Car Dies

[ike84]

I'm not well versed with the timing issues so I'll pass to blue one that one. I can talk for days about the injector leaks though. Our oem injectors are prone to sticking open. It's happened to several members. You will smell gas in your crank case when you open the oil fill tube and if you change your oil it will run out like water. This most often will happen after the car sits for a while. Piwis software (and durametric I think) allows you to turn off individual injectors to try to troubleshoot some issues but there's no great way to tell if an injector is leaking except for pulling them and testing. Testing is a process best done by reputable shops but it's not cheap. What is cheap is to retrofit 986.2 Bosch injectors - you'll pay less for them new than you will to have the old ones recalibrated. While timing issues will cause intake backfires, a leaking injector will not. I agree that it sounds as though you may have more than one problem. I would check your oil. If it reeks of gas and is thin as water you can at least start to nail down one issue.

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[blue62]

After getting more information from the OP in post #22 where he describes how the car reacts to throttle. And also the fact that it is backfiring into the intake.
Here is what I think is happening.

There is some issue with at least one cylinders valves.
OP names #4 cylinder.
There is some issue with the intake valve. it is not sealing at the seat.
Due to something like a broken spring. a weak spring. a collapsed lifter.
A sunken or damage valve seat. Something is preventing that valve from sealing properly.
The only way a backfire can happen in the intake is for burning fuel to get past the intake valve.
So I think there is an intake valve issue.

If there is a valve issue the fuel/air mixture is not burning properly in that cylinder.
So exhaust from that cylinder is rich in oxygen.
So when the exhaust from that cylinder get to the O2 sensor the O2 sensor sees only the oxygen. that's all it reads. So O2 sensor voltage goes low.
The DME/ECU sees this as a lean condition and adds fuel.
Now you have a very rich condition on that cylinder.
If there is a valve issue with more then one cylinder the same thing is going to happen.
The more misfires the more fuel is added by the DME/ECU

IF I am correct then the spark plug on #4 cylinder will smell of gas.
Or any cylinder that is misfiring
This is also why the OP smells fuel on start up.
Most of his misfires are at 1500 RPM or below
Also if a compression test is done #4 cylinder it will show lower compression then the other cylinders.

Now having said (typed) all this I could be wrong.
But I can only think of one way to get a backfire into the intake.
"Intake valve issue"

OP may also have injector issues. (Leaking)

[gabedrummin]

I will try to get my hands on some test equipment this week end , and report back the findings .Both heads had a valve job less than 2 thousand miles ago by Hoffman machine . But anything is possible . My idea was to swap injector from 4 to 5 to see if the problem follows the injector .Thank you for all your comments . You are all extremely knowledgeable and I am great full for the help..!

[blue62]

Originally Posted by gabedrummin

I will try to get my hands on some test equipment this week end , and report back the findings .Both heads had a valve job less than 2 thousand miles ago by Hoffman machine . But anything is possible . My idea was to swap injector from 4 to 5 to see if the problem follows the injector .Thank you for all your comments . You are all extremely knowledgeable and I am great full for the help..!

If I am correct with my guess that the issue is in the valves you will probably be able to see the affects the easiest with a compression test of all cylinders.
Any cylinder with valve issues will show a lower compression.

If you do a vacuum test your looking for 18-22 in.hg with a rock solid needle. like it is painted on the gauge.
If the needle quivers or ticks or drifts that points to valve train issues.

When you do the compression test:
Be sure to pull the fuel injector fuse
Block the throttle body butterfly wide open
crank the engine the same amount of time for each cylinder.
Record compression on each cylinder.

Let us know how you go.
Always interested in outcomes

It will be grand if it is just a leaking injector
Easy fix

[gabedrummin]

So vacuum test shows 21 Hg of vacuum , needle is not moving even when revving the engine needle dose not move .

[blue62]

Originally Posted by gabedrummin

So vacuum test shows 21 Hg of vacuum , needle is not moving even when revving the engine needle dose not move .

Your pulling good vacuum so it does not look like you have any vacuum issues.
Steady needle is good
When you do a snap throttle test the needle should drop to near zero then rebound a little above your idle vacuum then settle at idle vacuum.

Here is a site that you can go to and read up on vacuum testing.
It will be better that a back and forth here on the forum.

what-when-how.com/automobile/engine-vacuum-test

That article should help you out some.
sounds like your valve train is ok but do further vacuum tests (described in the article) to prove that out.
A compression test would remove any doubt.

If it is not a mechanical issue (valve train) I would start looking at fueling.
Fuel pressure and volume tests and also the injectors for leaks.

keep us in the loop

[gabedrummin]

Compression test shows cylinder 4,5,6 at 150 psi and 1,160 2 ,155 3 ,150 I used two different gauges and still got a difference of about 10 psi from bank 1 to 2 I also ran the car with cylinder 4 coil unplugged and it still backfire . Very confusing results . Bank one plugs looked black color where as bank 2 the insulators are cleaner .