Code 18 and performance issues
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Code 18 and performance issues
Hey guys, really need some help as this problem is driving me absolutely nuts.
'90 F-150 5.0L with a code 18 (SPOUT circuit open) and some performance/idle issues. Starts up good, maybe a tad high. Drops down really low, surges a few times and gradually settles down. When I put in the clutch to decel, the engine dies. Starts right back up every time after it stalls. All ignition components are new (including new module and Hall-effect assembly); replaced the IAC, HO2S, and PCM per diagnostic procedure (both were bad); and I cleaned the throttle body. Both me and the mechanic who inspected it checked for vacuum leaks and found none. Tested the wiring in the SPOUT circuit (continuity and load test) and it tested good. I have run the diagnostic procedures several times to make sure I didn't do anything wrong. I'm pretty sure the code 18 and the idle/stalling issues are related but I am totally stumped. All sensors except the knock sensor are brand new. Fuel pressure is good KOEO, is a little low KOER but is within specs. Regulator vacuum line has no gas in it.
Any ideas on where to look next?
'90 F-150 5.0L with a code 18 (SPOUT circuit open) and some performance/idle issues. Starts up good, maybe a tad high. Drops down really low, surges a few times and gradually settles down. When I put in the clutch to decel, the engine dies. Starts right back up every time after it stalls. All ignition components are new (including new module and Hall-effect assembly); replaced the IAC, HO2S, and PCM per diagnostic procedure (both were bad); and I cleaned the throttle body. Both me and the mechanic who inspected it checked for vacuum leaks and found none. Tested the wiring in the SPOUT circuit (continuity and load test) and it tested good. I have run the diagnostic procedures several times to make sure I didn't do anything wrong. I'm pretty sure the code 18 and the idle/stalling issues are related but I am totally stumped. All sensors except the knock sensor are brand new. Fuel pressure is good KOEO, is a little low KOER but is within specs. Regulator vacuum line has no gas in it.
Any ideas on where to look next?
No concrete ideas for you but it occurs to me that the spout circuit and knock sensor are kind of inter related.
I believe that what happens is that when you put the spout plug in it closes the circuit which then allows the computer to advance the timing as much as it can - until you get a ping (or knock) which the anti knock sensor detects and backs it off slightly.
On old school distributors we would advance the timing as far as possible - until it started pinging under load - and then back it off slightly.
Same sort of idea.
To test if the spout circuit is operative, I think you would use a timing light and see if the computer advances the timing as you rev it up some. Since there is no longer any mechanical or vacuum advance on the distributor, the computer controls it.
Pulling the spout allows you to set the base timing without any advance being applied, but if that circuit isn't closing you won't have any advance.
Which if it's the problem it would explain your symptoms.
I believe that what happens is that when you put the spout plug in it closes the circuit which then allows the computer to advance the timing as much as it can - until you get a ping (or knock) which the anti knock sensor detects and backs it off slightly.
On old school distributors we would advance the timing as far as possible - until it started pinging under load - and then back it off slightly.
Same sort of idea.
To test if the spout circuit is operative, I think you would use a timing light and see if the computer advances the timing as you rev it up some. Since there is no longer any mechanical or vacuum advance on the distributor, the computer controls it.
Pulling the spout allows you to set the base timing without any advance being applied, but if that circuit isn't closing you won't have any advance.
Which if it's the problem it would explain your symptoms.