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Did i just buy a lemon??


RangerXLT!

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Hey guys, not new to the forum, i was having issues with resetting my old login password, however here we go, please help! (If you don't want to read all the details below, just please tell me how to immediately FORCE the cel on!)

I just bought a 99 Ranger XLT, 4.0 v6, 81k, It's in great shape, everything seems to work, runs good, idles good, seems to be in great condition so I pulled the trigger, After owning it for a few days I feel like it may be lacking in power, however if I granny drive it I can average 20mpg (over 2 tankfuls) which is pretty good for a 4.0. It almost feels like i'm towing something, and it makes me think of my old 86 4cly STX which had huge power and could smoke the tires like nothing! This newer, bigger motor just doesnt have the pep or power my old ranger did, so I popped open the hood and started troubleshooting. Found a damaged wire, not sure if it's a original ford wire, anyways it was barely connected , burnt, and had rat teeth marks on it. I don't know where it's supposed to go but the previous owner had it connected to ground on the firewall. It's grey, so I looked up some wiring diagrams and found it could possibly be a CPS or IAT sensor wire, using my DMM I found the wire is neither, so I just repaired it and put it back on the firewall because the truck won't start without it. Anyways, so I go back and make sure the truck still starts, and it did but idled funny, then I realized I left the IAT sensor unplugged, and also the MAP was also unplugged (because I was looking at how clean it was), and what is weird is i got NO CEL with those unplugged. It struck me as odd, the CEL does light up when I put the key to the on position, then it goes out when I start the truck, as normal. After further inspection I think I may have a vaccum leak somewhere, and I also know my PCV is totally shot, but I don't get why I'm not getting codes! I'm afraid there is alot wrong with the truck and the computer is broken, not throwing codes, or I could just be paranoid... I even unplugged the MAP and IAT and drove around for maybe 10 minutes, no codes. Should I immediately get a code for driving with no MAP? Is there something I can do that should immediately set off a code without any type of driving cycle?

- If i find that it's not throwing codes as it should, whats the next logical step? I also already tried a very basic OBDII scanner, linked fine, zero codes thrown. All wiring and harnesses look in excellent condition (minus the mystery grey wire that will not let truck start if not grounded)

-Side question if one is so inclined to answer, what is typical vaccum I should get while running? Where should I test for holding vaccum? I threw my vac gauge on the line coming out of intake manifold and at idle it was about 16". As soon as I turned off the motor the vac was totally gone, should it hold a vaccum here, or do I need to test off a vaccum resivor that I don't see? It looks like there is one in the lower left but the vac diagram says it's a charcoal cannister, it's round plastic type deal with 2 vac lines connected to it.


PLEASE HELP! If I can prove this truck is a lemon with major issues I may be able to be refunded if that's the case. I could also be being my paranoid self... :bad: Thanks!
 
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adsm08

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You are being paranoid. Step away from the wrench and never buy a used car again.

Anyway, you are being paranoid. I don't know off the top of my head what that wire is, but if I try I can probably figure it out. Does it not crank, or does it crank and not catch when this wire is ungrounded?

A 99 4.0 won't have a MAP sensor, but starting the engine with almost any sensor unplugged should set a circuit code. It may be that yours will not set the light right away, but an unplugged sensor should produce a code during an on-demand test. Bear in mind though that just because it is OBD-II does not mean every little hick-up or rough idle will set a code.

Vacuum at idle will be 16 to 20 inches, 20 is optimum. Low vacuum indicates either low compression or restricted exhaust. If you hook the gauge up with the engine off and it starts higher then comes down and settles at 16, restriction, otherwise something is keeping the engine from forming a good vacuum. Once the engine is shut off the vacuum will go away quickly as the intake is not sealed, air is supposed to get in, but only at the throttle. Vacuum will be highest at idle as vacuum is just a measure of pressure lower than atmospheric. Throttle closed will give the biggest pressure drop.

Also, Lemon Law generally applies to new cars, on a 99 you will more than likely get laughed at.



Anyway, I think the first step here, if this were my vehicle, would be compression test.
 
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RangerXLT!

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Haha, just the opposite :) I love working on cars and can't put the wrench down! Thanks for the reply, but really, I want to test the computer's ability to throw a code... If two sensors are left unplugged, with vaccum leaks and a bad PCV, there should be SOME code, no? I want a quick way to throw a code and verify the computer is 'listening'.

The wire, no crank, no nothing. Dash seems normal, key does ziltch.. ground it and all is well.

-No MAP? I'm almost positive it is a MAP, it's right after the airbox in the intake tube and looks identical to all the threads about cleaning your MAP.

edit add; agree with lemon law statement, but the dealer has a clause with a 500mi 15day warranty. I'm very close to both actually, which is why I am twitchy on this dealio
 
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adsm08

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That's a MAF. Mass Air Flow. MAP is Manifold Absolute Pressure. Two very different sensors that do two very different things, but can be used to infer the same information.

MAF



MAP


Bet my left nut you have a MAF.

MAF is a two wire temp sensor, it has a cold wire used to measure the temp of the incoming air while it attempts to keep the hot wire 200*F higher than the cold wire and monitors the amount of amperage needed to do that. By doing this it can infer the oxygen content of the incoming air.

A MAP is part of a speed-density system and just provides information about the pressure on the intake. It needs a separate air temp sensor to calculate the density of the air coming in.

Unplug two or three sensors and drive it a few miles. The older ones weren't as sensitive and didn't always set circuit codes right away.
 
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RangerXLT!

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MAP, MAF, yeah :icon_thumby: your left nut is safe, and correct. Yeah its a MAF, but a 4wire one and yeah the temp thingy is just after it, IAT, looks just like a thermocouple that changes with resistance. Thanks again, and you're probably right with the paranoia... Still bugs me though, I even unplugged a spark boot while idling, no code there either. Well, nevertheless the truck is pretty awesome and I'll probably just keep it.
 

black_demon69

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did you check the cel bulb
 

RangerXLT!

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No, the bulb works. It comes on with key on engine off, as it should.:dunno:
 

Andy D

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I saw the Rat's CEL just the other day. I have had the truck 3 yrs.and always figured the bulb was broken. It goes away when the engine starts. It works, I'm not fixing it :D
 

RonD

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I would open the drivers door and check the sticker on the rear jam for the AXLE code number, read here:
http://www.therangerstation.com/tech_library/axle_codes.shtml

If your older Ranger had a 4.10 axle it would have more "pep" but not as good an MPG at highway speeds, your new truck may have 3.55 axle so less "pep" but better MPG.

I have the same 4.0l OHV engine and would kill for 20MPG, lol, 17MPG is the best I ever get, stock wheels and tire size, 3.73 axles, 4x4 and extra cab.

There is a Ground strap from the head to the firewall, this is the main Ground for the electronics in the cab.
Body parts are painted separately then bolted together, and usually with rubber grommets or mounts, so the bolting together of these parts does not mean they are Grounded together.
The Ground wires and straps around the engine bay are very important but often overlooked as people concentrate on the 12volt wiring, 12volts is only 12volts if there is a 0volt(ground) at the other end of the device :)
 
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Andy D

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The Rat has the more common 3.27 axles which helps the highway mpg. Drivin' Miss Daisy at 65 mph, I can squeeze out 21 mpg. I'm running 2.35 75 r 15s with loose rear brake shoes
 

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I have the same 4.0l OHV engine and would kill for 20MPG, lol, 17MPG is the best I ever get, stock wheels and tire size, 3.73 axles, 4x4 and extra cab.
On yours what is stock tire size? I only ask cause I see a pretty consistent 19.3 to 19.8 with what sounds like the same setup and 235/75R15. I do have the FM146 still though and drive like a granny most of the time.
 

RonD

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Yes, same tire size.

5-speed manual, in fairness I don't think I have ever driven it empty, it always has the canopy on and at least 400lbs of tool in the cab or back.
And I pass the guy who thinks he is driving fast..............so I am more like the "little ol' lady from Pasadena", if she finally got a fast car............Ford
 
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coopab

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ground strap connecting points

There is a Ground strap from the head to the firewall, this is the main Ground for the electronics in the cab.
Body parts are painted separately then bolted together, and usually with rubber grommets or mounts, so the bolting together of these parts does not mean they are Grounded together.
The Ground wires and straps around the engine bay are very important but often overlooked as people concentrate on the 12volt wiring, 12volts is only 12volts if there is a 0volt(ground) at the other end of the device :)
I'm putting my 99 Ranger back together and didn't take photos :shok:

I've got a ground strap about 18" long and don't remember exactly where it was bolted to a head and on the firewall. (same as cylinder head to bulkhead?)
I'm worried that if I attach it to the wrong head or the wrong connector on the firewall that it may interfere with something related to the installation of the intake manifold.

coopab
 

Andy D

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A wiper motor mount, if I recall right :D

Rat runs fine without it connected.??????
 

coopab

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dash gauges/indicators out of whack

RonD said:
There is a Ground strap from the head to the firewall, this is the main Ground for the electronics in the cab.
Body parts are painted separately then bolted together, and usually with rubber grommets or mounts, so the bolting together of these parts does not mean they are Grounded together.
The Ground wires and straps around the engine bay are very important but often overlooked as people concentrate on the 12volt wiring, 12volts is only 12volts if there is a 0volt(ground) at the other end of the device
I finally finished putting everything back together and true to what RonD says above apparently that head to bulkhead ground strap is important. My truck seems to be running just fine but
  • No reading on temp gauge even after warmup
  • Battery idiot light is ON
  • Battery Voltage gauge is in the middle of the L-H range
  • Multimeter shows 13.9 volts with engine running

I'm putting my 99 Ranger back together and didn't take photos :shok:

I've got a ground strap about 18" long and don't remember exactly where it was bolted to a head and on the firewall. (same as cylinder head to bulkhead?)
I'm worried that if I attach it to the wrong head or the wrong connector on the firewall that it may interfere with something related to the installation of the intake manifold.

coopab
Andy D's post indicates the proper place to connect the ground strap is a W/S wiper motor mount. I don't think that's where I attached it so I'm hoping to find a poor ground due to paint or other insulators.

I haven't driven it very far yet but it is showing no codes and two monitors "not ready." I suspect that may pass Mass inspection for a 1999 model year vehicle. Does anyone know for sure?
 
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