I just bought a 86' Bronco II with the 2.9L so of course I am new to the forums.

The problem is VERY rich fuel mixture causing fluffy black deposits on all the plugs and when the engine gets close to temperature, pressing on the accelerator will cause it to stall out and the only ways to get it started is to either WOT start it or let it sit for hours on end. I have done:

Replaced/done before even pulling codes(First thing I do to any used vehicle I buy):
Replaced: E-coil
Replaced: Cap
Replaced: Rotor
Replaced: Plugs
Replaced: Plug Wires

Replaced: O2 sensor (Double checked continuity on the harness from the O2 sensor connector on the O2 sensor side to the EEC-IV and ignition switch. Found the fusable link to the ignition switch was fried. Replaced with fusible link @20 gauge as listed in the book and continuity is now good. Ran engine and same thing happened (kinda expected since it appears its just the power to heat the sensor), double checked the fusible link and it was still good.)

Replaced: Knock sensor (Tested continuity to the EEC-IV from the connector, checked out)

Checked: Ohm reading from EEC-IV harness to the coolant temp sensor, seemed good @ 14k ~95 degree ambient temp sitting in the sun.

Checked: Ohm reading from EEC-IV harness to the air flow temp sensor, seemed okay. Higher than the coolant temp sensor.

First attempt at pulling the KOER codes, the engine of course stalled while it was going through what seemed to be a check on controlling the rpm. But I got a code about the TPS so I checked it and discovered it to be bad so I replaced it with a new one (disconnected the negative on the battery before doing so to clear the codes and KAM as I always do when replacing something).

Did a KOEO scan to double check the EEC-IV and got a 11 code.

Second KOER scan again resulted in the engine stalling before test completion and this time I got a code 25...this 'COULD' be due to the fact that its already running under either retarded timing or very rich fuel mixture.

Right now I am baffled and have many ideas on what may be wrong but would like to ask direction from veterans that may have run into the same issue as I because I would end up just replacing this, replacing that until it just works which of course will end up to be VERY expensive. I cant believe it would be the injectors since ALL the plugs look exactly the same.


Please help
durken

 

Run it for 30 seconds shut it off & remove the vacuum hose from the fuel pressure regulator. If it's wet with gas thats your problem. If it's not wet, follow the directions in your Haynes to check fuel pressure.

 

Did you check your timing? I would check your timing before doing anything else. Make sure that you remove the PIP bar before you adjust your timing. And adjust your timing after the engine is at optimal temperature. How is the Air filter? If that is totally clogged with dirt that will give you stalling and running rich. Did you have DTC 25 before changing the knock sensor? If not, I would look at he connection. Could have a connector not fully seated, or possibly a wiring problem. Did you check for KOER codes? If it's giving a DTC 25 after installing the knock sensor, I look into that circuit first. If you need help diagnosing the circuit, let me know. I'll try to help out best as possible.
Like 87 XLT stated, the pressure regulators on these trucks are known to go on you and give you problems. But sometimes the pintle inside the regulator gets stuck and will give you problems even if you don't smell gas at the line. But yes, follow the directions in the manual for checking fuel pressure.
There could be a lot of things causing your problems. First correct the KOEO codes. Get it fixed and then look for KEOR codes.
Check vacuum, compression and fuel pressures. Start with the basics and don't get caught up in the pull and pray method. I know it's frustrating and you want to fix it, but you have to develop a method of diagnosis. Sounds like you are on the right track.
Check the pcv to see if it's not sticking on you as well.

 

PCV valve is brand new.

KOEO gives me just an 11 System Pass.

Knock Sensor: I thought the only way the engine would know the existance of the knock sensor is to have the throttle depressed during that phase of the KOER test (asks you to hit the throttle) and when doing so, the engine dies and I get code 25. I Have tested both leads from the knock sensor to the EEC-IV harness end to end and they are good. Also yes it was dumping that code before it was changed and I do believe I have it installed right as I followed the instructions to the T and I do believe its making good contact to the harness. I will dig up some material on testing the knock sensor and test it.

Fuel Pressure Regulator: Definatly going to test this along with fuel pressure. Eliminating the issue of fuel delivery at least to the point of entry into the delivery manifold will be relativly easy once I buy a gauge and quick.

Timing: In the manual I have which is a Chiltons, it states that with the EEC-IV & TFI-IV system, no timing adjustment is possible. It does say however, that you can 'check' the timing by pulling the plug from the pip wire and have at it, but the manual says you cant adjust it. If this is false, I will promptly throw this one away and get a Haynes. I will check it anyway and post an update.

Air Filter: Brand new, totally clean. The old one was clean but for a few dollars and at the suggestion of doing so along with the fact that well it was a good idea to start with a known for sure clean one, I replaced it last night with the same results.

I just want to say thanks 87XLT and wolffpax for helping me not to fall into the 'pull and pray' method and follow the path of methodical diagnostics (hehehehe almost sounded kinda Jedi Masterish there ). I will test the above items and post an update with the results. Yes it was getting frustrating and having the virtual shoulder to vent on helps. Never fear, I will not give up, I am bound and determined on getting this fixed, always wanted a BII and now that I have one, I wont let this inconvenience push me away.


Thanks again, I will post back in the same thread with my results!

 

Ooops. My bad. Sorry about that. I should read these posts when I am more awake.
The base timing can be set. This is used as a reference by the EEC system. Once you plug the PIP back in, the computer takes control and adjusts the timing as needed.
I think I now know why you are getting the DTC25. You are not supposed to goose the throttle when directed. You are supposed to rap moderately on the exhaust manifold directly above the knock sensor when the Dynamic Response Test is ready. There is no need to depress the throttle at this point. 15 seconds later, a code will be set: check for code 25(ignore other codes at this point) If DTC 25 is not present the Knock sensor is okay. If it resets, turn the key off and wait for about 10 seconds. Disconnect knock sensor connector and inspect. Set the DVOM on 20V scale. With key on and engine off, measure voltage at the vehicle harness connector between the knock sensor(Yellow/Red)and signal return(black/white) wires.
Let me know how it turns out. The voltage readings will determine weather it is in the harness or ECU.
DTC will be set whenever the engine is not tapped.

 

Wolfpax, since this is acting up as soon as the loop closes i wonder if removing the connector from the MAP would prove anything? Strange that theres no codes. Can a MAP be bad & not code?

 

Seems like there should at least be a rich O-2 code. Since the O-2 is ignored at WOT, how does it run at WOT after it's warmed up?

 

At WOT it spews black smoke, really rich but it will run. Lower RPMs though are an issue, if you let it go down to idle, and try to give it gas, you have to feather it or else it will just die. I was not able to check the fuel pressure yet because the fuel gauge I bought does not have a small enough connector to go into the test port on the fuel deliver manifold. I am trying to track either an adaptor down or a new gauge that has the correct fitting. This will at least eliminate the fuel pressure question. One question I have after looking at the fuel pressure testing instructions posted by ken00, the range should be 35-45psi for all 86 engines. Is it my understanding that at idle the pressure should be closer to 35psi and higher rpms, the pressure should be close to 45psi but not to exceed or drop below that range?


Thanks!

 

The pressure is partially modulated by the engine vacuum at the vacuum fitting. At high vacuum conditions, the pressure will be lower than at low vacuum conditions. The instructions I use to test fuel pressure actually have you disconnect the vacuum line at the FPR, then plug it. The fuel pressure should then stay constant (and probably should be on the high side of that 35-45 psig range) regardless of what the engine is doing. You can then test the FPR's response to vacuum by manually applying vacuum to the FPR.

 

First off, fuel pressure is right on the fringe of 35psi (Took 80 bucks for a pressure gauge and the correct adaptor for the ford schroder(sp) valve but at least I have all the fittings for any kind of car pretty much :-/). When I disconnect the vacume line to the fuel pressure regulator it goes up to a steady 40psi. Now for the fun information....

I think I may have it. I have been getting code 21 (ECT sensor out of test range) alot and I figured it was because I was not able to run the car long enough to get it to a temp where it was readable while doing a KOER. When using my multi-meter and taking off the wiring harness from the EEC-IV, I was getting 14k Ohms which seemed fine. Upon inspection of the wiring, I discovered some electrical tape action going on so I pulled the connector off the ECT and put a loop in it. The ohms were not zero as expected. I pulled all the electrical tape off and discovered the ltgrn/yellow wire cut and someone had stripped back the wire and twisted them together. I cut off the ends, stripped the wire until I found some real good shinny copper and put a splice on it with heat shrink over it. Taped up the ends to ensure no moisture would get up in there and re-wrapped the wires to the connector and put the loop in resulting an Ohms reading of zero, resistance of zero from the EEC-IV connector pins 7 and 46 with no short to ground on the signal lead. Plug the connector back on the ECT thinking this is the fix and did an Ohms reading from the EEC-IV connector, 4.3 M ohms?! Impossible I say, so I disconnect the plug from the ECT and test right on the pins of the ECT and get the same results that fluctuated around a bit but stayed right around the 4 M Ohm mark. I had done a KOEO test and gotten a code 51 ECT sensor input exceeds test max before this discovery. Which was right after I did the fuel pressure test and the engine died so it was very warm since it was the longest period of time I have been able to keep it running.

Is this what happens when an ECT goes bad minus the wiring issue?

The main question I pose is could this be the root of my problem? It looks like I will have to drain the radiator, and pull the thermostat out to get to the ECT sensor. Looks like I will have to take back the vacume pump and the manual I bought to afford it :-/. 30 bucks for the ECT, 7 for a new thermostat (might as well replace it) 2 for a new gasket and 9/gallon for the anti-freeze. So looking at about 80 bucks depending on how much coolant is in there.

Thoughts before I do this?

 

If I remember correctly the ECT should read around 60K ohms/engine cold & about 5k ohms/engine warm. Sounds like you've found your problem.

 

Yes this could be contributing to the problems you are having. The ECT is one of several sensors that the EEC system uses to determine many different processes.
This is the temp and ohm relationships for the ECT:
Temp degrees F K ohms
---------------------------
248 1.18
230 1.55
212 2.07
194 2.80
176 3.84
158 5.37
140 7.60
122 10.97
104 16.15
86 24.27
68 37.30
50 58.75

The ECT signal affects air/fuel ratio, ignition timing, EGR flow, as well as idle RPM.
An open between the ECT and the ECM will result in a constant 5v signal at the ECM. A short will result in approx. 0 volts. Keep in mind that corrosion in the circuit results in higher than normal voltage due to the voltage drop the corrosion is creating. Corrosion equals more resistance and it is that extra resistance that will cause hard cold starts.
No need to drain the radiator. You have to remove the intake hose, Throttle body(perfect time to clean the throttle plate), and vacuum tube to the throttle body. You can get a wrench on that sensor. It will be awkward but it beats getting other parts that you don't have to change.
Hold on to the manual and vacuum pump. These will more than pay for themselves in the future when you will need them. Just trying to save you some time and money.

 

Well I went the route of draining the radiator and pulling off the thermostat housing and attacked it that way. It was a good thing because the thermostat and radiator fluid was looking pretty sick. Got the new ECT in there and put on a new thermostat, filled it up with coolant and fired it up. Much better!

It does seem to be a little on the rich side still but that could be because the o2 sensor has a bunch of gunk on it from when it was running very rich making the EEC-IV think its leaner than it actually is. Also the gas thats in there is pretty old (about 4 months I think) so I am sure this is not the best thing but its way low and I will be putting some fresh gas in soon. I am going to pull the o2 sensor out tonight and just see how dirty it really is. It would be a drag if I have to go get another one so soon but now that I know everything else is running great, it will be easier to digest.

I also had the battery disconnected while I was changing the ECT so it started with a fresh template.

While I was at it, I checked the timing and it was right on.

The next big project now that the engine is running much better is to figure out how to stop the leak from the steering gear shaft that connects to the pitman arm. I priced a reman and it came in at the tune of 180.00 so I am hoping that I can just pull off the old one, break it apart or something and just replace a seal or something. Anyone have experience doing this? My childtons does not show a breakdown of this at all.


Just wanted to say THANKS again to everyone that gave their input and the BII is almost ready for its maiden voyage!


Thanks!

 

Sounds like some serious progress. If you have a 2500 degree torch you can burn off any carbon deposits on the O-2 sensor, if a high speed run with fresh gas does'nt clear it up.
A friends 88 Ranger had a sloppy & leaking steering gear box, we replaced it with one from a burned up B-2 from the boneyard for 20 bucks. Might have brought him bad luck though as the Ranger burned up a couple years later. If yours is OK other than the leak, i think Napa will have the seal.

 

Crikey that was a pain. Got the seal kit and a pitman arm puller. Surveyed the possibilities and decided to pull the steering box off and do it that way. Wow what a pain it was but I got it done in about 4 hours total along with doing other various items to break it up a bit. Funny thing is, by 1 am I was so tired that it appears that I got the steering wheel out of alignment with the wheels so I will have to fix that tomorrow. Hopefully I can adjust it without having to pull the steering box off again. Then finish bleeding the power steering system, change the oil, top off the radiator and I should be able to make my first maiden voyage directly to the gas station hehehhehe.


Thanks again everyone, been a great help. Looking forward to the next project it assigns me or I decide to tackle.