Trouble with my 1990 Mighty Max

I got a 1990 Mighty Max a few days and have been trying to figure out what is wrong with it.

I will try to explain my problem the best I can but I usually not to good at explaining problems.

In the mornings or if it has been sitting for a while it is kind of hard to get to start. It will turn over several times before it starts. After it starts it will die right away. This usually happens a few times before I am able to keep it running with the throttle. (After it warms up it usually starts up normally) The whole time is it running very rough/missing. I have to keep it running with the throttle for a little while before it will idle on its own. It seems to idle "smoothly" but idles very high (I don't have a tach but I would guess around 1500rpm) When I start to pull out it will buck and jerk around but I can eventually get it up to speed and it drives almost normal but feels down on power and always runs rough and misses. It will also bog down and sometimes sound like it is backfiring in the intake if I try to give it alot of throttle. Sometimes when I am driving like on the highway going a steady speed and holding the gas steady it will suddenly bog down really bad almost like you cut the key off for a second or two then it will start going again. When I come to a stop and try to pull out it will sometimes bog out really bad and wont go at all and will usually die. I have got stuck in traffic like this a few times and couldn't pull out LOL. I have to crank it back up and try to pull out several times before I am able to get it going again.


At first I though it was mainly due to bad plug wires because they were very badly dry rotted and half the boot was broken off of each one. I assumed the spark was arching over to the head. I swapped the plugs and wires for a new set but the problem is still there. I have not been able to replace the cap and rotor yet but I have cleaned them. I also removed and cleaned the EGR, air flow meter, TPS and O2 sensor. I also put a new fuel filter on today. After all this it seemed to run a little bit better for a few minutes and then went right back to doing the same thing. I have a check engine light on too but I cant check it until I get a analog voltmeter. I tried to read it with my digital one but it cant keep up with the changes in voltage enough to try to read it.

Sorry for such a long post. Just trying to give as much info as I can so I can hopefully get this fixed

If it was sitting for a while, it could be that your fuel injectors need to be cleaned. I tried running FI cleaners with no success and then pulled my injectors (very easy), took them to a shop for testing, called Dr. injector. They were like 75% clogged. After cleaning, truck ran perfectly. The charge to test and clean was about $30/ injector.

Thanks for the reply. I was told when I got it that it had been sitting for about a year or so because of a bad fuel pump. There were some old tags behind the seat from 2010 so it may have been even longer. I will remove the injectors and try to clean them and see if it helps. If not I found some new ones for $29.99 each which isn't too bad but I hope cleaning them will help it out thought because I don't really have a lot of money to put into it right now :(

If you know anyone with an ultrasonic cleaner, I believe that is what the shop here used. A lot of small engine shops have them for cleaning carbs. I think you'll be pleased with the results. The shop insisted on new o rings, which are really cheap. Good luck, let us know how it goes!

My friend had a can of CRC "Engine Performance" cleaner and we put half a can of it in the gas tank this morning. It must work good and fast because the truck was running like it normally does when I started driving it and it gradually started running better and better the further i drove it. After just a couple miles it was running better than every. Now it runs almost normal and just has a little hesitation. I put a little over 100 miles on it since we put the cleaner in it and its doing great compared to what it was. It has not bogged out and died on me a single time and has only done the backfiring noise through the intake once or twice while it was under heavy load.

The cleaner did really good to get it where it now and I think actually pulling the injectors and cleaning them outside of the truck should get it running as good as new.

I was checking the cam timing and I think it might be one tooth off. When the crank is at TDC the dot on the cam pulley is pointing just a little bit above the little bump that I read it is supposed to be pointed at. I am going to re-time it my next day off work to make sure it is set correctly. After I set the cam and crank to TDC, where should the distributor timing be set at?

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Originally Posted by lush90

If you know anyone with an ultrasonic cleaner, I believe that is what the shop here used.

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Harbor Freight sells one for around $25.

The Hft one I have has been awesome, saving a LOT of $ and hassle, also! Had it for 4-5 yrs was $50 back then...

Reading the codes stored if your CEL is on could b every helpful.

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Originally Posted by lush90

Reading the codes stored if your CEL is on could b every helpful.

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I tried to read the codes but I'm not sure what the code it gave me was. I don't have a analog voltmeter so I made a test light from a small LED out of a car charger for a phone. I used this thread as a guide: http://www.mightyram50.net/vbulletin...k+engine+codes

The code I got didnt really follow the same pattern and the one in the thread above so I'm not sure if I was reading it right. I restarted the test and wrote the code down several different times to make sure I wasn't missing a pulse or something.

The code I got was : L-S-L-L-L-L-S-S then there would be a long pause and it would repeat the same code again.

I just wanted to update this thread to see if anyone had any idea what the code that I got was. I drove it around for a little while after I got it running decent and it started acting up again. It will crank and idle for a few seconds while the idle is high but as soon as the idle drops down to normal is just dies. It will stay running if you keep revving it up a little. If you try to rev it up quick or try to rev it to high it cuts out like it is going to die.

I pulled the upper intake off and its seemed like it had oil or gas puddles in the runners. It was really dark almost like oil but was verry runny and smelled like gas so I think it was gas that just turned black soaking in the carbon build up in the intake.

Could my injectors be messing up again and hanging open and dumping way too much fuel in it? If so are there any other cars that have fuel injectors that work in a 2.4 MM? There are not any fuel injected MMs or D50s in any junkkyards around here.

I dont see a code like that in my Haynes manual...

I don't see a code like that either. I've read that test lights with LED bulbs may give funny results because they draw such low amps or something. I'd try it again with just a plain test light and see if you get a different code. Keep at it, you'll get it figured out. Most of the time it turns out to be something relatively simple. I still question whether your injectors are clogged from sitting. I used several bottles of fuel injector cleaner with no noticeable improvement but when I pulled them and had them cleaned, it was like night and day. Mine never stalled though, it just ran rough over about 40 mph.

II forgot to mention that I checked it again with a analog voltmeter and got the same thing. I can try to get a video of the code that I get in case I'm reading it wrong.

codes are numerical. Not alpha.

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Originally Posted by vaprobe87

II forgot to mention that I checked it again with a analog voltmeter and got the same thing. I can try to get a video of the code that I get in case I'm reading it wrong.

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Yea. if you could get a video of the code that might help some

You may start here, good description of codes.

http://en.wikipedia.org/wiki/OBD-II_PIDs


MightyRam50.net has also got a code listing here. It doesn't show your code errors.

My Toyota MR2 does a similar routine of code reading. You actually don't read the letters. You would read the (Morse) code information. Like reading SOS signals in Morse Code. Check the error with an information sheet specific for your vehicle.

Example: .. ... .. ..... . ... .. then it repeats itself.

1990 will be OBD-1, not OBD-2 (OBD-II) sorry brad.

You mentioned it had been sitting because of a bad fuel pump. I take it that it was replaced? You might want to check that it has a good ground or check the fuel pressure to make sure it is good.

Yeah, I was told that it had been sitting for about a year or so because the pump was bad. The car lot I got it from said they put a new one in it after they got the truck. I will drop the tank when I get time and check everything out. I want to make sure there isnt a lot of trash in the tank and I would like to take a air gun and blow the lines out to make sure they are clear. i put a new fuel filter on it not to long after I got it so it should be fine.

If i get a pressure gauge to test it, how much pressure should it have?

According to Haynes: 38 psi at idle with vacuum hose connected to pressure regulator, 47 to 53 psi w/ vh disconnected from regulator