Ok, so im about sick of having to work on this truck every time i drive it!!!!!! I had code 331. I got all the vac lines fixed and ran perfect for a 200 mile trip. Got home shut it down for a few hours. when I started it again it stalled!! Now its back to a bad lag in take off power and shifting hard and just running like crap in genral. Sounds like the rearend is about to fall out when shifting in to overdrive. I had planned on installing new bushings in the rearend soon but nothing is warn or loose. Im thinking the trans mount is wasted from all the hard shifting. Is the knock sensor making this truck run like this? Thats the only code and its just popped up a few days ago. its a 91 bronco with 5.0/e4od and only 46,000 on it compleatly stock so far. I have checked every vac line,IAC,TPI,EGR. just had tune up before i got it. Just to eliminate them as the problem I am going to get MSD 8.8 plug wires,coil,cap and rotor as soon as I get paid. I havent checked fuel pressure or timing yet but will when I do the tune up. This thing is only getting 10mpg if that! any one have any ideas for increased mpg add on and what else to check? sorry this is so sloppy, im dead on my feet tired.

 

Code 225 - Knock was not sensed during KOER test.

To check the knock sensor, "knock" on the engine. Literally, while its idling, give the block a tap or two with a hammer. If the knock sensor is functioning properly, you should hear a drop in idle speed. If not, the sensor and/or the wiring to it is suspect.

There is no Code 331 in the EEC-IV litany of faults.

The symptoms you describe should typically be producing more fault codes than what you are getting. A failed knock sensor will cause the poor accelerator response simply because the ECM won't "know" when detonation (knock) is occurring, so it just won't let the system optimize performance so as to avoid the potential for knock when it cannot tell if detonation exists.

 

koeo,111 koer,225. Thats all. This thing is shifting bad again and falls on its face on take off. I just changed the air pump and fixed all the vac lines so no more 331. To top it all off, its useing a lot of gass!! Going down the highway at 65mph RPM is steady at 1900. I have checked all plug wires with dvm and all checked out good. As I stated in my last post it just had a tune up 200 miles before I got it. No fule leaks and I had to drop the tank and install a new floater, I replaced the role over valve at the same time. Also new fule filter. I pulled the throtle body when I got it and it looks new! This thing is so clean it dont make sence. I dont get it!! I have had f150s in the past that had melted vac lines,durnt wires, just a total mess under the hood and the things ran WAY better than this bronco. I love this truck and looked for years to find one in this good of shape but if thangs keep up this way Ill have no choice but to sell it. Thinking about useing a sledge hammer to check the knock sensor!!! least then Ill have an excuse to build this 351!! Edit, I meant past code 311 not 331

 

Ok I just went out and hit the motor with a hammer. No change in RPM. Few things I left out in my first post. The truck lopes like its got a big cam now and the RPM jump from 800 to 1000ish when at stop in gear. If I put it in park RPM is at 1000 to 1200, if I goose it they drop down to 800 untill I take off and stop again. Sounds like a vac leak but I pulled them all and checked them, all are good. Intake vac is good also. Ill run codes again tommoro just to tripple check.

 

Triple check the codes. Could be a bad IAC valve. Whether things look clean or not sometimes these sensors just fail.

 

I did a 12 volt test on IAC and tested good. That was my first tought. Could it be TIP? I tested it when I got the truck a month ago but maybe it went bad?

 

Well, Im stumpped!! ran the codes again today 3x. koeo,111, koer,111! Not sure whats going on. Now the truck is getting worse! Cold its not wanting to run lopes like its got a big cam trying to stall. After a while of driving, lets say 10-15 min the idol starts jumpping and just now comming back from parts store it was like driving with the breaks on in overdrive. The trans fluid is fresh as is the filter with in 1000 miles and is full. Fule pump is newer and filter on the pump is new only a week old, tank looked brand new! In line filter is new also so is air filter. Motor is clean no oil leaks and no smoke or any noise. trans case is leaking slightly around tail shaft but thats from the trans moveing around from all the hard shifting on broken mount. Havent had time to replace knock sensor yet but now its not sending a code. Going to check fule pressure and timming later today. I rented a fule pressure tester today but it didnt work gage was stuck!! Also something worth noteing, its running a little hotter than it did. Not a lot but now temp sets on the O of normal when before it was on the N all the time.

 

Does your speedo needle bounce at all going down the highway? If so you might be in need of a speed sensor at the tranny end of the cable. All of that sounds real familiar.

 

speedo stays steady and is dead on. Something is major wrong with this thing! Getting some popping like bad balljoint from the front and today when I shifted in to drive sounded like the drive shaft was going to jump out on me. Loud clang!! So now not only does it run like poo, I also have u joints going out and sounds like balljoints!! To top it all off, got the title back today and its got the wrong name on it!!!!

 

Does the idle improve at all once the truck warms up? Sounds like you are dealing with an atypical problem. No Codes indicates nothing happening that the computer doesn't "expect to see". This doesn't necessarily mean there is nothing wrong with the sensors. ECT and ACT sensors can both be "within expected parameters" but inaccurate because they are stuck. An ECT sensor "stuck cold" tells the ECM that the truck is ALWAYS cold when in fact the engine has warmed up. This causes terrible fuel mileage, rich running, fouled plugs but typically makes it very easy to start cold. The same sensor "stuck hot" will make cold starts a royal pain, run the entire system far too lean and cause all sorts of idle issues including poor acceleration and stumbling on tip-in and under heavy acceleration. Sound like anything familiar?

An ACT sensor with similar issues will have similar effects on the system but rarely be as obvious as a stuck ECT sensor.

To test either sensor, you need a meter to test resistance. The attachment is a chart showing relative resistance values at given temperatures. To get the sensors to the hotter temps without a running engine, stick 'em in the oven and set a temp. to test. (As if I really need to say this... they're gonna be HOT use caution).

 

Thanks for the info Greystreak and to answer your question yes and no. First start of the day after sitting all night I have to tap the throttle to get the truck to idle (every time). If not the truck will stumble and stall. Once warmed up the RPMs jump between 1000 and 1800 when in gear at a stop (not all the time, just from time to time). If I put the truck in park the RPMs are at 1000 till I tap the gas and then they drop to 500/800 RPMs (this happens all the time). Under hard excelleration (mash it to the floor) it may take a second but it takes off and goes. After driving at highway speeds for an extended period of time the truck noticably runs worse. What it feels like to me, something is causing the timing to go way off under excelleration and on cold start. One of my plug wires has gotten hot and the insulatior is cracked (I know this needs changed ASAP but it is now wrapped in heat tape and move away from anything metal). This weekend I plan on doing a tune up with MSD cap and rotor, coil, Excel wires and MotorCraft plugs, I know this will help but I dont think it will solve all the problems. Yesterday I got under the truck and velocity joint was stiff, both front and rear yolks were lose, trans mount lose...all is fixed now and truck excelorates much better and smoother but still has a miss to it. I am looking into those sensors today.

 

Well tune up is completed. New plugs,wires,cap and rotor. Had to get autolight plugs. I got a set of motorcraft plugs and they wouldnt fit. The motor in this truck has been changed. The guy that owened this truck passed away and I got it off a family member, so I have no way of knowing what all has been done to it in the past. I have to say with only 46,000 on it a lot has been replaced on it!!!! Any way, the tune up helped a lot but didnt totaly fix the problem. I tried to test the ACT but couldnt get a good reading off it. I just replaced the ACT. It had carbon build up on it any way. Still the idle jumps slightly at stops after warmed up and on cold start wants to stall but will now pick up on its own after a moment. Still has a slight stall on take off. I can live with he way its running now but thats just not how I do things! Im thinking the pick up in the distributor is part of the problem. Any one have some input on this idea? Im going out now and start retesting IAC,TPI,EGR. I forgot the ETC so im going to get a new one today also but my temp gauge seems to work fine. Maybe the knock sensor is causing all this? Its not setting off codes now but when I tap the motor with a hammer the idle doesnt drop. Will post results.

 

Have you cleaned the IAC? If the ACT sensor was as filthy as you say, there is a good chance you have a fair amount of coking in the IAC valve body as well. You can remove it and clean it. ONLY use fuel injector cleaner or carb cleaner that is safe for "sealed" or "coated" throttle bodies as other cleaners will strip this sealer from the valve body and just make the coking issues exponentially worse in the future. Take care not to get cleaner into the electrical end (solenoid) of the IAC.

 

I did in fact replace the IAC with a new one, didnt fix a thing! Just my luck!! But I found the problem!!!!! My cats were melted! took them off and this thing came to LIFE!!!!!! Im like a kid in a candy store!!!!! Mash the throtle to the floor and its GONE! My God does this this thing run now!! 55mph floor it and it'll throw ya back in the seat, HARD!!! I am SOOO happy with the way it runs now! I cant thank you all enough for all the help! I have a lot of work to do to it still but at least now its all body and performance. Few small dents and one small spot of rust and body is better than new. post some pic ASAP.

 

Clogged cats are enough to stall an engine completely and even burn valves. Glad you figured it out. Nice thing is that with a 91 you don't have to replace them.