nilknarf007 Posted March 19, 2020 Author Share Posted March 19, 2020 Mine was the same way, flat. Had to accelerate slowly. If you pushed harder on the gas it would not go any faster and would loose speed on a hill. I replaced the 1 barrel Carter that had the "feedback" system with a rebuilt one with no feedback. Replaced the ignition system which was the EECIV computer controlled to the DurasparkII and now runs great. All the power I need and gas mileage 20-21 mpg. Wow! Thanks for all the good info. It seems the timing was at least part of the issue. I put a timing light on it and saw NO MARKS. I shut off the engine and searched for marks and found nothing I could be sure looked like a manufactured mark. I did some reading and found a debate as to whether or not the notch was the factory mark. The debate seemed to be 50/50 so I made a white mark on the notch and tried again. Nothing. I put the timing light on the #4 plug and bingo, I saw the mark at about 15 degrees AFTER TDC. I advanced it to 14 degrees before TDC. The idle went up from a rough 650 RPM to 1300 RPM. Tried to adjust the idle speed but the adjustment screw didn't seem to do anything. Anyway, I took it for a test drive and it ran like it had 50 more HP. Came back and checked the advance, and discovered that the timing does not advance as you rev the motor. Questions: Anyone have any feelings as to the notch and it's relationship to TDC? I guess the lack of advance proves the computer is in limp mode? Any ideas on why the idle adjustment has no effect? I bottomed it out both directions and nothing. Link to comment Share on other sites More sharing options...
Gary Lewis Posted March 19, 2020 Share Posted March 19, 2020 Wow! Thanks for all the good info. It seems the timing was at least part of the issue. I put a timing light on it and saw NO MARKS. I shut off the engine and searched for marks and found nothing I could be sure looked like a manufactured mark. I did some reading and found a debate as to whether or not the notch was the factory mark. The debate seemed to be 50/50 so I made a white mark on the notch and tried again. Nothing. I put the timing light on the #4 plug and bingo, I saw the mark at about 15 degrees AFTER TDC. I advanced it to 14 degrees before TDC. The idle went up from a rough 650 RPM to 1300 RPM. Tried to adjust the idle speed but the adjustment screw didn't seem to do anything. Anyway, I took it for a test drive and it ran like it had 50 more HP. Came back and checked the advance, and discovered that the timing does not advance as you rev the motor. Questions: Anyone have any feelings as to the notch and it's relationship to TDC? I guess the lack of advance proves the computer is in limp mode? Any ideas on why the idle adjustment has no effect? I bottomed it out both directions and nothing. You may have multiple problems. But first, when you say "adjustment screw", you do mean the curb idle adjusting screw shown below. Right? If that has no effect then you have a significant air leak. On the 300 six the carb attaching nuts have a tendency of loosening, so make sure it is tightened down, but don't break anything. If that isn't it check all of the hoses and vacuum caps for cracks. David will teach you how to do the smoke test to check for leaks if needed. I'll let someone else speak to the notch. And yes the computer is in limp mode. You will need to to replace the ignition system, but you may get by with the existing carb. Link to comment Share on other sites More sharing options...
nilknarf007 Posted March 19, 2020 Author Share Posted March 19, 2020 You may have multiple problems. But first, when you say "adjustment screw", you do mean the curb idle adjusting screw shown below. Right? If that has no effect then you have a significant air leak. On the 300 six the carb attaching nuts have a tendency of loosening, so make sure it is tightened down, but don't break anything. If that isn't it check all of the hoses and vacuum caps for cracks. David will teach you how to do the smoke test to check for leaks if needed. I'll let someone else speak to the notch. And yes the computer is in limp mode. You will need to to replace the ignition system, but you may get by with the existing carb. Yes, that's the screw I'm adjusting. I'll check the other things you mentioned. Link to comment Share on other sites More sharing options...
nilknarf007 Posted March 19, 2020 Author Share Posted March 19, 2020 Mine was the same way, flat. Had to accelerate slowly. If you pushed harder on the gas it would not go any faster and would loose speed on a hill. I replaced the 1 barrel Carter that had the "feedback" system with a rebuilt one with no feedback. Replaced the ignition system which was the EECIV computer controlled to the DurasparkII and now runs great. All the power I need and gas mileage 20-21 mpg. 844rd You went from this carb to this one? Link to comment Share on other sites More sharing options...
844rd Posted March 19, 2020 Share Posted March 19, 2020 844rd You went from this carb to this one? The feedback one wires going to it for computer control. The one I put on came from O'Reillys Part#1-506 372.86 Rebuilt by TAMCO. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted March 20, 2020 Share Posted March 20, 2020 Wow! Thanks for all the good info. It seems the timing was at least part of the issue. I put a timing light on it and saw NO MARKS. I shut off the engine and searched for marks and found nothing I could be sure looked like a manufactured mark. I did some reading and found a debate as to whether or not the notch was the factory mark. The debate seemed to be 50/50 so I made a white mark on the notch and tried again. Nothing. I put the timing light on the #4 plug and bingo, I saw the mark at about 15 degrees AFTER TDC. I advanced it to 14 degrees before TDC. The idle went up from a rough 650 RPM to 1300 RPM. Tried to adjust the idle speed but the adjustment screw didn't seem to do anything. Anyway, I took it for a test drive and it ran like it had 50 more HP. Came back and checked the advance, and discovered that the timing does not advance as you rev the motor. Questions: Anyone have any feelings as to the notch and it's relationship to TDC? I guess the lack of advance proves the computer is in limp mode? Any ideas on why the idle adjustment has no effect? I bottomed it out both directions and nothing. Welcome Rob! When you checked the timing did you remove the SPark OUT plug? If not, you're not really checking base timing. Much like if you were to check a conventional distributor without disconnecting or clamping the vacuum hose. Not meaning to question your ability, just gathering clues. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted March 20, 2020 Share Posted March 20, 2020 That's a working truck! I like it. 😎 Soft-8's fit, but you might consider small side reflectors with signal lamps. I'd get busted around here for that, and it's always better if other drivers know where you are and what your intentions are. Link to comment Share on other sites More sharing options...
1986F150Six Posted March 20, 2020 Share Posted March 20, 2020 If that has no effect then you have a significant air leak. On the 300 six the carb attaching nuts have a tendency of loosening, so make sure it is tightened down, but don't break anything. If that isn't it check all of the hoses and vacuum caps for cracks. David will teach you how to do the smoke test to check for leaks if needed. Here you are: https://www.ford-trucks.com/forums/1478167-vacuum-leak-detection-effective-and-inexpensive.html Link to comment Share on other sites More sharing options...
nilknarf007 Posted March 20, 2020 Author Share Posted March 20, 2020 That's a working truck! I like it. 😎 Soft-8's fit, but you might consider small side reflectors with signal lamps. I'd get busted around here for that, and it's always better if other drivers know where you are and what your intentions are. Hadn't thought of that, but it makes sense. I'll take care of that today. Link to comment Share on other sites More sharing options...
1986F150Six Posted March 20, 2020 Share Posted March 20, 2020 Hadn't thought of that, but it makes sense. I'll take care of that today. Note that under the carburetor on the passenger side is a "vacuum tree" which has about 6 or 7 ports. This is attached to the intake manifold. Not all ports are used and some are covered with a rubber cap. During the years, the heat and exposure to the atmosphere reeks havoc on the rubber and it hardens and cracks or falls off. I have found on my son's 1984 and my 1986 [both with 4.9L], that there is one particular cap which is hidden by the "spaghetti" of vacuum hoses on the passenger side. This particular port is nearest the intake manifold and nearest the exhaust manifold [heat source]. On mine, it had cracked; on my son's, it had a large opening in the center. Be sure to look closely at that one. By the way, that smoke test was on a 1984 with the feedback emissions system still in operation [original]. Link to comment Share on other sites More sharing options...
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