Lift off Hesitation

[1timeVR4]

Hi all, hope you all had a good christmas.

Ive a slight problem with me car, PFL Manual VR4. At lowish revs (bottom half certainly) the engine has a slight hesitation when lifting off the throttle. She's been completly serviced recently, new plugs, magnecor leads etc etc and this made no difference.

I have an inkling that the dump valve may be causing it but honestly im not sure. When I bought the car it had a Free to Air dump valve on it, badly fitted.... one of the first mods I did was to revert back to a recirculating one. On advice from camskill I went for a Evo spec, adjustable, Forge Dump valve. I have tried the spring adjustment in many positions but none of them seem to quite cure the hesitation. Im now starting to think that maybe being designed for an Evo, the spring, even on its weakest setting, is to strong still. Would I be right in saying that even from standard an Evo runs more boost than a VR4?

Any advice would be appreciated, thanks.

[Nick Mann]

Is this lifting off from part throttle or full throttle before the revs build? When you say hesitation, the engine tries to stall at that point?

[1timeVR4]

Umm, more pootling about, second to third for example, when lifting to change gear there is a little jolt/ judder/ hesitation, Basically any throttle lift under low boost. Low boost is the key as it doesn't occur when driving enthusiastically

[Nick Mann]

So you have a manual?

Is it certainly a hesitation, or could it be worn engine mounts? That can give a jolt on gear changes if the engine is moving excessively.

Do you have any other aftermarket things fitted? MAP ECU or something?

[1timeVR4]

Yeah its a manual 1. No mapped ECU or tuning to speak of. Its definetly engine running associated, its almost a misfire on lift off.

[GTOpete]

My manual does the same thing- can go from feeling like a spark blow out stutter to almost like a mini fuel cut sometimes and its got worse since I put my desilenced /decat centre section in the fuji system. Ive yet to look at why its doing it as most of the performance bits will be getting taken off and replaced soon- should prob try hooking evoscan up to it and see whats going on when it does it.

[1timeVR4]

should prob try hooking evoscan up to it and see whats going on when it does it.

.......... and how would i do this?

[Nick Mann]

I'm struggling to come up with ideas other than DV at the moment. Is there someone local who can lend you their stock DV for an hour to see if that solves the issue?

[1timeVR4]

Im in west cornwall, Barney's in Bodmin i think, and AP motors is my closest 4wd rolling road

[Nick Mann]

AP have got experience with vr4's.

I'd suspect some of the boost plumbing somewhere, as it sounds like a small misfuel on lift off. Most likely is the dump valve as that is exactly when it should be operating. There must be other explanations but I am struggling to give anything certain - they are all unlikely and straw-grabbing, like MAF issue, timing issue, throttle position switch issue etc..

[GTOpete]

Well, I can help by ruling out a MAF issue as I swapped mine out after getting a fault code but the problem was still there.
I have a few BOV's I can try to see if that changes or solves the issue but I just havent got round to it yet. I think my legnum has a GFB bov that can be set back to a recirc so will give it a try at some point and see if that helps- the guy who owned it before me said his garage had turned it to mostly recirc but it doesnt sound like it!

Nate- Evoscan connects to the cars OBD port so you can see various things on the car in real time such as o2 voltages, maf frequency, TPS etc. If you do a search there are some good threads about it.

[1timeVR4]

What is the idle stepper control valve.....? could this be causing my problem

[BraindG]

my thoughts on this topic.

I never had this (or what i understand you to have) untill i fiddled with the MAF screw - the way i look at it (if its the same thing) is that the engine is spooling up to do a burst but then the revs level out and the engine just gives up, it hesitates gives a bit of a kick back/judder and life goes on..

Happens to me at pretty much all revs, but always the same conditions quick burst of the pedal, then easing off and allowing the revs to level of - if that makes sense.

think its a non issues brought on by excess O2

[1timeVR4]

wheres the maf screw?

[BraindG]

Have a looky here.

http://www.clubvr4.com/forum/showthr...ht=maf%2Bscrew

[1timeVR4]

done it, certainly made a difference, hesitation reduced cold and warm and a nudge more power i reckon, confirmed by the missus

[BraindG]

Yeah, you sure do notice the difference - But.. i take it that wasnt your problem then?