Vr4 stutter/hesitation

[Tebbyj]

Hi guys, am new here any help would be much appreciated.

Have got a 97 Legnum Vr4 only mods are a free flowing TB exhaust, and lowered springs.
Car has a weird stutter/hesitation problem, it almost feels like the car is running out of gas or you have lifted the throttle pedal. It only happens at low load, lower rpm conditions, as well as cruising at 50kph but not at highway speeds.

So far have changed spark plugs, adjusted TPS and tightened all hose clamps in a hope to eliminate vacuum leaks, all to no avail.
Anyone had this problem before and know of a fix?
Any help is much appreciated, thanks

[nos monkeys]

have you done an ecu error code check to see if it came back with any faults?

[Tebbyj]

have you done an ecu error code check to see if it came back with any faults?

Havent yet no, my code reader wouldn't connect properly, however have had no check engine light.

[nos monkeys]

you can do one with just a piece of wire and earthing it out, grab a piece of speaker wire and put it into the bottom right pin on the black plug and then earth it out and turn your ignition to on and count the engine check light if it flashed, the ayc light and abs light will also flash error codes related to them but the ones id look at would be if the engine check light flashes.

http://ftowa.com/html/workshop/workshopart07.html

heres a link here explaining how and showing you which pin to earth.

Also if you get any error codes they may be old ones so write them down then disconnect the battery for 10minutes to reset the error codes then take it for a drive then recheck the codes just to make sure they weren't any old error codes stored.

heres the link with what the codes mean for each light

http://www.clubvr4.com/forum/showthr...e-codes-update


otherwise have you checked all the vacuum lines are connected? Not sure if any of them could cause a problem but make sure the vacuum line for your fuel pressure regulator is hooked up and them ones by the throttle body.

[Tebbyj]

Okay cool will check codes, have checked vacuum lines all look in place and have clamps.
Car also seems to drop power after 5k rpm, is fine too this point and still pulls after just not as much as one would think.. could be related? could just be me not being used to big engine small turbo.

EDIT:
Just checked no fault codes on engine, ABS or AYC.

[nos monkeys]

I've only just got my first vr4 so i dont really know much about them but im sure mine drops power at about that rpm as well, seems like its got more power from 2500-5000 than 5+. but my boost gauge is only reading 5psi and i think i have massive boost leaks somewhere lol.

Since i got mine iv found 3 vaccuum hoses not connected, 1 being the fuel pressure one and then the wastegate lines were all over the show so im slowly learning about the engine and stuff. but the engine codes should show if there is a majorish problem otherwise it is probably just something simple.

[nos monkeys]

only other thing i can think of is maybe a semi blocked fuel filter or tired fuel pump but that shouldn't be it if its only stumbling with no load and low rpm. But im sure i read somewhere legnums fuel pumps stuff out a wee bit?

My flatmate had a 1800cc non turbo legnum and he said his kept trying to die on him like a fuel loss i never actually took it for a drive so not sure what the symptoms were but in the end it was a tired fuel pump cutting in and out.

[Tebbyj]

I've only just got my first vr4 so i dont really know much about them but im sure mine drops power at about that rpm as well, seems like its got more power from 2500-5000 than 5+. but my boost gauge is only reading 5psi and i think i have massive boost leaks somewhere lol.

Since i got mine iv found 3 vaccuum hoses not connected, 1 being the fuel pressure one and then the wastegate lines were all over the show so im slowly learning about the engine and stuff. but the engine codes should show if there is a majorish problem otherwise it is probably just something simple.

Okay cool thats good to know (mine isnt broken haha), haven't hooked up the boost gauge to mine yet but i intend to soon.
I noticed a sizable difference in mine after a went around and tightened all the hose clamps, spool up and power was definitely increased

[Tebbyj]

only other thing i can think of is maybe a semi blocked fuel filter or tired fuel pump but that shouldn't be it if its only stumbling with no load and low rpm. But im sure i read somewhere legnums fuel pumps stuff out a wee bit?

My flatmate had a 1800cc non turbo legnum and he said his kept trying to die on him like a fuel loss i never actually took it for a drive so not sure what the symptoms were but in the end it was a tired fuel pump cutting in and out.

That was my thinking too, maybe a fuel delivery problem but then i would think that it would happen more under high load conditions if that was the case. think i will change the fuel filter anyway, probably hasn't been changed in its life haha

[nos monkeys]

fuel filter would be more of high rpm thing if it lags but if its the fuel pump hesitating it could be at any rpm if it just turns on and off when it feels like it, but knowing me im probably way off lol someone else on here will have a better idea. Manual vr4s are ment to boost 9psi stock and autos 7psi if you didnt know. ( My jaguar was surging at high rpm and was fine at low rpm and that was a blocked fuel filter)

My gauge works fine but only goes upto 5psi when i have everything connected back to stock stuff and even when i pull the wastegate lines off so it should be free boosting it still only reads 5psi so thats why i think iv got a problem lol i checked the turbos for play and they had none so i just put things back to stock because that way its not going to be over boosting if my gauge is wrong or something. Going to get a boost leak test done when i get the cambelt done. ( writing that just made me realise today i brought a compresssor!) I'll try do a boost leak myself again tomorrow and see if there is a leak somewhere which is why my gauge only says 5psi

[Subaru ETA]

What spark plugs are in it?

[Nick Mann]

Is it more noticeable under light to medium throttle only in 4th or 5th and more prominent up hills?

[Tebbyj]

Plugs are Bosch platinum's gapped at 0.8mm.

Only happens on light throttle, any gear. Doesn't happen at all going up hills or under load, only when cruising at low speeds. Become more noticeable when crawling in traffic for example.

[Atik]

Does it still happen once the engine is warm/hot? I ask cos I get a hesitation when cold due to no O2 sensor. Thought if yours was faulty it could explain a slight hesitation on light throttle.

[Tebbyj]

It happens cold or hot but is more common when warmed up i would say.

[swinks]

My money on fuel delivery. If tired fuel pump then issuea are quite similar.
have you got afr gauge fitted and wideband?

Second thought is air leak prior to turbos, somewhere between maf and turbo entry. It won't show any fault codes, but engine is getting unmeasured air under strong vacuum conditions, i.e. cruise, idle etc.

[Tebbyj]

No AFR gauge or wide-band set up, will check fuel pressure and once i get my hands on a scan tool that wants to work ill look at sensor read outs.

Have noticed that a member on here had a similar issue that ended up to be a sticky ISCV in the throttle body so might pull that off and give it a clean while i'm in there.

[Nevesy]

I was having a similar issue, turned out to be a coil pack had failed.

[Tebbyj]

I was having a similar issue, turned out to be a coil pack had failed.

Okay cool, will look into that, it does feel like its spark or fuel related.

Pulled the maf off and cleaned it along with the throttle body today, also tightened some hose clamps car feels alot perkyer now but still has this hesitation issue

[elnevio]

I would strongly recommend getting all six injectors ultrasonically cleaned as a matter of course. This may well resolve your issue anyway, but is something that eventually needs doing! Post them off and get them back a few days later, for a total cost of around £100. Damn sight cheaper than new injectors.

Somewhere like www.injectorcleaning.co.uk is a good bet and give good info. I'm sure there must be NZ equivalents available.