ok so i have an 88 lo3 and it has idle issues , anyone know the correct idle speed ? i know how to do it " at least i think" im supposed to adjust it in drive and turn he screw @ the tb unit , now does 400 rpm in drive, does that sound right ?, it surges @ idle , goes from 1000 to 1100 , and it idles high and i think its making my car run rich because im getting a raw gas smell .

Mine was always 550 in gear, about 700 in park. Check for vacuum leaks, and check timing to make sure it's right. Mixture isn't adjustable on the TB without drilling out the cover over the screw - ECM should regulate mixture by retarding/advancing timing and changing injector pulse.

ok my timing is a little BTDC like not even 2 degrees , would that cause the raw gas smell , i had someone gas the car during idle and when you floor it it spits out a couple drops of black something " not oil or coolant" kinda like gas build up , also the screw that i messed with is the one one on the lower driver's side of the tb unit it pushes the throttle linkage bracket " my guess hold the throttle bracket in place to maintain idle"

adjust timing to 6* BTDC. if it's not advanced then you could not be efficiently buring all the gas in the chamber

really , 6* ? isnt that too much ? i have read that if advanced to much they will run like crap , " then again i've never advanced my engine that far" but i will give it try , as for the idle speed , any suggestions?

i think that is the stock advance. as for idling, try opening up the air adjustment screws. i don't know how it is on the lo3, but the lg4 carb has two screws on the front face, bottom, that adjusts how much air gets in. also try using carb spary to clean it.

Base timing for the LO3 was 0*BTDC I thought - mine was and I found another thread stating:

MAKE SURE you are disconnecting the EST wire BEFORE setting base timing - or it will not be right!

As I said earlier, "Mixture isn't adjustable on the TB without drilling out the cover over the screw" It's not meant to be adjusted as the ECM makes all the adjustments you need - UNLESS you have made alot of modifications like intake, exhaust, heads, etc.

i'm thinking about a completely different application. ignore me.
i'll look up in the manual what it says about the degrees cause i'm pretty sure LG4s are 6*.
don't know much about TBI, just saw that he posted something that looks like a carb and got confused. my mistake

Not only do you have to disable ECM timing control you also have to disable the idle air control valve (IAC) which must be completely closed to properly set the baseline idle. There should be a procedure similar if not identical to the one used for a TPI.

disconnect the IAC ? wouldnt that mess thing up bad ? i had a bad IAC and the car would die @ idle , let alone not have would just mean bad news, as for the procedure its off the hanes manual , disconnect EST while car is off the start the car and adjust . btw would a code #15 cause me to run rich and get that raw gas smell ? code 15 " coolant temp sensor" ?

Yes, The CTS DTC 15 is causing a rich condition because it's telling the engine that the temp is 20°F, brrr - really cold.

As for the idle I don't know how the sub-routine for the TBI idle works, it maybe that when the EST is disconnected it automatically closes the IAC so no air get through and base idle can be set.

My TPI is also an 88' and there's no way I'm going to get the base idle set without disabling the ECM timing control and completely closing the idle bypass circuit (passage.)

The ECMs ability to control the engine depends highly on good timing and idle baselines.

well, i'll try and set the timing to 0* TDC and then sodder the wires that lead to the CTS " since the previous owner decided to cut them , switch different cable color and the put on a cheap a$$ crimp " so i will sodder and shrik wrap that and a couple other looses ends , still curious about the whole idle speed , yesterday i messed with the star screw on the TB unit and now it lopes during idle , but thanks for the help for the info on the TCS rgarcia63!!

Any Updates?

yeah , now i know why my car runs a little rich... still nothing solid on the whole idle speed thing ...

I'll be doing one this weekend...let you know how it went.

ok UPDATE: today i cut those ugly crimps off and soddered a new connector leading to the CTS and also clipped and soddered another crimped cable " a white one" the goes down under the engine and has a weird connector . Conclusion is that i now have no SES light and am still running rich .... why gosh darnit why !! , btw garcia , how was that idel speed setup ?

Will be doing it today (Sunday.)

any updates garcia ? after soddering the wires on the CTS it runs rich " white smoke out the back " not coolant , raw gas , messed with the screw some more , and nothing .

Didn't get it done as we couldn't figure out how to take the ECM out of the timing loop because it doesn't have a "Set Timing Connector, and won't drive the injectors if the EST is disconnected.
Turns out the engine, harness and ECM are from a 94' C-1500. For this setup distributor & crank are aligned then a scanner is used to set the timing at zero DTC plus/minus 2°. Once the a new pulley is installed I can use TunerProRT to set the initial timing.

EEK! so it is virtually impossible to set a correct idle speed withe the above mentioned items ? btw , stop by the auto parts store and picked up a brand new CTS , but it looks like the old one dosent want to leave my engine , could it somehow have corroded and fused to the intake manifold ? " i dont want to strip it since it is made out of brass " any suggestions on how to remove that stubborn little thing ?" alos i found this old print out of base idle speeds and how to set them according to " them " it says 6* BTDC @ 400 rpms ( vin F ) and it has to be done in drive , does this sound reasonable ?

FYI: The emission sticker on my 92 L03 says 0 degrees TDC in Drive with the EST bypassed (tan & black connector). It ran 220k miles flawlessly set that way. Idled at 550ish in Drive, and around 700 in Park. Hope this helps!

I don't know what made me think that you had a late model V6. So let me start over. 0° DTC should be correct for your 88' Lo3 TBI.

For the minimum idle speed a precision tachometer is required unless yours has been calibrated it's most likely off about +/-100 rpm. A scanner will probably suffice - I use TunerPro.

This is from AllData.
When adjusting the timing, refer to the instructions on the emission control sticker inside the engine compartment. If the instructions on the label disagree with the procedure listed below, follow the instructions on the label.

1. Locate the timing marks on the crankshaft pulley at the front of the engine.

2. Clean off the marks and coat them with white paint or chalk, so that they can be easily seen.

3. Run the engine until it reaches normal operating temperature, then shut off the engine (the first time the fan turns on.)

4. With the ignition OFF, connect a tachometer to the distributor, and a timing light with an inductive pickup lead to the No. 1 spark plug wire.

5. Start the engine. With the engine running and all accessories off, use a jumper wire to connect diagnostic terminal B and ground terminal A of the 12-terminal Assembly Line Diagnostic Link (ALDL), located under the instrument panel.

If jumping the ALDL terminals does not prevent timing advance, the EST bypass wire (STC; Set Timing Connector) will have to be disconnected instead.

6. Aim the timing light at the timing mark. The line on the balancer or pulley will line up with the timing mark. If a change in timing is necessary, loosen the hold-down clamp bolt at the base of the distributor. While observing the timing mark, rotate the distributor slightly until the line indicates the correct timing.

7. Once the timing is set to specification, tighten the distributor hold-down clamp. Recheck the timing to make sure it did not change while the bolt was being tightened.

8. With the engine still running, remove jumper from the diagnostic terminal. (Removing the jumper from the diagnostic terminal while the engine is still running will usually prevent trouble codes from being stored.)

9. Turn the engine OFF and remove the timing light, tachometer, and ALDL Jumper, reconnect STC. If you're going to check/adjust the idle speed leave the tachometer/scanner connected and the ALDL jumper Connected, or the STC disconnected until you're done.

Minimum Idle speed (air rate)
1987-90 All W/FI & TBI: Ground diagnostic lead and turn ignition on for 30 seconds. Remove IAC electrical lead and remove ground from diagnostic connector. Start engine and set minimum idle speed to specified value (450 curb.)

thanks a load gracia !!!!!!!!!!!!!! , now about the 02 sensor that i think might have gone bad , can rich conditions ruin it ?

O2 can amke it rich.

if only i could show you what they look like , i have three of them right next to me 2 used ones and a new one , tomorrow i will post link and you tell me if good or bad , btw thanks for the pm go ahead and send the chart .

ok new bosch o2 sensor in and new IAT sensor and still runs rich , why is it still doing this i dont want to keep on buying new o2 sensors the last two were ruined just trying to fix the problem, and i dont want to ruin this one , can anyone give me a list of things that can cause a rich condition , btw i got the idle speed set to the lowest possible rpm's and nothing , still runs rich , do i bump it up to around 550 rmps and it starts to smoke bad and engine starts going chugga chugga chugga kinda like a surge in idle , and yes i had previously installed a new IAC , what could be the problem , btw i have a code 42 " esc module" could this cause rich conditions , note: my two connectors "grey and black " @ the ignition coil have broken clips i ordered new ones just waiting on them , so yeah a list of thing that can make my lo3 run rich would be nice .

Okay, install a NEW cts and set base timing at 6* and it should be all good. Just try it, if it does not fix it, god knows what's wrong then lol

new CTS was installed last week , did nothing just got rid of my code 15 , what else could set off a rich condition , and i know its a sensor or something eletrical because in my opinion nothing mechanical could set off a rich condition like this.

Birdstheword,
I believe there are coolant temp sensors in both heads as well as the intake. So I'm going to go out on a limb and say that the ones in the heads are for the ECM and the one in the intake is for the guage. So by just changing that one, you may have not made a difference as far as the temp that the ECM sees to adjust AFR. So, if it uses both sensors in the heads and takes an average of the two, you would still be low and thus adding more fuel. Idle speed and AFR are both run off coolant temp. So, unless you are trying to set your idle speed while at operating temp, you will be fighting a changing idle speed(from IAC) as well as AFR.

As far as idle speed, the 550 or 600 sounds right(in gear), and it will try to idle 50rpm higher when the AC is turned on. Make sure you remember that timing as well as idle is set at normal operating temp. Engine control is dynamic before that point and is changing to get the engine and exhaust temperatures to rise as quickly as possible to reduce emissions.

there is one on the passengers side and that is the cooling fan sensor " tells fan when to turn on " and on the drivers side there is another one wich is a coolant sensor and then theres another one in front of the manifold , both have good connections , now i think my idle air control valve is bad now due to the incorrect idle speed and rich afr. now i dont know what else i can do , im stumped i checked all wires to sensors and they are good , what can make an engine run rich , my intake and exhaust valves on the passenger side are set to 3/4 turn and where as my drivers side valves are set to half a turn , would this have any effect on afr ? " i highly doubt it heres a pic of what my injectors are doing , is this right ? any other suggestions on what my problem might be ? would a bad electronic spark control module cause this?

Gentlemen , i think i found the solution to my problem !, when installing new AC Delco spark pluggs , i gapped them at 45 !!!!! , isnt the factory gap 35 ? . So in conlcusion , by me gapping my pluggs wider i made my spark weak , so what do you guys think , could this be it ? can i still use the same pluggs ? or will i have to buy new ones?

I would not use those plugs again.
A wider gap won't weaken the spark, but will inrease the voltage required to jump the gap putting a strain on the rest of the ignition system.

so , since the gap is bigger and it need more voltage , but my stock igniton cant supply it , therefor giving it a weak spark?

It's more like one tank of gas whether you drive at 100mph, or 50mph it's still only one tank of gas, but the wear and tear on the engine is higher at 100mph than at 50mph.

only drove it 140 once . ever since then i drive @ 30 -45 mph dont really do highway driving im 7 miles away from my job, tomorrow i will regap the pluggs and lets see hw it happens

ok , re-gapped the pluggs to .35 and nothing , still the same rich condition , i dont know whatelse it could be , im about to lose my head , what could it be ?

ooooo ok i got you know garcia , duuuh ! you were stating that it will not make it weaker , just wear it out faster , ok , still any ideas on what else could make it run rich ?

my car 1991 LO3 auto is idling high at 1200-`1300 , and has a mis when accelerating from a stop ????? Did u fix your high idle?

Base timing on an L03 is 0 degrees BTDC!!!!

Disconnect the ESC (electronic spark control) wire and put it to zero. Turn off car, plug back in, done. Timing is set where it should be.

As far as the rest of it goes, I have no idea. Look for vacuum leaks?

I cleaned the IAC and while also spraying brake cleaner near the base of the TBI unit it revved up a little which told me I had a TBI Base Gasket leak too. So after cleaning the IAC it still was high, i went into the garage to call pep boys to check on base gasket then got in car to go pick it up and it was idling normal again. The IAC cleaning did the trick, but I still had a slight base gasket leak so I changed it and sure enough, it needed to be done but was not terrible, but needed it, so now it runs like a champ.
Mike Santo