SC making boost in nuetral...car accelerating on it's own new tranny slipping!!!

superdadsc

Registered User
My car has demon's and needs help in a big way!!! I got the tranny from Alan at Dirty Dog put in and was so excited to drive a SC that would run properly. Not a chance as there are to many issues and I don't know what to think or how to fix it. I swapped the blower, plenum and DIC onto the 94 auto that just got the new tranny installed. When we went to start the car it was running really rough and figured it was a vacuum leak. The car's cat on the driver side started glowing red hot. Shut it down let it cool and started again. Thinking it had bad gas I put some more in and the cat wasn't hot anymore, red hot that is. Took the car for a drive in the neighborhood and it stumbled and drove poorly but if you gave it 1/2 throttle it ran just fine. At this point I figured I had a vacuum leak and called Mike and drove the car down to his house to check it all out.

Driving to Mikes the tranny started slipping in OD. Great not even 30 miles and it's slipping. Plus when you put it in reverse it feels really strange like it is fighting itself. I get it to Mikes and we replaced tightened the egr plate. We found a vacuum hose that was sounding like a fog horn and the car was still stumbling running like crap. Then we noticed that when we gave the car some gas that the car went out of vacuum and into boost 5 to 7 lbs depending upon the amount of gas you gave it. Weird. How does it show boost in neutral.... clogged exhaust? Bad O2's?

We noticed if it started running poorly, after a few minutes that when you shut the car down it would run better for a bit then you would repeat that process and it would continue. So when I had to come home when it would start to loss power, I would be giving the car gas, boost is climbing and the car would have no power. It would stumble, sound like a truck drive like crap then I would throw it in neutral, restart it and I could accelerate again.

Then something really weird happened. The car would accelerate on it's own. It would rev up to 3.5k I would throw it in neutral and it would climb to 5k and I would shut it off. Then start the car again, car was getting gas like I had my foot on the gas but I had it behind the pedal to stop it from accelerating and the pedal was doing nothing. I wasn't moving but the car would rev and then after a few minutes it felt like someone was trying to floor it but the pedal was doing nothing.

The worst part was the tranny on first glance feels like it has very soft shifts and starts slipping on the highway the minute it go to much gas. Luckily on the way home there was a lot of traffic so I was doing 30 to 50mph on the way home.

To sum it up

Cat on driver side got red hot, got a little better but still hot.
Car makes boost in neutral or park
stumbles and will lose all power after being driven for a few minutes, restart and repeat process to get home.
Accelerates on it's own then it acts like it is getting floored
tranny slips

Two nice SC's and they both won't stop causing me trouble. Now I guess I have to switch everything over to drive the 89. Spent 2600 on a tranny that slips but I am hoping that it is somehow related to these issues but I don't know why OD would slip.

Help!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
It is a late model mustang tranny with SC internals so no TV cable. It's electronic.
There are no vacuum leaks but I guess we could have missed one.

How about the car accelerating on it's own.......cruise control malfunction?

Why does the car make 8lbs of boost when you hit the gas pedal in park?

Does a vacuum leak cause the cat to get so hot? Chicken before the egg scenario bad cat causing the O2 to malfunction or a bad O2 causing a lean condition causing the cat to heat up? Why one side and not the other?

What about the O2 sensor as the car seems to drive differently in open and closed loop?

Car ran flawlessly before the tranny swap so what could have happened in a 3 to 4 month period as it sat in my driveway?
 
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Spoke to alan and he stated that the tranny could be different things so we will look into that. If need to I will drive it to his shop when I get it running right.

Monday I will drop the exhaust and see what is there. Probably punch out the cats or see if there is some kind of blockage somewhere.

Frustrated in GA!
 
Sorry to hear, man. You have a bunch of stuff you've done and are feeling good and then wham! It's not running right.

I suppose that it may possibly be a plugged cat, but a glowing cat is indicative of a lean condition--way too much air in the air/ fuel mix.

I know that the transmission goes by what the TPS is sending it......could it be a faulty TPS or maybe the TPS connection had got unplugged? I had a faulty TPS on my Mustang after installing a bigger throttle body, and the car wouldn't shift right and felt like the tranny was slipping. Try to get a voltmeter to see if it's reading properly.

Mike's right on the vacuum leak. Check all connections and hoses, especially something like PCV hoses.
 
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I sprayed starting ether all around and nothing really changed no matter which connection I sprayed it on. I think it needs to be smoke tested.
 
Got the car jacked up and there is only one O2 sensor on the car and it is on the passenger side
There is nothing on the drivers side.

Going to gut the cat and replace the o2

It is a true duel setup so is one o2 on the passenger side adequate?
 
One O2? That seems odd on a 90 should be one in the exhaust manifold on the drivers side and a 3rd one,can't recall where the 3rd one is.

I may have your year wrong but one O2 sensor still seems odd.
 
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SC strategy requires 2 narrow band o2 sensors. One on each side. The tune can be modified to cause the car to pull o2 signals off of just one of the two, and by default it will stop looking at one of them if it is too crazy (and it sets a MIL).

California SC's may of have 3 sensors, but if they did I've not seen them. I'm not sure where the after cat feedback would go into the stock strategy.
 
The car is a 94 auto. We had a coder on it. It was throwing a code then counting the beeps we lost track then reset and there were no codes.:confused: The car has a custom exhaust. It is a true duel setup. One o2 on passenger side. The car ran flawlessly with the exhaust setup w/ one o2 before the tranny failed. Then upon restart with new tranny these issues showed up. So nothing was changed but the tranny so something happened when it sat for 3 months.
 
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Well I was wrong as usual. There was anothet o2 on the drivers side, I replaced it tonight, gutted the cats and took of the ic tubes and checked for any blockage. Everything looked fine but when I hooked up the Ic tubed, stock tubes with a DIC, I didnt use ultra blak so this time I did. Before I did the ultra black on the ic tubes I started the car. I had disconnected the cruise on the Tb and when I started the car it idled and then the car accelerated to 4500 rpm and I wasnt even sitting in the car. Then I resealed the tubes and it will sit over night.

What can cause the car to rev so high on its own? What causes the car to show 5 lbs of boost at idle in park with gutted cats? Could a vacuum leak do that?
 
So I let the car sit for a few hrs. Took the car for a spin thru the neighborhood. Bad idea! The car showed zero vacuum. I took the car out and it accelerated to 50mph on it own w/ my foot hitting the fing brake!!. I didn't even hit the gas pedal!!! ~~~!!

No boost at idle, maybe a few pounds but the car drives itself!

No one has any clue or no one has seen this before.

If by chance you don't like me or my post's for whatever reason if someone has a clue they should respond to help out a fellow member in the future.

I almost crashed the car coming down a hill in a 25 zone as with my foot on the brake hard was still doing over 50 and I had no brakes

202 views and 5 reply's. No one has a clue? I am starting to get really pissed.

I guess it is a vacuum leak!!
 
I am far from an expert, and far more knowledgeable people than myself have already responded, but I have to respond because I am sensing your frustration and maybe I can help.

My SC would also accelerate on it's own a few years ago. It turns out that my throttle cable had a burr in it that was causing it to stick. Very scary stuff indeed! Nearly messed myself. Lol.

Check the cable. You never know.

Sorry, but my limited experience/knowledge prohibits me from helping with your other issues.

I hope you get it running right.

Best of luck.
 
It's tough to diagnose, because it sounds like you have a few problems that are coinciding with each other.

I don't think that a vacuum leak would give you this sort of problem. You'd have severe idle problems (ie: would idle really high or would stutter and stumble and would stall out). It's possible that you do have a vacuum leak, but i'm not sure if it's the cause here.

Like I mentioned in my post in here before, it sounds like you have a throttle position sensor issue. Since you replaced the plenum, i'm assuming that you had taken the throttle body off or put on a new or different one. If you're using a different throttle body, troubleshoot the TPS first......try putting your old one on (if you've used a different one). If it is a Standard TPS, don't use it....they're crap. I used one and will never use anything else but a CTS/ Ford one.

Test your TPS voltage. If the TPS is shot, it will make your transmission think that your car is accelerating and will make the transmission either shift shouldn't or not shift when it should. It also sounds like your accelerator cable might be binding or sticking somewhere--make sure that the throttle body moves freely and that the cable isn't sticking.

I really think that your problem lies in the TPS and throttle cable. And that you need a tune, because the car is running extremely lean (glowing cats). Again, check all your hoses and connections and make sure nothing is disconnected. At any rate, I would park it until the problems are fixed.

Also, with the boost in neutral, I wonder if the vacuum solenoid (or is it called boost vacuum actuator?) isn't faulty or disconnected somehow. If it's not working or is faulty, it will start building boost or not building boost on it's own. I'm not a big expert on that vacuum solenoid thing, but from what I know, when it's dying or disconnected, it will cause issues with those things. Check to see that it's moving freely and that when you step on the accelerator (hood up, car parked), that you can see it moving.
 
Thank you for your reply. I have a feeling that the tb is a issue but i keep getting told that it is just a butterfly and have checked it an others have too but my gut tells me something is wrong with it. I am not saying that is the only issue but it is so weird that the car ran fine before sitting for a few months and now it seems like such a mystery
 
Whoa, that was a fast reply!

Yeah, with the TPS, as i'd mentioned, when I put a bigger Accufab throttle body on my Mustang, I couldn't get the stock Ford one off of the stock throttle body, so i'd bought a Standard one from the parts store, and then hooked everything up, and the car wouldn't run right. It would shift weird, or not shift at all, and would stumble, as if there was a transmission or even possibly a compression issue. With fuel injected cars, they're told how much fuel to give the car and when to shift the car.......so i'm wondering if that isn't the cause of your glowing cats, too.

Going on common sense, if the TPS is reading that you're in a higher gear when you're actually not--and flooring it when you're driving normally (because the sensor is faulty) it's going to be sending some heavy duty information to the computer that is telling it that it should be preparing all the other engine things for that sort of driving. I'm wondering if the glowing cats aren't a result of the computer trying to send more fuel to the system, and then the fuel trims are cutting back the fuel big time at the O2 sensors of what they're actually reading, resulting in a super messed up air/ fuel reading. For example, that's what those Ebay chips do--"adds 50 hp!" they're resistors that fool the computer into reading lean, and then people end up with a messed up engine.

The fact that your engine is reading way lean and that it's shifting weird--i'm almost positive that it's a TPS issue.
 
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If the TPS is on the right side of the TB Mike and I switched it out with another and there was no change.

Another clue the DIC gets real hot, within a minute from starting it the top of it gets very hot.
 
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If the TPS is on the right side of the TB Mike and I switched it out with another and there was no change.

Another clue the DIC gets real hot, within a minute from starting it the top of it gets very hot.

on the backside of the motor where you have the Christmas tree of vac hoses (usually right behind the Supercharger) are any of those hoses loose. One of those is actually for Brake vac and makes me wonder if its not loose.

With the problems you're having it sounds like a vac leak for the car will incerease idle speed to compensate the leaks, thus causing it to drive itself persay.

-Tim
 
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