EFI 300-6 drivability problems
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From: douglasville
EFI 300-6 drivability problems
Just acquired an 89 f150 with a 300 and a 4 speed and it has a misfire when its first started usually smoothes out real quick then as you drive as long as you drive it easy it does ok but if you have to get on the throttle quick it just sputters and dies will start back up instantly and if you let off before it dies it will stay running SO heres whats already been done,reman distributor and new module timing set back to factory setting(this fixed the problem for about 300 miles) plugs,wires,cap,rotor and air filter. fuel pressure regulator,the pressure regulator fixed it for about a day and its getting worse now has fresh gas in both tanks (full right now) both tanks work,also once you get it up to road speed its fine i ran 75 mph on the interstate with the a/c wide open and it did great until i got back on surface streets. the check engine lite is not on and it only gives code 11 when scanned all sensors are plugged in most are original ecm is original i just am no good with efi that is pre obd2 thanks for any suggestions also it passed emissions like this and even when its acting right it still has a dead spot around 2300rpm
Last edited by big ole ford; Oct 17, 2012 at 04:04 PM. Reason: left out info
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Have you checked the fuel pressure, or just replaced parts? If you can duplicate the problem while watching the fuel pressure guage it would be great. You did replace the fuel filter?
You say it has fresh gas in it now, was it bad before?
I will assume you have the timing at 10 degrees btdc with the spout unplugged and are using the correct set of timing marks (passenger side) and the right mark on the balancer. (its a tiny hard to see scribe line, not the big notch) My truck seems to like 12 degrees a little better than 10, as many do, has a little more power there, but runs ok at 10.
A decent voltmeter that can check frequency is a handy thing to have for working on these trucks.
Map sensors can do odd things, but are easy to check if you have a multimeter that has a frequency setting.
Have you checked the tps? The one on my truck would drop voltage, but not low enough to flag a code, but I could see it on a voltmeter. I replaced it and it got rid of my flat spot.
Sensors in general will only flag a code if they are out of range. This does not necessarily mean they are accurately reporting the condition they are supposed to be monitoring.
The specifics of testing pretty much anything on your truck are here in the forum somewhere. Usually the name of a particular item in the search box and "4.9" will get you close.
You say it has fresh gas in it now, was it bad before?
I will assume you have the timing at 10 degrees btdc with the spout unplugged and are using the correct set of timing marks (passenger side) and the right mark on the balancer. (its a tiny hard to see scribe line, not the big notch) My truck seems to like 12 degrees a little better than 10, as many do, has a little more power there, but runs ok at 10.
A decent voltmeter that can check frequency is a handy thing to have for working on these trucks.
Map sensors can do odd things, but are easy to check if you have a multimeter that has a frequency setting.
Have you checked the tps? The one on my truck would drop voltage, but not low enough to flag a code, but I could see it on a voltmeter. I replaced it and it got rid of my flat spot.
Sensors in general will only flag a code if they are out of range. This does not necessarily mean they are accurately reporting the condition they are supposed to be monitoring.
The specifics of testing pretty much anything on your truck are here in the forum somewhere. Usually the name of a particular item in the search box and "4.9" will get you close.
Thread Starter
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More Turbo
Joined: Mar 2008
Posts: 525
Likes: 6
From: douglasville
Have you checked the fuel pressure, or just replaced parts? If you can duplicate the problem while watching the fuel pressure guage it would be great. You did replace the fuel filter?
You say it has fresh gas in it now, was it bad before?
I will assume you have the timing at 10 degrees btdc with the spout unplugged and are using the correct set of timing marks (passenger side) and the right mark on the balancer. (its a tiny hard to see scribe line, not the big notch) My truck seems to like 12 degrees a little better than 10, as many do, has a little more power there, but runs ok at 10.
A decent voltmeter that can check frequency is a handy thing to have for working on these trucks.
Map sensors can do odd things, but are easy to check if you have a multimeter that has a frequency setting.
Have you checked the tps? The one on my truck would drop voltage, but not low enough to flag a code, but I could see it on a voltmeter. I replaced it and it got rid of my flat spot.
Sensors in general will only flag a code if they are out of range. This does not necessarily mean they are accurately reporting the condition they are supposed to be monitoring.
The specifics of testing pretty much anything on your truck are here in the forum somewhere. Usually the name of a particular item in the search box and "4.9" will get you close.
You say it has fresh gas in it now, was it bad before?
I will assume you have the timing at 10 degrees btdc with the spout unplugged and are using the correct set of timing marks (passenger side) and the right mark on the balancer. (its a tiny hard to see scribe line, not the big notch) My truck seems to like 12 degrees a little better than 10, as many do, has a little more power there, but runs ok at 10.
A decent voltmeter that can check frequency is a handy thing to have for working on these trucks.
Map sensors can do odd things, but are easy to check if you have a multimeter that has a frequency setting.
Have you checked the tps? The one on my truck would drop voltage, but not low enough to flag a code, but I could see it on a voltmeter. I replaced it and it got rid of my flat spot.
Sensors in general will only flag a code if they are out of range. This does not necessarily mean they are accurately reporting the condition they are supposed to be monitoring.
The specifics of testing pretty much anything on your truck are here in the forum somewhere. Usually the name of a particular item in the search box and "4.9" will get you close.
I have not actually replaced any parts except the distributor and module
i got the truck from an in law who was just pissed off at the truck because they couldnt fix it,however i did set the timing properly @10 degrees with the SPOUT unhooked and since have re-checked the timing.
as far as the rest of the parts they were installed by the last owner in the last 3-4 weeks he was no mechanic the truck even included a new timing gear kit,oil pump and pan gasket that he swore was going to fix it they have not been installed yet,I dont think it needs them honestly,as far as the fuel filter goes it was changed but it was a fram so i changed it to a more reputable brand(wix) and to my knowledge it hasnt had bad fuel just wanted to say it wasnt running on old gasoline, A side note is that when i got the truck it had bosch platinum+4 plugs i removed 1 to confirm it having new plugs and took them all out today and replaced them with the oem motorcraft didnt change a thing, i agree with the bad tps idea and will be buying a fuel pressure tester to check that as well thanks for the help!
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