Surging Issue, ideas/suggestions?

[JetspeedCamry]

Hey!

Ok, ive had this little issue for months now..and have just been putting up with it.

The motor is surging at partial throttle. Here are the conditions :
- Only happens between 1800 and 2400 RPM
- Can only "feel" it @ partial throttle/cruising/mild acceleration.
- Seems to happen in all gears, however 2nd, 3rd seem to be the worst. Can't feel any surge at 100km/hr in 5th or 4th.
- Sometimes if you accelerate while its surging, you can feel a power/torque drop (ie. requires more throttle the usual to get going).
- The RPM's don't visiblly "fluctuate", but you can hear it in the exhaust.

This problem didnt occur straight after i did my manual conversion (it was fine for a few months), but did start when the car was manual.

Now, ive changed ECU's, tried different AFM and changed fuel filter. None of those made any difference.

Discussions with a few people have put me onto dyeing fuel pump or dirty injectors.

The odd thing about it is that it happens like clockwork. Always at the same RPM and always during partial/mild throttle.

Any ideas would be great! And people that have felt it (yian...adrian?) can chime in too if you want and explain it in your words haha.

Thanks everyone

[JetspeedCamry]

Bump..no one can help?

[JetspeedCamry]

Can anyone help me?

[slide86]

if you are able to change the TPS then i would give that a go, maybe just check thats its adjusted correcly.

it could be a dying fuel pump, although you would think that it would lack power and surge through out the rev range, specially at higher RPM, when the engine needs more fuel.

any trouble codes, changing the ECU might erase them tho.....so there maybe none stored.

[TRAV-KE55]

sounds like a fuel related issue, does it have a MAP sensor or air flow meter, perhaps these are dying. Maybe even timming fluctuation, bang a timming light on it an rev it up and watch to see if the timming ramps correctly. How abou a stuffed pcv valve or vacume leak. possibilitys are endless. Hope these ideas give you something to go on.
Trav

[JetspeedCamry]

if you are able to change the TPS then i would give that a go, maybe just check thats its adjusted correcly.

it could be a dying fuel pump, although you would think that it would lack power and surge through out the rev range, specially at higher RPM, when the engine needs more fuel.

any trouble codes, changing the ECU might erase them tho.....so there maybe none stored.

I have another TPS that I can put on, however, i tested the one on there and it seemed to work ok as per the testing procedures. I have had my original ECU in for quite some time now, and no error codes are stored. And yeah, as you say, the FP is odd if it is going because of the conditions it does this. Perhaps FP Regulator/Pulsation Dampner or fouled injectors?

sounds like a fuel related issue, does it have a MAP sensor or air flow meter, perhaps these are dying. Maybe even timming fluctuation, bang a timming light on it an rev it up and watch to see if the timming ramps correctly. How abou a stuffed pcv valve or vacume leak. possibilitys are endless. Hope these ideas give you something to go on.
Trav

The motor has an AFM. I have swapped this over with 2 others and no difference at all.
The engine timing i will have a look at tomorrow. Ive set the base timing and what not, but never really looked at the ramp up...if it is out (how would I know??), what would be causing it?

Thanks for the suggestions!..keep them coming!

[3sgte]

Adjust the TPS so that the IDL switch turns off sooner when opening the throttle.

I.E. so that the IDL switch turns off at 5% throttle instead of 7%.
(Numbers are as an example only)

You are experiencing "fuel cut on decel".

[JetspeedCamry]

Adjust the TPS so that the IDL switch turns off sooner when opening the throttle.

I.E. so that the IDL switch turns off at 5% throttle instead of 7%.
(Numbers are as an example only)

You are experiencing "fuel cut on decel".

Thanks for that..interesting idea..ill give it a go tomorrow.

[JetspeedCamry]

Aighty, i adjusted the TPS back so the IDL switch now kicks off at 0.3mm (instead of 0.5). The surge has gone away a little now (woot!)...but its still there under reaaaly light throttle..like around 5% or so.
How far can i got back on this IDL switch? 0.1mm? How soon is too soon in other words haha

Cheers.

[slide86]

i guess you will just have to try, you will soon know if you have gone too far. it might stall and not run properly at all if you go to far

[JetspeedCamry]

Yeah ill probobly give it a go later tonight or tomorrow morning...but just wanted to know what other ramifications there are to adjusting it too early?? Apart from stalling etc if the switch doesn't switch, any other effects? (ie..why does the book specify 0.5mm to turn off, why not 0.1mm).

Cheers!

[3sgte]

Functioning IDL contacts will enable different ignition timing and idle speed correction control to occur when IDL has been reached. It also controls fuel cut on decel. If you are coasting down a long hill, the IDL contatcts enable zero fuel to be injected, saving fuel, and reducing emissions. Idle control may also suffer (but probably not too much)

The worst thing likely to happen is that the MIL (check engine light) will come on.
Take a bit more away, until you feel you can live with it.

[Jorrs]

get the injectors taken out and cleaned properly

[JetspeedCamry]

Thanks for the suggestions..its been quite helpful.
So, i adjusted the TPS back further, to 0.1mm before deflection. Didnt run too good!..idle fluctuated and if i just lightly touched the pedal, the idle would drop and the rpm's didnt pickup as smoothly.
Ive adjusted it back to 0.3mm and it seems to be good. Its taken out some of the surge, but not all of it. I can confirm its not all the TPS because im driving at say, 10% throttle and the surge is still there. By that time, the IDL switch is well and truly off.
So as Jorrs suggested, ill get my injectors out and take them to get a proper check/service/clean.
Opinions on getting a new pressure regulator?? Do fuel injection places test these too?
Other than that, there two other things related to fuel.....one is the pressure dampner...and the other i the fuel pump itself.

Thankyou so far to all those have helped..

[Jorrs]

yeh the injectors you will find if they are dirty make a big difference, if they are dirty then many problems can be associated, i had all mine taken out and clean for 114 $ , also you may not no when they were last done so yeh... hope you find out whats wrong !