My R33 is in "limp home mode", why/how to fix! :(

[chicane]

Hi All,

I am having problems with my R33 GTS4 with the ECU seeming to be in limp home mode (I can't rev it over 2500 RPM).. ive tried the following things:

- Reset ECU (Battery Disconnect)

- Pulled out ECU, diags return 5-5 (All OK)

- Changed Oil/Fuel Filter day before (all fine after changing these, drove about 25km on Sat night and 25km on Sunday morning)

- Problem exists still with Disconnected AFM

- Thoroughly cleaned AFM element/plug with electrical contact cleaner

- Just disconnected battery to ensure the ECU completely resets (will be left for about 6 hours)

Any tips/advice is appreciated.. driving under 2.5K rpm sucks!! and I'm worried it may be bad to drive in limp home mode for long..

chicane

[strutto]

Replace the AFM with a known good one...

[PranK]

is it a stock ECU?

i reckon its AFM too...

[sewid]

Loose AFM connection or broken AFM will cause this behaviour.

[chicane]

Hi all,

Thanks for the replies.

The ECU is stock.. the car is basically stock except aftermarket exhaust / K&N pod filter.

Is the AFM for N/A skyline the same as turbo? Could I try an AFM off a turbo skyline?

Regards,

chicane

[NuGGeT]

yes they should be the same

me car had the same problem, its really annoying and it turned out to be the afm, all good now

[Cecam]

Most AFM faults are just dry joints which are easy to repair if your handy with a soldering iron... swap it with a known good one and if that fixes it, just open up your one and it will likely be one of the pins that goes off to the socket will be bad...

[Guest RedLineGTR]

if you have some electrical contact cleaner give it a cleanup where the contacts are if it dosent work then oh well.

[chicane]

Yeah I've cleaned the AFM/plugs etc.. can anyone confirm if the AFM is the same between NA and turbo skyline?

cheers chicane

[chicane]

Hi All,

An update to the ongoing saga... after leaving the battery disconnected for ~6 hours yesterday (and after cleaning the AFM with electrical contact cleaner) I go back to the car and start it up, and revs past 2500 no worries. What im trying to work out is if my car was indeed in limp home mode, or it wouldn't go past 2500 rpm because thats when it switches from the O2 sensor to the AFM?

Manage to get home (~15km) in peak hour with no problems at all. This morning, I start it up, and after letting her warm up I'm sure its all good. Drive about 750m up the street to the main road, Stop at the stop sign, turn and then i cant rev past 2500 again :| I pull over, pop hood, disconnect afm plug when the car is running, car stops. So I plug it back in, start her up, and she can rev past 2500 again, drive all the way to work (~15km) with no problem at all.

What gives? I was thinking the problem may have been caused initially by the oil type K&N filter, and as my car was in the sun all day maybe some moisture got sucked over the AFM element or something.. I dunno..

One thing that is similar from this morning and Sunday night, was I could drive for about 1km, then after stopping, the problem arises..

Comments appreciated!

cheers

chicane

[PranK]

some sort of AFM plug prob or something, so what they said up ^ there, borrow a good one, test it - if its all good then pull yours apart and try to resolder everything or just buy a new one i guess...

I once accidently changed the type of AFM in my power fc to Z32 AFM and the thing was the same... wouldn't rev past 2500 and was coughing a lot...

[Ethan_R32]

Sounds just like my problem I had with my "T". I replaced the AFM with a good AFM, and it was like a new car.

[chicane]

Hi all,

Last night I headed down to a friends place to borrow an AFM from an R33 GTST (cheers AdamR33) , on the way down there the problem arose 3 times again.

- First, after travelling 5km from home on the freeway (100km/h) I stop at an intersection, turn, and the problem occurs - Cant rev over 2500rpm! I pull into a servo with car running, pop hood, unplug AFM, car stalls, plug AFM back in, start car, problem gone.

- I drive another 5 km, repeat process, then another 5 and repeat process.

Get to my mates, change the AFM over, and I've managed to drive 25km back home and to work today (10km'ish) with no problems.

Seems it was the AFM after all. Many thanks for replies helping me with this, now I need to find where to get a replacement/how to repair this one!

Is there any way I can measure levels on the pins to determine what the fault is?

Regards,

chicane

[Cecam]

I wouldn't bother measuring the levels. Remove the thin plastic lid (it is simply siliconed in place, be careful not to cut through the lid that folds back under though) and then you'll see where the pins go from the plug in the case onto the PCB. Theres usually where the problems at, you might want a fairly grunty soldering iron as the tracks/pads/pins are all quite thick so need some decent heat to flow the solder properly. Theres bugger all on the pcb (which hides under copper sheild), you might as well resolder that for good measure. Throw the lid back on and should be fixed...

Have fun...

[chicane]

Did you experience the same problem with your AFM? Just hoping that indeed this fix is applicable to my AFM problem..

Cheers

[Trust33]

what was the problem?

[FLO]

Check the fault codes on ECU and make sure its actualy a AFM problem.You could be on a bump stear.

[Alex Au]

that's for sure turn into "fail safe mode" & 99% is the AFM. I dunno how & what u used to clean your AFM.

1. U hv to take out the AFM & spary the elect contact cleaner(don't use other stuff...I use 3M & its really good) directly to the hotwire

2. leave the AFM stand straight & let the cleaner dry up

3. If u hv a wet type filter. Try use a towel dry it up a little so no more grease suck during engine run.

[chicane]

Hi thanks for the replies!

Since I had this problem I did initially try cleaning the hotwire in the AFM (the stuff I used was CRC electrical contact cleaner, same stuff really) I did what you mentioned.. and the problem still existed ;(

I borrowed a friends AFM (known good) and I have not had the problem once since I've used that (maybe 2wks now?) .. I have a K&N oil type pod, I dont think that has let any oil come through but I don't know..

I think I may have to just bite the bullet and buy a 2nd hand one.. I might pull it apart and have a look and see if anything is obvious (cracked solder tracks etc) but I think the hot wire could be at fault here..

Cheers

chicane

that's for sure turn into "fail safe mode" & 99% is the AFM. I dunno how & what u used to  clean your AFM.

1. U hv to take out the AFM & spary the elect contact cleaner(don't use other stuff...I use 3M & its really good) directly to the hotwire

2. leave the AFM stand straight & let the cleaner dry up

3. If u hv a wet type filter. Try use a towel dry it up a little so no more grease suck during engine run.

[Alex Au]

no...its the wet type filter hv too much oil on it...could cause the problem..everytime I chnage a new filter(HKS power flow) will hv the same problem..I need to clean it few times.....