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Topic: 5spd swap and high idle. (Read 1782 times) previous topic - next topic

5spd swap and high idle.

I swapped out the blown AOD in my cat a while back for a T5.  It still has the stock AOD computer.

It had a hard start and rough idle before the swap but I have since fixed the IAC and cleaned the throttle body.

Now, If i disconnect the IAC i can set the base idle and timing.  Ive got a pretty good probably 750 to 800 idle with the IAC disconnected (its tired so its not perfect).  When i plug back in the IAC it immediately bumps the idle up to 1k.

Ive got the stupid star wars dash so its hard to tell exactly what the idle speed is (between 1k and 1.2k).

Is there a line somewhere that tells the computer that its "In Gear"? Or should I run down another vac leak.  Ive replaced all the vac lines and everything except the MAP is plugged off.

And yes, the AC is off.
-Thanks

5spd swap and high idle.

Reply #1 –
Too high TPS voltage will cause the high idle...

5spd swap and high idle.

Reply #2 –
I had set the TPS at one point, I even swapped one in from my mustang engine.  Didn't seem to make any difference. 

I only had my buttstuffog meter when I set it.  Ill get my Digital from work and try setting it again.

5spd swap and high idle.

Reply #3 –
Try to back off the TB screw.See if the comp.,cares?
Old Grey Cat to this.88 Cat, 5.0 HO, CW mounts, mass air, CI custom cam, afr165's, Tmoss worked cobra intake, BBK shorty's,off road h pipe, magnaflow ex. T-5,spec stage 2 clutch, 8.8 373 TC trac loc, che ajustables with bullits on the rear. 11" brakes up front. +

5spd swap and high idle.

Reply #4 –
I had a similiar problem in my old XR-7...but I bought it that way...it has the SD 5-speed computer and an HO and it usually idled around 1200rpm....I beat my freakin' head into the wall trying to find it...the more I looked, the more I realized the previous owner hacked the hell out of the engine harness...never found the issue and ended up gutting the car....

Hopefully your luck is better than mine...lol.

-Don
Project 3G: Grandpa Grocery Getter-'85 Crown Vic LTD 2-door, 351W with heavily ported/polished GT40 heads, heavily ported/polished Typhoon Power Plus upper & lower intake, Comp Cams 265DEH retarded 1*, FAST EZ-EFI, HD T5, 8.8" 3.73 trac lock with extra clutches, 3G alt. swap, '99 CVPI front brakes, '09 CVPI rear disc brakes, '00 CVPI booster&m/c + wilwood adj prop valve.

Parted & Gone-'88 T-bird Sport, 351W swap, ported GT40 heads

5spd swap and high idle.

Reply #5 –
check for a vacuum line....

Whats your tps voltage set at? hows a stock 5.0 s.o. with a stick?
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

5spd swap and high idle.

Reply #6 –
Quote from: Haystack;216079
hows a stock 5.0 s.o. with a stick?


:D fun!

5spd swap and high idle.

Reply #7 –
The 5.0 SO with the T5 and AOD rear gears is fun.  You would think its got a serious engine by the way it spins that one rear wheel.

I have a 5.0 HO that I plan to tear apart but I am working getting the car painted.  So the SO has to move it around for the time being.  I like troubleshooting the engine more than body work.

Ive run down every vac line i can find.  If I put my hand across the valve body, when it stalls i can hear air being sucked in underneath the Upper intake on the driver side.  I have re-torqued the Upper intake and sprayed brake cleaner at the Upper/Lower gasket area, no change in idle.

I have a new set of upper end gaskets and I think I am going to pull  the upper and install the one from my HO.  I am wondering if one of the vac lines that thread into the intake are leaking.

When I am in there I plan on re-sealing the air temp sensor.  I am starting to think its an injector O-Ring.

5spd swap and high idle.

Reply #8 –
Broken vacuum lines under the upper were what caused a lot of my high idle problems. After I fixed those the idle started acting somewhat normal.
Matt
1984 Thunderbird - 89 302 HO, GT40 heads w/ Trick Flow springs, E303 cam, Edelbrock Performer 289 intake and 600 cfm 4bbl, Mustang headers, Jegs o/r H pipe, Dynomax lers, Mustang AOD and shifter, Mustang 8.8 w/ 3.73s, 3G alternator, Mustang front and rear sway bars, KYB SN-95 front struts and shocks, and 11" front brakes.

1988 Mustang GT - GT40 heads, Explorer intake, 70mm throttle body, 70mm MAF, Crane 1.7 rrs, E303 cam, Kirban Kwik shifter w/ Pro 5.0 deluxe handle, aluminum clutch quadrant and firewall adjuster, o/r h pipe, Dynomax lers, 3G alternator, aluminum radiator, and 3.27 gears.
 
1986 Cougar 5.0, 1989 Mark VII LSC 5 speed, 1980 Mercury Zephyr 4 door (sold)

5spd swap and high idle.

Reply #9 –
All my rubber lines are brand new.

5spd swap and high idle.

Reply #10 –
TurboCoupe50's suggestion to recheck the TPS is valid.  If you change the idle screw, it changes the the position of the throttle plate, requiring a readjustment to the TPS.  It's the first place to start...

5spd swap and high idle.

Reply #11 –
Thats a good point.  I will try that.  It likes to run with the FPR unplugged and the vac line capped. (Ive put a gauge on it and the pressure at idle is good) This to me says its running a bit lean and likes the extra fuel.  If I try to set the idle lower than say 750 it stumbles a little bit, rolls back n forth.  Ive double checked gaps, cap, and wires. IAC is good.

Once the car gets out of the low end funk it runs like raped ape.  I keep my SC tuned like a top.  It idles low and slow and buttery smooth.  I just wish I could get this to do the same.

Ill try resetting the TPS after I adjust the idle again.

5spd swap and high idle.

Reply #12 –
After setting the TPS, if the problem persists, eliminating sources of possible vacuum leaks would be next.  Start by pluging the big line to the big vacuum "T".  I have seen these develop a crack and leak.  On occation a Power Brake booster will leak, but you would experience a funky brake pedal.

Hope you have good luck tracking down.
 

5spd swap and high idle.

Reply #13 –
I set the TPS and it still idles high and or surges. When I got the car, it was badly neglected.  I didn't have an air filter or anything. Maybe ill put a video up later.

If the IAC is disconnected, should there be any vacuum draw through the IAC hole?  If I plug that with my finger it idles better.  If I take the IAC off i cant blow through it, so engine vac must be pulling it open. Maybe the return spring is worn and I should just buy a new one.

When plugged in the IAC goes up and down and can keep the car idling.  Ill have to try pulling codes again and see if it complains about anything new.  It didn't last time.  I am starting to wonder if its got low compression on one cylinder, I don't have a compression test set however.