timing help 1990 L98 base
Thread Starter
Instructor
Joined: Jan 2015
Posts: 124
Likes: 5
From: Cave Creek arizona
timing help 1990 L98 base
Had to pull the distributor on my 1990 L98 base and now need to time it. the FSM says to disconnect the tan with black stripe wire to bypass electronic spark timing. It says that it is a single wire sealed connector. The only tan/black stripe wire I can see is in the four wire connector that the FSM says not to disconnect. Is the FSM correct or am I just blind and cannot see the tan/black wire coming out of the wiring loom?
Thanks,
Thanks,
Drifting
Joined: Dec 2012
Posts: 1,504
Likes: 73
From: Georgetown TX
Had to pull the distributor on my 1990 L98 base and now need to time it. the FSM says to disconnect the tan with black stripe wire to bypass electronic spark timing. It says that it is a single wire sealed connector. The only tan/black stripe wire I can see is in the four wire connector that the FSM says not to disconnect. Is the FSM correct or am I just blind and cannot see the tan/black wire coming out of the wiring loom?
Thanks,
Thanks,
Racer
Joined: Sep 2007
Posts: 375
Likes: 18
From: Lawrenceville Georgia
This wire is some what hard to find, as it is tucked down into a large loom.
Look for the large plastic wrapped wire loom between the master cylinder and the rear area of engine. It will/should be sticking out of this loom. It may be a little dirty so the tan looks brown, but it is there.
Joel
Look for the large plastic wrapped wire loom between the master cylinder and the rear area of engine. It will/should be sticking out of this loom. It may be a little dirty so the tan looks brown, but it is there.
Joel
Instructor
Joined: May 2011
Posts: 164
Likes: 0
From: Bucks County Pa
More timing problems
i found the correct wire unplugged and set my timing at exactly 7* before td. Plugged the connector back together and cleared the code. Started the motor and it surged wildly from 1000 rpm to 3000. Never happened before. After it warmed up and went into closed loop the motor settled down and idled. Anyone have a clue as to what happened? The L98 is a cool motor but very quirky 😬
Team Owner
Joined: Jul 2004
Posts: 28,465
Likes: 3,288
From: Hartford WI
i found the correct wire unplugged and set my timing at exactly 7* before td. Plugged the connector back together and cleared the code. Started the motor and it surged wildly from 1000 rpm to 3000. Never happened before. After it warmed up and went into closed loop the motor settled down and idled. Anyone have a clue as to what happened? The L98 is a cool motor but very quirky 😬
Instructor
Joined: May 2011
Posts: 164
Likes: 0
From: Bucks County Pa
Why 7? IIRC, it was 6 stock. Reason I ask is that you take timing on the harmonic balancer which has been known to "walk" and thus give inaccurate timing. I would check the IAC counts to see what is going on. Also put a stripe on the harmonic balancer so you know if it ever "walks" on you.
Like I mentioned the motor has never surged at idle like it did this time so I naturally thought unplugging/plugging in the EST tan/black wire and the otherwise unexplained surge are related. I know how to static check the IAC by reading OHMS but dont know how to check counts. How is that check done ? and what number(s) should I be looking for ? If I'm able to do the counts test then what would be the step-by-step procedure to reset idle ?
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Team Owner
Joined: Jul 2004
Posts: 28,465
Likes: 3,288
From: Hartford WI
Engine at operating temperature. Everything but the motor off. Scan it for IAC counts. Between 20 to 30 counts. If it is more, turn the screw in, rev and let it settle down. If it is less, the system is demanding less air so turn it out, rev and recheck. This is assuming timing is good. No adjustment for TPS.
Instructor
Joined: May 2011
Posts: 164
Likes: 0
From: Bucks County Pa
I don't think I have a scan tool that will read the position of the IAC plunger to give me the counts number. The scanner tool and kit I have has an adaptor to connect to my ECM plug but it reads out "unable to communicate with engine". Its not a scanner malfunction the scanner works great on my 2002 pickup truck.
I was thinking of doing a manual reset of the idle stop screw as a way to check if the IAC is working properly.
1 Ground ALDL with a wire
2. Turn on ignition wait 30 seconds
3. Disconnect IAC harness
4 Remove ground wire from ALDL and start motor warm up until closed loop
5. Adjust idle stop screw to 550-600 rpm
6. Turn motor off, disconnect battery black cable to clear codes, reconnect IAC
I was thinking of doing a manual reset of the idle stop screw as a way to check if the IAC is working properly.
1 Ground ALDL with a wire
2. Turn on ignition wait 30 seconds
3. Disconnect IAC harness
4 Remove ground wire from ALDL and start motor warm up until closed loop
5. Adjust idle stop screw to 550-600 rpm
6. Turn motor off, disconnect battery black cable to clear codes, reconnect IAC
Team Owner
Joined: Jul 2004
Posts: 28,465
Likes: 3,288
From: Hartford WI
I don't think I have a scan tool that will read the position of the IAC plunger to give me the counts number. The scanner tool and kit I have has an adaptor to connect to my ECM plug but it reads out "unable to communicate with engine". Its not a scanner malfunction the scanner works great on my 2002 pickup truck.
I was thinking of doing a manual reset of the idle stop screw as a way to check if the IAC is working properly.
1 Ground ALDL with a wire
2. Turn on ignition wait 30 seconds
3. Disconnect IAC harness
4 Remove ground wire from ALDL and start motor warm up until closed loop
5. Adjust idle stop screw to 550-600 rpm
6. Turn motor off, disconnect battery black cable to clear codes, reconnect IAC
I was thinking of doing a manual reset of the idle stop screw as a way to check if the IAC is working properly.
1 Ground ALDL with a wire
2. Turn on ignition wait 30 seconds
3. Disconnect IAC harness
4 Remove ground wire from ALDL and start motor warm up until closed loop
5. Adjust idle stop screw to 550-600 rpm
6. Turn motor off, disconnect battery black cable to clear codes, reconnect IAC
That is the FSM method you outlined. It works If you are 100% stock AND IF you have no air leaks or any other issues AND IF your tach is spot on. IF being the operative word which it might not be. If your tach is off, and they often are, you may be setting it up wrong.