GTS-T bucking/hesitating before it builds boost

[planrforrobert]

GTS-T bucking/hesitating before it builds boost

Greets

I've owned my GTS-T for about a month now and have experienced bucking on and off since the start.  The weekend I picked it up it rained buckets and I chocked the poor performance up to weather, and set out to investigate once the weather passed (on the drive home the car would also want to stall occasionally as I came to a stop).  The weather was clear the following day, and a visual inspection turned up a torn fuel line leading into the fuel filter.  Replaced the hose and took it for a test drive- same issues, the car would want to stumble and stall at idle and buck under load. 

I work sales at a VW/Audi tuner shop and some of the technicians are keen on helping me get the car sorted at the shop, so after a few fits and backfires as the car warmed up that Monday, it ran smoothly on my way into work. I should note that it blew the boost signal vacuum line off the intake manifold during these fits...easy fix. I drove it off and on to work for a couple weeks with no issues. Last week on my way into work it started to buck and break up again (at the end of my 30-minute drive).  I had less than a 1/8 tank of gas and wondered if the fuel pump was picking up crap that was sitting in the bottom of the tank. Fill up on the way home and add Lucas Fuel Treatment to the tank- no change.  Took a day off work last week to put some time in with the car and found the three wires on the coilpack harness were either broken or frayed badly right at the connection on the top of the coilpack cover.  Replaced the harness with a new one from Wiring Specialties on Saturday and after a few times stalling out it finally idled correctly.  I took it out and drive it spiritedly for about 10 minutes and it ran really, really good.  I was feeling pretty good about my R32 at this point, so good that I decided to take the wife out to dinner in it later that day (the car sat for about 6 hours). We get in and it will crank and crank and crank but not start.  Great.  Let it sit overnight and it fires right up. That brings us to today. 

I drove the Skyline into work today and halfway into my drive it starts to buck again.  It happens before the engine starts to build boost and I can keep it from happening if I am light on the gas pedal.  I've been spoiled with OBD2 diagnostics in the VW/Audi world but am a bit lost with my Skyline.  I have read that hesitation/bucking out of boost may be an indicator of a bad MAF? I have a Z32 MAF and adapter harness ready to go in, and I have a new fuel filter and coilpacks/plugs at the ready, but I am not keen on throwing parts at a problem.  Could it be a fueling issue not related to the MAF? Anything else I should pay attention to?

I am sorry for the wall of text, but I wanted to make sure I covered every detail.

Thanks all

Mike

[planrforrobert]

Just got in it to head home from work, after for sitting for 8 hours it will crank and crank but not start. At my wit's end. Might I be looking at a faulty coil pack igniter? Trying to find a shop local to me that can scan the car.

[planrforrobert]

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Edited November 3, 2016 by planrforrobert

[R_34]

I lost the engine once after a trackeday on the journey to my home. I had to took of the CAS during the trackday, I plugged it back and finished the trackday but it seems that I didn't fully engaged the plug. After losing it on the highway it wouldn't start at all adn the fuel pump was priming but not running when cranking. Engaging the plus fully solved the issue.

 

Check the CAS plug if there is no damaged wire or if the CAS plug is correctly engaged.

Did you cleaned the maf ?

Check timing belt.

Check spark timing.

Are the plugs recent ?

How many kilometers on the odo ? Could be coilpack or PTU related they tends to break with time.

[GH05T]

sounds like coil packs maby, if its ok when cool and shit when hot... they would be my first go to.

if it brakes down when driving randomly then its fine i would go to the maf connector but i doubt it.

 

if your fuel pump noisy? are you getting good rail pressure?

[Missileman]

Z32 MAF will not work with the stock computer...

 

things to check

Try a known working R32GTST MAF

pressure / smoke test the intake system

fuel pressure test

coil packs

CAS

Alternator

 

[planrforrobert]

Z32 MAF will not work with the stock computer...
 
 

Crap, really? I missed that in my research.

Will be checking everything again tomorrow, including testing the igniter.

[Missileman]

Also, there is a tutorial guide somewhere on SAU on MAF sensor repair try and search for that

[Missileman]

When my MAF sensor played up it would drive normally and when It came to a stop and then when you went to move off, the engine would die like you hit a kill switch, and it throw a code for that sensor.

Edited November 3, 2016 by Missileman

[planrforrobert]

I plan to inspect/clean the MAF, recheck the coilpacks, and test the fuel system tomorrow when I have more time at the shop, but a visual inspection of the wiring to the CAS and MAF did not turn anything up. I was able to test the igniter just now.  Following the video below, I measured resistance forwards and backwards across the igniter.  Testing the 6 pin combinations in each direction, Base(+)->Collector(-) and Collector(-)->Base(+), I measured an open loop for all 12 combinations. Based on that video, open loop from Base(-)->Collector(+) is normal, but I should be reading a resistance Base(+)->Collector(-). Am I safe to assume that my igniter is toast?

 

 

 

 

Edited November 4, 2016 by planrforrobert

[Missileman]

I just tested mine and got a reading of 34~35K Ohms (+) base side -> (-) Collector pins

and an open circuit when you switch to (-) base side -> (+) collector pins

emitter pin was showing around 2K Ohms either way.

[Missileman]

Your problem did sound a lot like what the bloke in that video described.

[planrforrobert]

Your problem did sound a lot like what the bloke in that video described.

That's what I thought, and then my Skyline when and started up at the end of my workday. I'm going to see if it'll start in the morning (and stay running once warm) and take measurements one last time tomorrow and then move on. I have a known working CAS on its way as well as new coilpacks. I feel like I'm fixating too much on this one thing really need to spend time ruling out others.

[planrforrobert]

Alrighty...

New coilpacks, new plugs, cleaned MAF...still nothing. One of the techs at my shop and I got to talking about the cam angle sensor and he suggested that if the ECU is using that to determine engine speed, the tach should move while the car cranks. Sure enough, the tach does not move when the engine cranks.

[blind_elk]

I don't believe that is the case. I just tried it with my Pathfinder (it's on LPG and takes a while to start from cold). Also double-checked with the 32. While the engine is cranking, the tacho doesn't move at all, not until the engine is almost started. And, after all, its only doing about 300rpm while cranking.

You suggested you got some gunk from low fuel in the tank, so have you replaced the filter and had the injectors cleaned? Also, the coil ignitors are prone to problems when they get old, but usually only when they are hot - usually cooling them off fixes the problem, at least temporarily.

[planrforrobert]

Well crap haha.

Fuel filter was the only thing on my list I didn't get to today. Will change it when I do CAS.

[tridentt150v]

Maybe also check the fuel pump is working?  If you can crank it and it isn't starting it is either fuel or spark [yeah obvious I know] and it looks like you have pretty much looked at most spark issues.

 

[planrforrobert]

My confidence level is high that the pump is working. I can hear it run when the key is on, and when I pulled the old plugs they smelled of fuel (I tried getting it to start one more time before replacing the plugs and coils). Boredom got the best of me today, so I went back to the shop to install a fresh fuel filter...judging by how much fuel I spilled, the motor is definitely getting fuel.

[GH05T]

so your still using a Z32maf with the stock computer?

[tridentt150v]

2 hours ago, GH05T said:

so your still using a Z32maf with the stock computer?

That won't work..........issues written all over it.