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Trying to help a friend with his 1988 F150 with 4.9 (300CI) six cylinder. He has failed our emmision test several times due to high hyrocarbons. Max allowed is 220 and his has been anywhere from 415 up to about 600. The truck has high miles but runs good and doesn't seem to smoke. He has changed spark plugs, cap, rotor, air filter, pcv. Put in new thermostat to get the temperature up correctly. I had him pull the pcv out previously to cut down the hydrocarbons being recirculated back thru the intake and that helped but he still failed. Nothing seems to work. Today I set the timing to 10BTDC as it was severely retarded and sent him back. The hydrocarbon level actually increased so he failed again. With our test it is tailpipe only so they don't look under the hood. Any suggestions? O2 sensor, EGR, Catalytic converter?
Take it for a good drive and get it good and heated up. Running retarded could have cause some build up that is causing the engine to run poorly. Also pull the codes from the computer and see if any sensor is not functioning properly.
He got it pretty hot when he ran it thru again today, that's when the reading went back up some. I'm stuck here at work until midnight so I can't look at it until tomorrow. I'm going to check the EGR valve at that time. He probably needs to let me drive it for a couple of hours. I usually only have the two positions on my gas pedal. Down or Up! When I take a cylinder head off there usually isn't any carbon on my pistons.
Might also want to check fuel pressure and oxygen sensor, because it sounds like it is running too rich. I don't suspect EGR, but it could be malfunctioning as well.
He's already running 87 octane. When I set the timing at 10- BTDC he said it had some ping. I thought he would do better with 89 octane. I'm going to check the EGR tomorrow. Any way to test the O2 sensor or just change it?
UPDATE! We finally got the truck to pass. I changed the O2 sensor checked the timing again and it still failed. Hydrocarbon allowed 220 and the reading was still 415. Still not right. Then I found that when I removed the spout connector to the distributor the timing did not change. So, when I was setting the timing at 10 BTDC it was wrong as the distributor still acted as if the connector was in even with it out. Didn't notice the difference as I was shutting off the truck before and after the spout connector was removed or installed. I checked the connector with a meter and it has continuity. What would cause the timing to not change? Since I can't get it to change, any ideal of where to set the timing with a light? It seems to be about 15 degress off to make it run right. We just backed off the timing about 15 degress and it went right thru with a reading of 111.
Spark timing should NEVER change with SPOUT connector removed! Timing should be at 10 BTDC with SPOUT removed. Chances are that your catalytic converter has disintegrated! If you are passing CO and NOx but busting the HC test, more than likely it is the catalyst. Most 300's and 302's on F150 and E150 that work at or near their max GVW's blow aout their catalysts eventually.
I think you misunderstood the problem. The timing remains the same with the spout connector installed or with it removed. It acts as if the connector is installed all of the time, even if it is not. If I set the timing to 10 BTDC with the connector out as required, it runs bad as if the timing is off about 15 degress (which it is), so removing the spout connector doesn't work. What I meant about the timing not changing is, if you are checking the timing with a timing light and you install the spout connector and remove it while doing so it makes no difference in the timing or the RPM. Removing the spout connector doesn't change anything as it should. My original question was, Why doesn't removing the connector work, and where could I set the timing with a light (example -5 degress etc.) to compensate for the difference?
Are you just basing the spout not working at idle rpm? Do a key on engine running test, and then hook up a timing light (spout still plugged in). The computer will advance the timing 20 degrees from base timing so you can check to see if the computer advance is working. The computer doesn't move the timing in my truck much at idle, so it's not really noticeable when the spout is in or out.
Are you taking the spout off while the truck is completely off? I beleive the computer only check for the spout once, right when its turned on, so if you are taking it off with the engine running the computer won't know/care
The timing never changes on his truck with the spout in, out, or removing it while the truck is off or running. It never seems to make any difference. On my Bronco there is noticable difference in the timing and RPM if I remove or install it while running.
It doesn't make much difference when I pull the spout at idle on my truck - rpm, timing or otherwise. Can you rev the motor and see it advance with the spout connected? Do the check like I wrote about a couple posts ago. That will let you know whether or not the computer is or is not advancing the timing like it should be.