4.9 ignition running in open loop
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Junior Member
Joined: Jan 2011
Posts: 25
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From: maine
4.9 ignition running in open loop
for the longest time my 92 4.9 had a slight stumble at idle. it isn't steady or predictable at all, and seems to have gotten worse (or at least more noticable) since i've put headers on with a full exhaust. maybe it's because there's a less restrictive exhaust making the miss louder? at any rate tried to time it, but couldn't get the timing marks anywhere close. on top of that it made no difference if the spout connector was in or out, no change in timing would bring the timing marks closer to where they should be or fix that friggan skip. any ideas?
Senior Member
Joined: Jul 2008
Posts: 58,557
Likes: 1,165
From: Long Beach Calimexifornia
for the longest time my 92 4.9 had a slight stumble at idle. it isn't steady or predictable at all, and seems to have gotten worse (or at least more noticable) since i've put headers on with a full exhaust. maybe it's because there's a less restrictive exhaust making the miss louder? at any rate tried to time it, but couldn't get the timing marks anywhere close. on top of that it made no difference if the spout connector was in or out, no change in timing would bring the timing marks closer to where they should be or fix that friggan skip. any ideas?
Sounds like possibly a break in the wire inside the insulation somewhere along the SPOUT circuit. Are you showing voltage across the connection?
Whether that circuit completes or not has nothing to do w/ whether of not the ECU is operating in open or closed loop function. Just whether it will add additional ECU advance to base timing.