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Topic: Idle pulsation -- new issue (Read 2781 times) previous topic - next topic

Idle pulsation -- new issue

I tossed my HO TB and installed a 97 explorer TB after making the little mods.  Here's my scenario:

I start the engine cold,  everything works perfectly -- IAC does it's job to warm up and leaves me with perfect idle.  I take car out for spin for about 10 miles to get it up to temp and when I'm coasting down a hill I notice that it is surging a little with a frequency of about 2 small surges per sec.  When I get home, put the car in park and the surging continues 2 per sec continuously.  I kill the engine, start it right back up and the idle is absolutely stable and perfect.  Any idea what is going on?  Have I screwed up my ECU?
This doesn't sound like a hunting idle,  it's quickly pulsing continuously. 

Thanks in advance
'88 Bird 5.0, TW 170s, HO cam, Scorpion rockers, Explorer intake 70mm TB/EGR, MAF conversion, 24# injectors, 8.8 3.73 disc rear end swap, console swap, leather seats, 11" front discs, 15-1 rack, TC springs all around, x-pipe, BBK headers,  welded sub-frame, unlocked digital speedo.

Idle pulsation -- new issue

Reply #1 –
What codes pop up?
Quote from: jcassity
I honestly dont think you could exceed the cost of a new car buy installing new *stock* parts everywhere in your coug our tbird. Its just plain impossible. You could revamp the entire drivetrain/engine/suspenstion and still come out ahead.
Hooligans! 
1988 Crown Vic wagon. 120K California car. Wifes grocery getter. (junked)
1987 Ford Thunderbird LX. 5.0. s.o., sn-95 t-5 and an f-150 clutch. Driven daily and going strong.
1986 cougar.
lilsammywasapunkrocker@yahoo.com

Idle pulsation -- new issue

Reply #2 –
Quote from: Haystack;430878
What codes pop up?


Dumb question:  are codes only presented when the service light is on?  The service light is not on.
'88 Bird 5.0, TW 170s, HO cam, Scorpion rockers, Explorer intake 70mm TB/EGR, MAF conversion, 24# injectors, 8.8 3.73 disc rear end swap, console swap, leather seats, 11" front discs, 15-1 rack, TC springs all around, x-pipe, BBK headers,  welded sub-frame, unlocked digital speedo.

Idle pulsation -- new issue

Reply #3 –
Quote from: marianadeeps;430902
Dumb question:  are codes only presented when the service light is on?  The service light is not on.

Yes codes can be present without the "Check Engine" light being illuminated. My Thunderbird always throws KOER codes of 44 and 94 but the "Check Engine" light is never illuminated (it throws these codes because I removed the Thermactor system).
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

Idle pulsation -- new issue

Reply #4 –
The fact it only does it warmed up means the computer is using a sensor after it goes into open loop. that means more likely then not a sensor is sort of off and might be making it run funny. run codes and see what pops up.
Quote from: jcassity
I honestly dont think you could exceed the cost of a new car buy installing new *stock* parts everywhere in your coug our tbird. Its just plain impossible. You could revamp the entire drivetrain/engine/suspenstion and still come out ahead.
Hooligans! 
1988 Crown Vic wagon. 120K California car. Wifes grocery getter. (junked)
1987 Ford Thunderbird LX. 5.0. s.o., sn-95 t-5 and an f-150 clutch. Driven daily and going strong.
1986 cougar.
lilsammywasapunkrocker@yahoo.com

Idle pulsation -- new issue

Reply #5 –
Ok.  I had some time so I pulled the codes. 

The Key on Engine off,  I get 41.

Engine on,  I get 4  12    94  43   

looking at these definitions  41 is oxygen sensor circuit indicates system always lean 

4 ?

12 = idle control fault  -- not too descriptive.
94 =  torque converter clutch solenoid circuit failure  -- what the heck is this?  Sounds serious.
43 =  oxygen sensor out of self-test range
'88 Bird 5.0, TW 170s, HO cam, Scorpion rockers, Explorer intake 70mm TB/EGR, MAF conversion, 24# injectors, 8.8 3.73 disc rear end swap, console swap, leather seats, 11" front discs, 15-1 rack, TC springs all around, x-pipe, BBK headers,  welded sub-frame, unlocked digital speedo.

Idle pulsation -- new issue

Reply #6 –
My guess is o2 sensor. if you got a lot if free time you can switch sides to see if it follows.
Quote from: jcassity
I honestly dont think you could exceed the cost of a new car buy installing new *stock* parts everywhere in your coug our tbird. Its just plain impossible. You could revamp the entire drivetrain/engine/suspenstion and still come out ahead.
Hooligans! 
1988 Crown Vic wagon. 120K California car. Wifes grocery getter. (junked)
1987 Ford Thunderbird LX. 5.0. s.o., sn-95 t-5 and an f-150 clutch. Driven daily and going strong.
1986 cougar.
lilsammywasapunkrocker@yahoo.com

Idle pulsation -- new issue

Reply #7 –
KOEO
Memory code 41. O2 sensor not switching, lean indication.  Could mean you have no voltage from the sensor or a break in the wire from the sensor to the ECU.

KOER
code 4. ECU is for an 8 cylinder engine.
code 12 Idle too fast.
code 94 Smog pump thermactor system not functioning.
code 43 Right O2 sensor not reading, check for switching.  ECU pin 29.

Idle pulsation -- new issue

Reply #8 –
Make sure the wires to the O2's are not reversed.
Right side should be the Dark Green/Pink wire.
Left side Dark Blue/Light Green.

Idle pulsation -- new issue

Reply #9 –
Did you set the voltage on the TPS when you changed the sensor for the new TB? Also, did you re-use your HO idle air or the exploder idle air? The explorer's may function on a different voltage range than the HO IAC motor.

Idle pulsation -- new issue

Reply #10 –
Quote from: tbolt64;431116
Did you set the voltage on the TPS when you changed the sensor for the new TB? Also, did you re-use your HO idle air or the exploder idle air? The explorer's may function on a different voltage range than the HO IAC motor.


No.  I just adapted the Explorer TPS to connect to my harness connector and plugged it in.  Good idea on the IAC -- I didn't know that.  , I'm going to have to buy another IAC?
'88 Bird 5.0, TW 170s, HO cam, Scorpion rockers, Explorer intake 70mm TB/EGR, MAF conversion, 24# injectors, 8.8 3.73 disc rear end swap, console swap, leather seats, 11" front discs, 15-1 rack, TC springs all around, x-pipe, BBK headers,  welded sub-frame, unlocked digital speedo.

Idle pulsation -- new issue

Reply #11 –
If you used the h.o. intake egr spacer, your old one should bolt on.
Quote from: jcassity
I honestly dont think you could exceed the cost of a new car buy installing new *stock* parts everywhere in your coug our tbird. Its just plain impossible. You could revamp the entire drivetrain/engine/suspenstion and still come out ahead.
Hooligans! 
1988 Crown Vic wagon. 120K California car. Wifes grocery getter. (junked)
1987 Ford Thunderbird LX. 5.0. s.o., sn-95 t-5 and an f-150 clutch. Driven daily and going strong.
1986 cougar.
lilsammywasapunkrocker@yahoo.com

Idle pulsation -- new issue

Reply #12 –
Quote from: Haystack;431153
If you used the h.o. intake egr spacer, your old one should bolt on.


The IAC bolts on the TB but I used the original IAC from my SO TB.  Why would that be an issue -- it receiving the same voltage it always did even though the TB is from the Explorer.  I'm going to change out my SO IAC with the HO IAC and see if that make any difference. 

Thanks everyone for the great input.
'88 Bird 5.0, TW 170s, HO cam, Scorpion rockers, Explorer intake 70mm TB/EGR, MAF conversion, 24# injectors, 8.8 3.73 disc rear end swap, console swap, leather seats, 11" front discs, 15-1 rack, TC springs all around, x-pipe, BBK headers,  welded sub-frame, unlocked digital speedo.

Idle pulsation -- new issue

Reply #13 –
Check for vac leaks. Either s.o. or h.o. iac should work fine. see why your idle is too high. try turning down the idle.screw, if you can't slow it down, iac is bad or you have vac leakswhere you changed intakes, id lean to vac leaks.
Quote from: jcassity
I honestly dont think you could exceed the cost of a new car buy installing new *stock* parts everywhere in your coug our tbird. Its just plain impossible. You could revamp the entire drivetrain/engine/suspenstion and still come out ahead.
Hooligans! 
1988 Crown Vic wagon. 120K California car. Wifes grocery getter. (junked)
1987 Ford Thunderbird LX. 5.0. s.o., sn-95 t-5 and an f-150 clutch. Driven daily and going strong.
1986 cougar.
lilsammywasapunkrocker@yahoo.com

Idle pulsation -- new issue

Reply #14 –
I know that the trucks use a different IAC than do the cars, even though the plug-ins are the same. I found this out trying to use a fox body IAC off a 70mm TB on my F250 when I put the car-style typhoon fuel injection intake on my truck. I had a problem with the truck idling.

ALSO with the TPS you are supposed to set the initial voltage to .98 volts, according to legend, but so long as the ECM reads a change of something like 2.7 volts from starting point to Wide Open Throttle the ECM will be happy. You just need to make sure you get that much change from closed throttle to WOT.