Hello guys, so i have an s4 86 13b.

My car has been sputtering, bucking, and bogging out. so i had the injectors serviced and the mechanic said they where fine. so i tested the fuel pressure, it read 32 psi, so i changed fuel pumps. It ran perfect for about a day and a half then started to sputter again. so i unplugged the TPS and nothing changed. so i left it unplugged and unplugged the BAC, and no difference. so i left the BAC unplugged and plugged in the TPS and for the most part stopped. but you can still hear a slight miss. I've also changed spark plugs. and when it sputters and bogs out it eats gas extremely fast. so i cleaned the MAF and the BAC and it ran perfect for about half an hour and started back up. so now I'm currently running without the BAC plugged in, witch i know isn't bad since i don't have an AC pump. but i still hear a miss and if i go over 5k rpms it sputters. what should i do?

 

also i forgot to put that idle stay at about 900 to 1100 rpm's normal and will go up to 1500+ when idling while its doing it sputtering.

 

See if you can find someone who has a good MAF or see if you can access one temporarily off a good running car. Take yours out and install the borrowed one. See if there is a change. MAF s can and do go bad but not very often. You may have some bad wiring issues. Check the MAF first.

 

Sounds like your TPS needs to be adjusted, get it nice and hot (like 20 min. drive) than adjust, they get out of adjustment frequently

 

you mention all this fuel system checking, have you replaced the fuel filter yet? granted i doubt that is the issue, but still cant hurt

 

yes i replaced the fuel filter and sadly that hasn't changed anything. I'm about to check the FPR and see if maybe thats it. and I've tried different MAF's and the problem is still there. i thought maybe an injector but i figure if it is then it would be constant and not just every now and then. then maybe a ground on the ecu but i haven't been able to check yet due to not having a new gasket. any other ideas if its not the FPR?

 

i believe to have found the problem. check the coil packs and the secondary next to the firewall was weak and the other secondary has no spark at all. heading to barrys you pull it tomorrow morning to pull some off of a gtu out there.

 

yeah was going to suggest Trailing coils could be the issue but usually when the trailing coils go bad the tachometer will also die. obviously if you arent getting spark it is the problem.

 

okay, so i replaced the trailing coils with brand new ones. runs almost perfect. so i plugged the BAC in and about 30 minutes later, BOOM! starts spitting and sputtering again and losing power. i unplug it and it stopped. so i left it unplugged and went to a car meet. start my car up to leave and it starts acting up again. i start messing with the TPS and it stops. so I'm assuming its that. tomorrow ill go to auto zone and use their multimeter and readjust it and see if that changes anything. any other ideas?

 

and i noticed if i very lightly push the throttle it doesn't have problems, if I'm medium or hard on the throttle it sputters.

 

check/adjust the tps. then check timing

 

id double check the crank angle sensor to make sure your ignition timing is on.

also like barkz suggestion of a fuel filter.

full disclosure: i didnt read the whole thread after barkz fuel filter comment. so if you did it, my bad

 

okay, ya currently I'm working on installing my exhaust system, adjusting the tps. how do i check and adjust timing??

 

alright, the tps has been adjusted, the timing has been adjusted, and cleaned both the MAF and tps. i don't have the problem but only for about 2 or three minutes here and there. I'm going to replace the fuel filter again, and then the fps if it still acts up.

 

I had exactly the same problem as you a while back. Was my AFM.

 

afm? and I'm to the point it don't sputter anymore, however my idle surges sometimes.

 

Maybe its a small vac leak. Check around there's plenty of spots to have a leak from. If not check set tps again. My tps is pretty old maybe on its way out, but I usually have to set it a couple of times to get it right. Another thing I read up on was setting tps to ohms and not volts. Which did you do for yours?

 

originally was at volts but just recently set for 1k ohms

 

okay, so i got a new TPS and adjusted it correctly. got new coil packs and put them in. new ignition wires. cleaned throttle body and MAF. she running pretty good now. but for some odd reason it idles at 1k while freshly warmed (since i don't have cold start), then when i start driving it starts idling at 1500 rpms. sometimes falls back down to 1k. and it will only sputter around 5k+ rpms like a hesitation, but I'm not sure. what else could be the problem?