Cars having problems

BlntdEyez

BlntdEyez

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Ok well when I was leaving the track last night I got on the highway and ran it up to about 70 and let off the gas and the car stumbled. Everytime I let off the car like quits for a second. also when i let off the gas my tach will go down to about 1,000 rpm and then starts to fluctuate between 800 and 1,200 rpms. Any ideas? other than that car runs great.
 
If I stop at a stop sign it idles fine. it just stumbles when I let off the gas and the tach jumps.
 
Now the tach is starting to jump when im idling not much but a little. Maybe from 800 to 900 rpm.
 
From http://www.fordfuelinjection.com/?p=64:

Deceleration
The vehicle is moving and you lift your foot off the accelerator. EEC sense’s the TPS go to closed and VSS signal slow. This presents a few problems that are easily overcome. First we have to prevent stalling; this is why the IAB has been open, just in case the throttle snaps shut. After throttle closure the Throttle Air Bypass closes slowly closes. Then it controls idle as we reach a stop and move back into warm idle strategy. We are always thinking of emissions and burning fuel as we decelerate is a big waste. EEC turns the injectors completely off when RPM is over 1500 and the engine is over 140°F. Injectors begin operating under 1500RPM or if you hit the skinny pedal. If you don’t run a VSS you can run the risk of stalling when slowing down from over 1500RPM. EGR is turned off but the canister purge is opened to burn off fuel vapors from the gas tank. Timing can be advanced for two reasons; first with low airflow signals there is little chance of detonation. Secondly, advanced timing helps push back on the pistons, this helps create that engine brake effect.
Click to expand...

I highlighted with BOLD the symptomatic problem areas.
IAB = IACV(Throttle Air Bypass)(Idle Air Control Valve)
VSS = Vehicle Speed Sensor
TPS = Throttle Position Sensor
 
Well I went out to change the spark plugs. So I decided i'd disconnect the battery to let it relearn itself. After i got done I hooked it all back up went for a spin and it hasnt done it yet.
 
So..... does anyone have any special way to take off the IAC? Cause I tried today and gave up after about 2 hours. Gonna try again tommorow.
 
take trans out... lol! thats what I did... well actually the trans went and I was like better change that stuff now while i can still get to it. :) I know its a bitch just gotta keep on pluggin away at it use an assortment of tools to see what works best.
 
yeah i think it will help some gives you more room. which is crucial I did the egr and egr tube from up top last year so im sure you can do the iac.
 
Alright thanks alot man! I'm gonna give it a try again tommorow. I had to give up a little early today cause i had to go somewhere. But Im going to give it hell tommorow :lol:
 
IAC Selftest:

Testing: At hot idle, remove the connector. Does the engine idle drop? If yes it is working. If no, there is a fault with its operation.

I tried this and I'm not sure if my idle dropped or not. But I know when I disconnected it it started idling ruff. So I shut off the motor with it still disconnected and tried to restart it. Well... it would crank over act like it started and die. But when i reconnected it it would start and idle fine. So do you guys think its the IAC or VSS or something else?
 
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