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Discussion Starter · #1 ·
Long time lurker here.

Had to renew the tags on the Bronco a few weeks ago and failed due to a bad cat. Replaced the cat and passed, but, shortly after it started not wanting to idle while cold, misfiring, backfiring/popping can be heard via the intake/throttle body and can smell fuel.

So far we've replaced plugs, wires, distributor cap and rotor. TPS has been cleaned/tested and is within spec.

All the vacuum lines have been replaced with 5/32 rubber lines.

MAP has been tested using the procedure outlined here: Part 1 -Manifold Absolute Pressure MAP Sensor Test (Ford 4.9L, 5.0L, 5.8L) . Hz reading slowly decreased as it should when vacuum was applied and slowly increased as vacuum was released.

Only thing to note on it is spec says 152Hz at 0 Hg and this MAP started at 139Hz...however, it decreased in Hz proportionately as described in the procedure.

I'm now trying to replace the O2 sensor and I can't for the life of me figure out a way to get enough room to apply enough force to break it loose. I'm using a O2 socket and the sensor has been well soaked in lubricant...but, no matter which angle I come at it (underneath at an angle through the fenderwell or directly underneath between the transmission pan and dipstick tube) with only 2"-3" of room to move the ratchet, it'll never come off.

Is there some secret to getting to this thing that I'm missing?

I haven't pulled codes yet as the battery was disconnected before the tune up (my bad)...will be taking it for a spin here in a bit to try and get it to throw them. No CEL/"Emissions" light has come on since the problem started.

Any ideas or suggestions here would be greatly appreciated!
 

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1993 Bronco 5.8l Eddie Bauer
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Changed my o2 sensor last week used socket with a breaker bar or use a bar over your ratchet handle you need the leverage of a longer handle should work.
 

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Discussion Starter · #3 ·
How'd you get enough room to move it? Even my 1/2 breaker bar flexes too much...it just hits the frame.
 

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1993 Bronco 5.8l Eddie Bauer
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Long time lurker here.

Had to renew the tags on the Bronco a few weeks ago and failed due to a bad cat. Replaced the cat and passed, but, shortly after it started not wanting to idle while cold, misfiring, backfiring/popping can be heard via the intake/throttle body and can smell fuel.

So far we've replaced plugs, wires, distributor cap and rotor. TPS has been cleaned/tested and is within spec.

All the vacuum lines have been replaced with 5/32 rubber lines.

MAP has been tested using the procedure outlined here: Part 1 -Manifold Absolute Pressure MAP Sensor Test (Ford 4.9L, 5.0L, 5.8L) . Hz reading slowly decreased as it should when vacuum was applied and slowly increased as vacuum was released.

Only thing to note on it is spec says 152Hz at 0 Hg and this MAP started at 139Hz...however, it decreased in Hz proportionately as described in the procedure.

I'm now trying to replace the O2 sensor and I can't for the life of me figure out a way to get enough room to apply enough force to break it loose. I'm using a O2 socket and the sensor has been well soaked in lubricant...but, no matter which angle I come at it (underneath at an angle through the fenderwell or directly underneath between the transmission pan and dipstick tube) with only 2"-3" of room to move the ratchet, it'll never come off.

Is there some secret to getting to this thing that I'm missing?

I haven't pulled codes yet as the battery was disconnected before the tune up (my bad)...will be taking it for a spin here in a bit to try and get it to throw them. No CEL/"Emissions" light has come on since the problem started.

Any ideas or suggestions here would be greatly appreciated!
Also check your fuel pressure regulator if you smell fuel pull vacuum hose off the FPR if there's fuel coming out change the FPR.
Mine leaked ran rich smelled fuel had fuel in the oil changed oil and filter too!
 

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Discussion Starter · #5 · (Edited)
Also check your fuel pressure regulator if you smell fuel pull vacuum hose off the FPR if there's fuel coming out change the FPR.
Mine leaked ran rich smelled fuel had fuel in the oil changed oil and filter too!
Ok, thanks, going to try that now. Will report back in a few.

I paused trying to remove the O2 sensor for now and just got back from a good 30 min drive. Pulled the following codes:

67 - Already aware of this one.
67 - Already aware of this one.
13
13
1

Is it normal for it to repeat the codes? I used the jumper and test light method.
 

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Discussion Starter · #10 ·
Thanks for the help Balisong.

Just looked that up too...RPM low isn't much help, already know that one lol!

During the drive it's missing pretty hard, surging and would stall when coasting or coming to a stop. Would have to crank it it for 3-10 seconds to get it going again. Sometimes would stall again right away as soon as you touched the gas pedal.
 

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1993 Bronco 5.8l Eddie Bauer
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Possible Vacuum leak egr valve or egr tube ? Check vacuum lines my were broken in different places
 

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Discussion Starter · #13 ·
All vacuum lines are brand new 5/32 rubber hose I just installed yesterday and have verified no vacuum leaks.

Just verified fuel pressure regulator isn't leaking after pulling vacuum hose either.

Was going to replace the EGR just because...but, from what I understand there should be no vacuum to the EGR unless actually driving around? So that shouldn't be causing the issue while idling.
 

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1993 Bronco 5.8l Eddie Bauer
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IAC idle air control or MAP sensor?
Or coffee can check for holes or cracks on bottom especially!
 

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Discussion Starter · #15 ·
Cleaned and tested IAC. Confirmed power to connector and open loop from spade to the body. Even did volt test while running...1 at idle almost 5 at full throttle.

MAP has been tested too... confirmed 5v positive test and and 10.7v negative test. Hz reading slowly decreased as it should when vacuum was applied and slowly increased as vacuum was released.

Only thing to note on it is spec says 152Hz at 0 Hg and this MAP started at 139Hz...however, it decreased in Hz proportionately as described in the procedure.
 

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Discussion Starter · #17 ·
Verified it's not the IAC now, just dropped a new one in. I'm thinking it might be fuel related at this point. Going to go snag a fuel pressure gauge and will report back.
 

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1986 Eddie Bauer 5.0EFI AOD Full length headers Y pipe into single 3" Magnaflow 3" factory exit
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My 86 ran like absolute.crap like that, super rich, sputtering when my air intake temp sensor went bad, but I did have a code 54 for that. Check.your resistance on that $12 sensor, should be [email protected] also check your o2 sensor at the EEC PIN, my o2 signal wasn't making it.to the computer cuz of a break in the wire.
178945
 

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Discussion Starter · #19 ·
My 86 ran like absolute.crap like that, super rich, sputtering when my air intake temp sensor went bad, but I did have a code 54 for that. Check.your resistance on that $12 sensor, should be [email protected] also check your o2 sensor at the EEC PIN, my o2 signal wasn't making it.to the computer cuz of a break in the wire. View attachment 178945
Ooh, we have results! I'm getting 2.35v on the air intake temp sensor connected and only 19k ohms on the pins. Local parts store has one in stock so going to swap that out here in a bit.

I'm looking around for how to test the O2 sensor at the EEC...but, I'm not finding much. Would you happen to have a link to a procedure for testing that handy too?

Thanks!
 

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1986 Eddie Bauer 5.0EFI AOD Full length headers Y pipe into single 3" Magnaflow 3" factory exit
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Pin 29 i believe, here is a link to 86 stuff, study it, its very helpful.





This is from the EEC section showing o2 sensor pin numbers 29, the eec has numbers on it for reference.


178957
.
 
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