ok guys im in need of some suggestions, this is my idle when i slow down to stop. it only idles like this when the engine is warmed up. i have checked the voltage at my TPS to find .67 and a steady increase as i open throttle plates. i have already replaced IAC with a brand new one. i have gone around looking for vacuum leaks with carb cleaner and found nothing. anything else i can try? it sounds pretty sad when shes idling like this, and i have to shift her to neutral to get her to run better

 

I think it should idle at around 500 to 600 in drive with a V8. Should be on your emissions label under the hood.

 

yes it is supposed to but as you can see in picture i cant even get her to idle at 500 and she sounds like shes ready to stall

 

bump..

 

anybody?

 

Have you adjusted The minimum idle speed ?

 

yes i did, i know your not supposed to do this but i turned it up to bring idle up to normal but when i shut it off and restart it the idle goes to 1200 and i have to turn the stop screw back out. seems like its fighting with IAC to idle the car. but i currently have it set correct. thats when i replaced IAC cause i was told that and only that idles the car

 

As it will ;
regardless of where you physically set the idle with the screw, the computer will always try to achieve the idle RPM programmed in the tune

Why is your TPS volts set so high?

 

thats what it was set at when i bought the car. it was idling like this then as well. when i was looking at it i assumed it was IAC. what is the factory setting for the TPS? would this help the problem?

 

Proper IACV installation procedure ? Timing ?

 

Heat related failure of your injectors? Try ohm testing the injectors when cold and then again hot and see if any go lower than 12 ohms.

 

timing was reset to factory setting 6* BTDC. ill check the injectors and report back

 

Factory specs are: .54 Volts, +/- .075.

https://www.thirdgen.org/forums/post...610-post2.html

 

Sorry to be a pain but did you follow the reset procedure when installing the IACV ".If it sounds like its fighting with the IACV than I would reset it again, just to totally eliminate it from the list. I tried this simple technique first and it worked perfectly.


Reset the IAC valve pintle position by performing the following.

- Depress the accelerator pedal slightly.

- Start the engine and run for 5 seconds.

- Turn the ignition switch to the OFF position for 10 seconds.

- Restart the engine and check for proper idle operation.

 

yes i did set it but not like that. i set it by turning ignition to on, disconnecting the IAC plug, shutting off car, plugging it back in, then starting the car. when i first fired it up it ran great and i said to myself "problem solved" but as she warmed up it came back. i think the new IAC help the problem but didnt fully solve it since it only does it when its warmed up. ill try resetting it like that and see what happens

 

ok i checked the injectors hot and cold both times they were between 16-17 ohms none went below 12. also tried setting IAC like "ronusmc" suggested, and still runs same. i tried resetting TPS to .57 volts but once i hooked in the multimeter i got crazy number like 197.2 and just kept jumping around like crazy so im looking into new TPS and see from there

 

ok i got very sidetracked by a gas leak right under my fuel tank. luckily the previous owner cut a hole in floor to replace fuel pump so now i had a access panel. anyway i noticed some wet rubber hoses on my fuel lines going into pump clamped with hose clamps. i tightened them and fired her back up and she way spraying fuel all over my interior (OMG AWWW MAN) i shut her off and discovered a hose ripped open since they were so deteriorated. i went and got some new rubber fuel line and some new clamps. after i replaced all the rubber hose i fired her back up, the leak was gone but still had a low idle, so i loosened the TPS and turned it up a little more now she idles at about 1000 in park and about 500 in drive. i dont know if this resolved the problem but shes idling better now and seems more smooth. i would be interested to hear some comments or feedback (shrugs shoulders)

 

Minimum idle should be about 500-600, sounds like your tps might need replacing as well that'll cause sporadic idle

 

I hope you used high pressure "fuel injection" hose. Regular fuel hose won't last long at PFI pressure. You really need to double clamp the connections too since this is just hose slipped over cut off steel fuel lines with no barbs to help retain the hose.

 

yes i used high pressure hose but i only used 2 clamps per hose (one on each side) i thought the previous owner just jerry rigged it all up i pulled like 9 clamps off ill add some more clamps thanks for the info. if it is TPS can i safely run the car without damaging it the way it is 1000 in park 500 in drive i know the 500 in drive is ok but the 1000 in park seems a little fast? the girlfriend said no on the TPS right now

 

also i dont know if it helps but i believe im using regular 89 octane gas. should i use different? it is LT1

 

Probably
BUT
The TPS tells the computer how far you have your foot on the pedal ; so if it is set wrong ( like too high ) then the computer will be confused

 

tell when you get it fix because i have the same problem with my . i have change mass , tps , iac, and reset the idle and still nothing . I have not try the injector test how do you test those ?

 

i have a multimeter and set it to ohms, i pulled the connector off each injector and touched my probes to the 2 pins on injector to see if they were under 12 ohms like "ASE doc" described. how i have it now is, minimum idle set by getting car to lowest idle, hooked up multimeter to TPS, turned idle stop screw till volts went up by .1 on TPS, set TPS to .54 and replaced IAC. car still had no change in idle. i put TPS back to .67, and idle got better but still crappy and rough. then i turned it to .70, now car idles at 1000 in park and about 500 in drive and seems smoother. something still must be wrong cause TPS should not be at .70 right?

 

Does your engine light come on when it is cold my does and when it warm up the light goes out and that when it will stall at a red light or stop sign if i don'i keep my foot on the gas pedel to keep the rpm up so it will not stall out and if it below 45 degree it will just idle high and it want stall out even after it warm up to temp.

 

no i almost never see my SES light. only upon start up and once when i was driving to work one day but went out in next key cycle. i probably should have pulled codes but never thought of it now its too late lol, anyway to answer question no i dont have any SES lights cold or hot.

 

your problem could be different then mine did you check your fuel pressure? fuel filter, how are spark plugs? im gonna pull mine out this week as a last ditch effort

 

an LT1?

 

yes i have an LT1 in my Trans Am

 

in a 1987 trans am? got a picture? it is important to know which engine it is or people will tell you to try things that wont work... like setting the IAC...

 

yes here it is. also have build sheet, window sticker, and rpo codes its an LT1

 

no that is a tpi checkout your coolant temp sensor remember it being a bitch to get at on that engine... probably the original and worth testing

this is a LT1

 

thats out of 4th gen right?

 

yes there was no LT1 offered in a 3rd gen LB9... or the otherTPI

so if in fact you have a build sheet and RPO codes that specify LT1 i would hunt down the previous owner... and be creative...

but my guess is the CTS has failed and now the ecm believes it is -200 deg or so dumping a ton of fuel

 

ok i guess i was wrongfully informed. since the previous owner told me it was LT1. i dont have LB9 on my rpo codes i have L98 but anyways thanks for the info good to know. what is CTS? i already replaced the coolant temp sensor

 

CTS = coolant temp sensor.

it is on the front of the intake manifold where the base meets the block on the passanger side and it is closest to the ground of 3 sensors in kind of a triangle

 

ahh i see now the lb9 is the 305 the l98 is the 350 i have the 350

 

mine was in the head on driver side or am i thinking of the sender?

 

playing devils advocate here but "how do you know?" it is fairly common in the 3rd gen world to call a 305, a 350 to sell it.

not that it really matters for diagnostic purposes here but if you try to resell it and the buyer finds that it is infact not a 350 he might become angry

that is the sender for the gauge...

ecm is in the intake

 

the one with the circle...

 

honestly i dont even care what i have i know its a v8 but i will find out for posterity. wouldn't surprise me if PO lied, im finding out alot of stuff. i dont really plan on selling the car either. and i found the other sensor, it looks like a PITA to get to

 

how would a bad CTS cause low idles?

 

is the car smoking at all? exhaust smell different? rich? poor gas milage?

 

yes to all those pretty much

 

ah those are important

 

how?

 

when you turn the key to the on position without starting the car does your SES light turn on?

 

Post # 34 above
The CTS is the almost most important sensor in the engine.

If it is telling the computer the wrong engine temp ( usually too low when the CTS goes bad ) then the computer will be supplying the wrong amount of fuel to the engine ,
generally too rich so exh smoke , fuel smell , bad gas mileage ............

Replace the CTS , a $14 part

 

damn man stroll right on in answering questions like that... he needed time to twist in the wind before being spoon fed

after with holding info like smoking bad gas milage and smelly exhaust...

 

yes it does, but goes off when i start the car. i figured that was normal, cause its digital dash and oil pressure gauge pointer is reading 0 and is red its followed by 2 beeps. since motor is off it wont register oil