amxerhull
Lewiston, Idaho
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Joined: 04/07/2008
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Vehicle is a 91 Mallard Sprinter with a 90 P30 chassis. Engine is a TBI. I have read the excellent posts on how to advance the timing but I cannot find the "brown wire" that I need to disconnect in order to set the base timing. Is it always brown and what is it connected to?
Thanks for any help.
John
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1995brave
San Antonio, TX
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Check at the back of the distributor, the cable that goes into the wire loom will have a pull apart connector(single wire) that is the one you want. It will probably trip the check engine light when you reconnect(if it's running).
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thomasinnv
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it should be brown, and it could be located at the distributor/coil; or it may be near the ecm. it should be a single brown wire with a plug that can be disconnected.
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amxerhull
Lewiston, Idaho
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Thanks, guys. I'll lift the doghouse tomorrow and see if I can find the wire.
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bacollins
Lawrenceburg, IN
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The wire is tan with a black stripe, comes out of the distributor, there is a snap connector.
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amxerhull
Lewiston, Idaho
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Thanks folks, I found it. It was coming out the back of the distributor hidden down low. The connector and black stripe gave it away.
Just to review: I disconnect the wire, set the timing (using #5 plug wire) at 8-10 degrees, then reconnect the plug. If it pings on hills, back the timing off until I find the sweet spot. Anything else?
John
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FANDUDE
Bethlehem, Pa.
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That really should not ping at all after the timing is set correctly to the decal spec under the hood. Those have a knock sensor attached to the block that reports engine ping to the ecm. If a ping or knock occures, the ecm will adjust the timing at the distributor to compensate. It is continually adjusting the timing to get the max. amount of spark advance without ping or knock. The manual adjustment of the base timing is to adjust for wear in the timing components in the engine (dist. gear, timing chain and sprockets, etc.) Hope this helps.
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bacollins
Lawrenceburg, IN
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amxerhull wrote:Thanks folks, I found it. It was coming out the back of the distributor hidden down low. The connector and black stripe gave it away.
Just to review: I disconnect the wire, set the timing (using #5 plug wire) at 8-10 degrees, then reconnect the plug. If it pings on hills, back the timing off until I find the sweet spot. Anything else?
John
You will not hear it ping. As FANDUDE says, the knock sensor will retard the timing if pinging occurs. It is my experience that 10 BTC is about all you want to go. Beyond that, the knock sensor will retard the timing and performance will suffer. I have had two GM P series motorhome chassis with 454 TBI engines, both ran best at 6-8 BTC.
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Jim83Itasca
La Quinta Calif
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Just to review: I disconnect the wire, set the timing (using #5 plug wire) at 8-10 degrees, then reconnect the plug. If it pings on hills, back the timing off until I find the sweet spot. Anything else?
John
John, IF you have the timing tab at the 4:30 position (drivers side) then yes #5 plug is correct.....
Jim
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sum1
So-Cal
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amxerhull wrote:Thanks folks, I found it. It was coming out the back of the distributor hidden down low. The connector and black stripe gave it away.
Just to review: I disconnect the wire, set the timing (using #5 plug wire) at 8-10 degrees, then reconnect the plug. If it pings on hills, back the timing off until I find the sweet spot. Anything else? John Sounds good to me. Use Hi-test gas. I actually ran with a scanner when I did mine and as I remember, it didn't like more than 8°. My story didn't end there however. My computer decided to drop 10° at 63% throttle regardless of MP and RPM. I needed a new chip so I bought one from Harris Performance. Brian Harris said to reset the base timing to stock (4° BTDC) because his chip has some advance built in. Fixed!
Here's a link to the story:
'91 454TBI Timing Problem
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