Power Loss On Downshifts, Bouncing Idle And Slight Hesitation At Specific Rev Point -R34Gtt

[rondofj]

Ok so my car is doing my head in- have had to reluctantly create threads for all the issues which seem to be related and for which I aint got a solution yet. R34GTT with PT5558, powerfc, z32, injectors, 22psi on 98 pootrol etc.

Original problem for which I had to block off my stock bov (coke can) but which only solved half the problem:

60-70% power loss for 3-5 secs on downshifts esp under load/uphill etc, also happens (sometimes) on upshifts at full throttle but not as pronounced. During this time the map tracer on powerfc jumps 6-7 cells down and dumps a lot of fuel n retards timing. Basically utilises a very wrong map point for these 3-5 seconds. Tried out a member's z32 (thanks GtScotT), and couldnt really test it that much due to traffic, BUT yep it still does this, I feel to a lesser extent. Sometimes it didnt happen where I thought it would, but happened a few times to convince me my z32 is not entirely the culprit. Problem happens ALL the time with my z32 afm.

Recent problem-bouncing idle from 1300-700rpms (AAC valve was removed n cleaned a couple years ago and coilpacks are 8 months old Nissan items and doesnt misfire at all on high boost n load). During idle bounce the powerfc shows inj duty fluctuate betw 1.3-0.7%. The afm volts also fluctuate betwn 1.4-1.1volts at this time. Afm volts at idle is normally 1.1v and key ON is 0.5v. So ok. This problem occurs SOMETIMES only.

2nd Recent problem- during normal driving always at around 1700-2000rpms theres always a 'stickiness', hesitation, shudder and power loss ONLY at that point. Went through all the hoses with soapy water yesterday and couldnt find leaks/ ( idle was fine somehow and didnt change with the water spray). Problem happen ALL the time only at that rpm point.

All this leads me to believe some sensor somewhere is f***king up. Or electronics/ecu thing. I believe the problems are related even though the last two didnt happen before and is inconsistent.

I've attached my powerfc sensor check n volts at idle so you can see if its ok. Before I finish- I must add that a month ago I snapped my wastegate hose and overboosted to 30psi a few times with really LOUD machine gun misfire sounds from bonnet n exhaust before I realized what had happened. Lucky no damage, not sure if this screwed something up slowly.

[rondofj]

So does my z32 sound like the culprit? CAS? Or some boost leak somewhere. I forgot to add that with my ebc my boost in 3rd under load SOMETIMES drops all the way from 22 to 8psi! Otherwise it always fluctuates 2psi. Never steady. With the MBC it always held steady.

[rondofj]

My z32 contact joints at the plug are also re-soldered and sensor element sprayed with brake cleaner- that was last year. I have done most or all of the (basic but common stuff) that SAUers do in terms of maintenance n troubleshooting and cant figure out what it is this time round .. Any ideas folks?

[Ben C34]

Didn't this not happen with the nistune you previously had?

[rondofj]

Nope, except for that hesitation at low rpms happened like 5% of the time on those rare occasions for like 2-3 secs and was instantly gone, it was also more mild, something for which u kinda say what and then brush it aside. And usually happened only once/twice per drive. Something was giving way from then... :S

[rondofj]

Yavuz did mention that my O2 sensor was kinda on its way out but not to worry bout it for now, its also only 3 yrs old and my fuel economy is always 18-20L/100kms- short metro drives with the hard pulls now n then. So somethings fishy somewhere- some sensor/ electrical something

[AngryRB]

I can remember having a shudder/jerking at around 1500rpm on a light throttle, I was told it was related to the TPS so maybe look into that too

[GTSBoy]

'twere I you, I would try swaptronics with the CAS, and at the very least get a scope onto the CAS signal. You'll no doubt need Yavuz's help for these things.

Your BOV re-entry angle into the turbo intake has been an item of suspicion in these threads of yours hasn't it? Done anything about it?

[rondofj]

'twere I you, I would try swaptronics with the CAS, and at the very least get a scope onto the CAS signal. You'll no doubt need Yavuz's help for these things.

Your BOV re-entry angle into the turbo intake has been an item of suspicion in these threads of yours hasn't it? Done anything about it?

I put a coke can plate to block off BOV - this cancels out the BOV re-entry angle to turbo out of the equation, but problems still there yes. Car drives better though like this, and no stalling etc.

And yes CAS is my number one suspect, do I create another thread saying 'Help- Need NEO CAS for a day, Sydney Area' haha.. Scotty Nm35 was suggesting this sometime ago and I kept in mind. Even with the Nistune, the car was running inconsistently great / crap and quite tempermental at times, economy was the same crap 18-20L/100kms, and one thing is generally when the car is quite cold it runs pretty crisp (also no bouncing idle), once warm then you do notice a 'slightly sick car sometimes.. Temp sensor? Dunno, what do you guys think of my sensor voltages displayed on the powerfc commander above posts??

[GTSBoy]

Well, your fuel consumption is a joke. So you need to wonder about the various sensors that can cause that. Temp sensor, AFM #1 suspects. But you can test the temp sensor relatively easy, and you've swapped the AFM (with some small effect, so it's not in the clear asaiac).

[Dose Pipe Sutututu]

take a screen shot of your idle config screen.. perhaps your decel rpm is set too high around that 1700rpm region so you're always hitting it on cruise

have a read here:

http://www.skylinesaustralia.com/forums/topic/356756-r33-idle-issues/

[Badgaz]

i presume you were spraying soapy water to find a vacuum/boost leak....you would be better to do this properly, using a bike pump and blocking off the turbo mouth and putting a brick on the accelerator pedal.

it could also be a problem with the tps, some dirt may have got in there....

[Ben C34]

Does a bike pump provide enough air?

I always use a compressor.

Throttle open doesn't matter as it gets past the butterfly easily as as it isn't fully shut l.

[rondofj]

Yeh was tryin to find a leak, I know about the pvc pipe cap/tyre valve boost leak tester but you gotta drive to the servo, take off the afm there,stick in the pvc cap and then use their air compressor (read that bike pump cannot supply enough air), maybe I will construct that pvc pipe boost leak tester..:S

TPS - where on power fc do I read TPS voltage - is this the THR (throttle?) on the sensor check?? Voltage readings enough to confirm its good?

Coolant Sensor to ECU (not gauge) - is this the one to test/replace? Got brown plug in the NEO right. Also is this the THRM or WTRT on the power fc sensor check and voltage readings enough to confirm it works?

thanks - still learning and its fun :S

[Badgaz]

yeah it'd probably take a frickin age to fill the intake with air from a bike pump lol...especiallly if you do actually have a leak. i did mine at home with a baked bean tin can (yes it worked but not the best idea) and then pluged my air compressor into where the boost controller feed comes of the intake piping and pressurized the intake from there.

the TPS will be difficult...at idle it looks like its showing you the right voltage..i think its a variable resistor...so if it has some crud or junk messing with the mating surfaces it could give you an inconsistent resistance at the points you are having the problem, its easy enough to replace one of those...they have to show between 0.4-0.5volts at idle.

[rondofj]

This car is funny, started it and warmed it a good 5 plus or so mins while playing thru the powerfc commander, by then the idle had dropped to a nice steady ( no bouncing) 850-900rpms and engine note was purry and soft. And the drive felt like a 300rwkw+ car, very sharp, responsive, good low rpm torque, and hits quite hard on boost in 3rd, fries tyres easy, revs out 3rd pretty quick. Smiles all round and the way it should drive. This happens, say 20-30% of the time the car is perfect and you couldnt want more. Which rules out a boost leak cos else it wouldnt run perfect at all with a leak and I' ve checked for leaks and changed hoses/clamps how many times. Didnt check the losing 60% power at downshifts but it would have been there. I have noted that when the cars running perfect, its always after a nice good warm-up while stationary.

And the rest of the time it runs as if theres a boost leak- different groany note, no torque, feels like 240kw, hard to rev out 3rd quickly, thirsty and yeah you know its crap.

So definitely a dodgy sensor somewhere.

Edited July 28, 2014 by rondofj

[rondofj]

A couple powerfc screenshots as Johnnylite requested (dunno why its not upright). What is Ign Corr Map and Fin- these two values change between 15C, 20C, 23C and 32C I noted? After tge drive it was 15C, in the beginning it was 32.

Also is the WTRT voltage on the sensor check the volts from the coolant temp sensor to ecu or the other coolant temp sensor to gauge?

Edited July 28, 2014 by rondofj

[Dose Pipe Sutututu]

Fuel cut decel looks good, other screen is the master temp trim for ignition and injection.

Next is to borrow a CAS and a timing gun

[iruvyouskyrine]

I have a spare Neo CAS in Newcastle if you want to drive that far haha

[rondofj]

haha thanks man, will keep you in mind if I dont find one in Sydney.

Does anyone in Sydney have a NEO CAS that I could borrow for the weekend??

You can keep mine meanwhile, its fully functional just need to see if its the culprit of my problem. I have the timing gun and my base timings set to 15deg

Edited July 29, 2014 by rondofj