HI ALL,I HAVE A 03 TACO 3.4L DBL CAB,103XXX MILES....

I BOUGHT THIS ABOUT 1 1/2 MTHS AGO IT HAD A BLOWN HEAD GASKET...ALL HAS BEEN TAKEN CARE OF HEAD GASKET KIT,CHANGED THE W. PUMP,T.BELT...ANYWAY IT DRIVES FINE NOW...BUT NO MATTER WHAT I DO IT STILL HAS A LOW IDLE..FIRST OF ALL..ON THE TACH, I CAN'T TELL BY THE MARKS WHAT RPMS ARE WHAT BETWEEN 0-1000,(FSM AND ONLINE SEARCHING GIVES NO HELP) BY THE POSITION OF THE MARKS---THE FIRST MARK I ASSUME IS AROUND 200-300, THE SECOND CAN'T BE 500 CAUSE IT SETS JUS BELOW THE HALF WAY POINT..SO I ASSUME ITS AROUND 400..THE LAST MARK LOOKS LIKE AROUND 700-750 (IDLE IS SUPPOSE TO BE AT 750 -+50)..GOING WITH THESES ASSUMEING MARKS THE IDLE IS AT 650 (IN PARK) AND 450 (IN DRIVE),DRIVING IS FINE,GOOD PICKUP..ALL IS FINE....NOW HERES WHAT IF DONE;;;;;;

WITH MULTIMETER ON OHMS...OXYGEN,A/F,TPS,MAF ARE ALL IN FSM SPECS...THE MAF HAD A LITTLE ROAD DIRT ACCUMULATED ON IT AND THE A/F SENSOR,THE OHMS @68 DEGREES WAS JUS A BIT HIGH..BUT AFTER CLEANING ALL (EXCEPT TPS) WITH CRC QD ELECTRRONIC CLEANER THE A/F WAS IN SPEC NOW..AFTER DISCONNECTING (10 MIN OR MORE) THE NEG CABLE..THE TRUCK RAN PERFECT..750 RPMS (PARK), 650 RPMS (DRIVE)..I DID THOUGH ADJUST THE TPS A LITTLE,BUT THEN AFTER SHUTTING IT OF FOR A COUPLE HOURS..STARTED IT BACK UP AND IT WOULD BARELY IDLE,SO I DISCONNECTED THE NEG. AGAIN AND RECONNECTED IT ,,NOW ITS BACK TO THE ORIGINAL....650 (PARK) , 450 (DRIVE)...SO WITH THIS I'VE KINDA RULED OUT A VACUMN LEAK,SPARK PLUGS, PLUG WIRES...STRANGE...!!!!!..WELL..THE CAPTION SAYS IT ALL...ANYBODY?????

THANKS

 

You can make minor adjustments to the throttle cable where it attaches to the throttle body (unless yours is throttle-by-wire - not sure if the '03s have it or not and if adjustments can be made). This might give you and extra 100 RPM. Does the truck shake like it's on the verge of stalling? Maybe it's fine and the increments on the tach are not what you think.

They would've had to remove the throttle cable from the throttle body during the HG replacement so that's why I'm thinking maybe they put it back on just a little too loose??

 

thanks for replying, you know i think you're right, lemme take a look at the throttle cable when i get home..actually i changed the head gasket,but when i took off the throttle cable i jus took off the bracket and then pulled back on the throttle to take off the cable..i recall seeing those 2 adjusting nuts on the cable,maybe the prior owner adjusted there, no , it doesnt stall,when its at the idle in drive it just shakes a little..enough that u can tell the idle needs upped a little,i usually try to start with the easy checks first..like in this case,checking the throttle,but i guess i got a head of the game a little, thats why i jumped that far checking things ,because of my experience with my 93 excab 3.0 3vze and it had burnt ex. valves when i got it ..i had a problem with the idle also and had to replace the tps and oxygen sensor. that throttle body had an adjusting screw on the throttle lever and a idle speed adjusting screw..ok i'll stop..to much info (hahaha), oh, still try to find out what rpm those marks represent...thanks

 

On my tach there's 10 lines between 0 and 1. They're not spaced all equally from eachother, but that's just because of the design of the tach itself. Each line still represents 100 RPM though. I thought the tacos were the same style just white background.

 

Did you check out the readings on the throttle control motor while you were in there? I've seen a lot of dirt and deposits accumulate under that top plate so it might be worth cleaning too.

 

Thanks okie81..yea i did...i took that top plate off...it had some grime in there , checked ohms on it...its ok..in specs and also i did that motor operational test in the fsm...its all good..brian2sun...my 93's tach doesnt have the 100rpm increments but it does have increments that read around 300,500 and 800...strange on different model years having different readings

 

toyinhawaii,

Did you replace/clean the TPS, DP, TB or ever find the culprit? I noticed a similar issue with my truck on the way to work. RPM's always stuck around 800RPM @ Idle and today after she warmed up my tach indicates 300RPM @ Idle. The engine sounds like it is actually idling this slow and ECM is trying to compensate. Started it on lunch and its back at 800(Idle), took it for a spin and back to 300(Idle) it went. Not sure what has changed but will start by OHM at the TPS when I get time. Anyone have a suggestion?

 

I don't know if this is specific to your vehicle, but I have a 2001 SR5 that was experiencing the same problems. I cleaned the throttle body with Throttle body cleaner and the truck idles much better now. It now idles at about 650. I am going to clean it again and see if it improves any more.

 

jreask,

Disassembled the throttle body and throttle position sensor cleaning the TB thoroughly with carb cleaner and the TPS delicately with CRC electronics cleaner. Let things cure for about 30 minutes before wiping any residual residue and lightly lubricated some of the moving components of the throttle body and started reassembly.

Checked resistance at the TPS which reads correctly according to the FSM. This morning it drove 18 miles through city and hwy and the low idle issue did not present itself.

Let you know if it comes back.

Thanks,

 

I had a small hole in my tubing from the mass air flow sensor to the throdle body it made my 3.4 rattle a little when car was at idle