i have a 91 explorer that had no power at all so i took it to the shop. he fixed lots of problems but the big one has stumped him. When ever you accelerate it jumps into open loop and floods the engine like it's cold, but when its at a constant speed it will stay in closed loop. he found that there was an updated module to fix the oposite problem and with no other options he put that in. now the PCM is saying that it has a bad reading from the camshaft position sensor. It doesn't have a CPS. from what i understand this is because the california cars always had CPS's. Is there a place to get the updated module with out a california stuff (he couldn't find one) or does he have to put a CPS in. If he does have to put it in does that mean a whole new wiring harness. Any information i could pass on to him would be greatly appreciated, it's been in for 7 weeks and both of us really want it out of there.

 

Your mechanic needs to read the TSB's a little more carefully. It referred only to 1993 vehicles. It richened up the start up and cold engine A/F tables a bit toi keep the car from stalling when you put it in gear - something to sensativity to available fuels - so Ford's excuse was.

The fix was to replace the PCM with various ones from the 1994 model year. In 1994, all Explorers in 50 states got a Cam Position Sensor and SFI - Sequential Fuel Injection.

Another thing, the PCM pinouts obviously change right - since the new ones are looking for a CPS. And then with SFI, you can only get gas to the injectors 2X per rev instead of 6X as you're supposed to. It's gott to be running like crap if it runs at all. Your wireing harness has all the right side injectors hooked to one PCM pin, and same with left side on another PCM pin. SFI has 6 pins, one for each cylinder - see what I mean?

Your mechanic should know that the only thing controlling open or closed loop operation is the O2 sensors, well the coolant temp too since it must be warm before the O2's will work and thus the PCM holds it in open loop until the coolant temp gets to 160 or 170 degrees F. So iff the coolant temp senoor is OK, then you have a bad O2 sensors - and I think you only had one in a 1991 car.

Tell the mechanic not to mess with the PCM when he doesn't understand the implications. Then go bac to the basics. I'm not sure what you mean that the engine floods. If this is dramatic, maybe the fuel pressure regulator is bad and pushing too much fuel in? let me know when you get it all back together with the right PCM and then what symptoms you have. Can go from there. I have the TSB in a Word file I can send you if you want it - PM me with your email.

 

well the thing is it runs great sometimes. sometimes he can't get it to start then he won't touch it but try again in an hour and it'l start right up then it runs great untill it warms up and then it runs trerrible when it's war. both the o2 and coolant sensor are brand new he replaced them. some times it idles really rough and then randomly it will idle perfectly smooth but if you touch the gas it goes up and down again. the pressure in the fuel rail is perfect. all the inputs at the computer are all right and the old computer said that there was nothing wrong when he put the code reader on. but when ever you steped on the gas the outputs went wrong while the inputs stayed right. the basics have been gone over three times and its not there. we've already been told by ford that thats impossible but it's not.

 

Unless I'm missing something from what you said, you are mixing apples and oranges with the PCM's. I think you need to go back to square controls system and see from there. Just out of curiosity, what are the old and ne PCM numbers. Need the part number like F17F-12A650-TK and F47F-12A650-CMA. I wonder if the last one is what you have since this is the only Explorer PCM in the TSB that is for Fed and it is for a manual trans.

You mention too about the start/no-start aspect. The car doesn't even need the PCM signals to start. It can run the coil right off the ignition control module. This is how it initially fires up. Once a RPM signal is received at the PCM, the PCM steps in and conditions the spark signal - but doesn't trigger it. You mat want to check the connedtions there - might be dirty - might be a bad ICM. It is located right in fornt of your battery.

 

well the reason this all didn't make sense is really quite retarted, the company i bought the original engine from (aer manufaturing) put the wrong camshaft in. so the PCM couldn't explain why it was running like it was. it's fixed now, sort of. now i need to deal with the engine company who told us the engine was wrong and they'd send us a new one, now that we sent it back they said it's not wrong and they want another $1600 . thanks for tryin to help, ask you can see no one had any idea what was wrong. and tell all your freinds never buy from aer, my car was in the shop for over four months and with both engines and labor just under $6000 and aer as acusing me of intentionally breaking the engine. They even went as far as saying that i changed the camshaft.

 

Ok, now I am confused. The cams on these only change a little bit and that is only from an automatic to a manual transmission. The manuals got a little more seperation between the intake and exhaust timimg to give a little more umph on acceleration. The cam position sensor error is an obvious problem of installing the wrong PCM on your car. Even a manual/auto trans PCM would not give you the drivability problems you are reporting. None of this is making any sense to me.

 

We think they used a cam from a carborated version, like a ranger or bronco. which would mean that the valves were open for a shorter amount of time expecting a richer mixture. thats why when it was cold and pouring alot of gas in it ran fine but as soon as the mixture went lean the valves wern't open long enough for the right amount of fuel to get in. then the computer was confused and seeing the engine runing wrong at the right timing and mixture caused it to switch back to open loop when you acelerate.

 

The 4.0 was never carbuerated. The 4.0's parent engine, the 2.9 wasn't carbuerated. You have to go all the way back to '85 when the 2.8 was in production to get a carbuerated V6 in the RBV line-up. I guess my point is, they can't have used a cam from a carbuerated version because the 4.0 never came in a carbuerated version.

What is the current status of the engine? Does it run at all? If it does run, what are the symptoms? Is it even installed? Which computer is installed: a '91 computer or a '93 computer)? What codes is it outputting now? Does your mechanic still have the truck?

 

we actually got the new engine (second one) in and it runs perfect now. we've got it back. i don't know what computer is in it. I'm at college now but it's back in my home town so i have to run everything through my dad and he never asks the questions i want to know. i have a feeling that it has the 93 in it though. i do know that it isn't puting out any error codes. the only problem left is somthing about having aftermarket addons so he diconected the neons, fog lights, and subs. ford said it draws amperege from the fuel pump, have you heard of that before? my dad says it runs alot better without those on.

 

If the mechanic was referring to the TSB that came out in 1995, it changed 1993 vehicle PCM's with 1994 PCM's. This is the only PCM TSB I am aware of. If there was another or some other note in the Ford OASIS system, maybe he used a 93 PCM. My earlier point was that the 91 Fed 4.0 has MFI where all 3 right, and then all 3 left, injectors fire together. All 1994 PCM's fired each injector seperately, SFI. So if he used the TSB I was thinkin of, then he used a 94 PCM and that will never work with a 91 wiring harness. My guess is the 91 PCM is back in it.

That's good background MrShorty. I had no idea if a 4.0 ever had a carb on it. Even if it did, I can't see the basic timing changing that much due to a fuel induction difference EFI to carb. The motor still wants the same A/F, basically. I can't see the carb version (that doesn't exist) have such a more lofty cam than a EFI version.

As far as the electrical accessories, you'd have to be pulling a boat load of amps with that stuff to get the fuel pump to slow down. The fuel pump is pretty tiny and doesn't need much juice at all to run. Anyway, a simple test id turn the stero and lights off - how does it run? Now turn on everything, AC too - does it run any worse?

 

" the only problem left is somthing about having aftermarket addons so he diconected the neons, fog lights, and subs. ford said it draws amperege from the fuel pump, have you heard of that before? my dad says it runs alot better without those on."

Another simple test would be to put a fuel pressure gauge on it and see what difference having those hooked up makes.

 

Well if you think it's the 91 pcm i hope your right i'd rather have MFI. All i know is that he couldn't return the new one. I estimate that all the addons were drawing about 60amps, its a huge amp, four neons, and two pairs of fog lights. It does run alot better with out them acording to my father. The fuel pressure is right with those on, untill it accelerates then it can't keep up, it's a new pump now too. I was thinking it might have to do with the ground straps. The one going from the body to the engine is less than half the size of the ground wire for my amp. as for the camshaft thing the mechanic, aers techs, and some gm techs all came tho the consensus that it was a carborated cam but of course they probably didn't research if they cam with one or not. I'm just gonna guess then that aer machined it wrong.

 

Would be nice to know what that company is doing with the rebuilt motor pool. I am now hseitant for sure. Not that I would accept any motor that I did not build myself - but I wont recommend them from what you have posted.

So what gauge wire does you amp ask for. Mine wanted 8 gauge - about 3/4 the size of a battery cable. I thought that was nuts!

 

60 amps? Stock alternator supplies somthing like 90 A, so you're drawing roughly 2/3 of it's capacity. FP normally draws 2-5 A, battery needs some to charge, ignition system needs some to fire spark plugs, computer needs power, headlights (60W @ 12V) can draw ~5 A each plus current required to run the tail and marker lights. All things considered, I guess it is possible you have overloaded the electrical system, though I would expect it would effect other things in addition to the fuel pump. It seems people talk about getting a bigger alternator (130 A comes to mind) for so many toys.