1985 Ford Mustang Lean/Timing issues

1985 FORD MUSTANG
175,635 MILES • V8 • 2WD • AUTOMATIC
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FIXALLMAN_77808
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why is my timing when i checked it , advance to approx 28 degrees at about 2000 rpm, then retard to 12 by 3000rpm? I just purchased the car and noticed it will get weak under full throttle after about 2500 rpm and stop pulling by 4000. It's currently set at about 14 degrees at idle. The plugs say lean condition, and it seems to be thru out the rpm range. What should I look at first?
Sorry. Let me clearify. this is a 85 5.0 CFI intake, electrically controlled timing. Guessing this is a control issue. Thinking along the lines of o/2 sensor. I've checked my plugs after a short drive and after a long hard pull with emmediate shut down and check and have found the plugs to be showing lean condition. Little short on money after this purchase and am looking for help thru the net so as to work out a game plan of attack on this issue.
A lean condition from idle all the way thru red line seems to be the issue causing the computer to pull timing after 2000 rpm.. I appreciate the ansmer to my question. Felt I needed a little clearification on my engine type. Sorry for the lack of info.
Jun 6, 2009 at 12:04 AM
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MIKE H R
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the timing should be 12 degrees at idle with the vacuum advance disconnected and the hose of the engine glugged. After the initial setting the advance should increase with the increase in engine speed. There could be a problem with the advance unit. where it is loosing vacuum as the engine speed increases.
Jun 6, 2009 at 7:50 AM
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FIXALLMAN_77808
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[quote:84f6036785="M_J_RITZEL"]the timing should be 12 degrees at idle with the vacuum advance disconnected and the hose of the engine glugged. After the initial setting the advance should increase with the increase in engine speed. There could be a problem with the advance unit. where it is loosing vacuum as the engine speed increases.[/quote:84f6036785]




I left some info out of my initial posting. This is an 85 5.0,CFI intake, electrically controlled advance. This lean condition exists from idle thru full throttle and appears to be coming from th O/2 sensor reading and causing timing to be pulled after 2000 RPM. Just need a direction to follow to get my game plan on.
Jun 7, 2009 at 6:32 PM
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MIKE H R
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didconnect the battery and leave off for a few minutes, then reattach this could help and reset the computer so it picks up the correct settings.
Jun 13, 2009 at 1:45 PM
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FIXALLMAN_77808
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[quote:e0b09272c7="M_J_RITZEL"]didconnect the battery and leave off for a few minutes, then reattach this could help and reset the computer so it picks up the correct settings.[/quote:e0b09272c7]




Thank you for this answer, However I've had to do this several times with other repair issues in interior and it doesn't seem to help. Still getting a lean condition and miss. This miss seems to go away when I advance the timing beyond specs but it failed emmissions. Had to move it back to 12 before it would pass. So still looking for a possible solution.
Jun 13, 2009 at 3:38 PM
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MIKE H R
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The car has done it since you bought it maybe there is something changed that you don't know. What about the chip? Could the chip had been changed before you bought the car? I had noticed Summit racing had something to change the timing from one timing to another depending on what timing is for best performance.
Jun 14, 2009 at 7:55 AM
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FIXALLMAN_77808
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[quote:87d98d5e9d="M_J_RITZEL"]The car has done it since you bought it maybe there is something changed that you don't know. What about the chip? Could the chip had been changed before you bought the car? I had noticed Summit racing had something to change the timing from one timing to another depending on what timing is for best performance.[/quote:87d98d5e9d]


Thanks again for this info. I will check for a chip or tampering with the computer in my next tuning session. However in my first quote i stated an issue about the timing backing out at higher rpms. I have and 88 5.0 engine in my garage that I had in a Grand Marquie that did not back the timing out. It would stay at top advance after 2000 rpm thru redline. Also this engine is a multi port FI, where the 86 in the stang is a TBI. I thank you again for this info and will continue to work on this.
Jun 14, 2009 at 12:23 PM
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MIKE H R
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Something we have not talked about is the timing timing chain {belt} wonder if it would make that much of a diference? Or the timing tensioner. if the tensioner was weak and at higher rpm would let the timing to be off and would cause a timing issue. It's is something to think about. I will bring this topic up to other moderators and see if there is something we could be missing.
Jun 14, 2009 at 4:29 PM
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FIXALLMAN_77808
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[quote:c36c726b5c="M_J_RITZEL"]Something we have not talked about is the timing timing chain {belt} wonder if it would make that much of a diference? Or the timing tensioner. if the tensioner was weak and at higher rpm would let the timing to be off and would cause a timing issue. It's is something to think about. I will bring this topic up to other moderators and see if there is something we could be missing.[/quote:c36c726b5c]



To the best of my knowledge, and due to my experience disassembling and reassembling a 1979 302 in a in a ford fairmont, I'm sure that this particular engine design does not have a chain tensioner. The cam gear and crankshaft ger seem to be to close together to need a tensioner. And finally , I've checked the timing and it is stable for an engine with this much milage with only about 2 to 3 degrees of timing fluctuation under no load conditions. I believe this slight fluctuation cannot be resposible for a 20 plus degree retard after 2000 rpm. But i'm still learning.
Jun 14, 2009 at 4:51 PM
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2CARPRO JACK
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Have you checked fuel pressure with a manual gauge? If the engine is real lean, the computer may be backing down the timing to keep it from pinging.
Jun 18, 2009 at 9:49 AM
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FIXALLMAN_77808
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[quote:6f15a61641="2CarPro Jack"]Have you checked fuel pressure with a manual gauge? If the engine is real lean, the computer may be backing down the timing to keep it from pinging.[/quote:6f15a61641]



No, I have not. That is on my to-do list and I will see if this tells me anything. I think as you do this could be the issues. I'm looking to get a guage soon. Budget is what it is. What should I see in pressure? Any idea?
Jun 19, 2009 at 10:57 PM
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2CARPRO JACK
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Looks like 13-16 psi with a volume output of 1 pint in 30 seconds while cranking the engine
Jun 20, 2009 at 8:08 AM
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FIXALLMAN_77808
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[quote:66be5f92b5="2CarPro Jack"]Looks like 13-16 psi with a volume output of 1 pint in 30 seconds while cranking the engine[/quote:66be5f92b5]


Is this on the TBI system, or a carb. This engine is currently set up with the TBI.
Jun 21, 2009 at 1:18 AM
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2CARPRO JACK
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Thats what Mitchell calls for with TBI, they are low pressure compared to the new stuff
Jun 21, 2009 at 9:41 AM
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FIXALLMAN_77808
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[quote:e07adda511="2CarPro Jack"]Thats what Mitchell calls for with TBI, they are low pressure compared to the new stuff[/quote:e07adda511]



Good info to know. Thank You.
Jun 23, 2009 at 7:55 PM