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Wtf....coolant sensor?


rusty ol ranger

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86 Bronco II

I got this thing running a million times better then when i got it but still have a nagging issue

When the engine is cold (as in, overnight) it cranks forever before it starts. It also will not rev quick and will lean pop whenever you try to get after it....like a carb with no choke.

I unplugged the CTS and it runs pig rich...but runs great cold. So i bought a sensor and put in and have the same issue.

It runs amazing warm.

Im getting only 4.5v at the sensor...i know 5 is spec...is 1/2 volt deterimental?

The ohms when cold if i read it right is above 20,000.

Drops when warm.

Now the other kicker is i cannot get codes from it. I plug my reader in it stays on "000" and wont test anything besides kicking the fuel pump on. i dont even think its communicating with the ECM.

I got 5 volts on a wire at the ECM connector.

Could this be a failing ECM?
 


gaz

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@rusty ol ranger
Sounds like your are talking about 2 separate issues:
1) the 2.9l does not like to run when cold, mine never liked to run cold and I as much as practicsl, I avoided it.
2) HARD STARTING...now that is not a characteristic I expect to hear about a 2.9l; what I expect owners to say is that it starts nearly immediately.
• I would take a solid look at both the ignition components and the fuel delivery, until it starts fast and crisp.

Several simple conditions that can cause a slow start:
- poor spark plug gaps (worn out cathode)
- coil on it's last leg
- just before a fuel filter floats the goat
 

rusty ol ranger

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@rusty ol ranger
Sounds like your are talking about 2 separate issues:
1) the 2.9l does not like to run when cold, mine never liked to run cold and I as much as practicsl, I avoided it.
2) HARD STARTING...now that is not a characteristic I expect to hear about a 2.9l; what I expect owners to say is that it starts nearly immediately.
• I would take a solid look at both the ignition components and the fuel delivery, until it starts fast and crisp.

Several simple conditions that can cause a slow start:
- poor spark plug gaps (worn out cathode)
- coil on it's last leg
- just before a fuel filter floats the goat
New coil and plugs.

It starts fine when its cold if the coolant sensors unplugged.

Fuel pressure is 40psi
 

gaz

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There are a couple more components in that ignition system. Are you saying that the coolant sensor is bad?
 

rusty ol ranger

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There are a couple more components in that ignition system. Are you saying that the coolant sensor is bad?
I thought it was which is why i replaced it.

I also cannot get codes from it, and it runs good (cold) with the sensor unplugged
 

rusty ol ranger

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One question...i was just looking at a pinout diagram with a wiring diagram...and it shows all the sensors using the same signal return?? Pin 46?

88-91_5.0_EEC_Wiring_Diagram.gif


That doesnt make sense to me. Id like to probe the return wire to see if the signal is getting back to the ecm
 

rusty ol ranger

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Sorry to keep rambling (but it helps me to keep my brain working) but the ECM has to be getting the signal...since it runs good warm when its plugged in but idles high and runs rich if i unplug the sensor when its hot.

So that coupled with no scanner connnection almost has to be a bad ecm dont it?

Guess ill try swapping it with the one from my ranger and try it.
 

RobbieD

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That is a nice schematic, but I wouldn't put 100% trust in one which covers multiple years. In this case, 1988 through 1991; and it's also showing a V8.

Yours is a 1986 model, right?

I can shoot and post the Ford EVTM pages for the 1986 2.9 wiring, if you'd like, but I'm not sure if I have the Powertrain and Emissions manual for that year.
 

rusty ol ranger

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That is a nice schematic, but I wouldn't put 100% trust in one which covers multiple years. In this case, 1988 through 1991; and it's also showing a V8.

Yours is a 1986 model, right?

I can shoot and post the Ford EVTM pages for the 1986 2.9 wiring, if you'd like, but I'm not sure if I have the Powertrain and Emissions manual for that year.
I noticed it had 8 injectors and was 88-91 after i posted it. Funny when i did a google image search it said it was from TRS (here)...


Anywho yeah if you could do that thatd be great. Its an 86. 2.9 obviously. Sept 85 build date...so an early one if it matters.

This is the last thing running wise i need to fix. I could drive it like this...but it would annoy the piss out of me.
 

RobbieD

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Anywho yeah if you could do that thatd be great. Its an 86. 2.9 obviously. Sept 85 build date...so an early one if it matters.
1986 EVTM pages; if needed you can download them so you can zoom in.

Troubleshooting individual circuits, ECT in this case (page 43, 3-3, lower right), would be in the Powertrain book. I'd have to check if I've got the '86 book.

Keep in mind, that 1986 was the first year for the 2.9, and yours is an early build date. As far changes, we'd probably have to compare to the '87 schematics.

86 EEC 29 wiring 1-3.JPG


86 EEC 29 wiring 2-3.JPG


86 EEC 29 wiring 3-3.JPG
 

rusty ol ranger

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1986 EVTM pages; if needed you can download them so you can zoom in.

Troubleshooting individual circuits, ECT in this case (page 43, 3-3, lower right), would be in the Powertrain book. I'd have to check if I've got the '86 book.

Keep in mind, that 1986 was the first year for the 2.9, and yours is an early build date. As far changes, we'd probably have to compare to the '87 schematics.

View attachment 111984

View attachment 111985

View attachment 111986
So if im reading this right the green wire must be signal back to the ECM? Since the black wire runs to everything?
 

RobbieD

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Yes. I'm reading it as Black/White is power supply, should be 5 volts, and Green/Yellow as signal return.
 

rusty ol ranger

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So just to update this....

I dumped about 3 gallons of fresh gas in it (it was low) ran it about 15 minutes.

It sat for about a week now went out and it fired up as quick as my ranger.

Still wanted to stall as soon as i gave it throttle...but that stopped after about 15 seconds.

I can live with that. Still not getting codes though.
 

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My 87 always runs rough for a bit when first started but fires right off. Sometimes warm starts take a good bit of cranking… it’s annoying. Runs super good after that though.
 

rusty ol ranger

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My 87 always runs rough for a bit when first started but fires right off. Sometimes warm starts take a good bit of cranking… it’s annoying. Runs super good after that though.
My ranger seems to extendo-crank once in a while when warm too.
 

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