92 ls400 started surging during cold starts, ~160k miles

[threepwood]

It all started after making a sharp rapid left hand turn to beat a short left hand green arrow.

Suddenly idle dropped to near zero and pushing pedal to the floor could not keep it running.  Acted like it had water in gas tank, that's the only way I can describe it.  Could restart car and would run for another 30 feet and then it acts like it's running water instead of gas thru the engine (no power, extremely slow engine rpm increases with gas pedal floored then suddenly it would catch and take off like a rocket).  Note, tank was down to 1/4 tank of gas.

I nursed it home, put 4 cans of dry gas and 1 can of gumout in it and left it over night.  Was able start it next morning and stumbled to nearest gas station to fill it up.  Took it home and it started to run properly.

Now, every morning when I start the car for the first 3-4 miles it stumbles and acts like something other than gas is running thru it.  Fearing it was another ignition coil failing intermittently I put a power timely light on both coils and drove the car around.  Both coils are functioning properly during these surge incidents.

And this is Florida, so cold starts are not all that cold, as it was 88F here today.

What I'm looking for is known issues that might be causing this surging. Bad Egr valve, mass air flows sensor failing, maybe a screen inside gas tank plugged,  etc.).

Thanks for any suggestions you can make. 

[chc0318]

Check diagnostic trouble codes first.

[threepwood]

Will do, but will there be a code even without a check engine light?  No check engine light.  Just asking, I don't know.  But it has gotten much worse.  Can not drive car.  Sits there and cycles between near zero rpm and 400 rpm continuously at idle.

[threepwood]

No codes, just continuous flashing.  Just to see what would happen, I pulled the MAF sensor connector with engine runniing.  Engine died and now I get codes 12,24 and 31.  Cleared codes by pulling fuse and went for a drive in diagnostic mode.  Still a lot of hesitation but no stalling.  Came back home to check codes, still no codes, just continuous flashing.

[M.Yasir]

There could be number of issues, ignition coils would be my 1st guess another guess would be after spark plugs

I have also experienced hesitation in my 98 LS and it was due to multiple cylinder misfires, so i changed all the 8 spark plugs which solved the problem however i did not changed the ignition coils though

I believe in 92 LS there is no ignition coil which is direct on the spark plugs (coil on plug), there is a rotor and distributor cap with wiring harness running around all over 8 spark plugs so your issue can also lie somewhere in the wires again just a guess 

[threepwood]

My friend with a similar problem in his camero suggested I pull the electrical connector on the ISC (Idle speed control) valve and guess what, it started running fine.  But since I couldn't be certain it was closed when I disconnected it, I plugged the air line to it.   Call it the broomstick solution 🙂   Then I manually set idle hot with AC on to 1000rpm.  Have not had an issue since.  So I don't see any reason to fix it even though there is lots of info on cleaning it.  If anyone has a good reason, I'm willing to listen.