ROTICKA

Hey guys.
My T/A has been giving me all kinds of problems. Not that I'm complaining, it's all part of buying other peoples junk. Anyway, I have questions about timing. My Chiltons manual says that timing specs for my motor should be 6 degrees BTDC - IF - there is no emissions label under the hood. Problem... There is an emissions label under my hood and it says 0 degrees TDC. How can this be right? Never heard of a car set to that. Any way I have it set right now to 8 degrees BTDC. I don't have any high end pull. The low end is great. I can put my foot in it at 15mph and be sideways around a corner spinning all the way. But at 70 dropping down to third barely gives any acceleration. HP peak is at 4500 RPM right? It peters out at about 3200-3700. Does this mean my timing is too far advanced? Where the timing is set right now my idle speed is about 600 rpm low 1100 high. I have never owned a good running third gen, can anyone explain how the performance should feel? I wish I knew someone else with a third gen similar so I could drive it. Everything on the car is stock to the best of my knowledge. Infinite LG4 wisdom needed! Thanks guys!

five7kid

iTrader: (14)

Are you disconnecting the ECM harness when you set the timing?

Dens71TA

iTrader: (5)

My '84 LG4 sez to set timing at 6* BTDC. As five7kid said you have to disconnect the four-pin connector at the distributor when setting timing. The engine should also be warmed up.

Lots of fuel injected cars have the timing set at 0* as the computer uses that as a baseline. Once you connect the computer timing back up the computer sets it where its suppose to be.

Don't expect that much performance out of an LG4. Its a grocery getter engine and was used in many other GM vehicles besides the F-body. It will spin the tires from a stand still but any rolling acceleration is just about non-existent. All power is gone by 3500-4000 RPM. The performance(or lack of) you are experiencing is right on par with other LG4s.

ROTICKA

Thank you so much. I've been thinking in circles for a month now trying to get a good idea of how my car is running without taking it to the shop or paying anyone to look at it. You say my description is on par with any other stock LG4, SWEET! I can finally quit worrying about it and just enjoy driving it for what it is: A Trans Am! Yes I did unplug the ECM Connector, after I found it, that was my first problem. The book said it was there but it took about three weeks of driving the car out of time to finally find it. And after that.... well, easy! But it is really running okay at 0 degrees, do you think that 6 before would be better? What would you say are the benefits? Let me know and I'll try it. Thanks again for the peace of mind!

naf

iTrader: (7)

Setting the initial timing too high runs the risk of detonation triggering the knock sensor-telling the ecm to retard timing. This could possibly result in less overall advance. Recommend you start at zero then increase it a few degrees at a time until you find where your engine likes it-(based on the grade of fuel you can afford too).

ROTICKA

So if I'm running 87 octace, which should be fine for a 165 HP motor. What would 2 degrees advance give me - In laymans terms please - I kind of feel stupid but what signs will tell you that your car likes it in a certain timing degree? The more detail the better! Thanks guys!

naf

iTrader: (7)

Higher octane fuel will generally allow you to run more advance without detonation, all else being the same. Don't think the benefits will be worth the cost though. Run your car at zero for a few days then bump it up a few degrees. You should be able to judge by throttle response where it's happiest. Or just set it at 4 which seems to be a happy, safe place for most lg4 owners.

I posted earlier because ecm retard caused by detonation could cause the lack of power you're experiencing at higher rpms under load. You might or might not hear the pinging before the computer backs your timing down. You can test this easily by dropping your timing back close to zero and comparing the performance. Of course the problem could just be the lg4.

Mine used to be an lg4 but I didn't spend any time with it before the swap. I am using the carb and electronics still though.

Nate86

My Haynes manual specifically says not to do this... are you sure this is the correct procedure? I'm not saying you are wrong, but I've heard different ways of doing this and usually people tell me disconnect the EST and not the four-pin connector.

EDIT:

@ROTICKA,

You have good taste in cars. Check mine out:

ROTICKA

[QUOTE]Originally posted by Nate86
[B]My Haynes manual specifically says not to do this... are you sure this is the correct procedure? I'm not saying you are wrong, but I've heard different ways of doing this and usually people tell me disconnect the EST and not the four-pin connector


Nice car man! My Chiltons manual says: "To properly set the ignition timing, the EST must be placed in the bypass mode. On 2.8L and 5.0L carbureted engines, disconnect the 4-wire EST connecter at the distributor. (Fault code 42 may be set in ECM memory, and must be cleared once the procedure is completed). Proceed to Step 7." - When I was trying to set the timing with this thing connected, I was setting the timing to 0 degrees INCLUDING Advance, so the base timing was like 12 degrees after TDC... the car wouldn't even really run, just kind of lope. After disconnecting the 4 wire terminal I was setting the base timing to 0 degrees without the advance so it really made things work out right.( the 4 wire EST terminal is wires coming out of the firewall side of the distributor that lead into a weatherproof connector sort of between the distributor and the brake fluid reservoir down below the valve cover near the firewall). Got all that? If you have an LG4 with a 4 barrel that still has the ECM this is the correct way to adjust your timing. I learned the hard way!

Marc 85Z28

iTrader: (3)

Actually the HP peak should be a bit lower, like around 4200RPM. But that cam is very weak, and its powerband is only like 1000-3800RPM at best. You won't get much acceleration out of a stock LG4 at highway speeds.

Even with an advertised compression ratio of 9.3:1 for 85, the engine like MUCH more base timing than the factory recommends. Remember, thats an emissions label, and not an "optimum performance" label. Nearly all the LG4s I've worked on, including mine, liked 12 degress advance and ran happily on 89 octane with no detonation (either audible or knock sensor counts).

Nate86 - Don't listen to Haynes. And those guys are not familiar with CCC setups. The FI cars, TPI, TBI, etc, use a single EST brown/black wire that is disconnected for setting timing. CCC cars use a slightly different setup, and that requires disconnecting the large 4 pin connector like the original poster said.

ROTICKA

That's good to know. I thought that my lack of power above 3500 RPM was a timing problem. But now that I know That these motors crap out around there, 12 degrees advance sounds reasonable. Correct me if I'm wrong but this would give my lower RPM driving alot more punch, and my power would actually be useful around 3000 - 3500 RPM. Also can you place this? In park or neutral when I rev the motor and then let off the gas quickly there is like a quiet sputtering typer of backfire out the exhaust, do you know what I'm talking about and how can I diagnose and remedy? So many minds in one place, a wealth of knowledge, thanks guys!

Marc 85Z28

iTrader: (3)

More base timing would do exactly as you described. Better throttle response mainly, and a small amount of additional power in the lower parts of the RPM range.

As far as the noise you are hearing, called afterfire, well that's a very common problem. And its usually much worse when decelerating in a gear other than OD or when revving in P/N. Although its far too detailed to get into here (do a search ), I'll touch on the common causes in order of severity:

1. Exhaust leaks.
2. Rich exhaust.
3. Faulty diverter valve in A.I.R. system. Creates an exhaust leak.
4. Incorrect timing.
5. Exhaust design.

In my experiences, exhaust leaks have contributed to most of the problem. Eliminating the leaks helps tremendously, but not completely. I have no AIR, so that is of no consequence to me. Timing is good. I knew I was running rich on decel, and there was little I could do about that, even after spending countless hours tuning the carb. There is only so much you can do with a computer controlled carb, as the ECM has a major influence over part-throttle (or no throttle) fuel mixtures. For me, a ZZ4 conversion ECM and PROM solved my problem.

And the larger you go with pipes on these single exhaust designs on our cars, the worse it gets.

Again, do a search on this topic - popping in exhaust, afterfire, backfire in exhaust, etc will yield results.

naf

iTrader: (7)

Sounds like the power problem is the lg4. If you can run 12 degrees advance with no detonation, I'd recommend it and you'll notice the difference. Good luck.

Fast355

iTrader: (2)

Could be a fuel problem? When was the last time you changed your fuel filter? Also when was the last tuneup?

Finally it could be the powerband of the LG4 simply giving up. I know that my 180 horse LE9 305 that came stock in my G20 would give a F-body of the same era a good run for its money. In fact from 60-100 they were almost always 2-3 cars behind me. The LG4s cam is much too small and the exhaust is too small. Cam the engine and put a good exhaust and headers on it and it will come alive.

My 180HP LE9 305 responded well to headers and a different air cleaner very admirably.

Don't get me started about porting the heads, swapping the cam to a Comp XE-274H, the Edelbrock RPM intake, reworked Q-jet, advance curve kit, and 2,000 stall.

14.7 @ 98 1/4
9.8 @ 75 1/8
in a 5,300# brick with 3.08s, and useless P235/75/R15 tires, shifting at 6,300 rpm. Traction and a good gear might have put me into the low 14s or high 13s.

I could leave the current TBI 350 about 5 car lengths behind me in the 1/4.

naf

iTrader: (7)

ROTICKA-what kind of mileage are you getting? If you're not at 18-20 or better you may want to check your electronics. The solenoid could be running full rich for the primaries (low and part throttle) which could lead to the afterfire.

Fast355 is right, a cam and exhaust will wake that motor up. You can use the same electronics and if you don't go too crazy on the cam get better mileage and performance.

ROTICKA

I took the car on a 240 mile round trip last night. It's really running very well at 0 degrees. I averaged about 22 miles to the gallon, the whole trip was mostly highway with a few small towns - I hate speed zones! The high RPM kickdowns on passing were surprisingly quiet. Compared to what it has sounded like until recently. No major vibrations, even at 4000 RPM very smooth. I think that advancing the timing would ruin that high RPM smoothness. Vibrations make me nervous. Anyway the mods you are suggesting are good ideas, headers and exhaust are my first goals... unless that quadrajet craps out on me before then. Someday I'd like to RAM Air it. But those hoods are pretty spendy, not to mention the paint job! I think my catalytic converter is going out, it really smelled terrible this morning when it was warming up, I think I'll just take it out completely untill I get the headers and new exhaust on it. No emissions checks in Montana!

ROTICKA

You may be right about the solenoid Naf. I inadvertently left the car idling for about 20 minutes last night and the catalytic converter lit up like a cherry. That makes me nervous too. Thats probably why it smelled so bad this morning. How do I check that solenoid?

naf

iTrader: (7)

If you're getting 22 mpg you're probably good to go with the electronics. Did you let it idle with the choke on to warm up? This will let it run really rich, causing the smell and so on. Once it warms up the ecm starts controlling the mixture and leans it out properly. There is an outside chance that your O2 sensor may not be getting hot enough at idle, or needs to be replaced. I've installed a heated O2 sensor on mine and it helped with the morning warmup, about a $50-60 deal. You can check this with a dwell meter hooked up while it's idling.

Grab a haynes or chilton manual and it can walk you through all of the tests and adjustments for a ccc-qjet. Once you know it, you'll love it. The system is extremely simple, fuel efficient and verastile. It can self adjust to nearly any mod or change in displacement. The secondaries are still mechanical and can be tuned like any other q-jet. A rebuild is cake too. Remember, the ecm also controls the distributor advance and torque converter lockup, a swap involves making changes to these systems as well.

If you have any questions, let me know.