Major idle problem

blackcoupe81

Registered User
OK i am on here for some major help. I recently upgraded my throttle body to the 75 MM and my MAF senor to the 76 mm with the yellow sample tube which i think is the right one considering i have the stock blue top injectors on my 95 auto.
After doing this my car wouldnt idle good or run good and i changed the TPS sensor and the IAC only to find out that my Bypass vlave was fubared and not working at all.
So i tore down my superchager and ported the TB and the Intake penlum and reselaed everything, the blower top and the penlum to the case, and replaced the the Bypass valve and put it all back together and when i went to start it and it started up and immediatley died. And it kept doing this over and over. It starts but wont idle and when i give it gas it sounds like it si bogging down like it is starving for fuel.
So my question is could it be the TPS or the IAC causing this problem. I sprayed starintg fluid all over the enginge and did not find a vac leak the only place it took in the starting fluid was in the air filter (like it was supposed to) it ran on the the starting fludi but immedialty died afterwards.
So i thought i would post on here and see if any of you guys could help (XR7 Dave Cough Cough, since he is the guru of these cars). Any help will be really appreciated.

Thanks

Dan
 
I doubt that the TPS is causing the problem. Do you have a multimeter so that you could check the voltage the TPS is sending out? That's pretty simple.

If the problem showed up after the TB and MAF install, then my guess is that the problem is caused by not calibrating the new throttle body. It's nothing complicated, but the drivability can be off if you don't dial it in. You need to unplug the IAC and try to start it. Then turn the throttle adjustment screw until it can barely idle on its own. Then plug the IAC back in. If you can't get the adjustment right with the throttle stop screw, then there is another screw near the IAC (on most of the aftermarket TBs).

If that doesn't fix it, then I don't know what is going on.
 
The throttle stop screw should be setup so there is a 10 thou gap between the screw and the linkage stop, then turn it in 1-1/2 turns and lock it down. Then the bypass should be fully closed, then opened about 2 turns, then see if the car will idle at that point.

If it does, then unplug the iac, start the car and adjust the bypass until idle is about 150 below target idle rpm... don't use the throttle stop screw unless the bypass doesn't do anything for you, then the throttle stop needs to be backed off, but watch out for the butterfly binding inside.

Thats the proper way to setup a TB mechanically, but on the other hand, did you by any chance forget to hook up the vacuum line that goes from the driver's side valve cover to the air inlet tube?

Fraser
 
ok so i went and bought a new TPS and i have anothe IAC to put on and i ama going to put both of those on and reset the throttle body to the specs i was given. NOw a question i have is what is the correct posostion for the TPS i know the voltage shold be between .90 and .98 but every time i hook a volt meter to it i never can get those readings i always get over 1 volt so i was wondering if you guys could tell me the posistion that you have it on your cars or should i put into spec with the posistion it was in on the stock throttle body.
All help is appreciated and if u guys help me with this and i ever meet you at the shoot out i will buy u drink for helping with this. Because i am starting to pull my hair out with this situation. i knew when u modified a car it can be tricky but this is becoming ridicoules.

Thanks

Dan
 
The TPS voltage doesn't have to be right on the money, but it shouldn't be much over 1 V. There is an adjustment built into the EEC that "zeroes" the voltage, so to speak, when the car first turns on. I think between 0.8 and 1.2 is okay, but I am not sure of the exact numbers.

Before you rotate the TPS, try to set the throttle stop screw as Frit directed. Then check the TPS voltage again. If that is still off, then you probably need to rotate the TPS. If it falls within range, then you should be able to just open or close the air bypass to get the right amount of idle air.
 
still not working

okay guys i have done everything you told me to and it still wont idle. it fires up then immeditaly dies...............so i am thhinking it somthing else but i dont know what it is............any ideas:confused:
 
if i hold it 1500 and rev it up but as soon as i let off and it goes behlow 800 it stalls and it almost sounds like a miss in the driver side muffler when i am i am giving it throttle up it 2500 rpm
 
if anyone wants to call me at 765-430-2199 and talk to me i would appreacite it i just had some one tell me that i need tune for it to run right
 
if anyone wants to call me at 765-430-2199 and talk to me i would appreacite it i just had some one tell me that i need tune for it to run right

Yeah with that new MAF you need a tune .. or put your old one back on and see if that makes your car run.

- Dan
 
Okay, it could be MAF-related ... but the pop in the exhaust gives me a sneaking suspicion that your plug wires may be out of order. Did you check the 4-6-5 side of the coil pack?
 
The new maf won't have changed things enough to warrant a tune since it is calibrated for the stock injectors which he is still running. The stock maf transfer is what he would be running.

When you put the maf sensor back on, did you make sure the small o ring was still on the sensor? S_Mazza also made a good point.

Fraser
 
Sounds lean or out of idle control. With the PP TB you have to set the TPS as it is adjustable and could be wayyy high thereby not allowing idle control. It should be between .8-.95v ideally which should be pretty easy to set. While you are at it, verify that it transitions smoothly from 1.0 to 4.8v when you open the throttle (key on, engine off).

If it's lean that would be a MAF issue. Try the stock MAF and see if that works better. Sometimes the aftermarket MAF will be quite different than stock, regardless of what anyone says. Also, if the car is nearly stock, it may just need a little driving around to learn in the fuel trims. You have to get the motor up to operating temperature for awhile before learning will take place. Sitting still and trying to idle the car will never get you to the learning stage, you have to drive it.
 
well i got it all sealed up and back together and still no running oir idle. It pops like crazy in the exhaust and stalls out and i know there is no vacume leak now, its burning rich because i am shooting carbon out of the pipes.so now i am really stuck i just put new plugs in november and i didnt cross the plug wires so i am begining to wonder if my coil pack is going to ~~~~ or what i dont know and i am losing my patience with thisdamn car. so any suggeestions onwhat to look for now.


Dan
 
well i got it all sealed up and back together and still no running oir idle. It pops like crazy in the exhaust and stalls out and i know there is no vacume leak now, its burning rich because i am shooting carbon out of the pipes.so now i am really stuck i just put new plugs in november and i didnt cross the plug wires so i am begining to wonder if my coil pack is going to ~~~~ or what i dont know and i am losing my patience with thisdamn car. so any suggeestions onwhat to look for now.


Dan

If you want to get a new coil ive found that MSD makes a street fire coil and accell also has one.
 
OK i am on here for some major help. I recently upgraded my throttle body to the 75 MM and my MAF senor to the 76 mm with the yellow sample tube which i think is the right one considering i have the stock blue top injectors on my 95 auto.
After doing this my car wouldnt idle good or run good and i changed the TPS sensor and the IAC only to find out that my Bypass vlave was fubared and not working at all.
So i tore down my superchager and ported the TB and the Intake penlum and reselaed everything, the blower top and the penlum to the case, and replaced the the Bypass valve and put it all back together and when i went to start it and it started up and immediatley died. And it kept doing this over and over. It starts but wont idle and when i give it gas it sounds like it si bogging down like it is starving for fuel.
So my question is could it be the TPS or the IAC causing this problem. I sprayed starintg fluid all over the enginge and did not find a vac leak the only place it took in the starting fluid was in the air filter (like it was supposed to) it ran on the the starting fludi but immedialty died afterwards.
So i thought i would post on here and see if any of you guys could help (XR7 Dave Cough Cough, since he is the guru of these cars). Any help will be really appreciated.

Thanks

Dan

i recently installed a 75mm tb and 76mm maf on my chicken. it to ran very bad after install. would not idle for anything and shoot black carbon out the pipes something ugly. luckily for me i had already installed my quarterhorse and BE so Fraser worked me up a new base tune, and dah dah it runs great. it still needs some fine tuning but for the most part it runs even better then it did before i upgraded the tb and maf. so judging from what your saying its doing i would have to believe that you need a tune badly. also keep in mind that if your still running stock injectors, that could be a problem aswell. imo the stock 30lb injectors can not even come close to running a tb that big. the 36lb injectors wont be much better. if you decide to increase the injectors size i recommend 60lb. they can be turned down to what your engine needs, most likely they will never get over worked, chances are you'll never have to increase the size again, and in most cases they are cheaper then the smaller injectors when buying from Dave. hope this helps :)
 
so the saga continues, but i tihnk i have found the gremlin in my car. today i couldnt get it o run so i sroayed every joint and connection with starting fluid to see if i had a bad vac leak and nothing but when i sprayed the sir filter with fluid and kept going the engine ran like a champ telling me its not getting any fuel. So it comes down to the regulator (which i hope its not becasue that will not be fun to change if its where i think it is) or the filter which i hope it is. I doubt it's the fuel pump because i can stand on it and get it to run it just dies when i let off. So do any of you guys now exactly where the regulator is in case i have to change it and whats the best way to go about it. I am checking to make sure i have fuel pressue in the rail in the morning and if i got pressure there i will be leaning more towards the fuel filter, as long as i have 40 psi or better in the rail.


Dan:)
 
The regulator is the silver can on the fuel rail, near the rear of the blower, on the driver's side. There should be a vacuum line hooked up to it.
 
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