HELP!! 88 B2 wont pass low idle emissions in my state.

pblake

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Mar 3, 2021
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Location
ogden UT
Hello I recently bought a 1988 ford Bronco II XLT 4X4. It has been sitting for about 10 years before I came along.
I did some basic stuff to it and she fired right up and seems to run really well but when I took it in for the first time to get my state IM test done, it failed on the HC at idle speed. MAX is 220 and it got a 257, so close right? so I ordered the typical tune up stuff and took it in again(2nd test free). It got a 369! What the heck? Shouldn't it have gotten better? So on line I went, here is what I have done so far;
pre IM test, fresh out of the field.
Dropped fuel tank/restored fuel tank
Fuel pump
High pressure fuel pump
Fuel filter's
Fuel lines

Post failed IM test
6 spark plugs
Wires
Distributer cap
Rotor
Oil change
Cleaned upper intake
Fuel additive(injector cleaner)
Additive for ethanol where
Additive " guaranteed to pass IM"
2 tanks of Premium Gas(46 gallons)
1 tank of "Clear 88" ethanol free gas.(23 gallons)
Checked vacuum lines for leaks
Tested PCV, TPS, Air flow and other throttle related valves and sensors.
And a ton of driving on a temp tag.
So I just took it in today expecting it to pass with flying colors, well it got worse. I got 465 out of the maximum 220. Every thing at high idle is good between 54-94 of the max 220.
Other than catalytic converters I don't know what els to do. The truck seems to run great, its even peppy and thats hard to get out of the ford 2.9 V-6.
Any tips and tricks or suggestions would be greatly appreciated.
Thanks!
 

Shaggy

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Doesnt a tune usually increase RPMs?
 

miesk5

96 Bronco 5.0
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Yo pblake,
Welcome!
"High hydrocarbon (HC) readings usually indicate excessive unburned fuel caused by a lack of ignition or by incomplete combustion. Concentrations are measured in parts per million (PPM). Common causes include a faulty ignition system, vacuum leaks, and fuel mixture problems. Circumstances that can lead to a high HC emissions are:
* Incomplete combustion due to fouled spark plugs.
* Improper timing or dwell
* Damaged ignition wires
* Poor compression
* Vacuum leak
* Ineffective or faulty air management system (ECM control of air/fuel ratios)
* Catalytic converter intervention and HC concentrations
High HC readings at the tailpipe are an clear indication that there is a problem in at least one part of the system, but an HC reading that appears within "normal" ranges or is only modestly elevated is not necessarily a reliable indicator of proper or even acceptable system performance. HC readings at or near "normal" are possible, and not uncommon. From a malfunctioning engine equipped with a properly functioning catalytic converter. In such circumstances, truly elevated pre-catalytic converter HC levels will be masked by the catalytic converter and the potential for an HC problem must be further evaluated in the context of other readings of abnormal gas concentrations and AFR / Lambda readings." by http://web.archive.org/web/20060615114619/http://www.interro.com/techgas.html#anchorfour
 

pblake

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Mar 3, 2021
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Location
ogden UT
I will be working on it again this weekend. I think i am going to start with the intake manifold to be sure its not just a bad gasket (again). Im also going to remove, clean and reset all the emissions components like oxygen sensor, TPS and what not.
Ill let you know how it turns out.
Thank you for the info.
 

muddrivermike

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Jan 13, 2009
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Texas Arp
Hydrocarbons are Unburned fuel. When I was in the shops it was usually the distributor timing off. I cant remember if the timing needs to be advanced or retarded. Out side of that as mentioned above, anything that wouldn't produce the correct spark to burn the fuel. Now you can either adjust your timing, run hotter plugs, Orrrrr you can try pulling a vacuum line to lean out the mixture and see if that makes you pass then hook it back up.
 

chazzone

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Jun 11, 2013
Messages
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Do you have a reason to suspect the intake is leaking? If it had an air leak it'd be running lean, the opposite of what you have going on now.
Did you use Motorcraft plugs? It makes a difference.
Did you gap them properly? It's better to have a wider gap than closer.
What condition are the plug wires? Are they Motorcraft?
I'd definitely check timing. Advancing timing can mean a more efficient burn, thus lowering unburned hydrocarbons.
I'd also throw a coil on it. If the spark isn't hot enough, it'll have increased UHC.
I'd also make sure that the thermostat is correct. If it's not getting to operating temp, it'll run rich.
 

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