I have posted several previous inquiries regarding this truck, and I received some thoughtful suggestions. However, progress has been slow because I have had hardly any free time in the last six months -- and my mechanic is working on the truck as a favor to me (just charging for parts), so it's low on his priorty list also.

To sum up --

(1) The truck (a 2.9 ltr V-6 automatic) has a bad "lope," "surge," "stutter" (whatever you want to call it) under acceleration, to the extent that you sometimes have to shift down to 2nd to keep the revs up or the engine will die. Strangely enough, performance has been getting marginally better over the past six months (my mechanic uses the truck regularly for runs to the local parts house). It has its good days and bad days, but is definitely driveable. You just wouldn't want to depend on it in traffic or on the freeway, because it always has to be coaxed to run.

(2) The engine is a new rebuild, the computer is new, the distributor/alternator are new, spark plugs & wires are new and just about everything under the hood has either been replaced or checks out ok. My mechanic friend is an oldtimer with his own backyard shop. Although he doesn't have a lot of high tech test equipment, he has a substantial local reputation as a great seat-of-the-pants diagnostician. And he says that this truck has stumped him like few others in recent memory.

(3) At the urging of several people in this forum, I purchased a code reader several months ago and had both my son and my mechanic run some diagnostics with it. The results were predictably puzzling -- eleven error codes in the initial KOEO phase, but no clearing code (10 or 11) and no second series of codes. Instead, the code reader eventually repeats the first of the eleven error codes again, and then stops for good. The codes, for what they're worth, are as follows: 637, 123, 327, 654, 553, 552, 565, 558, 622, 626, 624. Most of these codes relate to circuits above or below recommended voltage, or solenoid/circuit faults. None of them seem to have any obvious relation to the symptoms displayed by the truck. (These codes have been pulled a number of times with the same results every time.)

(4) We haven't removed and cleaned the injectors yet, but according to my mechanic they don't show any normal signs of plugging or wear (he has a testing method, but I can't say what it is). He also wondered out loud during one conversation if there could be a problem with the intake manifold (due to the rebuilt engine not being reconnected properly), but he's skeptical that this would explain the truck's problems. Also, he reports that he hasn't been able to detect any vacuum leaks using the standard propane torch method.

Any suggestions, ideas, theories would be most welcome!!!!!

--btilland

 

Well you want to start wih the lowest code first, 123 is throttle position sensor high input. Thats a good starting place, check the wiring and see if it was connected back properly, the measure the resistence and see that it transitions smoothly. fix that and some of the other code will go away.
Dave

 

Hey, thanks. That makes sense. I'll get on the phone with my mechanic tomorrow, although he may wait for me to show up this Saturday. I'll let you know what happens.

 

My mechanic is a good buddy and has kept our various vintage (old) cars running for close to twenty years, but he does have his limitations and blind spots. He's largely self-eduated and rather defensive, especially when he feels that someone is trying to show him up. However, it's hard for me to second-guess him because, whatever he knows, I know far less.

He said today that he had put together test "kits" for Ford and Chevy cars and when someone brings a car in that is not running properly, he will replace things like throttle position sensors just to see if they make a difference. Apparently he has replaced the throttle position sensor in the Ford, but he may have re-connected the old one when the new one didn't produce any improvement. This seems a little "single-focus" to me, because there could be a number of things causing problems, including the throttle position sensor, so just replacing it alone might not show a significant improvement. Also, I would think that you would want to replace the sensor and then pull the codes again -- and I'm not sure he has done that. My feeling is that if you are getting a 123 code and it's the lowest one in the code series, there must be SOME problem associated with the sensor. But maybe that's naive.

He also said that he was confused by your comment about checking the wiring to see that it was "connected back properly," because the sensor was pretty much like a light bulb (his words) and one end just screwed into a socket. (I haven't seen it so I can't verify this.) However, I can see that when you say "check the wiring," you might not mean the socket/receptacle itself but the wiring going into (or coming out of) the socket. Is that it?

He also seemed confused about measuring the resistance and seeing that it "transitions smoothly." I know that he has an ohm meter (and uses it), but I'm not sure that he knows what and where to measure in this situation, although I could be totally wrong about this. I DO know that he doesn't have a clue about the "transitions smoothly" comment, so perhaps you could clarify that for me and I will relay it (gently) to him.

 

There is a procedure to get the codes that needs to be followed, check the tech section at the top od the forum on pulling the codes.
The tps is a resistor that moves when the throttle is moved it will change resistance between ground and the wire that goes to the ecm. They will sometimes get bad spots and not send a smooth changing signal to the ecm.
IF the test are not done properly, you may get a false error code.You need to get someone to run the test properly to read the codes and work from there. Sometimes the cheaest mechanic isn't the cheapest...
Dave

 

What Dave is referring to is testing the TPS sensor for proper functionality. You do that by connecting an ohm meter to the TPS sensors connector and slowly open and close the throttle plate. A properly functioning TPS will show a continuous and steady change in resistance as the plate opens and closes. If the resistance bounces around while opening and closing the throttle then you have a bad TPS.

 

Thanks to both of you. I think I understand the way the resistance test for the TPS sensor works, and I can communicate that to my mechanic.

As for the general process of pulling codes, I believe that we are following proper procedures. I know that my mechanic knows how to pull codes, and when my son pulled the codes at a later date he carefully followed the instructions in the manual that came with the code reader. We have pulled the same codes five or six different times, on different days, so I'm inclined to say that they are accurate -- or the best that we can do under the circumstances.

Some months ago, my mechanic actually took the truck to a couple of "real" shops in our small town, where professional courtesies are extended to him and he can ask for the occasional favor. The truck was hooked up to two different professional diagnostic machines and, according to my mechanic, "almost every code in the book" showed up on the readouts. The shops also tested for vacuum leaks, and neither of the "real" shops was able to come up with a clear diagnosis or point my mechanic in a constructive direction. I believe that one of them tentatively suggested faulty injectors, but my mechanic didn't feel that the diagnosis had much conviction and he still doesn't think that the surging behavior of the truck points to injectors. So I know what you are saying about cheapest not always being best, but this truck has had more than one person scratching his head.

 

I noticed in your first post that you mentioned replacing the distributor. Did you also replace the TFI (or ignition control) module? Does your distributor have a module with a big socket on it? If it does, and you didn't replace it I would pull it off and take it to Autozone and get it tested. If your distributor doesn't have this module on it, look around the federwall or radiator in the area near the distributor and look for a module sitting in a heatsink with a large wire harness plug coming off it anywhere. You can have this module tested, and I would recommend it. I had one go bad and my truck was doing about what yours is. Can't hurt to test it and eliminate it as a possible cause anyhow, doesn't cost you anything. You will need a special socket to remove the bolts that hold the module in place, it'll cost you a few bucks at a parts store.

 

I can't buy the injectors as the problem.. More then one clynder is running lean, so what ever it is Ita bigger then one injector and it hard to beleive all of them failed at once. Fuel pressure is one thing that could do it, as is the maf, throttle body, or Egr. Think of things that affect all fuel/air systems.
Dave

 

Again, thanks to you both. Lots of good, thoughtful suggestions. I will confer with my mechanic on Saturday and personally check some of them out. Dave, I think my mechanic came to the same conclusion you did regarding the injectors. But just for my own edification, what is the "maf" and the "Egr?"

Irishguy, I recall reading up on TFI modules a few months back and I believe that that the module in the truck is new (along with the distributor, but I'll verify that. Coincidentally, I found a webpage just a few minutes ago that gives resistance test values for a TFI Module (and I think it's the right one, because I recognized the EEC-IV part name for the distributor. I've heard that TFI modules can be quite unreliable, and even new ones have been known to fail -- or to be faulty right out of the box. The site indicates that the TFI module is easy to remove and test, but then it goes on to talk about something called a "Hall Sensor" in the distributor, which can go "bad" but is very difficult to remove. However, if the whole distributor is new (or a rebuild), odds are that this sensor isn't the problem.

 

Can you give us the KOEO codes that you got wth the code reader? It would help a lot. The maf is mass air flow sensor, the egr is exhaust gas recirculator. There is info on testing the module in the tech sticky at the top of the forum, you really need to look at it.
Dave

 

Hi --

I listed all the codes in my very first post in the string (along with a lot of other stuff!!!) That's where the 123 code came from. There were eleven in all, and as I said in that post, the reader just stopped after the eleventh, didn't clear (no 10 or 11 code) and then repeated the first code in the series again instead of pulling a second set of codes (which the instruction book said was supposed to happen. We pulled the codes 5 or 6 times, on two different days, and that's the way they came up every time.

 

It is normal for the KOEO codes to repeat, they should cycle twice then a pause then the continuous memory codes are sent. I am confused by the three digit codes, I thought this system used two digits. But anyhow, you have to fix those TPS codes first. You need to test the TPS and see if it is faulty. If it is replace it, then erase the trouble codes by unhooking the battery for 5-10 minutes. Hook the battery back up and run the KOEO test again and see if any of the codes go away. You need to eliminate the TPS codes as it looks to me, though I'm a bit confused by the 3 digit codes that you have three trouble codes in there relating to a failed TPS. Good luck.

 

I have an 88 Ranger w/2.9 & an 89 E-250 w/5.0L & I think that they only give 2 digit codes.

 

You are correct, 1989 is a two digit code.