I am really stumped about what is going on with my car...ok these are the mods the car came with.. its a 94 cobra: flowmasters, chip ( i have yet to find out what kind), a hoemade CAI w/ a pro-m 80mm maf, and all else stock that has to do with performance... the problem started after i replaced the maf from the old one ( i do not know the size), however, prior to the problem, the EGR was no longer hooked up to the main harness. The previous owner disconnected everything that has to do with emissions: the smog pump is gone, the tube connected the EGR to the header was cut and welded shot, the EGR regulator is missing. At first i tried to replace everything, but after taking it to the shop, and finding out the connection to the main harness was cut ( the one that leads from the regulator) i just plugged all the holes leading to the EGR. Also, there were exhaust leaks coming from the passenger side header and a tube that was left open which i could only assume used to connect to the smog pump. By the way, i live on FL. so there is no emissions, there is no need to worry about this. Anyways... after replacing the MAF which i thought was an easy task, i took the car for a test drive, there was instantly a noticeable difference in performance but slowing down was where the problem lies. The car accelerates better than before, the problem is when the car is reving over 2,500k and then then placed to neutral or i try to down shift, the rpm's drop dramatically below 600k and will die, i can keep it alive by steppin on the gas. ALso i have notice that if i keep the car in a lower gear while slowing down, it will stay alive. I have read almost all the posts before posting this thread.. and the closest thing i found was a problem with the TFI coil. but that cant be since i recently replaced the TFI coil with msd, changed the plugs no more than 2 months ago, and along with the new MSD TFI i also replaced the FMS 9mm wires with the same thing... what in the world would cause this ridiculous and annoying problem?? by the way the reason for my changing MAF's was because after running the codes on the comp, found out that the MAF was malfunctioning. EGR has always been blocked off so that cant be it either, the header leak was fixed, all exhaust leaks were taken care of! also, before the header leak was fixed, the car used to back fire when decelerating... now it does not backfire anymore, this all happened after replacing the MAF.... i called Fordanderson, and they checked everything on their records for my order and it was correct ... 80mm maf for 24lb injectors. pls help!!! and sorry for the insanely long post!
HELP!! car dies when decelerating?!?!help!!
- Thread starter Slowbra94
- Start date
Dump the codes and see what the computer says is wrong. Most auto parts stores will do it for free.
Then look for codes 27 & & 29 - Vehicle Speed Sensor (VSS) is an electronic sender mounted on the speedo pickup gear on the trans. It works the cruse control for both 5 speed and auto trans cars. On auto trans cars, it tells the computer to speed up the idle slightly as you slow down to a stop to keep the engine from stalling. Check to see if the electrical connector is plugged into it. Cost is under $30 and it is easy to replace.
Next look for codes 12, 13, 99 which are idle speed problems. The IAB controls the idle and is prone to getting gunked up over time. Remove the IAB (be careful about the gasket!) and throughly clean it with throttle body cleaner. If your throttle body looks dirty, clean it too.
Next check the TPS. Here’s a TPS tip I got from NoGo50
When you installed the sensor make sure you place it on the peg right and then tighten it down properly. Loosen the back screw a tiny bit so the sensor can pivot and loosen the front screw enough so you can move it just a little in very small increments. I wouldn’t try to adjust it using marks. Set it at .97v-.99v, the closer to .99v the better.
(copied from MustangMax, Glendale AZ)
1. Always adjust the TPS and Idle with the engine at operating temp. Dive it around for a bit if you can and get it nice and warm.
2. When you probe the leads of the TPS, do not use an engine ground, put the ground probe into the lead of the TPS. You should be connecting both meter probes to the TPS and not one to the TPS and the other to ground.
3. Always reset the computer whenever you adjust the TPS or clean/change any sensors. I just pull the battery lead for 10 minutes.
4. Check the procedure for your year, on my 90 I have to turn the idle screw until it just touches the tab, then insert a .010 feeler gauge and give it about one more turn. Then you adjust the TPS voltage to .98v, reset the computer. Start it up, if the idle is to low then turn the screw in until it is just right, then readjust the TPS voltage to .98v and reset the computer and start it up. The key is to adjust the TPS voltage and reset the computer whenever the idle screw is changed.
Next look for codes 41 & 91 - Code 41 or 91 - O2 indicates system lean. Look for a vacuum leak or failing O2 sensor.
The computer sees a lean mixture signal coming from the O2 sensors and tries to compensate by adding more fuel.
Look for vacuum leaks from hoses that are cracked or not capped off.
Then look for codes 27 & & 29 - Vehicle Speed Sensor (VSS) is an electronic sender mounted on the speedo pickup gear on the trans. It works the cruse control for both 5 speed and auto trans cars. On auto trans cars, it tells the computer to speed up the idle slightly as you slow down to a stop to keep the engine from stalling. Check to see if the electrical connector is plugged into it. Cost is under $30 and it is easy to replace.
Next look for codes 12, 13, 99 which are idle speed problems. The IAB controls the idle and is prone to getting gunked up over time. Remove the IAB (be careful about the gasket!) and throughly clean it with throttle body cleaner. If your throttle body looks dirty, clean it too.
Next check the TPS. Here’s a TPS tip I got from NoGo50
When you installed the sensor make sure you place it on the peg right and then tighten it down properly. Loosen the back screw a tiny bit so the sensor can pivot and loosen the front screw enough so you can move it just a little in very small increments. I wouldn’t try to adjust it using marks. Set it at .97v-.99v, the closer to .99v the better.
(copied from MustangMax, Glendale AZ)
1. Always adjust the TPS and Idle with the engine at operating temp. Dive it around for a bit if you can and get it nice and warm.
2. When you probe the leads of the TPS, do not use an engine ground, put the ground probe into the lead of the TPS. You should be connecting both meter probes to the TPS and not one to the TPS and the other to ground.
3. Always reset the computer whenever you adjust the TPS or clean/change any sensors. I just pull the battery lead for 10 minutes.
4. Check the procedure for your year, on my 90 I have to turn the idle screw until it just touches the tab, then insert a .010 feeler gauge and give it about one more turn. Then you adjust the TPS voltage to .98v, reset the computer. Start it up, if the idle is to low then turn the screw in until it is just right, then readjust the TPS voltage to .98v and reset the computer and start it up. The key is to adjust the TPS voltage and reset the computer whenever the idle screw is changed.
Next look for codes 41 & 91 - Code 41 or 91 - O2 indicates system lean. Look for a vacuum leak or failing O2 sensor.
The computer sees a lean mixture signal coming from the O2 sensors and tries to compensate by adding more fuel.
Look for vacuum leaks from hoses that are cracked or not capped off.
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