Still hitting fuel cut... Please help!

[fiyota]

This little issue is starting to drive me crazy. I spent a good several hours yesterday replacing all the gaskets on the intake manifolds & egr and replaced all the vacuum lines (making sure no loose ends weren't hooked up aswell), and I also checked all my ic piping for leaks... nothing was found.

So I fire it up after it's all put back together and take it for a spin... imediately I notice that my stumble when I stop hasn't gone away (sometimes stumbles so bad it stalls, or wants to stall and then I have a lopey idle for a bit)... so that worried me. But I kept driving it to get the motor warmed up a bit. The stumble got a bit better.. that's good. But, after it was warmed up I tried boosting a little bit, boosts quickly and hard the first few 6psi pulls that I did... So then I thought, well either I fixed the problem or I didn't, so I really get on it. Boosts really hard, my gauge gauge reads about 9psi and BAM my head flies forward and the check engine light comes on. Shit.. fuel cut.

Now. Since I'm about 99% sure I don't have any leaks anywhere. What else can cause fuel cut, I have a few ideas what my problem could be, but I would like some imput. Please let me know if any of these could be related, or if they are completely irrelevent to a fuel cut issue.

1. My O2 sensor wire got a little mangled by my exhaust manifold... does the ecu use imputs from the 02 sensor to help determine if it should cut the fuel?
2. My afm could be dirty/oily. My afm has had a k&n intake on it for several years and I don't believe it has ever been cleaned, would a dirty afm cause fuel cut early?
3. AFM itself could be bad. This i'm not sure of
4. I have another leak somewhere that I have no idea about. Replaced all the intake side gaskets, checked ic piping, and replaced the vaccum lines.

Any opinions?

 

[tlo86]

This little issue is starting to drive me crazy. I spent a good several hours yesterday replacing all the gaskets on the intake manifolds & egr and replaced all the vacuum lines (making sure no loose ends weren't hooked up aswell), and I also checked all my ic piping for leaks... nothing was found.

So I fire it up after it's all put back together and take it for a spin... imediately I notice that my stumble when I stop hasn't gone away (sometimes stumbles so bad it stalls, or wants to stall and then I have a lopey idle for a bit)... so that worried me. But I kept driving it to get the motor warmed up a bit. The stumble got a bit better.. that's good. But, after it was warmed up I tried boosting a little bit, boosts quickly and hard the first few 6psi pulls that I did... So then I thought, well either I fixed the problem or I didn't, so I really get on it. Boosts really hard, my gauge gauge reads about 9psi and BAM my head flies forward and the check engine light comes on. Shit.. fuel cut.

Now. Since I'm about 99% sure I don't have any leaks anywhere. What else can cause fuel cut, I have a few ideas what my problem could be, but I would like some imput. Please let me know if any of these could be related, or if they are completely irrelevent to a fuel cut issue.

1. My O2 sensor wire got a little mangled by my exhaust manifold... does the ecu use imputs from the 02 sensor to help determine if it should cut the fuel?
2. My afm could be dirty/oily. My afm has had a k&n intake on it for several years and I don't believe it has ever been cleaned, would a dirty afm cause fuel cut early?
3. AFM itself could be bad. This i'm not sure of
4. I have another leak somewhere that I have no idea about. Replaced all the intake side gaskets, checked ic piping, and replaced the vaccum lines.

Any opinions?

Sounds like its all your AFM, our afm's havent been known to be very friendly with k&ns and require a cleaning (could have the oil all over it messing with the meter, i stopped using a k&n and stuck to an apexi filter and now i just use stock toyota filters)... check connectors use electric cleaner on the plugs make sure they are clean try again, if so then you clean the meter itself. of course i dont have great advice on doing this i had the same problem and i used a residue free sensative electric cleaner on it.. left it overnight and problem solved.

and that isnt fuel cut that is just your car stalling it seems

 

[fiyota]

It is fuel cut... the ecu is storing code 34 after it happens (Turbocharger Pressure)... at 9psi the car bucks violently and the cel comes on for about 4-5 seconds.

So you think it's the afm that's causing the issue then. I know the ecu uses the afm as a reference for if it needs to cut the fuel or not, but does it also use the 02 sensor? It would make sense that it would, since it could see if it's running rich/lean/stoich right?

I'm going to try to find something to clean the afm with and then I'll check all the connectors to make sure they are clean.. do you recommend packing the plug with dialectric grease? Also, would I be able to remove the electroncis from the afm in order to clean it better? So I can use a harsher solvent to clean the housing and then something that's safe for the afm to clean the electronics themselves?

 

[thebuddrik]

did it just start this ?

 

[fiyota]

It started it a week or so ago, I thought it was just a big leak at my intercooler which has been patched up, so I bipassed it and found that it still does it. So I then yesterday tore the whole intake off and replaced all the gaskets vac lines etc... and it still does it. I had only been running this amount of boost for about a week before this started.

 

[tlo86]

grease would be very nice although i didnt hehe 2 years later here i am still works fine.

honestly i wouldnt even go that far, just use something for the sensor as it should be enough to get rid of the oil since its pretty light.

tap the afm with a wrench see if it mimics what your are experiencing

 

[fiyota]

hmm did some research on cleaning afms.... turns out the only way you can clean it is with freon gas so it doesn't craze the optical sensor...

so my question is, can I go to say, wal-mart, and buy a $16 dollar bottle of that a/c stuff that is designed for both types r12 and r134a, will that work to clean it?

 

[tlo86]

hmm did some research on cleaning afms.... turns out the only way you can clean it is with freon gas so it doesn't craze the optical sensor...

so my question is, can I go to say, wal-mart, and buy a $16 dollar bottle of that a/c stuff that is designed for both types r12 and r134a, will that work to clean it?

not sure about that honestly. i'd check the connector first

 

[fiyota]

connector is clean... no corrosion, both the afm plug and the harness plug are good.

The afm is really dirty inside tho. a fairly thick layer of goldon coloured grease.. I think that's my problem. If I knew somebody with a supra I would try a good afm and see if it solves the problem but I can't... So do I try cleaning the afm or do I just get a new one?

 

[jetjock]

Use of solvent on the electronics is at your own risk. The last guy I know who used a cleaner (the CRC stuff sold for hotwire MAFs iirc) killed his. Why people attempt this in the first place is puzzling because there isn't any cleaning that can be effectively done that way even assuming a need. My opinion is there almost never exisits a valid reason to clean this type of AFM. They are killed by people grasping at straws because they don't know how to diagnose the real problem properly. For example all it would take to eliminate the AFM as a cause would be simple measurement of the Ks signal.

Due to the nature of how the AFM is constructed if it works up through 6 psi the odds are overwhelming the electronics are good. If you really feel the need remove the electronics, clean the housing with whatever solvent you wish, then wipe the Karman pillar down with a dry cloth and check the pressure sensing hole is clear.

The O2 sensor is not involved in any way.

Lastly, I don't know how you "checked" the induction system but if it didn't involve pressurization it wasn't done right.

 

[mkIIIman089]

Just wondering, was this a complete 7M-GTE and electronics set swapped in place of a 7M-GE or is it some kind of hybrid in the traditional sense of NA-T?

 

[fiyota]

Fixed the leak. yes it was a leak. I don't know how I missed it.

IJ: you are absolutey right on that one, I did just do a once over of all the ic piping (or I thought was all of it).. I was actually in the process of rigging up my air compressor to the intake system (block off at the 3k pipe and hook coupler with an air fitting onto the turbo) when I found the massive whole in my ic setup. The pipe coming right off the turbo had cracked at the hose clamp leaving a big gaping hole. Cut it shorter to get rid of the broken parts and make it sit flush (toyota was closed today and tomorrow i will be ordering a new pipe).. and she holds boost fine now.

also, I wouldn't have cleaned my afm with anything other than a freon type cleaner (with ozone completing gasses and all)... but it turns out it doesn't need it. That was a last resort thing trying to track down what could be causing this.

Just a quick Q for you tho... what does the ecu use with the 02 sensor reading.. what is controlled by it.. I would assume adjusting the fuel mixture would be part.. but does it influense say, what the ecu determines as too much air to call for a fuel cut or is that strictly controlled by the afm?

Thanks all that have contributed in my thread!

mkIIIman... it was a complete gte swap.. basically had a wrecked parts car that I pulled everything out of (thus the mangled intercooler from the front end wreck)

 

[mkIIIman089]

Since you solved your problem.

Where did IJ. say anything?

 

[jetjock]

I assume he's referring to me. Since it's an honor to be confused with His Holiness I'll let it slide .

fiy: A leak is what I suspected. That hose is a common failure point and you aren't the first to repair it that way. Interestingly that hose on my car is original, as are all my intake hoses except the TB coupler.

Cleaning the AFM using refrigerant would require vapor cleaning as putting a boiling liquid in it wouldn't be wise. That said there would be no need to buy actual 134a. A can of air duster or electronic freeze spray is almost always the same chemical. Hold the can inverted to get liquid, upright to get vapor.

The best thing to use would be a solvent called Freon TF. It's no longer legal to manufacture in the US but can still be bought for a hefty price. Again though, because of how it's made the AFM is unlikely to fail because of contamination unless done by the owner or something weird is involved ie; mounting it upside down. Otherwise the odds of one actually needing to be cleaned are tiny.

The O2 sensor isn't involved with code 34 because the engine is in open loop during periods of high load. In fact (since airflow is one of two primary inputs that determine load) it's the AFM that keeps the O2 sensor from being involved. Input from the AFM is the primary variable used by the ECU to determine fuel cut. One other is involved but since it isn't a sensor input there's no way to diddle with it.

 

[Nick M]

Cleaning the AFM using refrigerant would require vapor cleaning as putting a boiling liquid in it wouldn't wise.

That is a nice way of putting it. You feeling ok?

 

[jetjock]

That should be "wouldn't be wise". Yeah, feeling ok. No more grumpy than usual.

Btw hows the little one doing? I saw the photo. Great pic of a tough guy being tender

 

[Nick M]

That should be "wouldn't be wise". Yeah, feeling ok. No more grumpy than usual.

Btw hows the little one doing? I saw the photo. Great pic of a tough guy being tender

Thanks. I talked to the wife yesterday. She gets more sleep than I do now. Just look at the stupid thing I said in the deceleration thread.

 

[fiyota]

woops sorry jetjock.. i meant to put jj but my finger must have slipped.. it was almost 3am my time when I posted that!