Idling Issues Again

nastybird93sc

Registered User
Hey Guys. Almost The Same Issues. I Had The Problem Of Running So Rich That The Car Would Not Run Do To The Plugs Being Fowled Out ( Where Liquid Gas Would Drip Off). I Changed The Intake To One That Had Been Modified And Added 42# Injectors With A 76 Maf And Changed The Fpr Just In Case. I Bled The Fuel Rail Before I Attemted To Start. Anyway, Now It Tries To Idle But Surges Like Crazy And Then Dies. I Had Put A New Crank Sensor And Cam Sensor Before I Did Everything Else. When I Changed The Cam And Crank Sensor I Was Trying To Fix Another Problem But The Car Ran The Same After I Had Changed Them ( But It Ran Good) Could The Crank Sensor Have Gone Bad Or Fallen Out Of Adjustment. Please, Someone Has To Have All The Answers. (lol) Thanks, Joe:)
 
Though you have 42's, sounds like they are delivering more gas then desired.
Not that you want to hear this, but a wideband O2 sensor would help identify the air/fuel ratio.
Your a/f may be so far out of range 'adaptive learning' may not be able to correct it, within a reasonable amount of time.
Then a chip to adjust A/F OR a MAFXtender from www.mafterburner.com
Also, running rich for long periods of time will damage your SC's O2 sensors.
 
I had a similar issue with my car except my plugs weren't fouled with fuel. I have stock injectors though. I ended up changing my TPS and IAC and it stopped surging and idling high. Im 100% positive it was just the TPS but I figured that with 195,000 miles on it and that I had everything apart anyways that I should just change it out. I also cleaned the filaments in the MAFS with a styli brush and some alcohol because I got some gunk build up from the oil on my K&N air filter. Assuming the cam sensor is adjusted properly, I think your problem might just be a magnified version of what my car used to do because of the larger injectors. You could even unplug the MAFS for a few seconds and see if it makes a change for the better but it will only be momentarily. If the attitude doesn't change or gets worse it most likely isn't your MAFS, but if it does change for the better it may indicate a bad MAFS. In my experience if it is a bad MAFS depending on the car, when its unplugged it will run smoother or better but eventually kill the motor at idle. My car runs great but when I pull the plug on the MAFS the attitude stays the same for a few seconds then the engine dies. This isn't a professional opinion or even an educated one, just a hunch.
 
Thanks Guys. Well, When It Is Surging Like So I Try To Hit The Gas To Get The Rpms Up And Keep It Running.but, It Seems To Make No Difference When I Hit The Gas. So Maybe I Will Try The Tps Sensor Next And Then The O2's. It Was Running Rich Before. That Is Why I Decided To Go Ahead And Put The 42's In. Thanks,joe:)
 
Checked It And Double Checked It, The One That Was On The Car When I Bought It Was Bad. But , It Was Acting Different At That Time. I Changed The Tps With One Off Of One Of My Other Sc's And No Real Difference. Not Sure If The Idle Air Would Make It Flood. Does Anyone Know If Sc's Have A Wot Switch That Could Be Bad, Telling The Car That It Is At Wot And Flooding It? Thanks, Joe:)
 
I CHANGED THE COMPUTER WITH ONE FROM MY OTHER 93 AND STILL WON'T RUN. DOES ANYONE KNOW WHAT WOULD BE CAUSING IT TO BACKFIRE LIKE CRAZY? THANKS,JOE:confused::mad::confused:
 
>Added 42# Injectors With A 76 Maf<

If it is not bad plugs, wires, cam sensor, crank sensor, balancer, DIS, MAF (Check codes)
(76 maf may need a different color tube to match injectors)

Backfire, it's running rich! (as you have already written). Fills the exhaust or whatever with gas and bang.:eek:
I have found 42# Injectors do NOT always behave as 42's (..rich A/F). (get a wideband sensor)
Or MAF signal (A/F ratio) is not matched with your injectors (rich A/F). (get a wideband sensor)

Then a EEC chip to adjust A/F, OR a MAFXtender from www.mafterburner.com (costs less than chip)
 
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Other Things you may want to check.

A C&L 76mm MAF needs a purple sample tube for #42 injectors.

You can test the voltage on your TPS ,it should be set around
.98 - volt. you can test volts by using the middle wire on the TPS
eletrical plug-in. this is the wire I test for a 1990 SC.

Randy
 
The Thing Is, That The Car Was Like This Before The 42# Injectors. The 76 Maf Has The Sample Tube For The 42's Or As They Say It Is Calibrated. I Tried To Check The Code By Means Of The Jump Over And Testlight Method That I Found On Here. All I Can Count Is 5 Flashes Pause 2 Flashes Pause 2 Flshes. Then It Has A Long Paues And Repeats The Same. But I Can't Seem To Figure Out What That Code Is If It Is Even A Code. Thanks,joe:)
 
Well, I Was Having A Problem With The Shifter Once And Did The Test With It In Neutral But I Have Done The Test 2 Times Since With The Car In Park And Same Thing. I Just Can't Seem To Figure Out What Would Cause It To Run Rich All Of A Sudden.thanks For All Of The Help Guys. Keep It Coming If You Got More. I Am Still Trying Everything I Can. Thanks,joe:)
 
>I Just Can't Seem To Figure Out What Would Cause It To Run Rich All Of A Sudden<

The car's EEC starts using A/F based on a ' temperature vs A/F table' in open loop. Open loop does NOT use O2 sensors.

Then after a period of time/or ECT, the EEC switches to the base table for A/F in closed loop. Closed loop uses O2 sensors.
(If the required corrections to A/F are to large for the EEC to correct, the EEC defaults.)

MAF is used in both open & closed loop and tells the EEC how much Air is entering the intake,
then EEC determines how much Fuel to add, later in closed loop corrections to A/F are based on O2 feedback.

Also, I assume you have cleared the EEC memory by disconnecting the battery. This clears EEC A/F corrections based on O2 sensors.
(and have healthy O2 sensors & MAF, and NO vacuum leaks)
 
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>I Just Can't Seem To Figure Out What Would Cause It To Run Rich All Of A Sudden<

The car's EEC starts using A/F based on a ' temperature vs A/F table' in open loop. Open loop does NOT use O2 sensors.

Then after a period of time/or ECT, the EEC switches to the base table for A/F in closed loop. Closed loop uses O2 sensors.

MAF is used in both open & closed loop.

{I assume you have cleared the EEC memory (A/F corrections based on O2 sensors) by disconnecting the battery, and have healthy O2 sensors}



I HAVE DICONNECTED THE BATTERY BETWEEN EVERY ELECTRICAL CHANGE(SENSORS AND EEC CHANGE).AS FAR AS THE O2'S, THEY SHOULD BE GOOD. BUT I WAS PLANNING ON CHANGING THEM NEXT, JUST IN CASE. BUT IT SEEMS THAT I AM COMING TO A DEAD END. NOONE AROUND HERE HAS A SCANNER OR ANYTHING TO HOOK UP TO IT AND I REALLY CAN'T AFFORD ONE RIGHT NOW. AS FAR AS A CHIP, I AM CLUELESS AND SKEPTICAL ON PRE BURNT CHIPS. THERE IS A DYNO LOCALLY BUT NOONE AROUND HERE HAS THE FAINTEST IDEA ABOUT SC'S AND HOW TO TUNE AND AT THE MOMENT I HAVEN'T HAD ANY EXPERIANCE IN IT MYSELF. NOT SURE WHERE TO GO WITH THIS REALLY. THANKS,JOE
 
Well, if you don't want to get a chip, then the cheapest way to go is a MAFXtender from www.mafterburner.com for $100.
One would adjust the MAFXtender until you get stoich at idle, using method below.

Then without a wideband O2 sensor you could monitor A/F at idle with an electrical tap to your narrowband O2 sensors
whose voltage would switch around 0.5 V, where stoich is A/F= 14.7.
If the voltage is predominately above .5v it is rich or if O2 voltage is mostly below .5v A/F is lean
(Also, running rich for long periods of time will damage your SC's O2 sensors.
 

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:)
Well, if you don't want to get a chip, then the cheapest way to go is a MAFXtender from www.mafterburner.com for $100.
One would adjust the MAFXtender until you get stoich at idle, using method below.

Then without a wideband O2 sensor you could monitor A/F at idle with an electrical tap to your narrowband O2 sensors
whose voltage would switch around 0.5 V, where stoich is A/F= 14.7.
If the voltage is predominately above .5v it is rich or if O2 voltage is mostly below .5v A/F is lean
(Also, running rich for long periods of time will damage your SC's O2 sensors.



I CHECKED THAT SITE OUT, AND THE ONLY THING THAT WORRIES ME ABOUT THAT IS THE STATEMENT AT THE END(Please note that use of the MAFXtender™ requires extensive retuning of your vehicle!!!!!). BUT, MAYBE IT WAS THE STOCK INJECTORS THE FIRST TIME MAKING IT RUN RICH CAUSING THE O2'S TO GO OUT AFTER AND THEY ARE THE PROBLEM NOW. WISHFULL THINKING PROBABLY. AS IT IS NOW(RUNNING RICH) AND LETS SAY THE O2'S ARE THE PROBLEM. HOW SHOULD THE CAR ACT IF I UNPLUG THE O2'S? THANKS,JOE:)
 
>HOW SHOULD THE CAR ACT IF I UNPLUG THE O2'S?<
Provided you clear the EEC memory first, it might be leaner.
(again, could be 42's acting like 50's...rich)
However, on the side of caution I would not go WOT,
until checked out on a dyno, or wideband O2 sensor.
At WOT I have read home gamers using a A/F from 11 to 12.2 / 1.
 
:)

I CHECKED THAT SITE OUT, AND THE ONLY THING THAT WORRIES ME ABOUT THAT IS THE STATEMENT AT THE END(Please note that use of the MAFXtender™ requires extensive retuning of your vehicle!!!!!). ....)

From the website "i.e. altitude, humidity, temperature = density variations"
These parameters affect a N/A car much more, than a supercharged car(with properly operating O2 sensors).
Give them a call and see what they recommend.
 
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