performance issues with new vr4

[avn33]

i just picked up my second legnum vr4 a couple of weeks ago. I was forced to sell the first one for some extra cash but now that ive got some more cash back, i thought id pick up another one.

the first one i had had a 3 inch exhaust system, k&n filter and aftermarket blow off valve, and the think went like stink! so fast.
The second one i have now is completely factor except i put in a pod filter today.

it seems to have some issues though. when the car is cold, like first thing in the morning or when i get in it to go home after work, it goes hard for a factory standard car. but after 5 or 10 minutes it is as if the turbos are no longer there.
even in the cold, you can put your foot down and it will boost hard, and then just kinda die, again just like the turbos had just been switched off. i took it to a performance place today and he put a boost gauge in it to check out psi ratings. all tests from that were good. he was unable to find anything wrong with it other than to suggest a good tune up.

anybody else experienced similar issues with these? like i said, it goes hard when it goes. but the throttle/boost/acceleration when you floor it is not constant. it goes then kinda backes off and there is a definite sound from the engine like something has just sprung a leak when it happens. like its sucking in too much air or perhaps not enough.

any help is greatly appreciated.

[-LegnumVR4-]

Could be a number of things, hoses coming lose, fuel pump etc. Hard to know unless seeing it in the metal. Tried a Diagnose test on it? Its listed in the members area on how u do it.

[avn33]

tried searching here but couldnt find any reference to a diagnose test. can you point me in the right direction?

[bernmc]

SOunds like you may have an intermittent boost leak. May be worth fitting a boost guage and driving around for a while. Check all your pipes and make sure that they're on properly, and have a look at the standard dump valve- they're notoriously dodgy!

[avn33]

the guy at the performance shop did that. he said it was boosting fine the whole time. (well fine for a stock standard vr4). cheers for the info about the dump valve.

[AllBeItMine]

nup. the answer is heat. if your pod filter is just sitting in the engine bay, after 5 mins and the car's heated up, its just sucking hot air. bad for performance

[avn33]

yeah thats a valid point. however, the pod was only installed yesterday. this has been happening since i got it.

[Nick Mann]

The first thing to try if you are unsure as to how it is running is to try an ecu reset. Simply disconnect the battery for a few minutes, then reconnect and try again.

The diagnostics info is in the members area. Worth joining?

I think you could be simply finding the difference of the poorer air flow on this VR4 than the old one. Could you get any figures for the performance? 1/4 mile times, or 0-60 (0-100 I guess for you!) or power? I believe that the stock exhaust throttles the car at high revs, so if the power loss you are talking about is over 5500 rpm then it could well be that.

[Kenneth]

My opinion is heat buildup also.

before removing the catylictic converter I had the same issue when boosting for any reasonable period. I could feel the power die off. with a de-cat it takes much longer for this to happen.

[avn33]

im thinking then that perhaps i should get the exhaust system replaced and then see how it goes. im looking at at 3inch system.

ive had it suggested to me also that it may just need a good tune up. like new spark plugs and leads, oil and filter change that sort of thing. how much bearing do you think something like that could have on it?

[Kenneth]

im thinking then that perhaps i should get the exhaust system replaced and then see how it goes. im looking at at 3inch system.

ive had it suggested to me also that it may just need a good tune up. like new spark plugs and leads, oil and filter change that sort of thing. how much bearing do you think something like that could have on it?

yeah, a tune up wont go amis. You might want to change the fuel filter while you are at it... when dirty they can cause interesting problems.

[Andre]

Wat about the situation where you have a good cold source and u run a cold air intake and then you boost cut.What causes the boost cut in these cars and how do u get rid of it.I boost cut if i press out in 4 gear at low rpm like if the load affects this aspect.I boostg cut below 10 psi but it feels very strong.I would like to run at least 13psi i have a huge front mount and a decat 2.5 inch exhaust system.I just need to get over the boost cut situation

[Kenneth]

Wat about the situation where you have a good cold source and u run a cold air intake and then you boost cut.What causes the boost cut in these cars and how do u get rid of it.I boost cut if i press out in 4 gear at low rpm like if the load affects this aspect.I boostg cut below 10 psi but it feels very strong.I would like to run at least 13psi i have a huge front mount and a decat 2.5 inch exhaust system.I just need to get over the boost cut situation

What you are refering to boost cut is based on airflow and rpm. If you want to avoid it, try changing down a gear rather than loading up the engine at low RPM.

[Andre]

I want to run more boost so i want to avoid boost cut all together so how do i adjust the emanage to suit the boost cut situation

[avn33]

could someone point me in the right direction for the diagnostic test? i am a member now but cannot find it anywhere.

[Physician]

Hi avn,

http://www.clubvr4.com/forum/showthread.php?t=5456

[Physician]

My initial thoughts were that it was fuel starvation at higher boost ...... but I'm guessing that you would have a slightly different physical reaction to that you describe ...... probably a sort of 'pinking' or maybe even total 'cut out'.

I agree with Nick Mann that you should firstly try simply disconnecting the battery for a few minutes and then test it again.

Check all the tube feeds on the firewall as well .... remove each and refit to ensure a tight fit. Look at:

http://homepage.mac.com/rgdavies2000/.Pictures/VR4-docs/vr4engine/C_1.jpg

[avn33]

cheers for that physician.

[avn33]

new updates:
So the car has been to mistubishi, who hooked it up to their computer thing. They found no codes related to the engine (only one around the ABS). They gave it an oil/filter change, and sent me on my way, saying that nothing was wrong with it. but it was still just as lacking in boost when i got it back.

So, it was suggested to me that i get it dyno tested/tuned. I agreed. So i took it along to the boys at Torque performance who put it up on the dyno.
Results from the dyno were very interesting. it only produced 106kw at the wheels. Im told that they could also hear detonation in the fuel and that the mixture of air and fuel was very very rich. So rich in fact that it seemed to put the computer into some sort of safety mode, forcing the radiator fan to turn on and blow stinking hot air back into the air filter.
so they took the pod filter off and just ran a pipe out the front of the engine. Then threw it up on the dyno again. BANG! 139kw at the wheels. no detonation, a/f raitio was fine and an extra 35kw.
they suggested that i put the standard cold air box back on and get rid of the pod filter.

now, i was talking to another performance place. they said that they have never heard of a pod filter decreasing performance. they found this diagnosise very strange. and to be honest, i kinda do as well.

its not like i went out and installed a pod filter and all of a sudden the car ran really bad. The car was already running really crap. I installed the pod filter to try and boost performance.

i've had all the plumbing checked. there is no boost leak, no leaks in any vacuum hose at all. so whats next? im gonna try and put another cold air box on give it one more go.
anyone know where i can get a standard cold air box from? any other suggestions?
i mean i see these cars with pod filters on all the time. they never seem to have any problems like this.

[bradc]

Remember that our engine bay is very very hot, and that sucking in hot air can reduce performance.

My ecu is actually faulty and every so often my car goes into fail safe mode as well, when that happens it backfires like mad, I disconnect the battery terminal for 10 minutes or so, then the car works again for another week or so. I'm getting a replacement ECU soon.

Also, 139kw isn't very much, my car was 154kw at stock, and 159kw with the exhausts. What boost was your car running at on the run? Mine runs at 10psi across most of the range, most of the cars run at 8-9psi though.

Even better, could you scan in the dyno plot?

[avn33]

ill try and scan in the plot latter. it was running 8.8 psi both times.

[avn33]

also, i just ran a diagnostice test on it and i got this: 31 Detonation sensor .
mean anything to anyone?

[zentac]

If your getting detonation then your ecu will back the power off for you. Normally you get det when the Air/fuel ratio isn`t correct, normally when it runs too lean ... too much air and not enough fuel. Normally these cars run really rich, so If your running standard boost then it sounds like youve got a problem with yout fuel delivery somewhere. Either pump, pipes, injectors etc..

[richy rich]

nick man


i just read all this maybe this is the same prob you are getting.

[avn33]

If your getting detonation then your ecu will back the power off for you. Normally you get det when the Air/fuel ratio isn`t correct, normally when it runs too lean ... too much air and not enough fuel. Normally these cars run really rich, so If your running standard boost then it sounds like youve got a problem with yout fuel delivery somewhere. Either pump, pipes, injectors etc..
yeah, this is exactly along the lines of what im thinking about as well. will look at those soon.

[bradc]

I was thinking about your car quite a bit last night, and something occured to me, I saw a prefacelift auto dyno sheet once, and that made 140kw ATW, so I wouldn't worry too much about your power output, and 8.8psi is fine as well.

The detonation is very scary though, maybe it was happening only with your pod filter, try reseting the ECU, and see if the detonation code comes back.

[avn33]

I was thinking about your car quite a bit last night, and something occured to me, I saw a prefacelift auto dyno sheet once, and that made 140kw ATW, so I wouldn't worry too much about your power output, and 8.8psi is fine as well.

The detonation is very scary though, maybe it was happening only with your pod filter, try reseting the ECU, and see if the detonation code comes back.

its still there. What is this code trying to tell me? Is it saying that the detonation sensor is broken or is it saying that it has detected detonation?

[bradc]

it is saying it has detected detonation, which is a really bad thing :(

[ako]

Weird... I didn't think these threw out an error code when they detected knock.

Mine would just retard the ignition something chronic until it stopped knocking, then carry on its' merry way!

The error code (well, IMO) means the sensor is fcked, and your ECU has gone into an over-rich limp mode, and the knocking is happening because the ECU can't monitor knock at the moment.



I'd say try new plugs in a colder heat range - its worth a shot and besides, it can't hurt to change them - make sure you're running 96 or 98 if you can.. Oh, and a new knock sensor.

That filter wont be helping at all either. More heat - more chance of it knocking. I'm also wondering if there's a boost leak somewhere making the wee turbos overspool and drive temps through the roof, there's no real reason for an otherwise stock car to be acting like it was.

[The Vee]

Is the knock sensor giving a false reading to the ecu and knocking back the timing? Can you actually hear it detonating? /Hmmm

/Sorry ako, didn't notice you already mentioned the knock sensor

[zentac]

Is the knock sensor giving a false reading to the ecu and knocking back the timing? Can you actually hear it detonating? /Hmmm

I seem to remember reading (cant be arsed to read it all again) that he did state that one of the tuning places he went to said they could hear det.

[The Vee]

I seem to remember reading (cant be arsed to read it all again) that he did state that one of the tuning places he went to said they could hear det.

Found it - yes he does in No 19 :thumbsup:

[Nick Mann]

nick man


i just read all this maybe this is the same prob you are getting.


Not the same as me. The first description sounds similar, but when I was losing power I had zero boost. I think I have put my problems down to a sticky actuator on one or other of the turbos, but I can't be sure. It only did it for a few days and then the problem went away again!
I had full power and 1.2 bar, or almost no power and 0.0 bar.

[AllBeItMine]

if they changed the pod filter and it got 35kw's then i would suspect wiring around your AFM. it might be loose, which would explain your fueling issues and they knocked it when they took the pod off.

i initially thought it was an air leak somewhere as that would explain the over fuelling, but if your AFM isn't plugged in correctly or has a faulty connection that would explain the fueling and the knock sensor error code.

[avn33]

if they changed the pod filter and it got 35kw's then i would suspect wiring around your AFM. it might be loose, which would explain your fueling issues and they knocked it when they took the pod off.

i initially thought it was an air leak somewhere as that would explain the over fuelling, but if your AFM isn't plugged in correctly or has a faulty connection that would explain the fueling and the knock sensor error code.
I have had the AFM replaced during testing with no better results.

In response to earlier questions, yes there was audible detonation. Should i replace this sensor or leave as is?

[avn33]

what about cam timings? I was also told to get those checked. Any validity in that?

[bradc]

well if there is detonation then there is definately something wrong, but as ako said, the detonation detector might be faulty as well.

This is getting really hard :( It makes boost fine, sometimes it detonates, and the detonation error code comes up, and sometimes it makes a perfect amount of power.

ABIM might be onto something, you might have a loose connection somewhere that causes a lot of problems at times, and at other times runs fine.

[zentac]

if they changed the pod filter and it got 35kw's then i would suspect wiring around your AFM. it might be loose, which would explain your fueling issues and they knocked it when they took the pod off.

i initially thought it was an air leak somewhere as that would explain the over fuelling, but if your AFM isn't plugged in correctly or has a faulty connection that would explain the fueling and the knock sensor error code.

But this would give an engine management light.

[avn33]

But this would give an engine management light.
yeah. There is no engine management code in the ecu.
guys i really appreciate the help. as you can probably guess, this is getting pretty damn frustrating. Im at the point where i think i might have to sell it and start again. But i so don't want to. Manuals are so hard to come buy and manual with tan leather interior is even harder!
anybody recommend a good place to get it sorted with? they are obviously gonna need good diagnosis skills.

[bradc]

excluding mitsi dealers, you could try road race and rally in penrose, or maybe Gary Capper down in Pukekohe, both of those places are very good.

[psbarham]

sounds daft but check the cam position sensor multi plug , its near the afm (trace the wire back) if thats giving a bad signal the ecu will think the cam timing and therefore ignition timing are out by a couple of degrees and adjust the timing to suit

[avn33]

ok, i've come to the conclusion that the problem appears to be all around air flow.
The standard air box is just not up to scratch (although i will say it is a lot better than a pod filter in there).
So, I think ill get a custom air flow system built. cold air box maybe or just run some piping down to the front. any suggestions? how much does a cold air box cost? know anyone good to do this sort of thing

[avn33]

i should probably add that the car has been in a crash at some stage and has had the front bumper replaced. i think this has screwed up the air flow. something might be blocking cold air coming in. But i cant find it.

[dickytim]

ABIM has a good cold air system, but it would require you to move the battery into the boot, I have also got a power issue mine is flat from 4,000rpm and misses at 5500-6000 and feels like the rev limiter comes in at 6,500rpm, time for a battery disconnect while I wash her :)

[avn33]

finally! its all better.

i took it back to mitsi yesterday to get them to check to detonation sensor.
I told them about all the issues i had had and they said they'd have a look at those as well.

well they called me back later after looking at it saying that there is nothign wrong with it apart from the knock sensor still showing error codes. after i gave the guy a bit of a speel (sp?) about how it has to be broken somewhere and him giving me some rubbish about how he drove it as hard as he was going to and that he wasn't going to risk his life to test drive the car at 7000rpm, we agreed to replace to knock sensor.

while he had the manifold off to get at the sensor, he found the back three spark plugs like completely shot, so he replaced those and the sensor.

Now the car is boosting hard all the time. hot, cold doesnt matter anymore.

[bradc]

great news. Do you think it was the spark plugs or the knock sensor in the end?

[avn33]

great news. Do you think it was the spark plugs or the knock sensor in the end?
to be honest, i have no idea. i think it was the plugs but i like to say it was the sensor (only coz my brother told me to do the plugs a long time ago and i was like, nah won't be the plugs.) /pan