91 TT Boost leak or MAF or what?

[SmokeyMCN]

I dont know exact boost because my boost gauge reads in mmHg not PSI but im losing around 2 Psi when im at full boost

Anyways ... The problem here :

For example, First gear, I red line it or just change gears at a higher RPM when the turbos are boosting, in second theres either really bad hesitation or the car just f*** up... I put my foot on the gas but nothing happens, Its like the car is off, The boost gauge goes from negative to 0 but thats it, RPMS drop and then after about 30 seconds of nothing happening and the rpms dropping the rpms with start to bounce (With my foot on gas) like itll rev up about 1000 rpms, then drop back down to where It was and keep doing that, If I put it in neutral and hold the gas down, itll do the same thing , itll bounce between rpms, until I let the rpms drop back down to about 1200 rpms then accelerate itll be fine,

But if I drive the car normal, changing gears at 3000rpms or so, and not letting the turbos kick in, the car can get me from point A to point B fine.....

I tried to find a leak but I cant :/

Some one told me its my MAF? but I wouldnt know... this happen to any one before?

[nissanfreak12]

It definitely sounds like a boost leak. Get a boost leak tester, it will be the best investment you will spend about $20 on. I found a leak I had no idea I had.

Check the ECU for codes

Make sure the connections are good between the plug and MAF, usually it has green corrosion on it. More than likely its not the MAF, they tend throw a code. When a MAF normally goes bad, you can't rev it past 2k or 2500, can't remember which one, and the car runs like crap. They have been known to do odd things, check for boost leaks first before throwing money at it. MAF are expensive.

[t.mcginley.jr]

^ also try cleaning the MAF with electrical contact cleaner or better yet, MAF cleaner

[SmokeyMCN]

Soo Saturday night I changed the MAF from my non turbo zx to my twin turbo, and may I say It worked like a charm, Saturday night I had a blast with the car(since it hadnt ran this well in like 2 months ) sunday was also great, as well as on my way to school today. Unfortunately after school it was hot so I turned on the A/C and im cruising on my way home when I notice I hit the gas pedal and nothing happens.... same s*** is back -.-

Soo my next question is, If its not the MAF why did me changing the MAF fix it for 2 days?

If It is the MAF, why the fk did this one fck up too?!

and where can I find this boost leak tester at?

The thing about it now is that even though its happening again, it doesnt happen as often as it did before I switched the MAF....
I would run an ecu diagnostics test thing but it would give me so many codes because theres like 8 different plugs in the engine bay that are unplugged -,- been like that since I got the car, So I wouldnt know what is the actual issue, theres alot wrong with the car....

The specific symptoms this time is when I red line, change gears, but the car is pretty much off -,- unless I let the rpms drop all the way to like 2k then itll be good to go again...

[nissanfreak12]

Still run the ECU diagnoses, put what codes you get, we can help you decifer them or at least point you in the right direction.

Boost leak tester you can get at Z1, Specialty Z, TT.net classifieds. I made my own, all you need is it have a plug where the MAF goes and the ability to push air into it without letting it escape.

How is your fuel pressure? Is your TPS set correctly? Did you clean the connectors to the MAF before installing the NA one? What is the voltage at the battery with the AC on/off?

You my get a lot of different codes because you have a lot of things unplugged, still good to run it. Which things are unplugged, this could be some of your problem.

[SmokeyMCN]

alright ill get to that ecu code later today.No I didnt clean the connection, didnt think it would matter? ill definitely get to that. Also I dont have a fuel pressure gauge so I dont know... I have an oil pressure gauge im assuming, because it looks like oil pressure but it could be fuel? I have a jdm cluster
and I wouldnt know the voltage either, are you thinking maybe the a/c messes with the maf electrically?

[SmokeyMCN]

So I just went down stairs and took off the MAF and cleaned the connection with some alcohol and q tips and while it was off I decided I would do the ecu test ( with the MAF Off) just to see if it would atleast tell me the MAF code to make sure the ecu was reading accurately .. anyways with the MAF off the codes I got were 12 and 34

then I went and put the MAF back and connected it and then did another ECU test and only got code 55 -.-

soo.....

[nissanfreak12]

Well I think your problem could be code 34. Even though it didn't come up again after you put on the MAF. 34 is your detonation sensor, when your engine hears knock, it retards the timing. This will make your car bog down and is very crucial on a TT motor. Check the connections in the plug for the Detonation sensor, if there is green crap like you probably had in the MAF connections, this will cause problems. Actually, I would check all the connections and clean them. If they are corroded, it will make your car run like poo, trust me its worth cleaning them.

Code 12 is MAF, that is normal, but when you cycled the ECU like for testing, it may have cleared out the codes. Run the car again, more than likely the code 34 will come back up. The other issue that runs with code 34 is just a broken old Det sensor harness. When you look at it, look at the side going into the engine. If this is broken, severely cracked, or just hanging on by one wire, replace it. Do not drive it like that, or if you do, take it easy, no boost.

To replace, if needed, normally you have to take apart your engine to get to the det sensor and harness. That is a lot of work, or you can get a relocation kit from bernie on twinturbo.net and that will move it and make your car run better. You still may have a few issues cause it may read basic engine noise instead of just knock, but its much better than running with a broken sensor. Check your timing as well and put the ecu in mode II, this will read how your O2 sensors are functioning. You could just be running a lean condition causing the car to knock at times therefor the hesitation.

[SmokeyMCN]

Okay, great to know that we are getting some where, so could you please explain to me what this sensor does to the car exactly when it senses something wrong? As for engine noise I do have a lifter tick that comes and goes, Ill definitely keep driving it to a minimum but just for my personal understanding what exactly happens that makes it bog down and why is it not good to drive the car like this? What will it lead to?

Ill definitely run the codes when I get home, im in class.

What I dont understand is, this problem started happening when I got the car back from my friend fixing the A/C for me, prior to that the car ran great!!
But ill definitely check the connections too, i know the corrosion makes a difference because I recall having an issue with my non turbo with a conncection and i fixed it by just cleaning it, but could you point me to where I can find it in the engine?

I appreciate all the help

[t.mcginley.jr]

When it throws code 34, the ECU puts the car is "safety mode" which like nissanfreak said it retards the timing some and limits boost to 6psi. This is to keep the engine at minimal stress in case it really is knocking, it will keep the damage to a minimum. Usually though the sensor itself is bad, or the connector is bad. Some people in the past have put in a resistor to basically eliminate the knock sensor but that's dangerous. It's better to relocate it to the back of the engine so that it's still operational and you can service it easier. There's no real damage or sideeffects from driving with code 34, unless your engine really is knocking but it would be pretty noticeable.

As for what this has to do with the A/C, I have no idea lol maybe your friend messed something up or got a connection mixed up? Corrosion can happen on any of the connectors, but the main ones to check are the MAF, TPS on the passenger side throttle body, coil packs, and injector connectors.

[SmokeyMCN]

I went back and I tested again and yes it is only code 34, I checked the connections, there was no corrosion but I still cleaned it, Didnt fix anything, still running code 34. So im thinking of either bypassing it for now because I'm planning on selling it or relocating it, thinking again though, this is the only reason I want to sell it....... haha
But any ways Will it solve the problem for now if I just disconnect it?
or will that make it worse or do the same thing?

Should I relocate it or bypass it?

[t.mcginley.jr]

If you disconnect it, it will be the same as it is now because its not working anyway

You should just relocate it, its really not that much work, take the upper plenum off, take the lower plenum off and your looking at the sensor. Then just buy a longer bolt for the back upper plenum bolt and bolt the new knock sensor on there and plug it in. Or if you didn't want to do that, buy a new sensor AND subharness for it. Then just unplug the one that on there now, bolt the new knock sensor on at the new location and plug that one in with the new harness. You'll just have the old connector sitting back there but it won't hurt anything.

http://www.yugobernie.com/det_sensor.html

[nissanfreak12]

^^^This.

It could just be pure coincidence it started after he did the AC. These cars are known for that.

[SmokeyMCN]

So i relocated my knock sensor and im out of safety boost but my issue about the car like'shutting off' is still happening, only thing that changed is I have more power now and have full boost but still the same issue... any ideas? :/

[t.mcginley.jr]

When does it shut off? While your driving or idling or..?

[SmokeyMCN]

Well it doesnt technically shut off.... but like the symptoms are like its just off , Its not while im idling the car is good at idle,
it happens randomly or like lets say im cruising in like 4 gear goin about 50 @ about 3Kpm, I take my foot off the gas, while still in gear, then when I step on the gas its as is nothing happens... the boost gauge will move from - to 0 but nothing happens, the rpms just continue to drop as if my foot is off the gas, but when I tap the gas or press it all the way down, the boost gauge acts as if something should be happening becuse it goes from - to 0.... and then if I continue to hold my foot on the gas, (with nothing happening while in gear) evenutally it will catch it self and start going again... like when the rpms drop down for example from 3k to like 1800 it will start going again, but then itll stop and then go and stop and go , until I put the car in neutral and let the rpms drop all the way down to idle rpms then start going again.... now it doesnt ALWAYS happen .... and ever since I fixed the knock sensor it happens at diff times, It used to only happen when I would boost hard and change gears or something or let off the gas, now its happening when I dont boost lol Like I can boost 1st thru 4th gear pretty fine now lol but now it seems when im cruising and take my foot off the gas or something, but like I said its not always happening so I cant exactly pinpoint it... any ideas?

And if I were to put the car in neutral from 3k rpms when it starts acting up, itll do that Rpm bouncing thing the MAF does from like 1800 to 2500 until I let go of the gas and let it drop down to idle for a second and then im good to rev

[SmokeyMCN]

Dont give up on me on this one :x lol

[SmokeyMCN]

bump?

[nissanfreak12]

Have you checked for boost leaks, like with a boost leak tester?

[SmokeyMCN]

No i havnt, Ive been meaning to get around to buying one but I know for a fact that I do have an air leak somewhere and I kind of pinpointed it and made a thread about it if you could check it out please 91-tt-clutch-booster-vacuum-leak-t567551.html

[nissanfreak12]

Another thing to check, how are your O2 sensors?

[SmokeyMCN]

I think theyre fine? My ecu doesnt read any o2 sensor codes

[SmokeyMCN]

Some one mentioned to me TPS adjustment or replacement... anyone nknow anything about it?

[nissanfreak12]

I think theyre fine? My ecu doesnt read any o2 sensor codes

Your ecu has two modes, mode II checks the O2 sensors. The ecu may still see is as good, but they may not be doing the exact job they intended to do. It could very well be either rich or lean.

For the TPS, free fish today...

http://www.twinturbo.net/nissan/300zx/f ... ensor.html

[SmokeyMCN]

So how can I test forsure if the o2 sensors are good or not? And would the o2 sensors or tps make the car act like this?

[SmokeyMCN]

So how can I test forsure if the o2 sensors are good or not? And would the o2 sensors or tps make the car act like this?