91 2.9 ranger running like poo

Alright guys, i picked up this ranger a few days ago and it runs like complete butt hole.

Sometimes starts strong idles good for a second then starts missing and smells like fuel.

Sometimes starts then dies and wont start again for a while.

Already checked fpr for raw fuel and its good, replaced ect, fuel filter, cap, rotor, plugs, and wires.

Has a consistant CEL, and will not pull codes with the koeo or koer tests. Comes back on even after removing the battery terminal.

I'm at my wits end with this truck.

Welcome to TRS

Reads like you bought someone else's problem.

I assume you did a road test before buying it so knew about some of the problems.

Engines are not to complicated, adding the electronics made them simpler and more reliable.
1991 Ranger will have 25 year old wiring and probably more than one owner that did "repairs" or added "stuff".

So really not to usual to have some problems.

On the upper intake toward the front will be the IAC(idle air control) Valve, all fuel injected engines need an IAC valve to set a stable idle, idle screws won't work, no Jets.
It is held in place by 2 bolts remove them and pull IAC Valve off the upper intake.
Have it's wires connected and turn on the key, it should open all the way, then unplug its wires and it should close, plug wires back in and it should open.
If not then use a volt meter to test Red wire to make sure it has 12volts(battery voltage) with key on, if so replace IAC valve.
Engine will barely idle with bad IAC Valve or will just stall, and will be hard to start, not enough air getting in


You were on the right track with FPR(fuel pressure regulator) if you smelled fuel.
Its vacuum hose was fuel free which is good.
Now there is the fuel injectors.

In the engine fuse box is the EEC relay, it powers the EEC(computer) but also the fuel pump Relay(not the pump) and it powers the fuel injectors.

When you turn on the key the fuel pump should run for 2 seconds then shut off, safety feature, it won't come on again until engine starts, or unless you turn off the key then turn it back on to get another 2 seconds.

So try this test.
Turn key off and on 3 times
Pull out EEC relay, shuts off fuel injectors
Crank engine, it should not fire if there is no fuel, spark is still on

If it does fire then there is a leak of fuel into intake.

Repeat test, but this time pull off the coil to cap wire so no spark
After cranking pull out each spark plug and check which one is wet with fuel, that will be the one with leaking injector.

You may be able to tell just by pulling spark plugs and looking for the darker plug, the one running rich.

Having CEL on but not being able to talk to computer could be a sign of computer failure, it is rare but not a never happens.
Since it is well past warranty, lol, you can open it up and have a look at the circuit board inside for signs of damage.
Good look here at what it should look like: http://www.auto-diagnostics.info/ford_eec_iv

Not related to smelling fuel but important for 25 year old system, the TFI spark system.

Read here on troubleshooting this system: http://www.therangerstation.com/tech_library/TFI_Diagnostic.shtml

I appreciate that info sir! Yeah i drove it, it was sitting in a field for 6 years had the back window broken out. So I'm wondering if the ecu got water damage.

I'll try your methods you stated and report back if any of yhem were the issue.

I did unplug the iac to see if the idle changed, and it did. Just not very much.

I assume fuel was gone after 6 years or you drained what was left out of the tank?

After that long the fuel in the injectors would dry out to a varnish so they could be the problem

JackV said:

I appreciate that info sir! Yeah i drove it, it was sitting in a field for 6 years had the back window broken out. So I'm wondering if the ecu got water damage.

Click to expand...

Water damage is unlikely, the EEC itself is weather-proofed and fairly protected inside the cab.

The wires and connectors are much more likely to be damaged from age or weather than the EEC itself.

check the coolant sensor for the ecm(not the gauge), i had issues with that on my old 88 bronco, it will fail and tell the engine it is hotter than what it is and lean the mixture out, causing a now start/stalling issue especially running around town when engine bay temps are higher, and wouldn't start until it was cool.


the codes not being able to to pull is no surprise, the wiring is starting to get brittle on these older trucks, run a voltmeter and trace the wires back to the ecm making sure you have a good connection.


older but the pinouts should be the same.



(source)
http://www.grandmarq.net/oldfuelinjection/images/eec04.gif


they didnt really change the eccIV wiring, but one could get some wire taps, wire, and a toggle switch, and tap into close to the ECU to get the test to work,

pin 46 and 48 on the ecu should be the ones you are looking for, i would check with a volt meter and see if you get good continuity between those pins and ecc test plug, if you do use a paper clip, if not you should be able tap into it, and use a toggle switch for a jumper(what i am going to do if i ever have a ecciv vehicle again)...


its been a while since i have worked on ecciv, i like the OBDII much better.....