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Discussion Starter #1
Hello,

I have been working on this car for awhile and I'm stumped as to what is wrong. In the last few months I have installed the following on this motor:
1.New timing belt, water pump, and tensioner.
2. New proper Injectors
3.plugs, wires, cap and rotor. Did not replace distributor.
4. Rebuilt the cone on the supercharger.

Everything was running well for about 2 weeks when it suddenly started running really rough. Brought it home and saw raw gas being sprayed from a crack in the driver exhaust manifold. More gas dripping from the tailpipe. Pulled all the plugs and they look good. With plugs out I turned to on position to see if the injectors were open, but could not see anything. How can one test a distributor? I looked at it with the cap and rotor off to see something obvious but nothing of note.

Thank you for the help.

Tyler
 

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Seems very unlikely gasoline would be dripping from your exhaust, since the tailpipe gets hot and would vaporize it. It could be water, which is a normal combustion product and often drips from a tailpipe, especially after idling. Also not likely to be gas spraying from the exhaust manifold because a) gas is not carried through the exhaust manifold and b) your X would catch fire quickly. If you are sure gas is leaking, check the injectors just replaced or fuel rail they connect to.

Suddenly running rough could be many things, but a broken vacuum hose comes to mind. You can test your distributor with a timing light. You can also buy a cheap OBD-II code reader ($15-20 online) and use a free app like Torque to read any error codes coming from the engine controller.
 

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Discussion Starter #3
Thank you for the reply, Springfield. I know it sounds crazy, but it is gas spraying from a 2 inch crack in the manifold. It is throwing a code of P0300,( general misfire if not mistaken). I am stumped. Never seen something like this before. I am reticent to pull the supercharger and adapter plenum in order to gain access to the injectors and fuel rail. Those gaskets seem like one time use and the lower one is $40 everytime i take it off(2 times in the last month). I will if I have to, but I wish there was a way to check those components without the teardown. Could it be the ECU is bad and signaling through the ground wires to the injectors, keeping them open? I will check all the vacuum hoses to eliminate that possibility. Any and all help is most appreciated.

Thank you
 

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2001 Xterra 4WD Auto 3.3L NA V6
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Just a head's up on OBD readers. The cheap ones usually read only the P codes. The BlueDriver for about $100 reads all 4 families: P, B, C, and U. The dongle is what you buy; the app is free.

Stop and take a deep breath. Now that you're calmer and can think more clearly, ask yourself, 'What would cause gas to get out of the intake manifold into the exhaust manifold, only to exit a crack in it?
  • Fuel being sprayed in enough quantity during valve overlap, and with enough air pressure to push it out
  • Fuel being sprayed into the cylinder and then being exhausted without being consumed
  • A major leak between the two manifolds (failed gaskets?)
  • Valve timing is set improperly (timing belt jumped a tooth, or not installed just right?)
  • EGR malfunction
  • Vacuum hose or other hose hooked up wrong
There may be more possible causes, but these are some ideas off the top of my head.
 

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I have seen leaking fuel injectors make all kinds of problems. I know you just changed them but maybe one came with a problem?
 

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Discussion Starter #6
Well, Thank you all for your time and help. Here is my update:

I replaced the cracked driver side exhaust manifold. I tore down the engine to below the intake manifold. There I accessed the broken knock sensor. I checked the wiring to it and it looked good. I cleaned and inspected the fuel rail and all related components and everything checked out normal. The injectors all have a resistance across the two leads of approximately 12 ohms. This measurement was taken with the injectors in their respective cups in the fuel rail. When the key is in the 'On' position all of the injectors are being supplied 12 volts and none of them are grounded. Without the supercharger installed and while cranking the engine, i have observed the pulsing ground via a simple test light connected between the positive side of the battery and the prong side of the tester touching the ground lead of the injector wiring plug. these tests were performed with all injector components installed. I had to drain and refill the oil, as it was inundated with raw gas. I also replaced the distributor. I checked the compression of the engine cylinders. I found 1,3,5,2, and 6 had approximately 150 lbs and #4 had approximately 140 lbs. I also installed a new knock sensor but relocated it to the back bolt of the supercharger. It is well grounded. After not finding anything wrong to explain what had happened, I reassembled the engine and started it. It started up perfectly, during the time it took me to set the timing with my light, I looked back by the tailpipe and again noticed a significant amount of raw gas dripping from the exhaust system. I have again torn the engine down and rechecked everything, running all of the aforementioned tests.

Has anyone ever experienced something like this? I feel like through the process of elimination that there might be a problem with the computer, but it only manifests once the engine is running. Perhaps once the engine is running, the computer then supplies a constant ground rather than a pulse. With the engine torn down, however, I cannot run this test. Have I missed something?

Thank you for taking the time to read this.
 

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One of the fuel injectors could be stuck open. once i had a leaking injector fill a cylinder with gas to the point the engine would not turn over.

Or could the fuel presser regulator be leaking in to the vacuum line attached to it?
 

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Discussion Starter #8
I replaced the fuel pressure regulator, fuel pump, and filter. I am able to observe the fuel rail system under pressure and all functions properly with the key in the on position. I agree that it must be a stuck open fuel injector, but only once the engine is running. Even while cranking, the ground signal is a pulse, not an always on. I can only create the condition while the engine is running.
 

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The only points of entry for gas to get into your engine and therefor the exhaust are the fuel injectors and the intake manifold via a bad Fuel Pressure Regulator, but there are sensors that could cause it to run rich.

I recommend clearing the codes and watching for the pending codes to see if you are getting a p0301, p0302, p0303,p0304, p0305, or p0406 before the p0300 sets in. This can tell you a lot. If it's the FPR it typically will go to a p0306 first since the FPR vacuum line is directly above the intake tube for cylinder 6.

Likewise, it can help you diagnose the injectors by cylinder number.

If it goes straight to p0300, you could have an issue with sensors that are giving false readings to the computer resulting in a rich condition.


It is possible that the replacement FPR is bad. Pressureize the fuel rail and pull the FPR vacuum line off the back of the intake manifold to see if gas dribbles out.

It is also very possible for one or more of the fuel injectors to be stuck open regardless of the signal it is getting. Did you try spraying cleaner through them while you had them out and disconnected? Nothing should go through when there is no signal. A single stuck injector will not give you a p0300 though. It will give you a single cylinder misfire.

All that said, It is also possible that you have one or more REALLY lazy O2 sensors resulting in a huge increase in gas coming from the fuel injectors because the computer sees it as running too lean. Lazy O2 sensors do not always trip the O2 sensor code.

Did you check for spark from each of the spark plug leads?
The distributors are know for self destructing bearings. Pull the rotor and look down in the well for any metal shavings.

As mentioned, it's possible that the timing belt has jumped a tooth or two.
 

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Discussion Starter #11
Thank you for your reply, Satito.

Since the last time I posted on this, I have done additional work in trying to figure out why the injector(s) are stuck open. Currently the supercharger and lower plenum is off in order to better observe things. When I pressurize the system nothing is stuck open. The injectors are closed and the fuel pressure regulator functions properly. I have removed the spark plugs and can visually observe no fuel entering the combustion chamber while the system is pressurized. Additionally, when I depressurize the system (removing the fuse for the fuel pump) and turn the engine over, I am able to observe via a test light, a pulsing ground signal from the computer to each injector. The distributor is brand new and the timing belt is on correctly (as I took the painstaking steps to remove all of the tin shields to observe the correct placement, just to be sure). I have not replaced any of the O2 sensors however. It only seems to have the stuck open injector problem when the engine is running. My next step is to put the thing back together and run it again to observe the test light ground signal with it running. On a side note, for others that may encounter a similar problem, I had to drain and refill the oil too, as I observed gas in the oil via the dipstick. Hopefully when I run it this time, everything will just work properly and I can move on! haha, yeah right! As you mentioned, Satito, I will clear all codes and once running will then see which cylinders are showing the misfire. Having eliminated the actual injectors and FPR as culprits, my suspicion now turns to the wiring, the computer, or perhaps as you mentioned, the O2 sensors. I will report back once I figure this all out. Again, thank you for your reply. I hope I can resolve this issue soon and get this truck back on the road!
 
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