1991 300 I6 2wd EFI HELP!!!

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Old 07-30-2012, 02:05 PM
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1991 300 I6 2wd EFI HELP!!!

Ok, I bought this truck when I was 17 years old. I came from a long line of non-mechanical people (however with the help of a book I was able to sucessfully replace an automatic transmission on an 83 ranger) so my knowledge is limited, but I want to learn and know if i do enough research I can learn how to do what i need to do with your help.

Ok I bought this truck in 1996 and she ran beautiful. around the spring or summer of 99 I noticed a miss, so i changed the plug and wires which gave me a little improvement, but not a whole bunch. I let it go and for the last 5 or 6 years she has pretty much sat except for out yearly trips to the lake where im hauling camping equipment and a 24' pontoon boat. She still has some power, but she misses like crazy. so this spring due to financial reasons I down to this old truck and it's time I take the abuse I have given her for so long and treat her right. I have a long road ahead of me, but i want to start with the engine.

Let me explain the miss or choke out, not sure which i would call it. it was running so rough it wouldn't stay running in idle. I changed the spark plugs again a few days ago, and the fuel filter. Made a big improvement, but still have problems. when i start it cold I have to rev it up to a higher rpm (not sure what rpm because my guage goes screwy. (it will be sitting at 1000rpm and jump up to 3800rpm without the motor accelerating) Once i rev it for a few seconds it will idle pretty good with an occasional miss maybe one ever 15-25 seconds. not bad at all. As soon as i put it in gear it either stalls out or chokes down to barely running for about 3 seconds and revs up on its own to catch back up to idle speed. (putting it in drive is worse than putting it into reverse for some reason). once i hit the gas to go forward or reverse I have to pump the gas to get it to stay idling. If i were to just step on the gas it would bog down and choke out. It may catch itself and run. once i get going in 1st gear it has a constant miss maybe every second. If i gun it, it seems a bit better to maybe every 2-5 seconds. The big problem is when I hit second gear, or when i try to maintain speed at 55. the truck misses so violently it make the whole truck shake. Once the truck is warmed up i can barely hear a miss and cant feel a miss when i go from stopped to go. However the shifting of gears always bogs it down to barely running where the battery guage drops trying to keep the truck rolling.

Today i took the air filter off and tried to run it. Huge improvement with 1st and 2nd gear, but still missing awfully when trying to maintain speed and still bogging down really low when popping into drive. What do you think my next step is.. distributor? i didnt change the wires. they didnt help last time I changed them so i figure they wouldnt this time.. Oh and last time I changed the plugs was the 1st time i ever did it and when i changed them this time they old ones i put in a long time ago were loose. I'm positive that was what was giving me some performance issues. Oh and I took it to the shop maybe 7 years ago before she sat all the time and they ran some kind of injector test and said all the injectors were doing good, So i'm ruling that out since it was missing before that test was done. so its not injectors, plugs, fuel filter or air filter. all these things (other than injectors have helped improve, but not fix the problem) any suggestions? I also tried to take it to autozone to see if they could give me some codes, but their tool only goes back to 1995. what should i do next?
 
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Old 07-30-2012, 06:50 PM
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Have you looked at the distributor cap and rotor?
 
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Old 07-30-2012, 08:32 PM
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it looks ok, but i havent taken it apart. i'm going to take it off and take a look at it. im guessing this isnt my problem, but i'll check it before i go any further.
 
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Old 07-30-2012, 09:06 PM
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Ok i took the distributor cap and rotor off. I never have looked at aworn out one before so im not positive to be able to tell if its worn. I can see copper on the tip of the rotor and it appears to be pretty worn. I also notice a bit of white corrosion on the inside of the cap on each point. I'm going to replace it because i'm assuming that this probably isnt a standard thing. I'll let you know the results. Any addition advice would help also. I really think we are fuel related. Oh I also took the breather valve that goes into the air filter next to the oil cap and i notice a very tiny bit of white smoke when shes running. I don't see any coming out the tail pipe, but i thought i would tell you all about another symptom.
 
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Old 07-30-2012, 09:10 PM
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now that i think about it, i think one of the screws on the distributor cap were loose. I'll examine that tomorrow. hmmmmmm.... now im thinking.
 
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Old 07-31-2012, 01:03 AM
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Replace the cap and rotor.
 
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Old 07-31-2012, 03:48 PM
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cap and rotor replaced. One of the sides of the distributor base was broken so When i put the new cap on i used a long bolt with a nut to keep the cap fastened to the base securely. Before I decided to start it I took the IAC motor off and cleaned it out. While I was pulling it off I noticed one of the screws going into the throttle body was very loose. I unscrewed it and cleaned it and put it back on the screw that was loose has been stripped at one time or another. I'm guessing this it my problem. I put it back together the best I could and now it doesnt start at all. I'm not sure if its the cap and rotor not working right or the IAC motor. I get a backfire once in a while but it sounds like its not getting spark. Im soo screwed now. WHat do I do?
 
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Old 07-31-2012, 06:53 PM
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OK I got her running again.. I'm an idiot. I didn't have the rotor in the right way. I'm good now. Tomorrow my friend is bringing his tap set home and we are going to tap out the throttle body where the IAC motor mounts on to the throttle body. Right this minute the truck is idling good, but as soon as I pop it into gear she almost chokes out, but then regains composure and sits idling very rough. I'm hoping being able to snug the IAC down tight is my problem. I will let you know what happens.
 
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Old 07-31-2012, 09:42 PM
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Weird, I changed the oil tonight and it seems to idle worse than it did before? is this a common thing? It may be sucking more air cause the oil is thicker? i'm confused.. oh well.. ill take care of the throttle body tomorrow and see what happens. You know I bought this truck from a dealer in 1996 with 60k miles on it. I've only ever taken it to 1 garage. it really erks me that someone has busted the distributor housing and stripped the threads on the IAC motor. Sure I may have stripped it worse than it already was, but I wasn't aware that it was stripped. Surely you should be able to put a little force onto it without it stripping out. that duude lost all business with me.. hes a jimmy rigger. and supposed to be a professional... bah.....
 
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Old 08-01-2012, 02:54 AM
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Check all ur vacuum hoses and see if ur PCV is clogged.
 
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Old 08-01-2012, 07:41 AM
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Vaccum hoses dont appear to be messed up at all. I'll look at the PCV, thanks. I am sure this IAC motor is what was causing some on my problem, but i'm guessing this isnt the whole issue. Im going to get that fixed before I mess with the PCV..
 
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Old 08-01-2012, 02:01 PM
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You MIGHT need a new distributor - if the shaft bushings are worn it will run like crap.
 
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Old 08-01-2012, 02:29 PM
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Possibly could also be out of time a bit. If you have a repair manual handy, I would look into that as well on how to do it. Been so long since I messed with a distributor equipped motor, that I don't entirely remember.
 
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Old 08-01-2012, 04:09 PM
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Yeah that could be a possibility. I'm checking these sensors 1st before I go tearing into the distributor. I think thats a last resort. I have an oil leak or transmission leak, not sure which. I notice it's damp on the back side of the motor where the tranny meets the engine, but i'm not entirely positive if its coming from the tranny or the motor. Its way back in there. I'll have to climb up in there to look. It might be coming from the valve cover in the back which could be causing my problems, but I dont think thats it honestly. This engine has been missing way longer than that leak has existed, reguardless for now i'm not worried about the leak. I put a piece of cardboard under the truck where i seen the leak and got 3 drips in 3 days, so right this minute its not a big deal to me, but some day that will be a fix. right now i have to get the engine running good, and then an entire new suspension both front and back.
 
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Old 08-01-2012, 07:47 PM
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Possibly a rear main seal leak.
 

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