low power runs rough

[Ken the BEAST]

My 87 supercab 2.9 runs rough and is lacking pretty bad in the power department. (i floor it and it barely even accelerates). I have had this problem for a while. I have replaced the dist. cap and rotor, the tfi plugs and wires, throttle position sensor and i am extremely frustrated and out of ideas. (and yes the timing and firing order are perfect)

 

[RyanL]

While your problem may be a little more extreme than mine, it sounds like we're in the same boat. See if your fuel pressure regulator is leaking fuel out of rear from the vacuum tube - mine had a small leak which took a few seconds before it started to drip. I also found that my fuel filter was getting clogged (located inside the frame rail midway) contributing the problem. There's also a 22Kohm resistor located up on the firewall which can make it run like crap from what I hear - I checked mine, but it was fine. See if you're getting codes like I was (I had a couple stored in memory even they though the CEL wasn't on) which may point you in the right direction. Good luck, you're going to need it.

 

[Ken the BEAST]

is there a way to tell if your fuel filter is clogged or should i just get a new one? Also where is the resistor located on the firewall and how did you check it? and thanks im gonna need all the luck i can get.

 

[Earl43P]

A lot of AP stores will loan you a fuel pressure gage, check the idle pressure and watch it as you rev it. Then pull the fpr vacuum line and repeat. It's all in the Tech Library. Vacuum gage might help too, ask if they loan those.

Then, buy parts...fuel filter is a good start. Knowing more is cheaper in the long run. Test.

http://www.therangerstation.com/Magazine/Summer2003/VacuumLeaks.htm
http://fordfuelinjection.com/?p=41

 

[RyanL]

Yeah, if it's been a while or you don't know when the fuel filter hasn't been changed you should just go ahead a replace it. While the engine is running, pull the 30A maxi blade fuse for the fuel pump under the hood and let the truck die. That will relieve most of the fuel pressure. Just be careful when you pull the clips and fuel lines off of the filter because a little might come out on you (don't put you face right under it!). On mine, that resistor which I speak of is in a small yellow plastic rectangle with a wire going in on one end and other going out the other end. It was fairly close to the steering column and rapped up with electrical tape (from the factory it looks like) sticking out of the flex loom a little. It also said "resistor" right on it. To test it, I just took the leads on my multimeter which were fairly sharp and poked them into the wire on each side and was able to get a reading. Ford really should've had a better way to test it with connectors on each end or something on it. They should've at least mounted the damn thing. After you change your fuel filter you should look into your secondary fuel pump as being a source of your problems (I think that you have 2 pumps on your truck, one of which is located somewhere along the frame rail too). I guess you could unplug it and see what changes as a test. If you unplug it and it doesn't do anything, you know that it is dead. Someone with the duel fuel pump system can probably give you better pointers.

 

[Ken the BEAST]

Ok tomorrow i will go get a fuel filter and see if i can come up with a fuel pressure and vacuum testers. I tested the fuel pressure a few days ago but not while revving the engine. It was within specs with key on and at idle. I checked the fuel pressure regulator too and it wasnt leaking fuel at all.

 

[Big Jim M]

Just check'n in

My 87 supercab 2.9 runs rough and is lacking pretty bad in the power department. (i floor it and it barely even accelerates). I have had this problem for a while. I have replaced the dist. cap and rotor, the tfi plugs and wires, throttle position sensor and i am extremely frustrated and out of ideas. (and yes the timing and firing order are perfect)

Tell us you do know how to check the timing.. many guys don't know how to do this on our lil rides..
Then the first thing to check on rough running engines after plugs/wires would be the compression.. That is more suspect than fuel pressure etc would be for rough idle.
Big JIm

 

[RyanL]

Correction: I told you that the resistor block was yellow; it's actually grey with a green/yellow wire going in and out of it. I'm sorry, I was thinking about that other thing down by the coil which I think is just a splice block of some sort.

 

[Ken the BEAST]

yes i know how to check the timing ive checked timing and firing order like 15 times just to be sure.I tried pulling wires off the dist. when the engine was running and cylinders 2,3,and 6 didnt seem to cause any change. I checked the spark plugs and the electrodes were bent so i went today and spent 42 bucks on lithium core autolite plugs. so i fixed that problem. oh and my buddy that owned the truck before me told me that the fuel filter was new and the fuel pressure was ok. My buddy told me it might be the injectors are clogged so i bought some fuel additive to clean the fuel system. It is still running like crap but im tryin.

 

[Ken the BEAST]

Ok so the fuel system cleaner didnt do crap (i didnt really expect it to but...)
This truck is starting to really piss me off i have had a few tecnichians look at it already and they couldnt even figure it out. I think ill shove a stick of dynamite up its tailpipe and just walk away.

 

[RyanL]

Ok so the fuel system cleaner didnt do crap (i didnt really expect it to but...)
This truck is starting to really piss me off i have had a few tecnichians look at it already and they couldnt even figure it out. I think ill shove a stick of dynamite up its tailpipe and just walk away.

Having all the techs in the world look at a vehicle doesn't do much good unless they are extremely familiar with the vehicle in question. Every different vehicle has there own common problems and parts that usually fail. Give us a little more. How's the truck running otherwise? Is it impossible to start. Do the exhaust fumes stink badly of fuel even after it's warmed up? It's possible that you could have a bad injector or two, but there are a number of other sensors which can make it run real crappy which you should check into. You're fuel pressure regulator might be bad, but I doubt that it would cause that much grief, but may be contributing to the problem like mine was. I just replaced mine because it was leaking a little bit of fuel out of the vacuum port in the rear (easy to check while it's running). Mine was running all cruddy too and it turned out to be mostly due to a flaky TFI which you said you already replaced. How does your 2 wire temperature sensor and your intake air temperature sensors check out (easy to check resistance and/or voltages of those with a multimeter)? Check for codes (I had some even though no check engine light was on). One of the main sensors that I would check into is your MAP sensor since it controls a lot in these vehicles. I know that it's a little unethical, but grab one from the parts store (Napa has them for about $55), pop it in and if it doesn't do anything take it back the next day. Let us know if you come up with anything.

 

[Ken the BEAST]

Ok here we go so heres whats been happening. When i crank the engine after a few secs it kinda slows a bit and makes a slow groan, but starts immediately after. The exhaust fumes do not smell of fuel only thing you can smell is the injector cleaner ive been using. I finally put a tester up to it and i got codes 63 (TPS signal too low) and code 98 (hard fault). This made me think it was my tps so i swapped it and set it with the screw deal and a multimter and no dice same code. So i was going to check if the wire for the tps at the eec-iv was getting voltage to see if it was even exchanging info. Idk if this would cause me probs but im open to ideas . Now as far as my temp sensor it has only 1 wire and it is broken right now (i need a new end). I do not know where the air temp sensor is. I also am not sure what kind of voltages to check for from which wire on those sensors. I think i know where the MAP sensor is but heres the deal I currently am out of a job and cant afford any parts unless i am sure that it is the prob. I dont even have 55 bucks right now so im screwed there If you could give some info on these things though it would be much appreciated (and btw thx for all the help so far)

 

[RyanL]

Ok here we go so heres whats been happening. When i crank the engine after a few secs it kinda slows a bit and makes a slow groan, but starts immediately after. The exhaust fumes do not smell of fuel only thing you can smell is the injector cleaner ive been using. I finally put a tester up to it and i got codes 63 (TPS signal too low) and code 98 (hard fault). This made me think it was my tps so i swapped it and set it with the screw deal and a multimter and no dice same code. So i was going to check if the wire for the tps at the eec-iv was getting voltage to see if it was even exchanging info. Idk if this would cause me probs but im open to ideas . Now as far as my temp sensor it has only 1 wire and it is broken right now (i need a new end). I do not know where the air temp sensor is. I also am not sure what kind of voltages to check for from which wire on those sensors. I think i know where the MAP sensor is but heres the deal I currently am out of a job and cant afford any parts unless i am sure that it is the prob. I dont even have 55 bucks right now so im screwed there If you could give some info on these things though it would be much appreciated (and btw thx for all the help so far)

If you found the single wire temperature gauge sender unit, you're burning hot; the one in question is like no more than 3 inches to the left of that one. The intake air temperature sensor is on the center intake riser on the driver's side (right below the idle control valve). As far as voltages or resistance readings go, I couldn't find them anywhere on this website so I scoured the web and I think that I found them on ford fuel injection.com (or some crap). I'll see if I can find them for you and I'll post them up unless someone has the specs. The real kicker is that I have the actual Ford Factory Service Manual for '89 Bronco IIs, but I'm missing the third book which has all of the diagnostic crap. I had a Chilton's years ago, but from what I remember it wasn't too helpful anyway (was only good if you really didn't have a clue to what you were doing). I would also look more into the TPS issue because I think that can cause headaches too. Are you certain you cleared the codes after changing the sensor?

 

[RustedRanger]

After changing parts did you unhook the battery for 15-20 minutes to clear the computer? I know it's something simple but many overlook it.

 

[RyanL]

Link to check the intake air temperature readings: http://www.fordfuelinjection.com/index.php?p=29
Link to check out the coolant temp readings: http://www.fordfuelinjection.com/index.php?p=28