odd problem when checking timing

[Rodney Gold]

86 L98 - I disconnected the brown wire with black stripe near the booster and proceeded to start the car - wouldnt idle at all (Was perfect before the disconnect and i hadnt touched the dizzy)
Reconnected and the problem persisted. Eventually I disconnected the battery , waited a few mins and reconnected and it started and idled properly again?
Is this normal?

 

[ex-x-fire]

Yeah thats normal, sometimes they'll even set a code. Try checking the timing after the car is fully warmed up, you may have to give it some gas to get it started.

 

[TedC]

I have not seen a similar issue on either my 1988 or 1989 L98. The ESC wire is tan (light brown) in color. If you fail to reconnect, then drive it, the engine check light will go on. I'm wondering if your base timing is way off. How is your MPG? I would try setting it again with a fully warmed up engine.

 

[Rodney Gold]

Hiya , thanks for the replies
Well , my mileage is quite good , I average at 16.5l/100km which is in line with my 96 Camaro and good for a V8 which is mostly driven "spiritedly" in town and heavyish traffic.
I didnt warm the car up - which is probably the issue - says to do so on the sticker on the side of radiator.
Don't think my timing is way off tho - I do tend to advance more than stock for that little bit more vooma - we have quite high octane gas here - round 97. Im probably sitting on 8 degrees rather than the recommended 6. Just wanted to check tho. Never hear any pinging whatsoever.
Im used to old school distributors where I dial in total timing (without vac) at 3500 rpm with a dial back timing light.
These modern newfangled computerised engines are out of my league

 

[Schrade]

My '87 got just over 27 (highway; right at 59 - 60), 22-23 combined, after sweeping the intake/plenum+runners/TB/injectors of carbon.

97 octane? You get this at the airport?

Just out of curiosity here, why did you disconnect a wire?

 

[vetteoz]

Just out of curiosity here, why did you disconnect a wire?

You have to disconnect the Electronic Spark Control ( spark advance) wire while setting inital advance otherwise the ECM still has control of the timing .
Advance at idle it is usually off the tab ( 30 degrees + ) and can't be seen .The engine has to be fully warmed up to idle with ESC wire disconnected

 

[roger longman]

My '87 got just over 27 (highway; right at 59 - 60), 22-23 combined, after sweeping the intake/plenum+runners/TB/injectors of carbon.

97 octane? You get this at the airport?

Just out of curiosity here, why did you disconnect a wire?

In most other countries you can get 97 octane. 91 octane is regular......Roger.

 

[GRAND SPORT #12]

ok timing not one hundred percent sure but on computer cars disconecting the wire you stated is correct to get to what the manufacture calls base timing without computer adjustments or overide the old days you undid the vacume advance hose..one coment is why are you running 97 octane is your timing real advanced because if the motor is stock you are actually losing hp using that high of an octane. only need that high of an octane to prevent detonation. so if not save your money use a lower octane for your vehicle which acutally fires hotter.

 

[vetteboy86]

The vehicle should not stall or run poorly with wire disconnected. If the base timing is close, it should run. As has been pointed out, with the EST wire connected, spark advance at idle could be 30+ degrees.

 

[Rodney Gold]

Well , unleaded here in South Africa is 97 octane , thats all you can get .
I generally set my timing to where it starts pinging and then back off 2 degrees. That has been a quick and dirty way I have used quite often

I been advancing the vettes timing a bit more , hear no ping , but at a certain point of advance , the idle lopes a bit so have backed off
I'm wating for an obdI cable and will do some data logging and see exactly where I am.
I might be running a little more CR as I am not using the steel shim gaskets but am using Cometics or Felpros so did skim the difference tween the steel and the other ones off the heads.
Im contemplating going to intake and carb , I have driven and seen the effects of this on quite a few C4's (edelbrock performer and holley 770 street avenger) and they seem a lot more potent and especially a lot more reliable then when they had the TPI on - apart from which I know holleys and holley tuning backward.

 

[JAKE]

On my previous 86, not only did I have play with the throttle foir a minute or so to keep the engine idling with the wire disconnected but if I allowed the engine to idle that way for a extended period of time the exhaust headers would begin to glow red. Retarded timing causes that; that is, timing not being controlled by the ECM.

A SES code gets set when the ECM detects the engine idling with the wire disconnected, so the battery needs to be disconnected for a minute or so to clear it when returning the system to normal operation.

Jake

 

[JAKE]

The vehicle should not stall or run poorly with wire disconnected. If the base timing is close, it should run. As has been pointed out, with the EST wire connected, spark advance at idle could be 30+ degrees.

I encountered the exact same idle issue as he has on my 86. I posted more on my experience above.


At idle, more like 20/22* BTDC according to what Diacom reported to me on my 86.

Jake

 

[aklim]

I generally set my timing to where it starts pinging and then back off 2 degrees. That has been a quick and dirty way I have used quite often

I been advancing the vettes timing a bit more , hear no ping , but at a certain point of advance , the idle lopes a bit so have backed off
I'm wating for an obdI cable and will do some data logging and see exactly where I am.

How did you determine it wasn't pinging WITHOUT an OBDI cable? Hearing it is different as to whether YOU hear it or the ECM. Knock sensor is way more sensitive and will back timing off BEFORE you hear it.

Besides, what you are doing seems to be based off old school knowledge. Problem with that is you will advance timing all across the board. So, just because it works well here doesn't mean the timing isn't too much over there. Better tune the chip to advance the timing where it is needed and keep it stock for the setting

 

[Rodney Gold]

I know it's old school.. I'm waiting for an OBD1 cable to see where I am , at the moment its "seat of the pants" and I do realise that the timing map might be wrong as I advance ... Im just playing around right now as I'm not used to these modern newfangled puterised engines...
I just find the car rather lackluster compared to stuff I have had and am trying to get the best "feel" right now - at some stage I will be going 383-heads , headers , cam , carb , non puterised dizzy , stall and rear gears etc.

 

[aklim]

I know it's old school.. I'm waiting for an OBD1 cable to see where I am , at the moment its "seat of the pants" and I do realise that the timing map might be wrong as I advance ... Im just playing around right now as I'm not used to these modern newfangled puterised engines...
I just find the car rather lackluster compared to stuff I have had and am trying to get the best "feel" right now - at some stage I will be going 383-heads , headers , cam , carb , non puterised dizzy , stall and rear gears etc.

It is probably going to be wrong since it isn't linear from the timing graph I saw a few years ago where we had some points needing more computer advance than others. When they are newer technology, it is working on the same idea. Instead of you listening for knock, they use a microphone, so to speak, that is more sensitive than your ear can be. As such, the timing advance can be way more precise. IF you advance it by say 5 degrees, it might feel good way down low but up high, it kills power. Why not let someone else tune it and leave it at 6 degrees?

Perhaps it feels lackluster because your stuff that you had was already tuned and this isn't? I found that the proper tuning after I put on headers and a SR manifold by Lingenfelter really made the car wake up.

 

[Rodney Gold]

I just stuck it back to 6 degrees - I was 2 degrees out on the "seat of the pants" feel thing , 2 degrees advanced. I bought it with brand new tyres - 255/50/16's , off idle , it won't light the tyres. It will if I reve it 1000 or so on the brakes.
I just did a head gasket change and a full service , new plugs , wires , FF , aircleaner , oil , oil filter, o2 sensors, belt and so on , also removed all the stuff that went onto the exhausts (Air pump/smog stuff - we dont have any emissions requirments here) - apart from that and removal of cat done some time ago , its dead stock and has done 54000k miles.
I might not be getting 100% full throttle as I stuck a small cable tie on the end of the kickdown cable to shorten it slightly so that it kicks down a little earlier than "burying your foot in the carpet", I would estimate the cable tie is about 3-4 mm , 1/16th + thickness , so Im losing that much of the last bit of full throttle - will see if i can adjust it the "right" way just now and see how it feels then. I looked at changing the diff ratio to a 3.3 or 3.5 but it's a huge and quite expensive mission over here.
My stock 94 Camaro feels nippier to me.
I had a C3 that was taken out by a guy that skipped a red light , that was seriously fast , low 12's on stock tyres - but it was quite modded.
I dunno what mods would be really effective on the motor I got in the C4 that the ECM will be able to handle without reprogramming or bigger injectors etc.
We dont have great tuners in respect of vettes where I live , they and their engines are pretty rare In South Africa - I do have access to EFI live and HP tuner , but not sure they will work with this engine , they will work with my Camaro.

 

[aklim]

I might not be getting 100% full throttle as I stuck a small cable tie on the end of the kickdown cable to shorten it slightly so that it kicks down a little earlier than "burying your foot in the carpet", I would estimate the cable tie is about 3-4 mm , 1/16th + thickness , so Im losing that much of the last bit of full throttle - will see if i can adjust it the "right" way just now and see how it feels then. I looked at changing the diff ratio to a 3.3 or 3.5 but it's a huge and quite expensive mission over here.

My stock 94 Camaro feels nippier to me.

I dunno what mods would be really effective on the motor I got in the C4 that the ECM will be able to handle without reprogramming or bigger injectors etc.

We dont have great tuners in respect of vettes where I live , they and their engines are pretty rare In South Africa - I do have access to EFI live and HP tuner , but not sure they will work with this engine , they will work with my Camaro.

Have you tried adjusting just the detent cable? I'm not a trans expert but I think you can make some adjustments on the detent cable or even the computer program to do that.

I think the LT1 engine would be nippier than the L98.

Reprogramming is always a plus since the factory tends to be conservative and has to meet emissions. What you do with it after is your problem not their's. I would recommend getting it tuned up by the tuners.

There are tuners that can write you a tune and send you the chip. Won't be as good as dyno tune but better than stock.

 

[Rodney Gold]

Ive adjusted the Detent cable so I get full throttle. Im going on a nice 300km Muscle car run tommorrow - will see how it all pans out then.
Addendum
Car went well on the run , had it up close to 235kph and it seemed to have more steam to go faster , wasnt on a long strech of road so couldnt really wind it up - great economy tho - 11 litres per hundred km which is excellent - especially as we were travelling at 120kph+ - Did some twisty stuff on B and C grade roads and the car handled well
I suppose I cant expect the car to be a fire breathing tyre shredding monster with 240 hp on tap...