10 psi bog sesh

[chitrees]

Hey guys,

A little intro and history to the car. It is a 91 r32 w/ controller, fmic, bov. Before I got it, it was sitting in a garage with couple years old fuel. I drove it home with that **** fuel (idk might play a factor).

Let's start with the symptoms.

1. Unable to start at any temp. (will only start if I "feather" the pedal)
- I cleaned the AAC valve and throttle body. Car now starts without feathering, but not instantly like a normal car.

Also, the car would die out at idle easy sometimes. Getting a new ignitor solved this problem.

2. There is a ticking sound on the intake side; it sound like a pencil tapping (I'm assuming that this is an injector). Note: When i rev the engine, I can't hear the ticking anymore (maybe because of the loudness of the engine itself); however, when the car is coming back down to idle, the ticking comes back at a faster pace and then slows down back to its original idle speed pace.

3. The main symptom

At any gear, when I reach 10 psi whether it be WOT or LOT(little open throttle?), the car bogs/hesitates/judders and does not accelerate anymore past its current rpm unless I ease off the throttle. If i open the throttle at a hairline keeping the boost under 10 psi, the car will slowly continue to climb rpm no prob.

Note: If I am in idle, I can WOT and the car will climb nicely. Bogging occurs when in gear. Car has power to lose traction initially in 1st but starts to bog (or lose power) when it catches (reaching 10psi threshold?).

Now what I've done.

1. New battery.
2. Cleaned AAC, throttle body, MAF (did not check resistance. Don't even know what the resistance should be.)
3. Basically new ngk bcpr7es-11. Not fouled.
4. Sealed coil packs with liquid tape, electric taped the boot, and lubed her up with dielectric grease Resistances came back to 0.9 ohms.
5. Re-sleeved intercooler piping for boost leaks. (Note: I have not checked for a vacuum leak yet).
6. New ICM.
7. Checked the CAS. Injectors click away as does the plugs.

I am going to have to check the MAF and TPS resistances to ensure that they are operating normally. Anybody know the range?

[ToroGTS]

Here are a couple things to try:

-replace your fuel filter with a 300zx oem one, it wont fit in the bracket and that is fine zip tied to something.
-go back to stock spark plugs, especially if this tends to be aggravated by the temp of your engine.
-really this seems to be a typical ignition coil issue. Go to splitfire, new oem, or ls2 coils.

This 'ticking' is almost certainly your injectors. When I first started working on rb's I was concerned about this until I saw the same on several healthy engines and used a stethoscope to confirm where the noise was coming from. The noise 'disappears' when you rev becasue the pulse becomes so rapid it becomes a consistent buzz rather then repetitive tick noise.

[chitrees]

Oh I forgot to mention that. Ya the first thing I did was change the filter and the strainer on the actual pump.
Stock plugs? The bog isn't temperature dependant.
In what way can the coils still be bad? Their resistances are what they should be. Some did arc when I pulled them out when the car was running, so I gave them a makeover. Will they still arc under load despite the layers I added? I don't want to drop a couple hundred on something that may not be the problem.

Oh ok. Why does it seem to be a single ticking sound? Is it just one injector doing it, and if so, why? Shouldn't they all be ticking?

[Skym]

Stock ECU can pull ignition timing, run engine rich if knock is detected which causes a big V dip in torque in the midrange on torque plot on dyno chart.

I think tune is out and ECU needs to be retuned with Nistune or similar which can solve starting, idling, bogging problems.

Also the bog can be caused by leaking BOV or leaking gasket under stock BOV. Sometimes the stock BOV is modified which causes the engine to bog. Switching to Synapse or similar type of BOV fixes this problem.

Sometimes the bog can be caused by a leaking coilpack. Grey tracking marks on both sides of the coilpack, just under mounting bracket gives this away.

[chitrees]

Yes….Dr. Skym House has arrived. Ok, today I cleaned out my plugs (they were a little black around the thread but not the actual electrodes. They were brownish grey so ok) and gapped them to .8(turned out they were 6's not 7's), and changed the TPS signal to .47 V idle contact, and reset ecu (i did the "fix hesitation sticky" method).

Here's the symptom:

https://www.youtube.com/watch?v=haKpmb5AMl0&feature=youtu.be

The changes today helped in reducing the intensity of the bog, except in 5th. Video is WOTish until I slowly climb it in 4th to 4k to show it can.

I also have a video (crappy) on the BOV/ticking:

https://www.youtube.com/watch?v=nNo__7ZgVDo&feature=youtu.be

Would it be more wise to hook back up the recirculation/wastegate? valve(is this the "elbow" off of the intake pipe over the engine)?

[Skym]

All I need is a PHD.

It looks like a fuel cut on ECU is engaging in that first videoclip. Check for intake leak before MAF, as a airleak there can make the ECU hit the boost cut earlier than it should, usually just over 3000rpm. If the airfilter clamps onto a adaptor with a intake hose clamp, change the airfilter to a bolt on type of airfilter (Apexi). Temporary fix is to tighten the intake hose clamp on the airfilter.

If the fuel cut happened at 2500-3000rpm, then I would think MAF problem / failure (or wiring to MAF or wiring into MAF plug problem).

The stock BOV should recirculate the air, as any air loss behind the MAF due to the leaking BOV, the stock ECU can't see the loss and make adjustments to fueling, ignition.

If run a MAP sensor on intake manifold, the ECU can adjust to more or less air. Same with ethonal content if run on E85 with an aftermarket ECU, ethonal content sensor from say GM.

[chitrees]

If it was the MAF, wouldn't it mess up fuel quantity when I was in 4th around 4k? Is it that my MAF only works with that low flow of air(under 10psi?) and malfunctions under load? Or does a malfunctioning MAF produce symptoms throughout the whole rpm range?

[chitrees]

Have you seen this symptom manifest due to a problem with the turbo(waste gate sticking or something?) Or is this more of just a fuelling issue? I'm not 100% on any boost leaks but I'm fairly confident.

To mini test my FPR, if I take my vacuum hose off should it idle higher or lower? Would the increased fuel pressure make it idle higher or lower due to it being rich?
Idk, when I wiggle my injector connectors, the engine idles lower (coughs up) like I took out a coil pack. Issue/normal?

*Can a damaged exhaust manifold produce these symptoms? Like a missing or cracked bolt? Or should the car still climb but with difficulty?

[Skym]

Sometimes the MAF sensor gets oil on the hotwire and can't burn off the deposits. Cleaning with CRC MAF cleaner can help to solve this problem.

In some cases the hotwire inside the round part of the MAF burns out and only relies on the IAT (Inlet Air Temp) sensor that is next to the hotwire (flat blade looking thing).

In some cases there's intake airleak just behind MAF (cut in rubber intake piping between the ribs, loose intake hoseclamp, cut in piping under intake hose clamp) which produces similar symptoms to a missfiring coilpack (engine starts to stutter).

But sometimes it can be as simple as one coilpack leaking, which can cause the engine to intermittently missfire throughout the whole rev range. Usual initial symptom of this is loss in torque at lower rpm.

The internal wastegate spring can fail due to age, but get a rattling sound on back of turbo (wastegate flap rattling around at idle).

With FPR hose vacuum hose rmeoved, blocking the nipple on intake manifold, this should increase fuel pressure by roughly 7.1psi. If engine runs richer the revs should drop. If runs leaner the revs rise.

Exhaust manifold airleak is fairly obvious, as it starts breaking the studs off (replace them every 10 years or so as part of routine maintenance) around 5th, 6th cylinders due to exhaust swinging (exhaust hanger bushes get old and stretch). Some put a exhaust flexi in the front pipe to help prevent this from happening with aftermarket exhaust manifolds (same flexi pipe mod you see on Honda's).

Also if put a wideband o2 in the exhaust, the A/F ratio will head towards 17.0:1, as more oxygen is entering the exhaust system and the o2 sensor picks up on this.

One way to test for exhaust leak is turn engine on and get someone to block the end of exhaust for few seconds at a time and listen for exhaust leaks. If the engine stumbles and there is no leaking sounds, then most likely there isn't an exhaust leak.

Sometimes the wires into the plugs can fall out or be damaged. Adding some tape (forget the brand name) around the wires to help the connectors to grip onto the wiring.

[ToroGTS]

Ok I didnt read through all of this yet but I did watch the video. This is very similar to typical MAF failure syptom which is to basically rev limit the engine at ~3500 rpm regardless of engine load. 100% this is not a lean out, knock, timing pull type situation. It seems almost like the MAF signal is topping out at some point and as a result timing and fueling are only adjusted to a certain point. Do you have a buddy with an rb20 MAF that is known to be good that you could swap with just to try it out?

[chitrees]

No Toro I unfortunately don't. I still need to check my voltage output on my MAF, BUT the thing is I can go past 3500-4000 rpm. In near the end of the video I slowly climb up just past 4k if kept under 10 psi; I'm confident it will continue to climb. The road I was on was narrow and bumpy and I had the camera so I didn't want to go too high.

[chitrees]

Cleaned.

Can I diagnose a malfunctioning hot-wire physically or do I have to test the MAF electrically to determine this?

So if an intake leak produces symptoms similar to that of a leaking coil pack which is a misfire (is this like hiccups in the rpm but continues to still climb, or can it misfire to the point of no more acceleration?) throughout the range, I think I can rule those out.
I feel like it climbs well now after the gap change and pack sealing but stops at 9-11 psi.
Loss of torque at low rpm? I know if clutch dump I can spin the tires until it reaches the 10, from there it bogs. Idk, does this rule out coil packs?
I do need to check out that accordion hose for cracks for sure. I do know there is oil residue in there for sure and in the down pipe of the FMIC. I'm presuming this is a damaged (oil seal?) in the centre housing? I know this is not good but on a scale of 1-10 how bad is it?

Ok, waste gate should be good. No sounds there.

My car idles back up/higher when I block the nipple on the IM, so my car is running lean? So if the increased fuel pressure normally makes the car run rich and idle lower, could my injectors possibly be clogged due to my car being lean? I'm not sure here if these conclusions follow from the removing of the vacuum hose or from blocking the nipple.

But wait…ya I'm pretty sure my 6th cylinder stud is out and half of the circle/bulging part of the manifold is off, like cracked off. I have pictures but don't know how to post them without the url. When I rev the engine at idle, I don't hear any air leaking out. Doesn't smell like fumes either, idk. But with this crack, my car should be running rich right due to the high AF ratio right? Could extreme air enter the system through the manifold while under boost which causes richness and therefore no more acceleration? Or does this potential unmetered air stay out due to the higher pressure in the manifold under boost?

Thank you for the full answers.

[Skym]

You're welcome. If stops at 10-11psi, then that most likely is ECU tune related. The ECU will pull ignition timing up until around 6000pm.

With FMIC, podfilter, frontpipe, catback exhaust with no cat it should reach roughly 13.5psi.

Also check the little vacuum hose next to throttlebody (facing firewall) that connects to brass piping on the side of the intake piping which goes over the top of the engine. Sometimes that not being connected can cause engine to bog a little bit.

[ToroGTS]

I hate to disagree but in my opinion this is 100% not the result of timing pull. Even massive timing retard will still allow the engine to rev out at a semi normal rate, you will just make almost no power as the flame front moves closer and closer to the open exhaust valve. The only exception being when retard is induced for launch control where the retard to so great the explosion is partially occurring in your compressor housing, and even then rev limiting is used to ensure it does not rev out.

It appears you are having a failure of spark at a certain degree of cylinder temperature & pressure. It's likely one of two things:

1.) "Spark Blow Out", due to weakness in the ignition system: plugs (improper gap, heat range to hot ect.), coils (weak spark, discharging to head), ignitor chip (though you have replaced..), break in wiring harness that is unable to deal with rate of ignition signal or something, ect.

2.) Failure of ignition control:

These are the sensors involved in ignition control:

-TPS (obviously not the problem since you are fine at all conditions out of peak boost)

-Knock sensor x 2 (Not suspect as they ONLY result in timing retard under knock detection, unless of course your issue is actual lean detonation, Do you have a wideband? can you verify this is not the case?)

-Coolant Temp sensor (Only used to switch from cold fuel/ignition maps to hot maps, and extrapolate for temps in between or cold starts in combination with the little cold start valve above fuel rail & throttle body)

-Crank angle sensor (functions solely to provide an indication of when the exhaust crank is at 0 or 120 degrees rotation, for the purpose of ignition and injector pulse timing. Tends to fail or work in general and not at a specific rpm)

-MAF (Used primarily to select cells from timing/fuel maps, and not directly to initiate spark event which is primarily controlled by CAS, this can fail in numerous ways and produce strange symptoms)

So on a basis of the above information the only sensor I would suspect is the MAF which can be ruled out by swapping with a buddy or probing the back of the connector on pins 2 & 4. Bring the voltmeter in to the car and observe ~1V cranking, ~1.1V approx at idle, and approx 2V at 2500 rpm... you should see a greater rate of voltage increase as engine load/boost increase, but it should be without any gaps in reading or diversion from a generally exponential curve beyond positive manifold pressure. It really seems like in your video that you hit a certain air flow rate, there is a disruption of your air flow signal, the engine stumbles half a second and recovers until you are at the same flow rate a moment later and the cycle repeats.

If all the above control inputs can be ruled out, then you are only left with one culprit, being the ECU it's self. I've seen ECU's fail in numerous ways, and they all look perfect visually, as the failure is within the transistors or capacitors themselves. In rare cases you take off the outer case to see a capacitor visibly leaking a dark fluid that hardens on the circuit board. If you are running a stock oem ecu, there is no reason to suspect the factory tuned 28 pin eprom chip has somehow changed. If you are on a chipped ecu, running a piggy back like Apexi SAFC or similar this could be a source of your problem.

Verify that you have no intake manifold leaks by hooking up a vac/boost gauge and reading a min 16''hg vac pull at idle. If you have wideband then you can cut your o2 sensor signal return wire (copper brown color single wire running from ECU harness, use bullet connectors so you can reconnect at will) and your ecu will default to the ignition/fuel maps on the eprom and run fine. I do this for all oem style ecu's including nistune when tuning to narrow in base maps.

[chitrees]

Thank you for responding Toro. I greatly appreciate your disagreement for the purpose of more ideas. I really want to veer away from the ecu and leave that as my last option. It is a stock ecu and has been sitting for a couple years, I'd assume that factory settings were in place still.

I feel like I can rule out Spark Blowout except for the harness. I'm not 100%
if the harness is secure but I know if I wiggle it during idle, idle doesn't seem to break up. Coil packs are really 50/50. I mean I know resistance wise they are in spec(0.9ohms) and were leaking (I took one out at a time during idle and observed them arcing to the head). I sealed them up and checked them again and arcing is greatly reduced. It only arcs if i place the pack really close to the head, and even then it is a small arc. Does this mean that this pack is susceptible to leakage under load?

Unfortunately I don't have a wideband. The only information I have is that the plugs were just brown at the electrodes and black around the thread. I don't know how long plugs take to foul up but mine were relatively new. I'm not getting black smoke at idle or when this symptom presents itself.

In regards to the CAS, I spun the wheel to check the injectors/spark. Did I change the timing? Due note that this symptom was still present prior to CAS test.

I'll get back to you on the MAF.

START UP ISSUE

Car will combust initially but will not start. It will only start if pedal is depressed/"feathered". [COLD startup]
Car will start up (sometimes) by itself but with struggle. Will start a lot quicker with pedal depressed. [WARM]

Manual taks about the AAC valve. Cleaned that, and adjusted TPS to .49 V.

Idle is constant. I got it at 8-900ish to prevent it from stalling if i apply electric load by turning the wheel all the way and holding it there. If I put it at its factory rpm, it will usually stall out with wheel turning.

Is this a timing issue? Not enough fuel at startup? You listed TPS under ignition control (I thought it acted solely as an auxiliary control for fuel quantity?) Is it responsible for ignition control by way of timing or intensity? What does setting it to .5 V closed contact actually do? So is the TPS adjusting fuel or ignition when I play with it during startup, or both?
Maybe an vacuum leak?



I feel like these two symptoms are the effect of one cause...