Already searched the archives, and didn't find a problems similar to mine...)



Ok, the car is an S4 TII with Rtek 1.7, 550s/720's, Walbro 255, TB mod, no emmisions, top mount, and running stock boost.


I was trying to lower the idle, since it was a bit high, and for a while, drove it around with no problems.





Recently, and this first started happening while driving regularly on the freeway, I notice a VERY OBVIOUS bog/hesitation when I press the throttle all the way down, very suddenly.

The engine won't completely die, but it also won't rev past 2000rpms (not under load).


Got new spark plugs, and the same thing happens.



I can only get to higher rpm's if I'm VERY gradual/slow on the throttle, but even then it seems like it's misfiring and and the powerband is not smooth.






I know this could be any number of things...

Grounds?
TPS?
Vaccuum leak?
Fuel pump?
Plug wires?




Any ideas will help, thanks in advance...

 

still struggling...


checked AMF, TPS, and air temp sensor, with a Digital Multi-Meter...everything looks good in conjunction with the FSM...



changed plug wires, and still hesitating at wide open throttle.






help please...I'ma cry.

 

also..tried and vise-gripping fuel return line closed to bump up fuel pressure...same ****.

 

I had a very similiar prob with my S5 t2, Bought a new tps, wasn't it, bought new plugs, wasn't it, swapped in another ecu, wasn't it. It ended up being the afm, it had some dead spots as it slide open, Full throttle it would fall on its face, Gradually roll it to the throttle and it ran great. Needless to say thats why I am running a standalone now.

 

thanks Chris, I'll check it out...



you happen to have a spare S4 TII AFM lying around?

 

THIS WILL SOUND STUPID.... unplug your TPS....

If it the same **** i had going through.... this will fix it.... but thats IF... hers the thread, scan it till you get to post 27.... but the whole thing is interesting, still havent got it un-kinked completely,

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/quick-pulsation-dampner-663131/

 

Probably not your AFM. Could be a vac. leak. I'd remove everything from the UIM etc. Replace your fuel-injector grommets/seals and then be extra careful when reinstalling everything.

Also set your timing and re-check your TPS.

Make sure there are no cracks in your TID etc.

 

If not AFM I am also thinking vacuum leak. Double check everything for vacuum leaks because you might not have got everything sealed up when you did the TB mod. Also the TB mod will cause it to die or hesitate bad if you WOT from idle or lower rpms.

 

yeah, the TB mod will definitelly cause a burb at about 2800 when romping.... but i was getting a lot worse than that after driving for like an hour. The whole range was bogging at 2000 plus.... it was weird, then i unplugged my tps and it smoothed out.... funny thing is that after a few days and some tinkering, and reinstalling my thermal wax and secondary plated outta frustration.... i reset the TPS, ( which was wayy off for some reason, (i had set it 1 billion times previous) and then the car was peachy... oh and my TPS was working fine (tested with DMM) and i even tried a friends workng TPS, same problem...weird

 

I unplugged the TPS, and the problem was still there - only it was running rough throughout the entire powerband.




I've had the TB mod for, like, ever...but this just started happening.









Thanks for all the input, dudes.

 

I am telling you, its the afm. Don't trust it. Just swap it out with a buddies real quick. I also have the tb mod, never given me any grief.
Let us know.

 

my car was doing simalir things when driving it turned out to be a clogged fuel filter always a good place to start when a cars acting up under throttle

 

aaaaaaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhhhhhhhhh hhh...tested AFM out on Ryan/kompressorlogic's car...








...it's good.







I'll check fuel filter.







thanks again Ryan.

 

[QUOTE=Angry Earl;7114968]I unplugged the TPS, and the problem was still there - only it was running rough throughout the entire powerband.



Damn.... hoped that would help..... surry...

 

Check voltage at your fuel pump/swap for known good FP. Probably not the problem but I've heard of Walbros dying with low amounts of miles.
Adding an extra ground to the ecu ground on top of the engine is never a bad idea either. Don't rule out your coils either

 

new fuel filter, same ****...






fuel pump?

 

I'm having almost the same issue as you (it actually started at the last unnatural gymkhana) except my car is running a PowerFC and is thereby MAP sensored. I'm thinking its a bad coil or TPS, so sometime within the next couple days I'm going to swap out the coils/unplug the TPS and see if that does anything for me. If you get around to trying out some different coils, be sure to post back your results.

 

are you positive that your leading/trailing wires are going to the correct spark plugs, one time I put mine on wrong and it felt exactly like your symptoms.

 

It was Colonel Mustard in the Dining Room, with the butter kniffffffffeeeeeeeeeeeee!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!












It turned out to be the FUEL PUMP , after all...






swapped in a new Walbro, and everything is peachy...










thanks again all....

 

Cool, Glad you got it figured out.