power drop off

[vr4goleta]

hey all
i have 90 model jspec vr4 (completly stock), a few months ago it started running shit, just driving normally it would run perfect but as soon as it came on boost the power would drop off and it would run jerky and rough until i got over about 5000rpm then it smoothed out, i replaced spark plugs, air cleaner and fuel filter (which did nothing). i then added fuel doctor and it ran sweet for about a month. but now driving normally it runs rough and jerky, but when foot is flat it seems to come good again.
i am thinking of getting the injectors cleaned and tested, but if anyone can give me help, it would be appreciated

thanks logan

 

[GSR94T]

things to do when any of my cars have run shit like what youve explained, one of these usually fix it up: spark plugs, i noticed you didnt mention leads - get some magnecore leads in there :twisted: , and also get timing checked
but yeah you can get the injectors cleaned properly too.

 

[vr4goleta]

i checked the resistance of the leads a few months back when it first started playing up and they seemed to be in spec. and i just checked the timing then and it looked to be about 12 to 13 degrese btdc which 12 +-2 is spec. any other suggestions

 

[to4garret]

when you checked the timming, did you ground the wire on the firewall?

also, try changing your fuel filter, make sure your plugs are gapped to atleast 0.8mm

 

[mannynz]

The coil put outs 25,000+ Volts or much more on the leads.
And your resistance meter puts out ???

 

[to4garret]

The coil put outs 25,000+ Volts or much more on the leads.
And your resistance meter puts out ???

what are you talking about?

 

[vr4goleta]

this wire on the firewall you speak of, correct me if im wrong but is that the black plug right next to the washer bottle? i remember having to do that on a ce lancer to get it down to base idle, but i thort that was just with automatics

 

[to4garret]

this wire on the firewall you speak of, correct me if im wrong but is that the black plug right next to the washer bottle? i remember having to do that on a ce lancer to get it down to base idle, but i thort that was just with automatics

nope thats with most mitsi, including these, you just need to ground it, then check your timming as per usual.

 

[CLuTZ]

Could be lots of things- I cant believe how many people dont datalog!! !


Here's a few things to try-

Leads
Coil Pack
Crank Angle Sensor
ECU
Spark Plugs (gapped correctly)
Fuel Pump
Fuel Filter
Leaks in your intercooler piping
Leaking b.o.v


Where abouts are you located?

 

[EVO-00X]

^^^ I wrote a list like that myself and thought aaahh fuk it! :lol: Too many things to mention. I'm leaning more toward the CAS and would be the first thing I'd change. Pays to have spare sensors for most things and that way you can just swap them over to find the fault by process of elimination :wink:

 

[mannynz]

The coil put outs 25,000+ Volts or much more on the leads.
And your resistance meter puts out ???

what are you talking about?

You cannot test ignition leads with a normal multi-meter.


Best you swap leads with some one and be sure.

 

[rob323]

Testing the leads won't show if there are any pinholes through which the spark is shorting out through either.

Have a look at the back of the car around your exhaust, is there black crap from it running too rich? If so, pressurise the intake to check for vacuum leaks.

 

[vr4goleta]

i eathed that wire on the fire wall and re checked timing, i cant have looked properly the 1st time cos it was 1, maybe 2 degrees btdc. adjusted to about 12 degrees btdc. and it runs fucken sweet again!!!!
thanks heaps to all that helped
altho i dont really understand how ignition timing slipped that bad

 

[iluszn]

man you must have been estatic that its running.. posting that up 3 times

 

[3zercrowd]

man you must have been estatic that its running.. posting that up 3 times

:lol: Fixed......

 

[EVO-00X]

i eathed that wire on the fire wall and re checked timing, i cant have looked properly the 1st time cos it was 1, maybe 2 degrees btdc. adjusted to about 12 degrees btdc. and it runs fucken sweet again!!!! thanks heaps to all that helped altho i dont really understand how ignition timing slipped that bad

So it was timing (could also have been dodgey CAS) Hey, when you moved the CAS did you set the basic timing to 5 degrees BTDC with the terminal earthed out? Reading above sounds like you put it to 12BTDC with it earthed :lol: Its supposed to be 5BTDC earthed, then when you disconnect the terminal from earth it'll go to around 12 BTDC.

 

[vr4goleta]

oooops yeah that is how i did it
altoho i did re-adjust it yesterday, earthed it, set it to 5 btdc, and un earthed and it was at 12 btdc, took it for a run up the coast last night.
i can now hear the bov (stock) again, but i found at revs below about 3000rpm with a bit of load (top gear about 100-110kph going up hill) it had a slight drop of like original tho not as bad (high rev range is sweet) correct me if i am wrong but this is clearly a timing issue. would you suggest maybe setting it to 14 btdc

 

[rob323]

No, set the timing to the factory setting and leave the ecu to control the timing as it's supposed to.

The most probable cause for your power drop off at low revs would be phantom knock, and the ecu is pulling the timing because of it. You will need to put a datalogger on it to find out for sure though.

 

[vr4goleta]

hmm i have heard alot about these datalogers, but where do find them, and how much

 

[GSRSOL]

I have been having a similar problem with mine, I changed spark plugs today and its sorted it right out. Car absolutely flies now.