2.9 runs like crap

[pimtool]

I originally put this in the bronco2 section, but i think there is a little more traffic here.

89 bronco 2, auto trans, manual t case

I just got an 89 b2 thats obviously been neglected.

New fuel pump, filter, plugs, wires, cap, rotor, set timing.

It starts and runs ok, bit of a miss at idle. If i slowly press the gas it revs fine.

If i open throttle quickly it boggs and coughs, If I power brake it will miss pretty bad. it does seem to run a little better warm than cold.

I cant seem to locate a map sensor, tps voltage seems to move smoothly as throttle is opened.

I just put a another fuel filter on it, the one I took off that was a week old was full of rusty gas.

I pulled the injectors and sprayed them out with carb cleaner, that seemed to help for a few minutes.

So, I guess what I am asking is should I go after the fuel system and replace all of the fuel lines front to back and clean fuel rail and injectors or is there some other engine management sensors that need to be checked first. possibly O2 sensor?

Thanks

 

[RonD]

MAP sensor is usually located on the upper firewall, follow a vacuum line.

Fuel injected engine computers(EEC) monitor coolant temp to set cold/rich and warm/lean air fuel mixes.
This is often called the ECT(engine coolant temp) sensor, it is the "choke" since there is no carb.
This is a two wire sensor usually located near the dash board temp sender(this is a 1 wire sender).

If the ECT isn't telling the computer the engine is cold then it would run rough until it warmed up.

It is an easy sensor to test, just use an OHM meter when its cold, then after engine is warmed up test it again.
OHMs should get lower as engine temp gets higher.

I would clean out the gas lines where you can.

 

[jhammel85]

I'd check it for codes to see what pops up. Even if the light isn't on.

 

[pimtool]

Thanks guys, I found the map. I unplugged it and the motor quit. I think im looking at a fuel delivery problem. I think i will go ahead and clean the fuel lines, rail, and injectors and see what happens.

 

[RonD]

While unplugging the MAP sensor and getting a result means it was doing something it doesn't mean it is working as it should.

A 3 wire MAP sensor should have 5v, Signal and Ground wires
Usual layout is 5v is closest to the vacuum connection, ground farthest, signal in the middle.

You need to test the MAP with wires connected, I use pins, sewing pins, to pierce the wire, put them at different spots along the wires so they can't short together.
Key on Engine off, you should have 5volts DC between 5v and Ground.

Now set meter to Hz, most digital multimeters have a Hz setting, this is to measure frequency, and needed for testing FORD MAP sensors.
You test Hz by putting meter probes on Signal and Ground wires

With engine off you should see 155Hz +/-4hz
With engine at idle(highest vacuum) it should be down around 80Hz +/-4hz, if engine is cold it will be higher because idle is higher.
As you raise RPM, vacuum drops, so Hz will go up with RPM

The MAP is an important sensor on the Speed Density system, it literally controls how much fuel is injected, one of the big 3, TPS, RPM and MAP

 

[pimtool]

Thanks for the info RonD,

I think the map is jacked. I checked it, at first it seemed pretty close to specs. It was at 144 Hz and about 55Hz, then it was all over the place it would drop out to 0 and go up and down.

I am gonna re check when it dries up a little to make sure it wasnt the bad connections or something.

Thanks a bunch.

 

[pimtool]

I went ahead and bought a new map sensor, that didnt help. Im gonna try and return it tomarrow and get a fuel pressure tester just to see where its at.

I pulled codes 86 and 89 come up first

86 = shift solenoid failure
89=converter clutch override circuit failure
So both trans solenoids are either shot or unplugged (awesome!!!)

After i started it and let it run for a minute I got 41, 77,and 74

41= system lean/ o2 not switching

77= operator error dynamic response test

74 = Brake on/off circuit open-not during self test

I think the last two were because i didnt snap the throttle , turn the steering wheel, and press the brake pedal during engine running test.

According to this the o2 isnt doing anything, but is that enough to cause it to run that rough under load? Now I am really curious about fuel pressure.

Any thoughts or opinions are welcome.

Thanks.

 

[RonD]

Not sure an EEC requires it but did you disconnect the neg. battery terminal for a few minutes during or after swapping out the MAP sensor.
Often these computers need to be reset when a sensor is swapped, and then driven for a few miles to "learn" the new parameters.

Lots of codes, maybe EEC is starting to go.

Many recommend swapping O2 sensors at 80-100k because they do wear out.
I think the EEC-IV did have an Open Loop and Closed Loop system
Open Loop is used when engine is cold, in this mode the O2 sensor is ignored, the EEC runs engine rich with advanced timing, this is the Choke for EFI engines.
The ECT sensor "tells" the EEC when engine is cold and warm.
If you only ran the engine for a few minutes code 41 should not have come up since O2 was off line, or maybe it was a history code, but didn't come up the first time??

An O2 sensor also can't generate a signal until it is above 650degs, the chemical reaction can't take place under that temp, so only after a few minutes of running will an O2 sensor generate a signal, which is why the EEC is set to ignore it until engine is warm.
You can test the O2 signal with a volt meter after engine has warmed up, it should be 0v(not hot enough or dead) to 1v, Ford EEC-IV parameters are .1 to .3v is lean, .8 to 1v is rich, so sweet spot is .4-.7v
EEC also has an O2 timer, this is for restarts when engine is warm(ECT) but O2 sensor won't be hot enough to give a valid reading, I don't know how long the timer is set for but a few minutes would be my guess.
On startup the EEC's O2 timer would start, once it expired the EEC would only look at the O2 voltage if it was in Closed Loop as set by the ECT.

If EEC is not going into open loop, as it should when engine is cold, then it might spit out a code 41 because O2 would be at 0v and not working yet(not hot enough).

Which could be the ECT sensor, if it is not "telling" the EEC that the engine is cold then engine would start up in Closed Loop so not run well until it was warmed up, but your rough running is cold or warm, so back to EEC not responding correctly.
ECT is easy to test with an OHM meter, measure OHMs Cold and then Hot, should be a wide difference.

I might disconnect the battery and then pull all the EEC connectors and have a look at them, make sure they are clean, then reconnect.
Also make sure all near by grounds are clean and tight, almost all EEC controls are by grounding the component, not giving it 12v.
i.e. all injectors have 12v when key is on, EEC grounds an injector to fire it.

You can rent fuel pressure testers, some auto parts stores or equipment rental places, should be 30-40psi

 

[kimcrwbr1]

Pull the vacuum line to the fuel pressure regulator and smell for fuel if so replace the regulator.

 

[pimtool]

Its raining like a bastard now. I did notice a ground wire hanging in the breeze that is coming out of the wire loom that has most of the sensors on it.

Unfortunately, I did not reset computer when I tried the new map sensor and I already returned it. (dang it...)

I did have a shit ton of codes for all the sensors I unplugged. I unhooked battery for a bit and the codes listed above are the ones that came back.

When you say EEC connectors do you mean the plug ins for the TPS, ECT, and so on? Or the main computer inside near the passengers feet?

I guess the next step is to ohm out the ECT. There was no gas coming from the vacuum line on the regulator, but I did not smell it to see if it smelled like gas.

Fuel pressure took 3 key turns to get to 32psi, but it stay there while running and went up to 40psi when I throttled it.

 

[pimtool]

Finally, got a chance to look at it again. ECT ,IAT ohm out at 25k cold and 10k hot.

I pinched off the return fuel line line and it seems to run wayyyyy better. So I will replace the regulator and go from there.

Thanks for all the help guys.