. The symptoms are identical to a problem I had before replacing my TPS.

I could be wrong. Let your truck tell ya!

And welcome to the forum. We demand photographs, here, because we're voyeuristic lunatics. I think it's a little-boy thing, who knows.

[geezer101]

Hi new95max, welcome to mightyram. To me it sounds like a sensor is on the ropes but hasn't completely failed yet. When the light comes on does it affect the engines' behaviour at all? I'd offer the same advice Roy has put up there for you - grab a manual or google it and see if it'll throw you an error code during a diagnostic run. Doing an ECU check is really easy and doesn't involve the dark magic us mere mortals fear (it is easier if you have a local auto store that offers a full ECU diagnostic and can run a print out for you) :thumbup:

[BradMph]

Can you reset those by disconnecting battery for a few minutes. Probably after what Roy mentioned also. Those positioners are notorious. The wife's car threw an error on a TP, replaced it and it still throws it occasionally.

[new95max]

Thanks for the info. I changed my dirty ass air filter (looked so clean and new from the top side upon first inspection but the bottom was as dirty as I've seen!) and the light has not come back on. Got my manual at a used book store today. I'll get the voltmeter soon and let yall know what happens. Post pix soon too.

[royster]

Those dirty~ass air filters will cause some havoc. And it's a reminder that often, the simplest answer actually is the solution.

[new95max]

Yeah another day & 50 miles after the air filter change and everything seems A-OK!

[BradMph]

We have manuals to download here on the forum also. ;) Glad to see another success story.

[new95max]

Well crap... The light's back on and off and on and off... Looks like the air filter wasn't the problem. I have my multi meter in the truck now so when the light comes on again I'll be able to check it out. I'll also look into the ECU for signs of corruption.

[royster]

The light doesn't need to be on for you to hook up the voltmeter and get readings. Just follow the book instructions and it will tell you what's wrong. Do let us know what it is, when you find out.

[new95max]

The light doesn't need to be on for you to hook up the voltmeter and get readings. Just follow the book instructions and it will tell you what's wrong. Do let us know what it is, when you find out.

Ok, took a while for me to find an analog voltmeter but the code it's throwing is the o2 sensor. I am really new to diy mechanics and the Chilton manual is confusing the heck out of me. How do I test the sensor to see if i have bad wiring or a bad 02 sensor? could the code be symptomatic of a larger problem??? The truck is starting to burn oil at start up and I'm going through about 1 qt every 1500 mi.

[camoit]

The oil will cause the O2 sensor to go bad. You need to replace the valve guide seals. It's no to hard of a process just time consuming. The trick is to do them one at a time using a good air compressor to keep them from falling into the engine. I have have herd of some people putting a small rope in there and turning the engine over by hand to fill the void. But compressed air with a compression tester adapter is the way to go.