azwhitemouse

On a 1995 4.9L I 6....I have the low RPM miss like a lot here seem to get. It misses between 1200 and 1900 rpms, Code comes back 173... HEGO (HO2S) Fault/ Rich....I went to check the sensor and had water in the connection. I cleaned the water out...same code. I used some WD 40 and let it dry....and checked codes while it was unplugged...same code.... Plugged it back in and ran codes again...same code....any ideas? Is it the HO2S or something else giving me the code? Please, any idea what I should be looking for before I change the O2 sensor..... Thanks ahead of time..

azwhitemouse

Well I changed the oxygen sensor and still the same code. Still runs like crap around 35 mph up to around 45 or so. Put some injector cleaner in the tanks and that made it smell funny but still isn't helping. Talked to a mechanic who said something is making it run rich so I changed the air filter with no help there either. He said if the injector cleaner doesn't help maybe it's the fuel pressure regulator....not sure if I have $108 to try it and see if that does it and if it doesn't then do something else.....wish someone had a educated idea on this because I'm tired of switching parts and hope for the best. I wish for the old days when it acted like this I could go to the choke and do some good..... it runs fine while it's cold but as soon as the temp reads even to the "N" in normal then it begins to sputter and miss like a choke problem, but I'm not even sure there is a choke on this........

azwhitemouse

Last post I had tried the air filter with no luck. I was told to try the fuel pressure regulator, but then I was told if it was the regulator the truck just wouldn't run. I don't know if that's true or not. My friend who teaches auto mechanics at the high school told me maybe it was the throttle positioning sensor. I replaced it with no luck. I talked to the service writer at the Ford dealer here in town and he said it sounded like the ignition coil was going bad. I changed the coil, and still no help. I have so far changed one injector that had melted and burned the PCV hose through. I changed the valve cover gasket while the intake was off. Found a few rotten vacuum hoses and replaced those. I did the typical tune up (plugs were gaped at .075".....don't know how it even ran) Changed the fuel filter and cleaned the connection at the Brain box that goes through the fire wall on the driver's side. Doesn't matter which tank I run off so I can't believe it would be the fuel pump(s). I read a post on here saying the coolant temp sensor could cause my issue. I took out the thermostat and put it in boiling water and it was stuck tight. I thought maybe that was it! It made sense that if the thermostat was stuck and the truck was running hot but the temp sensor was saying it was still cold that would make it run rich sort of like a stuck choke on the old fashioned carburetors, and maybe cause my problem..... Didn't help. I've spent over $450 chasing this little miss with no luck. Everything I have changed was a problem but just not the one that was making it miss. I'm down to the pressure regulator unless some one has another idea. HELP!

azwhitemouse

I ran across a youtube video related to my miss. I am waiting for the part and should have it in a few hours. According to this video there is a service bulletin about my issue. He says the throttle body mounting gasket was the culprit. I went and pulled the gasket (took all of 5 minutes) and saw exactly what he was saying i would find. The replacement gasket is a Fel-pro #60846 and costs $1.49 and O'Reilie's will have it around 14:30 today. Here is a link to the video if any are interested.
I will post again after I see what happens. I'm going to be mildly pissed if it fixes it for $1.49 when I spent $450.00 chasing the problem.

A list of what I replaced;
Thermostat gasket
Thermostat
Thermostat housing
Coolant Temp sensor
Ignition Coil
Fuel filter
02 sensor
Valve cover gasket
Manifold gasket
Throttle positioning sensor
Injector (one was melted)
Injector O-rings
Spark plugs
Wires
Distributor and rotor
Assorted broken, burnt, and dry rotted vacuum hoses/lines
Assorted Cool tape and heat shield so I don't re-melt hoses

Later.

azwhitemouse

Well at least it was only $1.65 and I was really optimistic when I saw how bad the throttle body gasket was. But, it still has the miss. About to flip a coin to see if I try the fuel pressure regulator (the fuel pressure tested out at right on 50 running, with a slight drop and gain when reved up) I'm running out of ideas. Maybe take the distributor out and find some one to check it out?

azwhitemouse

I think the throttle body gasket was it after all. My confusion was because with all that was done I forgot to reset the timing after the tune up. After setting the timing and changing the gasket it seems to be running fine now.

azwhitemouse

Still acting up. Got a new Fuel pressure regulator and tried it. Still not fixing the miss. Cleaned it up and got my money back, so that was cool. Only thing I can think is the advance in the distributor is off. Not sure if it's in the ECM or the pick up coil in the distributor. Might take it in Monday to get it professionally checked....I'm all out of ideas.

sdmartin65

My 95 4.9 has a similar miss. Replaced pip in distributer and that reduced the miss. Replaced entire distributor and that fixed it. When the old distributor was spun there was a slight bit of movement in the bearing, guess that was the cause and makes sense.