Subaru WRX 1993 jerking/stumbling

[Guest]

Sounds like afm, knock or ect. I dont get how the boost and the stumble are related. It does it when its up to temp as well?

[Marky]

Key point is that the ECU does not watch boost in closed loop, the MAP sensor is only there for boost cut sensing and thats it - it doens\'t try to "maintain" a certain PSI number on these older cars

The solenoid clicking open and closed will change what PSI you see but it won\'t cause a misfire, ditto for it won\'t change anything the ECU is doing

I have no idea what the problem is but you can ignore the boost solenoid - the only thing it is doing by the sounds of it is being put into limp/failsafe mode which is entirely normal if the ecu finds another problem

For it to be missing and stumbling at idle as said, look at sensor / ECU faults

[syneptik]

what sensors affect idling? or could cause the car to go into limp mode? without making the check engine light coming on?

has any one heard any thing bad about reconditioned air flow meters? are they fixed after they are reconditioned or ?

another thing i forgot to mention was, when i had the fault logged for a faulty maf ( i had bad idling and didnt drive very well during vacuum)

I went and bought a second hand air flow meter. when i installed it, the idling was better and drove better during vacuum but the first hour or two of driving the car wouldnt boost at all really. this came right after a while.

then i went and got my original maf reconditioned

[Timmah]

 syneptik said:

has any one heard any thing bad about reconditioned air flow meters?

I\'m running one in my car ATM. No issues

[syneptik]

did anything electronics do it by any chance?

[syneptik]

what sensors affect idling? or could cause the car to go into limp mode? without making the check engine light coming on?

[B4_685]

Have a read

Hope it helps!!

[syneptik]

cheers for that ;D

sick of spending money on replacement parts though just to find out it hasnt worked lol

might be giving up shortly

[Timmah]

 syneptik said:

cheers for that ;D

sick of spending money on replacement parts though just to find out it hasnt worked lol

might be giving up shortly

Why not take it to Armstrong Subaru ?

[syneptik]

thats the first place i took it and all they did was plug it in and tell me i had a maf fault

[Marky]

Try another one

I have had a MAF die literally within 8 hours use

They can behave perfectly fine up to a "point" and the problems you\'re having reek of a MAF issue - maybe try borrowing a working good one from someone here just to absolutely rule it out

[Timmah]

 Marky said:

Try another one

I have had a MAF die literally within 8 hours use

They can behave perfectly fine up to a "point" and the problems you\'re having reek of a MAF issue - maybe try borrowing a working good one from someone here just to absolutely rule it out

I was experiencing the same issue with my car when my AFM wasn\'t 100% plugged in.

[Marky]

There ya go that was option B - it could be a wiring fault or something also (since your problem comes and goes maybe it could make a lot of sense...)

[syneptik]

i only know one person with a afm of the same sort, and i asked him if i could borrow his and he said he doesnt want to start stripping his engine apart hes a bloody tosser

intermitant wiring issues are so hard to figure out though

[Marky]

If you have a multimeter then try watching the AFM signal voltage yourself when driving

You can do it right at the ECU if you find the right pin and have the multimeter sitting in view

Basically youll learn quick enough what voltage youll normally see at say idle / cruise / full throttle whatever, if it starts to do its stumbly thing and the voltage is doing something mental then... well it\'d help point the finger I spose

[syneptik]

could maf be fail intermitantly?

[syneptik]

Hey,

went a head and bought a second hand MAF, and the problem is fixed

so will be contacting anything electronic and hopefully will be getting a refund.

Cheers for the input guys.

[TBiz]

hey mate my mates v2 sti 96 wrx did this he changed the boost solenoid replaced all boost lines check all intercooler connections and also changed his idle control valve sensor and his bov was not set hard enough and then once i adjusted that it was better but leaking. this worked but was failing cylinder 4 sparkplug due to overboosting while the jerking was happening . after that it was fine.