Clogged Injector?

[mede8er]

My 993 is showing a misfire #2 cyl condition....changed the plug wires and cleaned the dizzies and rotors, slight change, still getting the reading from Scantool.....

I can unplug #2 injector without any change to idle.....

Did a search, no results.....Can these be cleaned.....

[mede8er]

She's clogged alright.......

By depressing the nozzle with a 1.5mm allen wrench I could blow through it...then it clogged up again.....

[kang]

Try some injector cleaner. If that doesn't work, replace it.

[mede8er]

Hmmmm...cleaned it and bench tested it with 12 volt supply..I hear it opening and closing.....but it doesn't work in car....

I'll switch it with #1 and test if it's the injector or the wiring.....

[kang]

That sounds like a good test.

Something to consider is removing all your injectors and having them cleaned and flow matched at a place like this: http://www.rceng.com/service.htm (I heard of them from a trusted source but have no personal experience with them. I am not associated with them either. There are a number of injector cleaning services out there.)

This is something I’ve been thinking of for some time. I’ve heard of big improvments after a service like this, but I suspect the improvement would depend on how bad your injectors were to begin with. I don’t have any real reason to suspect there is anything going on with mine…

[mede8er]

I don’t have any real reason to suspect there is anything going on with mine…

Nor do I.....engine ran very strong prior to this.....actually it's strong running on 5, hehhehheh...

I'll post results for others later....

[mede8er]

I'm not gonna get away easy on this one....

#2 injector works fine in #1, #1 won't fire in #2.......must be a wiring issue.......

What controls the firing of the injectors???? ECU????

Plenty of spark there.......

[kang]

How is the injector grounded? To the engine or fuel rail? Perhaps there is a bad ground on #2?

[bazar01]

I believe injectors are powered up to 12V with ignition switch ON and firing is by grounding thru ECU.
With ignition switch ON, check for +12V on one terminal.
The other terminal should either go to a ballast resistor or straight to ECU for grounding.
Not sure if 993 has a ballast resistor.
Test for other terminal for continuity up to the DME plug.
Maybe it is just a dirty or loose connection in the plugs.
I would test with ignition OFF.

[mede8er]

Hmmmmm.....12 volts through both terminals w/key on........

[bazar01]

Checked the 1995 993 engine electrics M2.10.
All 6 injectors getting 12V from a common source pt. #1 to one terminal in each injector plug.
Other injector terminals go to control unit MFI-01 terminals 17, 35, 5, 34, 23, & 16 for injectors 1, 2, 3, 4, 5 & 6 respectively.
So check terminal # 23 in the ecu for injector #5 grounding.

http://www.cannell.co.uk/993_Workshop_Manuals/Porsche%20993%20Manual.pdf

[mede8er]

Thanks bazar....makes sense that 12 volts passes through injector until the ECU sends a shunt.........

I'll check that tomorrow........

[mede8er]

Hmmmm...I think those numbers correspond to a 55 pin connector....

I have an OBDII 84 pin connector........1997 3.6L..........are they the same......

[grmnxtc]

97/98 wiring sheet says same as above, but 96 (with 88 pins?) says:

3,4,5,32,33,31 for cylinders 1 -> 6.

Hope that helps.

Clive.

[mede8er]

Thanks guys...I'm gonna ring this out in the morning........

[mede8er]

Hmmmm......pin 26 AND pin 27 on my 88 pin connector show continuity to #2 injector (negative side).......

[mede8er]

Update.....

Every pin I send 12 volts through shows continuity with #2 injector......

Gotta be a major fault in the wiring.......

[kang]

Is your harness subject to that old recall? Perhaps it was never replaced...

[mede8er]

OK...problem solved....took apart the 88 pin connector and cleared the short.....

Best part is the DME was undamaged....I'm picking up a programmed box from Steve at Rennsport and I'll keep this as a spare....

Kang, I was thinkin the same thing but I think this fault was different...

Thanks for the help!!!!

[1980 911 sc]

dumb question, but how did you know it was a misfire? I have a 97 vram motor in my 80 targa and I am loving it. Unfortunately, once the car warms up, like 20 to 30 min of driving, i start to get a vibration during accelleration from the back of the car that I can feel through the seat. Also, once the cold start cycle is done it idles kinda rough. I has a cyntex chip so i figured the rough idle was from it runnin a bit richer than normal. I figured before I start worrying about trans/clutch etc. i should give her a good old fasioned tune up. just waitin for it to warm up some.... i got plugs, caps, and rotors.