Advance Timing For L98's
Race Director
Joined: Nov 2003
Posts: 12,221
Likes: 446
From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
It was recommended that I see your post here as I am having my issues. Having done much research and with "email talking" with Patrick at Super Chevy Magazine he thinks I may need to replace my ECM. This makes sense to me since it is on a daily driver 1987 Corvette with 176,000 miles on the odometer now. But freshly installed newly built motor. Here is the link to my original thread: http://forums.corvetteforum.com/c4-s...ng-richer.html
Here is what I have written today:
Yesterday I attempted to start the Corvette once again.
This past Friday I replaced a broken up Idle Air Control Valve Connector as pictured below. While this was a necessary evil the connector does not come with colored coded wires. Careful attention to connect the new wires into the same wires as on the old connector was done. I also replaced the Electronic Spark Control Module on the chance that this may have been bad. Since I previously checked the spark plugs and finding the #1 plug to be fouled richly, the other plugs were seen as slightly rich but mostly burning normally. So on this day I had replaced all 8 plugs with fresh ones. Many attempts at starting the engine gave me zero results other than good cranking but not catching fire. It also resulted in having to trickle charge the battery over night. This being the New Years weekend I refrained from further work on the Corvette to avoid the wrath of my wife.
This being Monday (yesterday) I again made my attempts to start the car. But first, I pulled the #3 wire, attached 1 of the good plugs I replaced and grounding it onto the header I saw that indeed spark was coming thru. Onto the even side of things I did the same thing with the #4 wire and spark again shown working. This puzzled me, good spark, having smelled fuel as if in my attempts to start the engine caused me to flood it in my attempts. So now I pull plugs #1-3-4 & 6, these being the easiest to get to. These plugs all looked just like they did when I pulled them out of the box to install. No signs of spark or fuel having touched them. This has become my problem now not being too rich as I first thought.
I called the gentleman who built this engine and who got me running in the first place to get his opinion. He suggested that I try to put some fuel, or not having that, spraying some WD40 into the Throttle Body to try to get some fuel into the thing to start it. I am apprehensive about doing this as it is not like my muscle cars of years past with a carb on top of the intake. I would not hesitate doing so on a carb'd engine having done so many times before. But this is a TPI Fuel Injected engine so my hesitation. Your thoughts on this?
At any rate I am now at a cross roads as to what to do. I am wondering if for some reason installing the GForce Chip after the HyperTech Chip had been running without issues was such a good idea. Is it possible that this chip swap caused some unforeseen problems? The HyperTech Chip is back in again with no better results in starting the engine up.
Or, thinking further, could the Fuel line, Filter or even the Fuel Pump be an issue now? In my email yesterday I mentioned "Popping Corn" sounds while attempting to start the engine. I had by way of cell phone the engine builder listen to the start up process and he says it sounds like it wants to start and I am hearing the spark firing but not enough fuel to ignite. That one BIG POP that I heard last week, is it possible it ignited in the runner/plenum area and knocked out 1 or more Fuel Injector from working properly? I of course can't tell and I did several times run my Code Scanner and every time it flashes a "12" as in normal. No codes to indicate what if any problems there might be.
I am waiting for a programmer to return my Factory Memcal Chip from the ECM with the reprogramming being done to my new engine specs. As I indicated in my earlier email, he suggested I go to an adjustable Fuel Regulator. Before making my car any richer and spending money I will wait to see what happens with the newly programmed Chip.
Actually the link to the sensor connector just replaced: http://www.autozone.com/autozone/par...ntifier=342412
Here is what I have written today:
Yesterday I attempted to start the Corvette once again.
This past Friday I replaced a broken up Idle Air Control Valve Connector as pictured below. While this was a necessary evil the connector does not come with colored coded wires. Careful attention to connect the new wires into the same wires as on the old connector was done. I also replaced the Electronic Spark Control Module on the chance that this may have been bad. Since I previously checked the spark plugs and finding the #1 plug to be fouled richly, the other plugs were seen as slightly rich but mostly burning normally. So on this day I had replaced all 8 plugs with fresh ones. Many attempts at starting the engine gave me zero results other than good cranking but not catching fire. It also resulted in having to trickle charge the battery over night. This being the New Years weekend I refrained from further work on the Corvette to avoid the wrath of my wife.
This being Monday (yesterday) I again made my attempts to start the car. But first, I pulled the #3 wire, attached 1 of the good plugs I replaced and grounding it onto the header I saw that indeed spark was coming thru. Onto the even side of things I did the same thing with the #4 wire and spark again shown working. This puzzled me, good spark, having smelled fuel as if in my attempts to start the engine caused me to flood it in my attempts. So now I pull plugs #1-3-4 & 6, these being the easiest to get to. These plugs all looked just like they did when I pulled them out of the box to install. No signs of spark or fuel having touched them. This has become my problem now not being too rich as I first thought.
I called the gentleman who built this engine and who got me running in the first place to get his opinion. He suggested that I try to put some fuel, or not having that, spraying some WD40 into the Throttle Body to try to get some fuel into the thing to start it. I am apprehensive about doing this as it is not like my muscle cars of years past with a carb on top of the intake. I would not hesitate doing so on a carb'd engine having done so many times before. But this is a TPI Fuel Injected engine so my hesitation. Your thoughts on this?
At any rate I am now at a cross roads as to what to do. I am wondering if for some reason installing the GForce Chip after the HyperTech Chip had been running without issues was such a good idea. Is it possible that this chip swap caused some unforeseen problems? The HyperTech Chip is back in again with no better results in starting the engine up.
Or, thinking further, could the Fuel line, Filter or even the Fuel Pump be an issue now? In my email yesterday I mentioned "Popping Corn" sounds while attempting to start the engine. I had by way of cell phone the engine builder listen to the start up process and he says it sounds like it wants to start and I am hearing the spark firing but not enough fuel to ignite. That one BIG POP that I heard last week, is it possible it ignited in the runner/plenum area and knocked out 1 or more Fuel Injector from working properly? I of course can't tell and I did several times run my Code Scanner and every time it flashes a "12" as in normal. No codes to indicate what if any problems there might be.
I am waiting for a programmer to return my Factory Memcal Chip from the ECM with the reprogramming being done to my new engine specs. As I indicated in my earlier email, he suggested I go to an adjustable Fuel Regulator. Before making my car any richer and spending money I will wait to see what happens with the newly programmed Chip.
Actually the link to the sensor connector just replaced: http://www.autozone.com/autozone/par...ntifier=342412
That said, have you verified you're getting the appropriate 160-steps of opening thru your new IAC/IAC connector? If it's not working properly, you may not be getting enough air, let alone spark/fuel.
Did your problem start EXACTLY with the switch from chip A to chip B -- with no other activity in-between?
Team Owner
Joined: Jul 2004
Posts: 28,495
Likes: 3,298
From: Hartford WI
Here is a better idea. Don't advance the timing and get the tuner to set it up right. Best way is to put it on a dyno. By advancing the base timing, you are advancing it for the entire curve. When the ECM hears pinging, it retards timing and power. Sometimes you can't even hear it. If there is anything left on the table, that should be the tuner's responsibility. Simply advancing it is like adding a couple of inches all over the suit. It might make one point fit better but it might make the rest of the suit look stupid.
Thread Starter
Advanced
Joined: Nov 2011
Posts: 99
Likes: 0
From: Budd Lake New Jersey
Here is a better idea. Don't advance the timing and get the tuner to set it up right. Best way is to put it on a dyno. By advancing the base timing, you are advancing it for the entire curve. When the ECM hears pinging, it retards timing and power. Sometimes you can't even hear it. If there is anything left on the table, that should be the tuner's responsibility. Simply advancing it is like adding a couple of inches all over the suit. It might make one point fit better but it might make the rest of the suit look stupid.
now thats some good advice thanks!
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
What Aklim said.
Spark knock starts a long time before it becomes audible to the ear.
By the time you hear it you could be doing damage.
The tune done right controls the timing its not the other way around.
If the knock sensor tries to retard timing because the dist. was advanced youre on the losing end of performance and dont even know it.
If its stock leave it alone at 6 deg.
Spark knock starts a long time before it becomes audible to the ear.
By the time you hear it you could be doing damage.
The tune done right controls the timing its not the other way around.
If the knock sensor tries to retard timing because the dist. was advanced youre on the losing end of performance and dont even know it.
If its stock leave it alone at 6 deg.
Race Director
Joined: Nov 2003
Posts: 12,221
Likes: 446
From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
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