Hyper4mance2k

iTrader: (40)

I am Having a 1450-2275 rpm surge. If I apply enought throttle to normally cruise with in this rpm range there is a throttle surge. This happens in any gear and in neutral. If it's reving through that rpm range the Idle just falls about 800-1000 RPMs then climbs back normaly. It continues to surge if held at part throttle, but reved past 2200 rpms it rund D ****. I have replaced and reset the TPS muiltipule times. I cleaned all my grounds, and reground the sensors on the ECU, checked that the pressure sensor pill is intact and inplace. It's a S4 GXL with a K&N, SAFC, and leaky rusty stock exhaust. It has done this before and after the SAFC install, so I know that is not the issue. Any Ideas?

RotaMan99

Verify the RPMs with a digital meter from the auto store. To many times I have seen the stock tach, including mine, being off by 100-1000rpm. I havn't paid attetion in my car but I know the ECU advances the timing at around 1100rpm. I don' tknow how it does it underload if you were in a gear that low and if that would cause a "power surge".

Other then that, I don't know.

InsomniacFC

iTrader: (4)

Mine was surging a bit and I sanded all the smoot off the spark plugs. Runs great now. Probably won't fix your problems, but gross spark plugs FTL.

Hyper4mance2k

iTrader: (40)

nothing to do with the rpms on the tach, but the engine surges through that RPM range. new plugs, wires, and MSD... it did the same thing before and after the MSD. I'm hunting a ghost...

RotaMan99

while driving my car around I remembered that mine does do a slight surge (not up and down just a jump in power) around those rpms at VERY light throttle. From the sound of the exhaust, it seems the ECU runs the engine on one rotor then kicks in the other. I noticed this a while back but never thought about it.

680RWHP12A

sounds like a tps issue
fuc it put a weber on it! lol

Hyper4mance2k

iTrader: (40)

LOL! I miss my weber... it drove so much better then this EFI crap.

RotaMan99

Its not a TPS issue. Its how mada designed the deceleration and light throttle system. They cut the front rotor and only run the rear.

Hyper4mance2k

iTrader: (40)

exactly. so what can I do to fix this problem it seems like it's cutting fuel too soon, then like it's adding too much fuel to compensate then it surges...

RotaMan99

Well, there is no fix because its not a problem.

A few years ago I tried adjusting the TPS, I think I had it adjusted to 1.20v or something at idle or a little lower. I was able to get the "fuel cut" down a little further in throttle but it made the car run worse in another area. I can't remember where or what it did.

Make sure that there is no dead spots in your TPS at light throttle, that could make the power jump even more.

Its not that the ECU injects to much fuel, its that you have another 70hp or so being made when the front rotor kicks in..

Are you getting bounces when it kicks in? Such as low and high power surges untill it levels out? If so, check ALL your mounts. I found on 2 of my transmisions that the center mount of lateral movment was gone. I have yet to put a new one on so I can't tell you if THAT is the problem to the surges or not. My car is the same way.

Hyper4mance2k

iTrader: (40)

i'm prettuy sure that when i'm at 15% throttle in neutral and the engine surges ftom 1500 rpm to 2000 rpm it's a problem. I need a video...

Hyper4mance2k

iTrader: (40)

no ideas other than TPS? I mean come on!

MazRx7FD

iTrader: (2)

Im curious, off topic... i noticed in your sig you have a fc33.... what is that?

curious.... O.o

RotaMan99

I would need a video to confirm how its surging if you can get one.

The only ways I can think of is some how the timing is advancing and retarding, which I very highly doubt it, or possibly the BACV is opening and closing, which I highly doubt too, or maybe the injector duty cycle varies which im guess would have an effect if something was up with the AFM. I suppose if something was wrong with the AFM that possibly the timing could change too? I would have to look in the FSM.

Does it surge while in neutral?

I might be missing something but thats all I can think of.

Hyper4mance2k

iTrader: (40)

1) there was no FC3S in the United states. All FC's coupes are FC33 and verts are FC35. When USDM cars are called FC3S it pisses me off.

2) yes it surges in neutral through the same RPM. when cold and when warm. If I start it cold. the idle revs to 3k then slowly comes down. as soon as it gets to 2k it starts surging, and it doesn't stop until the thermo wax has closed enough for the fast idle to be below 1400 rpm.

RotaMan99

Whenever mine did this it was always the TPS. 1kohm never solved it. I had to set it to 1v. Its strange but 1v seems to work with S5 TBs and 1kohm for S4 TBs. I don't know why but thats what I find.

Underload mine would never surge though, only when free reving.

HAILERS

To prove it is/is not a TPS problem............disconnect the plug from the TPS and see what the results are. Simple as that.

IF it is a TPS related issue, then I suggest you have been setting the TPS with the water thermowax not fully extended and or the fast idle cam is not all the way its cam when the TPS was set to output one volt dc at pin 2G of the ECU.

There's another possibility of the surge which would be a cracked turbo inlet duct AT the connection to the turbo.

And another thought is to re-rig the thermowax/fast idle cam per the FSM and not forgetting to check the gap b/t the throttle plates and the throttle bore after you set the rig for the cam. The FSM mentions that.

And I saw the mention in a post above that said only one rotor was disabled when letting off the throttle (TPS related). In fact I've seen that remark a couple of times in the recent past. I'm under the impression that when you are driving along and let off the throttle, fuel is cut to both rotors. I'm fairly certain that is the way things work. If someone is in doubt, just put a meter on one of the primays injector wires and go for a ride and let off the pedal. Then do the same with the meter on the other primary injector wire. I'm fairly cetain that BOTH injectors cut fuel when you let off the pedal while driving. See if I'm not right.

RotaMan99

That is right under full decel. When your at very light throttle and slowly decelerating, the front rotor is cut. ever heard that farting exhaust noise

HAILERS

IF your driving along at a steady pace, then let off the throttle just a tash, you'll see the AFR on the wideband go richer. Like it WAS at 14.5 aft and you let off just a tash, NOW it'll read something like 13.5 afr, as in richer.

If one primary injector was cut, I'd think the afr would go leaner, not richer. But I've a couple of meters laying around and someday soon I'll attach one primary to each meter and watch the voltage. I expect when I let off a tash the meters will read the same and if I let off the throttle while driving at a steady pace, the meters will read alt voltage when I do that.

Like I said, I've seen that remark made by seperate people on this forum and my gut disagrees pretty much with the one rotor being cut when the pedal is let off. I don't ever remember seeing that when I used to fool around looking at injector voltages while driving.

The only time I ever see any remark about a rotor having fuel cut is when a stock turbo is boosting more than what the factory set in the ECU.

RotaMan99

I will have to find it again but the training manual tells you what happends. I first heard it was the rear rotor getting cut but the training manual says the front rotor.

Thats strange that it goes rich, is that on a t2? If so you think its the same as the n/a?

I couldn't be ignition cut. Weird....

HAILERS

I have both na and turbo cars and if watching a wideband and the throttle is lifted a smidge, the afr will go approx a full afr richer. This has been noticed by several people on this forum that have widebands. IF the throttle is lifted fully the afr goes full lean or as lean as a given wideband controller will show. That would be 22afr on a Zeitronix and approx the same on a TechEdge.

Where in the FSM do you see mention of one rotor being cut? You mentioned that in your last post.

I look at section F2, page F2-75, OUTPUT DEVICES and look at the part concerning fuel injectors and I see no mention of one rotor being cut during deceleration other than rear side when rpm's are over 8500 rpm (series five).

About the afr going rich when the pedal is just lifted a smidge.........I think that is acting like a accelerator pump on a carb car, so that when you stab the pedal again the car won't bog from being too lean. Others have other ideas. It does happen though.

It might be mentioned that duing deceleration (not lifting off just a smidge but LIFTING OFF the pedal), the timing goes into a more retarded timing.

The original poster should try disconnecting the tps plug and seeing if that makes a difference in his problem. At least the tps can be removed as a cause or made the cause...depending on what happens.

RotaMan99

I found an area in the S4 Training manual where it says it cuts the front rotor here

Page 41. Here is what it says

To prevent vehical bucking during deceleration. To Prevent abnormal temperature increase inside converter. Fuel cut at front and rear rotor or front only.

I wonder if the afr goes rich until front rotor cuts and then both cut. The amount of throttle difference between the front rotor cut and both cut on my car is tiny.

It does mention this but does not give the degree. Just says, timing retard during fuel cut on deceleration. I know the timing does retard form where it was during cruise or accelerating, I just don't know how far.

HAILERS

Under GENERAL INCREASE: To improve driveability (when feedback correction is stopped)...........would and does explain the increase in afr when the pedal is released a smidge. Makes sense.

I still have doubts about a single rotor (injector) getting fuel cut. I noticed the *(Austrailia only)* and that makes me wonder. Someday soon I'll just watch two meters during deceleration and see how things come out.

RotaMan99

The engine, during light decel on one rotor runs just like a blown motor during light decel, except comes back to two if you press the throttle any more. The fact that my engine will jump slightly when the front rotor kicks back in verifies this. Although a meter will only tell for sure, im 99.9 % sure thats what happends. The jump in power is felt more in the lower gears below 2000rpm

HAILERS

I concede the one rotor cut under certain conditions. I just got out the two LED lights used for tps setting and put longer wires on them. Put one in each primary socket on the ECU and went for a ride. If one lets off the pedal just a tash, then one rotor gets it's fuel cut off and the other stays working. IF you let off all the way fuel to both rotors is cut.

Evidently thats for driveability purposes along with additional fuel when you let off the pedal just a tash.

Sorry original poster. I guess you gave up or fixed your problem.