Too much air and no fuel(lean). Its starving.
Too much fuel and no air(rich). Its drowning.

 

same thing happened to me in my 88 t2, i wouldnt be able to go pass 3.5krpm, but recently it jsut went away without me doing anything to it, i have no idea how it happened, i want to konw wat it is, so i can fix it so it never comes back again.

eric.

 

yes but the only thing i can think of that would cause this is my throttle position sensor , and i dont know much about how it works or what it even does .. i may be replacing it with another but i dont think it will fix the problem i really dont konw what the problem is coming from but its not cool

 

i blocked off all the emissions **** too.

eric.

 

mine will go away or at least seem like it did but then it comes right back in seconds to minutes, i dont know what the deal is, and mine wont even go past 2k or so, and when its the worst it wont even be able to drive above 1k or it will just be bucking and bogging and driving like crap and thats like its idling driving at 1k so something is really weird

 

It is hard to tell without looking at it.

Check the ignition coils, spark plugs.... you never know unless you look.

 

mines did it all the time, at 3.5k but need the car to go to work and **** so i drove it daily reving up to 3krpm only. it just recently went away like 2 days ago, im trying to figure it out as well, if i know anything ill let you know.

eric.

 

yea but mine is way worse i have to bog it into gear going 1000 rpm and thats it or it will not go at all which is pretty bad, i dont think its the coils / spark plugs because it will be fine at first but then somethin is triggering it to get messed up but it idles fine juist wont go anywhere beyond the idle

could something be causing it to go into closed loop or something ( dont know if thats even what its in), but i took off the 02 sensor completely and that changed nothing, but what else could cause it to go into the closed loop (if thats even what is it just guessing again)

 

Im stumped, ask Aron Cake. I hope you get your car fixed.

 

I had the same problem on my S4 TII



I Unplugged the Air Temp Sensor... and the car came back Alive again..

I sufferred so much till i finally foudn the solution...

u can come back and thank me when u go do it now :P

 

me too, ive been fixing this car since last september when i got it , right now its so close but yet so far ...

maybe i should just buy a beater to drive while i work on working out all the problems. how about a honda those make a good beater i had 2 90-91 civics, an 88 integra and a 88 accord lxi , and they all could handle my beating on it redlining over 1000 rpm over where the redline starts, honda is the best beater

im actually just kidding im broke , if i was rich i would just take my car to a shop and throw make them fix it

 

yes but what is the purpose of this air intake temp sensor, whats it do ? ill take it off if it will fix the problem but i still dont get how it is even creating a problem

 

that's why it took so long for me to diagnose, and made no sense to me either...

cuz who woulda thought a Temp sensor could affect the car so much..

but it did..

when u unplug it... the ecu "defaults" to 20* C for the air temp...

all it does.. is read the temp.. and lean out if it's hotter, and richen if it's colder... (slightly in both cases)

i think what happend was the sensor was throwing out some wack Off the chart signal... either STUPIDLY high or stupidly low...
causing the AFR to go mental...


I unplugged... and have since been eating 350Z and Pontiac GTO's up

 

i been running without my 02 sensor since i got the car, the bogging didnt start until i put in a new motor with a new hybrid turbo. i broke my t2 air thermo sensor so i went to the junkyard and got ones from na's, i didnt think it would make a difference. i didnt take out the air thermo sensor and it stopped the bogging.

eric

 

update , i removed teh air thermo sensor and it didnt change anything

the car seemed fine at first but once it was warmed up thats when the problem started and began getting worse

i am beginning to think it is a vacuum leak or something, i dont know what it is...anyone have any ide? it is fine when i first started it this morning, then after like 5-10 mins driving when its completely warmed up is when it starts giving me the problem again. I dont know what could be the cause. This is just has my mind boggled

 

are you getting a check engine light at all?
i forget how to check the engine codes on an S4, but see if you can pull any codes from the ECU.

also make sure your AFM is working properly. a screwed up or disconnected AFM will give you symptoms like you are describing.

also THROUGHLY check for vac leaks. a great way to do this is to take one of those butane refill canisters used for lighter refills, and then spray around the engine bay (fluid comes out as a gas). when you hear the idle go up, then you know that's where you have a vac leak.

- Aaron

 

no check engine lights on the warning lights, pretty sure the afm is fine since i swapped it with another and it still did the same thing

as far as vacuum leaks im thinking maybe this is what it is, im assuming under heat the leak is expanding and becoming noticeable and when not under heat it is holding pressure , but this is a guess

 

Sorry, but there's no way in hell I'm going to try and troubleshoot this over the Internet. It could literally be anything at this point, though since it is intermittant, I would look for an electrical cause.

 

i have no idea either really and from here i am really only guessing, i wish there was someone around here that could help me tune my car up but it seems like there isnt anyone to do the job

 

Have you tried making and using this code checker for the S4? It's cheap, and helpful.

http://www.teamfc3s.org/info/article...odes/main.html

 

well another thing that may make a vac leak unoticable when cold is the fact that the engine is reving higher. also some of the warm-up systems, like the air bypass valve, will compensate for the vac leaks.
once you drop the RPMs a vac leak becomes much more noticable in terms of the quality of idle, etc...

- Aaron

 

all my emissions are removed and the bac is removed also, it idles fine and everything but when given gas when warmed up it wont rev

when cold tho it revs fine, its once it warms up then it becomes a problem

 

Did you look at that code checker on page 3 of this thread? It could help you make sure the basics are working properly, and give you a baseline from which to work.

I forgot to mention in that post that you should make it with two different colored lights, so that you can monitor it while driving (one color would signify x1, and the other would signify x10).

 

i have yet to get the parts to make this but i hope to do it soon, right now im just relaxing on here ...lately the car has been giving me a headache lol

 

Good luck.

Problems like this always make me suspect that metal pieces expanding as they warm up are the culprit.

There's a good thread somewhere on this site that tells how to use your multi-meter to monitor the voltage outputs at your ECU plugs. I think it would be interesting to see what your injector outputs look like as you increase RPMs. If your meter does duty cycles, that would be even better.

I was thinking how I would go about troubleshooting this problem. I guess I'd first try to look at my fuel system pressure, and if that was good, I'd use my multi-meter to monitor my injector signals from the ECU--especially what they look like when I try to rev the motor, both cold and warmed up. If that doesn't identify the problem, I'd look at all my ECU output signals and compare them with the FSM. After that, I'm not sure what I'd do.

This is one of my many brainfarts, but I keep wondering about your fuel pump output and your fuel pressure regulator. Accordingly, I'm wild-guessing that you might check your wiring to the fuel pump (especially at the relay), and your fuel pressure. If you lack a fuel pressure tester, maybe you could just pinch the rubber RETURN line almost closed to momentarily increase the pressure, and see what effect that has (I don't know if that would actually work, but it seems like it should--you'll be trading volume for pressure). Don't leave your lines pinched all the way closed, because it'' dead-head your pump and burn it out.