HC means too much fuel, OR unburned fuel. Fuel pressure could be too high, and the ECM trying to cut the spray time, but if the regulator is not functional, it can't.
In repairing the engine i found a bad regulator and replaced it.
It had a hole in the regulator diaphragm and was feeding raw gas into the intake manifold through the vacuum line.
Though on the fuel rail there is a can unit with no vac line back behind the intake my Haynes manual does not cover what this is. Can not even ask the parts place how much if you don't have a name for the part.
Does the evaporative canister system work, or is it purging extra vapors into the intake willy-nilly?
it passed the functional test??
When you had the head off, you de-carboned the piston tops, right?
Did not shine them, but removed all excess carbon from the piston tops with a wire brush. was not much to begin with
Is the PCV working? Is it possible the PCV lines from the separator under the intake manifold leading to the bottom of the upper intake are full of crud with built-in HC's to feed to the engine?
Cleaned Inspected and found nothing wrong.
Basically, its either too much fuel, or fuel coming from 'somewhere else'. The somewhere else can be a 'storage point' that lets the HC's go whenver it wants to rather than on schedule... so to speak.
you may be right just did a drive of 191 miles to my VA clinic for lab work and only got 21.3 mpg. all highway at 65-70 mph. but where??? is the problem don't want to throw more parts at the truck just guessing.
The O2 sensor flips between .1 and .9v as it goes from lean to rich. "low=lean" meaning the O2 will send a 'lean' signal to the ECM when there are extra O2's in the exhaust gas. It does not know HC's from Bob. So, when an O2 dies, or doesn't work so well, it gets lazy, and flips slower, or doesn't flip at all, and just stays 'low'. That would mean the ECM thought the mix was lean, and it would be adding extra fuel to try to make the O2 come back to life and send it a 'hi' indicating it was too rich. There is a limit in the 'fudge factor' allowed. You would need to gain access to all the ECM data to know what's going on. The ECM may not throw a code, as all it knows is that "the O2 works now and again, so it must be OK, right?"
Anyway if an O2 fails, it fails to produce no volts, and that means 'lean' to the ECM.
If yours is old, it couldn't hurt... You can test them with a propane torch, but I never had any luck trying to hold the torch, the O2, and a VOM and have them all function at the same time without burns or dropping something.
tom
One of the first things replaced was the O2 sensor(code41) after fixing the smoke problem from the bad valve seals as i knew it was bad when i got the truck.its only got about 300 miles on it now.
Also replaced the MAP, EGR valve and EVP sensor(code31) TPS replaced and set at .97 volts, hand cleaned injectors while I had them out. good spray pattern.
And replaced the EGR Vacuum Solenoid.
New cap,wires. rotor, and plugs. tested coil over 1 1/4 inches of spark before the spark broke.
Cleaned IAC valve/motor. ( buzzing noise and slow to return to idle. Works right now)
Before the smog test i ran the truck for about 30 miles after the battery cable had been off.
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Tbars4
How many miles on the truck 913XX.
That is the site i found it on.
..I did some quick searching on the 88 Ranger TSB's and found nothing pertaining to that. It may be worth taking that info to a Ford Dealer since you are in California and see if they have any info on a recall, TSB, or repair as a result of the EPA listing..
I checked with two ford dealer service departments they knew nothing.
Wanted me to bring it in for diagnosis and repair. I am on a fixed income (disability) and don't have that type money.
Plus i have done most of the checks that they would do(i still have my tools and test equipment) and likely they would just throw parts at it till they got lucky. About the only thing i can not test is the smog.
I am a mechanic (heavy equipment, marine, electromotive equipment, generator(both ends as i am also a electrician.) mining equipment,)so i have a system of troubleshooting that works in most cases.
I just never liked to work on peoples cars and trucks so i never worked that part of the trade.PITA. I only do my own.