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Discussion Starter #1
So since the beginning of this summer I have gradually been rebuilding my bronco from sitting for +/- 5 years, and neglect before that. I rebuilt the valvetrain, replaced almost all of the fuel system (tank, sender/in tank pump, fuel filter, some lines, injectors, high pressure pump, FPR) and basically all of the ignition system. I built/pieced together a 100% new exhaust and put in a new Bosch O2 sensor, and rebuilt the valvetrain, so one would think the engine would run perfectly.

I have been driving it around a bit and I cannot seem to get the lean code to go away. I either messed something up in the rebuild or used bad parts, because cylinder 5 is not getting full compression, and its because of the valvetrain (valve not closing all the way, presumably) and you can hear a loud lifter tick, but only on that cylinder.

Anyway, it starts up and idles fine. I can drive it normally, and it has a pretty decent amount of power. But once I take it over 2000 RPM, there is a popping noise coming from the intake (detonation from running lean?) both when under load, and just revving in park. Again, 2000 rpm and under it is fine, but say I am accelerating hard, the popping starts, a CEL comes on (I scan every time, its always for a lean code) and the motor runs hotter when this is happening.

Any ideas as to what this could be? I have been trying to figure this out for months, and I still haven't got it. I want to drive this truck but I know it is really bad to under these circumstances.

Thanks, JB
 

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seafoam it and clean up the IAC and maybe you need to set a base idle
 

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Take off your valve covers and recheck your valve lash. Also make sure your rocker arms are riding on the valves correctly.
 

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Discussion Starter #5
Thanks for the suggestions. I'll try seafoaming it with some spray I have. The IAC is brand new so I don't think its that. The idle is a bit low right now, by like 100 rpm or so, so I will adjust that and then see. There are no vacuum leaks that I can find.

This motor has rocker arms that are directly bolted to the heads, not on a post or anything, there is no way to adjust those is there?
 

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cylinder 5 is not getting full compression, and its because of the valvetrain (valve not closing all the way, presumably) and you can hear a loud lifter tick, but only on that cylinder.
I've never rebuilt an engine.
Wouldn't the most likely cause of this be a bad hydrolic lifter?

With hydrolic lifters, I don't think that there is any valve lash, and that they are not adjustable. Again... I really do not know.

IF you pulled your valve cover, and ran the engine *surround the valvetrain with cardboard to protect the rest of the engine from splashing oil.* would you be able to see the valve not behaving the same as the others?

How low is the compression on cyl 5 compared to the others?

What code do you get when you pull codes?
 

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Discussion Starter #8
cylinder 5 is not getting full compression, and its because of the valvetrain (valve not closing all the way, presumably) and you can hear a loud lifter tick, but only on that cylinder.
I've never rebuilt an engine.
Wouldn't the most likely cause of this be a bad hydrolic lifter?

With hydrolic lifters, I don't think that there is any valve lash, and that they are not adjustable. Again... I really do not know.

IF you pulled your valve cover, and ran the engine *surround the valvetrain with cardboard to protect the rest of the engine from splashing oil.* would you be able to see the valve not behaving the same as the others?

How low is the compression on cyl 5 compared to the others?

What code do you get when you pull codes?
Yeah, I was thinking this too. The new lifters I put in were suspiciously cheap, and did not know until after the rebuild that you were supposed to soak them in oil beforehand (though I did do the 2000-2500 rpm break in). So its possible one of the lifters is bad.

The compression on cyl 5 is about 125-130 psi, and the others are 150-155 psi. Does this sound about right?
 

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The compression on cyl 5 is about 125-130 psi, and the others are 150-155 psi. Does this sound about right?

Again... I'm not really qualified to comment on this, but I seem to recall reading that the lowest cyl should not be less than 75% of the highest. 150 * .75 is 112, so it would seem that 125 is ok. I don't know what the minimum compression is that is needed, but I would guess that compression, is not your problem.

I'm thinking though that an open EGR valve, when it shouldn't be open could give you pinging.
Also that a clogged CAT could give you problems at higher RPMs.


HowTo diagnose a plugged catalytic converter
BogHog... Use a vacuum guage, good explanation.
To diagnose a plugged catalytic converter, you can check intake vacuum or exhaust backpressure. To check intake vacuum, connect a vacuum gauge to a vacuum port on the intake manifold. Start the engine and note the vacuum reading at idle. Then increase engine speed to about 2,500 rpm and hold steady. Normal vacuum at idle for most engines should be 18 to 22 inches Hg. When the engine speed is increased there should be a momentary drop in vacuum before it returns to within a couple of inches of the idle reading. If the vacuum reading is lower than normal and/or continues to drop as the engine runs, it probably indicates a buildup of backpressure in the exhaust. Remember, though, that intake vacuum can also be affected by retarded ignition timing and valve timing. What's more, some engines are much more sensitive to small changes in intake vacuum than others, so checking backpressure rather than intake vacuum may give you a better indication of what's going on

Another suggestion by BogHog was to remove the O2 sensor in front of the Cat (which will allow the exhaust gases an avenue of escape) and see if the engine runs better. If it does, the Cat is plugged.

Plugged Cat test with pressure guage...
http://www.youtube.com/watch?v=IzyvL5tQLzU
 

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Discussion Starter #10
The compression on cyl 5 is about 125-130 psi, and the others are 150-155 psi. Does this sound about right?

Again... I'm not really qualified to comment on this, but I seem to recall reading that the lowest cyl should not be less than 75% of the highest. 150 * .75 is 112, so it would seem that 125 is ok. I don't know what the minimum compression is that is needed, but I would guess that compression, is not your problem.

I'm thinking though that an open EGR valve, when it shouldn't be open could give you pinging.
Also that a clogged CAT could give you problems at higher RPMs.


HowTo diagnose a plugged catalytic converter
BogHog... Use a vacuum guage, good explanation.
To diagnose a plugged catalytic converter, you can check intake vacuum or exhaust backpressure. To check intake vacuum, connect a vacuum gauge to a vacuum port on the intake manifold. Start the engine and note the vacuum reading at idle. Then increase engine speed to about 2,500 rpm and hold steady. Normal vacuum at idle for most engines should be 18 to 22 inches Hg. When the engine speed is increased there should be a momentary drop in vacuum before it returns to within a couple of inches of the idle reading. If the vacuum reading is lower than normal and/or continues to drop as the engine runs, it probably indicates a buildup of backpressure in the exhaust. Remember, though, that intake vacuum can also be affected by retarded ignition timing and valve timing. What's more, some engines are much more sensitive to small changes in intake vacuum than others, so checking backpressure rather than intake vacuum may give you a better indication of what's going on

Another suggestion by BogHog was to remove the O2 sensor in front of the Cat (which will allow the exhaust gases an avenue of escape) and see if the engine runs better. If it does, the Cat is plugged.

Plugged Cat test with pressure guage...
http://www.youtube.com/watch?v=IzyvL5tQLzU
Thanks. However its not either of these...I am running cat-less (at the moment) and my EGR is actually not opning at all (code 33). I only get 2 codes when I check, which is 33 and 41 (lean).
 

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yo,


DTC 41, 42, 85 OR THREE DIGIT CODES 171, 172, 173, 179, 181, 182, 183 & 565 are received , Check for proper HEGO Ground; in Catalytic Converter Diagnosis TSB 91-12-11 for 86-91 Bronco, F Series, & Econoline
Source: by Ford via Steve83 (Steve, That dirty old truck) at http://www.supermotors.net/registry/media/747751

DTC 41, 42, 91, 92, 136, 137,139, 144, 171, 172, 173, 175, 176, 177 & some Possible Causes for Rich & Lean HEGO The engine temperature must be greater than 50°F (10°C) to pass the KOEO Self-Test and greater than 180°F (82°C) to pass the KOER Self-Test. To accomplish this, the engine should be at normal operating temperature
Source: by Ryan M (Fireguy50) at fordfuelinjection.com
DTC 41; "...KOEO; No HEGO sensor switching detected or disconnected. HEGO is bad, not connected, or missing. KOER; HEGO sensor indicates system lean. HEGO is going bad, missing." read more
Source: by miesk5 at http://fullsizebronco.com/forum/showthread.php?t=155932&page=2



DTC 33 is triggered when the EVP sensor is not closing; so EZiest & cheapest checks are to inspect & repair/replace repair any bad vac lines. for a <$ vac line test; I pull em off and use the straw sucking test; one finger over one end; includes EVP testing & Links
Source: by miesk5 at DTC 33 is triggered when the EVP sensor is not closing; so EZiest & cheapest checks are to inspect & repair/replace repair any bad vac lines. for a <$ vac line test; I pull em off and use the straw sucking test; one finger over one end; includes EVP testing & Links
Source: by miesk5 at http://www.fullsizebronco.com/forum/showthread.php?t=175236

DTC 33 & 34 "...DTC 33 is triggered when the EVP sensor is not closing.... To prevent the EGR valve from opening when the engine is cold, the vacuum line to the EGR valve may be connected to a parted vacuum switch or a computer-controlled solenoid. Vacuum is not allowed to pass to the valve until the engine is warm. EGR isn't needed when the engine is cold, only when it is warm and under load. Any of these codes could indicate a faulty EGR valve as well. as well as a problem in the ...vacuum solenoids' Miesk5 note; TAB & TAD; so repair those vac lines 1st..."
Source: by Larry C
 

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Discussion Starter #13
thanks for the suggestions.

UPDATE: I was messing around today trying to figure this deal out still, and I figured if it was running lean, i would try to trick the motor into running rich(er). So I unplugged the o2 sensor, thinking this would do it, and it didn't, nothing really changed, it still popped when I revved it. BTW, it doesn't pop when you slowly rev it, just when you punch it real quick. Should have said that before. Anyway, I plugged it back in and unplugged the coolant temp sensor (the computer one not the gauge one) and started it up, and it would not drop below 1400 rpm's or so, and the exhaust smelled rich. IT would rev like before, smoothly but with pops when you punch it. Could it not going down to idle in this situation indicate a vacuum leak or something else?

I am really stumped here. My next idea is to remove the EGR and block the hole in the intake with a piece of metal with a gasket, and block off the vacuum line that goes to it, as suggested earlier there may be a vacuum leak there.

Thanks a lot, JB
 
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