Timing question
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Timing question
Ive got an '88 with the 302 MAF/SFI conversion. Ive been trying to track down this problem for about a year now: ive got a lot of pinging when i use anything less than 93 octane. I was doing some work the other day and had to move the distributor. Today i was setting the timing back, set it to 10 degrees. Then i plugged the sprout back in and observed the timing. It was at ~15 degrees at idle, then as i slowly increased the throttle, the timing jumped immediately to 30 degrees and i could feel the RPMs jump a couple hundred. This occured at about 1000 rpms and it jumped to like 1400. Then it held at 30 degrees as i continued to increase the throttle.
Is this normal?? I thought it was supposed to be a gradual increase in advance as the throttle increases. Possibly this could explain why i get a lot of detonation at highway cruise. Thanks for your help
Is this normal?? I thought it was supposed to be a gradual increase in advance as the throttle increases. Possibly this could explain why i get a lot of detonation at highway cruise. Thanks for your help
Lead Driver
Joined: Aug 2006
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From: Sand Lake, MI
Yea sounds like a problem, initial advance just putting the spout back in should add more then 5degs? and yea the timing should advance smoothly with the rpm increase.
Did you check for error codes, would think the computer would have something to say about it.
Did you check for error codes, would think the computer would have something to say about it.
Lead Driver
Joined: Aug 2006
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From: Sand Lake, MI
The computer does via the ICM but it does so with info received from other sensors not just IDM input. Like ACT, ECT and tps for example.
Rapidly fluctuating info because of a bad/weak connection might be causing what you see, or yea could be a problem with the ICM or computer either one.
Does engine first run cold verses been running for several minutes and up to running temp have any effect on what you see? IE "cold soak / Hot soak" timing advances smoothly when first run cold but once up to temp timing begins to jump? If so I'd suggest the ICM.
Rapidly fluctuating info because of a bad/weak connection might be causing what you see, or yea could be a problem with the ICM or computer either one.
Does engine first run cold verses been running for several minutes and up to running temp have any effect on what you see? IE "cold soak / Hot soak" timing advances smoothly when first run cold but once up to temp timing begins to jump? If so I'd suggest the ICM.
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I'm letting it cool down and I will check it in a little bit. It does always seem to run better in the morning then in the afternoon. I thought it was a fuel pump dying. It seems like I replaced the ICM only 2-3 years ago, but i cant remember.
Lead Driver
Joined: Aug 2006
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From: Sand Lake, MI
Be sure and remember to use the included thermal paste if you find you need to replace it yet again. Clean the surface on the dizzy, spread it evenly.....well you probably already know that.....
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I checked it again with the engine cold. I still did the same thing, though im not really surprised. I will run fine in the morning on the way to work, then on the way home in the afternoon it will run completely different. Its like sitting at work all day is not long enough for it to "reset". Who knows. Im gonna go pick a new ICM and see what happens.
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Today i replaced the ICM and changed the rotor while I was in there. Fired it up, reset the timing, and noticed no improvement. Still jumps to 30 degrees at about 900 RPM. In fact, i could not get it to idle at 950 rpm, it would either jump up or let down. A little more info, i have a computer from a 92 mustang in there so that i can run the MAF and SFI. I had to replace the computer a while ago but the numbers were the same.
If it turns out that the ECM is at fault, could it just be as simple as getting a tune? I dont the ECM was brand new when i bought it, so maybe it has a different program in it? What do you think?
If it turns out that the ECM is at fault, could it just be as simple as getting a tune? I dont the ECM was brand new when i bought it, so maybe it has a different program in it? What do you think?
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From: Concord, NC
What is closed-throttle TPS voltage? I have read that the mustangs are pretty sensitive to keeping this below 1V.
When I did my MAF swap, I had the same problem with pinging. I never did figure it out, so I have swapped back to the stock truck computer and wiring.
When I did my MAF swap, I had the same problem with pinging. I never did figure it out, so I have swapped back to the stock truck computer and wiring.
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I actually replaced the TPS yesterday...I checked the voltage and was getting some funky readings so i just decided to replace it. No change. Ive had that mustang computer in there for about 15 years or so. Last year the computer crapped out on me and i got a replacement. But I dont think it was brand new, and now im wondering if the PO had a tune and it has some weird program now. I wish it were easier to locate another mustang computer.
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So today I finally got a code!! I think I'm the only one who celebrates when i get a code. Normally when i have problems the computer never throws codes and so i get no help. Today i got a 51, ECT sensor reading to high. I bought a new one, but when i looked at the connector it was in pieces. So tomorrow i will get a new connector and see what happens....
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Joined: Jun 2006
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From: Ottawa, Ontario
The timing advance you are seeing is normal for the mustang EEC and the truck computers aren't much different though the truck timing curve is likely a little more conservative. I have found this 5.0 I have in my truck now pings more than the 5.8 ever did and it's running on the same computer, so I'd wager it has a lot to do with the motor itself.. some are more detonation prone than others.