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the reason i have found that cleaning the ten pin connectors works well is because the vehicle reference and the signal return both run through these connectors and often times they will short in the connectors. The vehicle reference in the 5 colt wire that the comp sends to sensors including tps which is one code i got when i was having crappy ide found out there was not voltage between the comp and it. it also runs to the map and egr as well as act, and the coolant temp sensor. the signal return iss the ground back to the computer for the vehicle reference.l
 

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I have a problem. This started about a month ago.

After driving to work (about 30 minutes), my idle will be about 1500 rpm. It sure makes driving suck, with the engine pulling all the time, it messes up shifting and is annoying when at a stoplight.

If I turn the car off, then back on, the idle will be normal (about 1000).

Anyone know what I should check?

Totally stock '90 GT.
 

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IJCOBRA said:
If I turn the car off, then back on, the idle will be normal (about 1000). Anyone know what I should check?.
Pull the IAB off and clean it well. That might help. Otherwise "do the ten pins" as found elsewhere in this HUGE and OLD thread!!
 

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Wangstang, your the freak'en man :joy: .....I've been chasing the problem for atleast a year...What a great day in my life......Thanks again
 

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Bringing this back from the dead.

I had the hanging rpm's inbetween shifts even when I was driving normal. The car would continue to drive itself for a few seconds after letting off the gas, and 1500rpm idle. Turns out it was my throttle body. I changed the IAC, TPS, ACT sensor, got a new intake manifold (not cause of the idle), and the RPMs would still hang. Put my stock throttle body on and it idles normal again. Stupid BBK/Edelbrock.
 

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Mine does it sometimes, and my TB/intake is stock.

I plan on doing the "10-pin" when I swap to a Cobra intake (it's on it's way, it's chromed, and I can't wait!).

Also got a Pro Products chrome 70mm TB. Hopefully all that work fixes the problem, and blings as well!
 

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TTT
Thanks Wes
 

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I cleaned my intake-air bypass (IAB) solenoid with carb cleaner and it fixed my problem.

I also tried to adjust to TPS voltage. Best I could get was 1.020 volts or so. It was initially much higher.

Seems to have fixed my surging idle upon start-up and high-idle after freeway driving.
 

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Discussion Starter #190
Hey, it's still here, if you have something to contribute please post.
 

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actualy the voltage thing is a myth..

the eeec IV and higher processors read the tps voltage every time you turn your key on and store that value in memory as closed position.

the only thing that 1 volt does is if you are OVER 1 volt at idle the car wont use the idle fuel maps and timing maps.

but being below it does not effect performance at all at wide open or part throttle nor will it noticably effect throttle response.
 

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Discussion Starter #192
twinturbosaleen said:
actualy the voltage thing is a myth..

the eeec IV and higher processors read the tps voltage every time you turn your key on and store that value in memory as closed position.

the only thing that 1 volt does is if you are OVER 1 volt at idle the car wont use the idle fuel maps and timing maps.

but being below it does not effect performance at all at wide open or part throttle nor will it noticably effect throttle response.
buzzzzzzztttt. wrong answer in some ways. the 94-95 EEC does indeed store a new voltage reading at start up. The 87-93 EEC's do not. Even with the 94-95 units the voltage reading still needs to be in a certian range for reference to it's preprogramed tables.

Wes
 

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twinturbosaleen said:
actualy the voltage thing is a myth..

the eeec IV and higher processors read the tps voltage every time you turn your key on and store that value in memory as closed position.

the only thing that 1 volt does is if you are OVER 1 volt at idle the car wont use the idle fuel maps and timing maps.

but being below it does not effect performance at all at wide open or part throttle nor will it noticably effect throttle response.
incorrect, that is an SN-95 thing, not a general EEC-IV thing that applies to the foxes

Eric
 

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This is it!!! Those stupid 10-pin connectors have been apparently causing my rolling idle issues. Spread the pins, re-assembled then also adjusted the TPS voltage. Not only do I no longer have the idle issues, but the throttle response is amazing now. Thanks everyone for your feedback.
 

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still having idle problem, PLEASE HELP

Hi guys, thanks a ton for all the info in this thread...but after I checked the TPS voltage (.98v w/key on, same w/engine running) *and* disconnected the black and white EFI connectors, crimped female side a bit and re-greased, I am still having this idle issue.

I already searched the forums for a long time, couldn't find anything else helpful so please excuse me if the answer is on here somewhere because I must have missed it. So anyways, here we go:

Problem is only when car is rolling. Basically it wants to idle at 1600rpm anytime I'm moving, on start-up idle is at 12-1300, then drops to 800-900 as it should, no problems there. But once I'm rolling, I can push in the clutch and the engine goes to 1600rpm no matter how fast engine was turning before, and can have it in/out of gear and it still wants to idle too fast. The weirdest part is I can have it out of gear, clutch out, just coasting, idle at 1600rpm, then come to a stop for a stop sign/light/etc, and juuuust as I'm coming to a stop the idle drops back to where it's supposed to be, 8-900. What the heck?

It really really sucks trying to drive/cruise around slow, any ideas people? Any and all help would be great. I just bought this car back as it was my very first Mustang *and* one of the nicest ones I've seen, and I REALLY REALLY REALLY need to fix this idle prob! Thanks for any and all help...






91 LX 5.0, originally auto, converted to 5-speed, done so well one can't tell it didn't come stock that way. I'm assuming it's still the orig computer. TFS TW heads, E303 cam, cats have been hollowed out (so I was told), and no air pump. Underdrive pulleys. Intake is all stock except for 1/2" spacer under stock intake. That's all the mods that I think could have possibly anything to do with this issue.

UPDATE: I just got done cleaning my IAB, it was filthy, took about 30 minutes and a dozen cotton swab thingies. Went for drive, thought it helped at first but nope, still doing same thing. I can be cruising at 30 MPH in 4th gear, about 1200 rpms, I'll clutch/put shifter in neutral and rpms will jump to 1600. Then come to stop at light, and rpms will drop to 1100-1200 for a couple seconds, then eventually fall to 900 or so where it should be. ARGH!!! Please advise ASAP, this is driving me insane!!!
 

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cleaned IAB, didn't fix prob

Bump, please see my update above...
 

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TTT...anyone?? Not sure where else to go or what else to try, it really stinks trying to drive and having my newly-bought-back car trying to run at 1600 rpm when I'm rolling whether it's in gear or not...?
 

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VSS not hooked up? Where is it on my car?

First, thanks for the response. 2nd, I bought the car from the original owner who performed the conversion...and though he did the mechanical parts ok, he didn't finish it off correctly which I had to do. I ended up having to do the research to figure out why it would start w/out pushing in the clutch (had to plug in 2 different plugs under the dash) and then someone else here on the Corral was awesome in helping me locate a factory T-5 wiring harness which I had to install to get the reverse lights to work.

So, I would not be surprised if the Vehicle Speed Sensor was not hooked up, where would I find it?

EDIT: Ok, after doing some searching regarding the VSS I'm sure that I did hook it up when I replaced the AOD wiring harness with the correct factory 5-speed harness. Plus my cruise works just fine...so I'm back to my last question now, which is this:

SO IT'S JUST *SUPPOSED* TO WORK LIKE THIS?
The car is *supposed* to bump the idle way up to 1600rpms when taking it out of gear while moving or by pushing in the clutch? After reading about the VSS just now, someone said something about the idle will fall back down under 6mph, which seems just about right for my situation...but why then does it seem like my car tries to pull 1600rpm even when in gear and cruising? Have I finally made that long awaited turn around the bend (gone insane) or is this a seperate issue?
 

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Discussion Starter #200
zekenator said:
TTT...anyone?? Not sure where else to go or what else to try, it really stinks trying to drive and having my newly-bought-back car trying to run at 1600 rpm when I'm rolling whether it's in gear or not...?
The EEC is supose to idle the engine up while in motion but at closed throttle, the idea being that you don't stall out as easily if you all of a sudden put it in gear or punch it. That said it usually keeps the idle while in motion around 1200-1400 RPMs from what I recall. SO...

You mentioned that you have an E-cam and that the car was an auto converted to manual.

Take a look at the EEC and see if it's an auto version or a manual version. If it's an auto EEC, I suspect that the idle up is a result of EEC opening up the IAB more than it would if it were a Manual as an auto car, with the throtle closed but still in gear is actually still under load so the values and ammount of IAB opening needed for the auto setup would be a little more than a manual setup where the engine is under no load with the throtle closed and the car is out of gear. Good example of that load is the drop in RPM's when a car is put from park into drive and then idles back up to where it was at. Yes, I am aware that the tq. converter does not engage completely at idle speed even in the stock format but the car will roll forward with out any throtle manipulation if it's in gear on level ground so it's loading the engine.

On the E-cam, the loads and vac. signals it sends back to the EEC via the BAP/MAP and MAF are different enough at idle compared to the stock EEC that it has a tendency to bump idle RPM up a tad, many times resluting in an idle speed of almost 1000 RPMs. The signals that the E cam sends at just off of idle are different as well and could be makeing the EEC get readings that make the EEC think it has the engine at 1200RPM's based on it's stored tables for the stock cam when it is really got the engine doing a little more.

Two other things that stick out to me as well that may be an issue is the VSS as was mentioned before, but I don't think that's it. The other being where you are getting your 1600RPM value from. If it's off the stock gauge it's probably wrong, the stock tachs are known to have issues with keeping the exact RPM displayed and can often times be off by 400 RPM.
 
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