Truck dies while driving

[RyanL]

Well as far as it sounded, your TFI did sound like it was on it's way out and had the classic "no start when hot" syndrome. It does sound like it's running and starting a little bit better (aside from the stalling of course). It does sound like your MAP may be busted too, but of course check the vacuum hose going to it and make sure it doesn't have a leak (or any other leaks in the system). That cable that you referenced is the kick down cable to drop the transmission into passing gear when you stomp it. Some vehicles use a vacuum hose while others use a cable. In most newer vehicles (last 1 years it's all electronic. Look around on the web and you should be able to find pictures of the whole thing. Sorry I can't be much more assistance about the cable but I don't mess with them (I only owned one automatic in my life about 20 years ago and it wasn't for very long). Also, you know about the cable tie trick to get rid of all the slack in the cables, right? Look around on here, I think that I saw a how-to on this site with pictures. I think that both the transmission and throttle cables need it.

 

[Nelson674]

Also, you know about the cable tie trick to get rid of all the slack in the cables, right? Look around on here, I think that I saw a how-to on this site with pictures. I think that both the transmission and throttle cables need it.

I did see that trick posted around here some place. Those cables can't be that expensive to just replace though, could they?


So I was digging around under the hood looking for that MAP sensor and saw a wire that looked out of place. It was just a single wire all by its lonesome self hanging out around the passenger side of the distributor and headed for the firewall. I gave it a light tug just to see where it went and it felt suspiciously loose. Kept pulling and discovered that it was connected to nothing at all... Looks like the insulation had been pinched and the wire corroded until it broke. I didn't have time to find the other end before I had to leave for work but I traced it back to its origin. It starts at the starter solenoid/relay? (seen it called both). Its attached to the same post that the positive terminal on the battery is attached to. Just a few inches from its start, there is an inline fuse. Then the wire was heading in the direction of the firewall. I checked the fuse(as if it would matter) and it was fine. Reading on the fuse is "7A125V". I don't see it on the wiring diagram I have.

Anyone know where this wire is supposed to go?

 

[Nelson674]

I read somewhere that you can check the MAP sensor by just unplugging it or something. Unplugged the MAP sensor and the truck wouldn't start. Starts fine with it plugged in. The RPMs are at about 1500 when I start the truck and then work their way back down to 1000 or so. Is that normal? I guess I never payed that much attention to it before.

Also the truck doesn't die when I put it in gear anymore. The RPM drops a little but it will idle in gear around 900.

Dont have any more time to work on it today. Gonna take her for a spin tomorrow and see how shes does.

 

[stevealvey24]

Just because you pulled the plug on the map sensor doesnt mean it isnt bad. My truck would run fine for a week, two days, an hour, ten minutes, i replaced both fuel pumps and nothing, tps sensor, iac, new distributor, different computer, speed sensor, new injectors and still nothing. Left the computer unhooked over night and the next day when I hooked it up and took off down the road it would stay at 2000rpm until I was almost at full throttle, then it would pick up and haul ass down the road. Put a map sensor on and aint had no trouble yet. The funny thing is that not once did the conputer throw a map sensor code. Hope this helps lol.

 

[Nelson674]

Just because you pulled the plug on the map sensor doesnt mean it isnt bad.

Yeah, I kinda scratched my head when I read it. Figured id give it a try anyway..

If I remove the MAP sensor from my truck can a parts store like Napa or Carquest test it to make sure its bad?


Also anyone have an idea on that broken wire?? That has to be causing some sort of problem! I looked everywhere yesterday and could not find the other end

Here is that wire. Its the red one coming from the starter relay? to the black inline fuse. After the fuse there is a little bright blue crimp connecter attaching it to the black wire that is in my hand. It was headed in the direction of the firewall and under the blower motor?. I pulled the carpet up and the lower dash cover off. didnt see anything out of place where all the wires come in to the computer.


Is this wire factory? Maybe it was being used to power an accessory. stereo amp or CB? The end that is broken is very corroded, like it has been this way for a loooong time. Still sparks if you get it too close to a ground point though

 

[RyanL]

Yeah, I kinda scratched my head when I read it. Figured id give it a try anyway..

If I remove the MAP sensor from my truck can a parts store like Napa or Carquest test it to make sure its bad?


Also anyone have an idea on that broken wire?? That has to be causing some sort of problem! I looked everywhere yesterday and could not find the other end

Here is that wire. Its the red one coming from the starter relay? to the black inline fuse. After the fuse there is a little bright blue crimp connecter attaching it to the black wire that is in my hand. It was headed in the direction of the firewall and under the blower motor?. I pulled the carpet up and the lower dash cover off. didnt see anything out of place where all the wires come in to the computer.


Is this wire factory? Maybe it was being used to power an accessory. stereo amp or CB? The end that is broken is very corroded, like it has been this way for a loooong time. Still sparks if you get it too close to a ground point though

I'm about 95% sure that it isn't factory.

 

[RyanL]

Just because you pulled the plug on the map sensor doesnt mean it isnt bad. My truck would run fine for a week, two days, an hour, ten minutes, i replaced both fuel pumps and nothing, tps sensor, iac, new distributor, different computer, speed sensor, new injectors and still nothing. Left the computer unhooked over night and the next day when I hooked it up and took off down the road it would stay at 2000rpm until I was almost at full throttle, then it would pick up and haul ass down the road. Put a map sensor on and aint had no trouble yet. The funny thing is that not once did the conputer throw a map sensor code. Hope this helps lol.

Man, talk about throwing parts at it! Yeah, the ECUs in these things aren't all that great. Sometimes you get lucky and get a code, but it's usually only when a sensor is "out of range". Just because it's reading in range doesn't mean that it's working properly. For example the MAP sensor might be telling the ECU that you're at an elevation of 6500ft when you're really at sea level or something. It's going to run like complete crap or maybe not at all. Luckily it's much easier troubleshooting these kinds of problems in newer systems with OBDII. I have a OBDII to usb adapter and a few programs on a netbook. I just hook it up and can see exactly what all the sensors are reading while it's running.

 

[RyanL]

I did see that trick posted around here some place. Those cables can't be that expensive to just replace though, could they?

Well, they might not be too expensive but I bet that they're like that right from the factory (maybe not as bad, but I doubt they're tight). The cable tie method seemed a little too half-assed to me so instead I went to a hardware store and grabbed myself the smallest u-bolt cable clamp I could find and put it on there (you're going to need a real small one to grab a cable that small). That way I can adjust exactly to where I need and also take up slack later if I need to by sliding it further up. I think you may also be able to use a cable clamp that they use for bicycle brakes (if they still use the style that I'm thinking of).

 

[stevealvey24]

I completely agree with the advantages of OBDII. But as for the map sensor it can work fine for absolutely every amount of manifold pressure except that one reading where the square wave signal if screwed up. That what mine was doing. It seemed if I caught the one reading of a certain manifold pressure it would die, it was always on the lower end to. If i drove my truck home and ran balls out, it wouldnt die. Just sayin it sounds wierd but its possible.

 

[RyanL]

I completely agree with the advantages of OBDII. But as for the map sensor it can work fine for absolutely every amount of manifold pressure except that one reading where the square wave signal if screwed up. That what mine was doing. It seemed if I caught the one reading of a certain manifold pressure it would die, it was always on the lower end to. If i drove my truck home and ran balls out, it wouldnt die. Just sayin it sounds wierd but its possible.

I also think that it's more common for a MAP sensor to die completely (along with the engine) rather than play games, but it does seem like he's having some sort of issue with his on the vacuum side of it.

 

[Nelson674]

Well I took it out for a drive yesterday and it went well. Drove the back roads around here for about a half hour/16miles. Seemed to run fine, that TFI sure made a difference.

I decided to go for it and drove it to work. Got me there and back, It had a little hiccup at the stoplight but never died on me.

I guess at 60 bucks it wouldn't hurt to just replace the MAP sensor so I know it wont be a problem. Napa and carquest both told me they had no way of testing it if I brought it in.

Discovered a lot of other stuff that could use a fixin this last week.

$ and time...



Thanks everybody for all the help.

 

[Nelson674]

replaced the MAP sensor and fired it up. Didn't notice much of a difference. Still runs pretty much like it did with the old one. I tried clearing the codes and rechecking. Maybe I didn't do it right but the code 22 is still showing up.

The guide here (http://www.therangerstation.com/tech_library/OBD_I.html) says to unplug the jumper wire when the light starts flashing to clear the codes. didnt seem to work because I did this and checked for codes before starting the truck back up and the codes were still there.. Codes stayed there when I turned the truck on again.

 

[kimcrwbr1]

Reset the computer every time you mess with a sensor. Even if you unplug it for a minute. Did you disconnect the battery for 1/2 an hour also after you erased the memory. Disconnecting the jumper erases the memory and disconnecting the batt resets the hard faults and sets the new values.

 

[RyanL]

replaced the MAP sensor and fired it up. Didn't notice much of a difference. Still runs pretty much like it did with the old one. I tried clearing the codes and rechecking. Maybe I didn't do it right but the code 22 is still showing up.

The guide here (http://www.therangerstation.com/tech_library/OBD_I.html) says to unplug the jumper wire when the light starts flashing to clear the codes. didnt seem to work because I did this and checked for codes before starting the truck back up and the codes were still there.. Codes stayed there when I turned the truck on again.

I think that you cleared them correctly. I can't remember if I turned the ignition off after pulling the jumper wire out or started it right up. You could always clean up the MAP sensor and take it back, just say that you ended up not needing it. Maybe someone else can chime in but you might get that code if you have some sort of vacuum leak. BTW, there's a good chance that the bad TFI ruined your plugs from running out of time and crap. I think that it cost me less than $10 for a set of copper core spark plugs last time(that's all you need, don't let them try to sell you $40 ones).

 

[kimcrwbr1]

Then drive it at medium speeds for at least 20 minutes go thru all the gears run the a/c and test it again while the engine is hot to confirm any repairs. You want 11-1-11 if you still have problems it is more than likely internal/mechanical. Have you checked the timing chain, pull the dizzy cap and with a wrench turn the crank both directions a little and see if the rotor responds quickly. If you center it on the timing marks you can measure how much slop is in the chain. turn it CC till the rotor turns make a mark or take note of the position and turn it the other til it slightly moves and count the marks.