need some help with a few problems

iscrni · Oct 7, 2013

hi so i just recently picked up a 99 ford ranger, regular cab, 4x4, 3.0l automatic engine with 127k miles. so forgive me if i am asking dumb questions, i am new to ford rangers, this being my first one and all.

so my first question is, i went to get my ranger inspected and the guy said it wasnt connecting with the machine, i wasnt any of the fuses, and it wasnt the machine, he checked both. is it a faulty cpu or something, any ideas?

my second question is the when going down the high way the truck wont really go past 3k rpms. i can put the pedal to the floor and it just stays at 3k, in first and second it will go past 3k, maybe 3.5-4k in first gear before it shifts. but after that i can have it floored and wont go past 3k. is this normal? or is it a bad fuel pump? or maybe the same issue causing the OBD machine (if thats what its called) not being able to read?
please help,
oh and one last thing, i am new to the forum so if i posted in the wrong section im sorry.

RonD · Oct 8, 2013

Welcome

Yes, right section

'99 vehicles will use the OBD II(on-board diagnostic) system for communications with scanner, pre-'96 used OBD I.
Not being able to connect to the system does indicate a wiring or computer problem.

Most OBD II scanners/readers get power from the OBD II port, is this what they did?
And I assume they didn't have power or they wouldn't have checked the fuse??

They used the data port inside the cab on drivers side lower dash?
Does your cigarette lighter work, that is often on the same fuse as the OBD II power?

3,000rpm sounds like the rev limiter kicking in, this should only happen in Park or Neutral, rev limit in gear is usually above 5,000rpm.
This is, of course, controlled by the computer.

When you turn on the key is there a CEL(check engine light)?
This should come on when the key is turned on and then go off after starting engine.
No CEL would also mean a computer issue(or someone removed the bulb

)

So........it does read like a computer problem, the computer has a "limp mode" which allows the engine to work and truck to be driven in the case of some computer failures.
But without being able to connect to the computer there is no way to test it.
I would double check all fuses(inside panel), test for power at the OBD II port, check connections at the computer(PCM), passenger side under dash, unplug them and inspect for corrosion, then reconnect, and test OBD II again.

There are $15-$35 OBD II bluetooth adapters and free apps for smartphones so you can test OBD II yourself.
Google: OBD II bluetooth

The '99 may have a factory PATS anti-theft system, need coded keys to start engine, if this is the case then swapping out computers also means adding your current keys to new(used) computer, so just a heads up on that.
Good read here about Ford PATS:
http://www.explorerforum.com/forums/showthread.php?t=234975

Also as a heads up on the 3.0l engine have a read here about the cam position sensor:
http://www.therangerstation.com/tech_library/camshaft_position_sensor.html

iscrni · Oct 8, 2013

thank you for all the helpful information,

they did try to use the port on the drivers side, and the lighter does work, at least last time i used it. and is this rev limiter in the same computer that controls this?
as far as the CEL, no it is not on in the truck, and the bulb is their, when the key is turned to the on position to start the truck all the dash lights, light up and go away once the truck is actually running as for the other things mentioned, i will look into and i appreciate all your input.

RonD · Oct 8, 2013

There is just the one "computer", Ford calls it the PCM(power control module), also know generally as the EEC(electronic engine control), either is correct in it's description.
This also controls shift points in trucks with automatics.

Yes, rev limiter is in this computer, it is a preset parameter in the computer, but is only used when certain conditions are set, like transmission in Park.

Ford also has the GEM(Generic or General Electronic Module) located behind the radio, while it is similar to a computer it is not referred to as a computer, it runs:
Warning chimes and warning lamps
One-touch down driver's side window
Daytime Running Lamps
Heated rear window
Windshield washers and wipers
Battery saver
Remote keyless entry
Illuminated entry with remote keyless entry
Interior lighting
Electronic 4x4(along with the 4x4 module, yet another computer type device

)
Speedometer
Probably a few more I am missing, but nothing engine related here.

So CEL does light up with Key on, that is a good sign, could just be a problem with the OBD II port wiring.

Does the radio look like the factory one, people often install upgraded radios and butcher some of the wires behind the dash, or add other things and end up disabling "wires that don't do anything", lol.

I would focus on getting the OBD II port working, that will get you any current and "history" codes that may point to an issue on why the rev limiter is coming in while in gear.

iscrni · Oct 8, 2013

OK thanks, and the truck does have an aftermarket radio, i pulled it out to see how it was hooked up, its didn't seem to have a harness to it and that the wires were all connected together but i wouldn't think that would cause this type of problem?

need some help with a few problems

iscrni

New Member

RonD

Official TRS AI

iscrni

New Member

RonD

Official TRS AI

iscrni

New Member

Sponsored Ad

Sponsored Ad

Staff online

Members online

Member & Vendor Upgrades

Latest posts

Truck of The Month

Recently Featured

Follow TRS On Instagram

Latest Album Photos

TRS Events

25th Anniversary Sponsors

Check Out The TRS Store

Sponsored Ad

Sponsored Ad

Sponsored Ad

Amazon Deals