I have a 91 DA, which is running extremely rich on one cylinder. I pulled the plug wires one by one, and when I got to #4 there was no change in idle. I pulled the plug (again) and it was fouled (again). The blackness on it is dry/chalky, so its not oil. The car has been doing this since I bought it, and I have replaced the following:

Cap
Rotor
Plugs (twice)
Plug wires
Fuel filter
Etc.

I can smell gas inside the car at idle, and the ecu is throwing a code 43 (fuel supply). Since I swapped injectors from cylinder to cylinder, that more or less eliminates the fuel supply effecting just #4. The tach sometimes hunts at idle, and usually idles kinda high (1100-1300), but not always. I pulled the wires one by one off the igniter and recrimped/greased them, but this had no effect. I also checked for vacuum leaks, cleaned the IACV and FITV, and ran seafoam through the system.

As of now I believe it has something to do with either the igniter or the coil (when I looked down in the hole there was some black dust). Everything that I have read doesn't seem to point either of these 2 at making only one cylinder run shitty.

Anyone have any idea what might be causing this?

 

Bad cap?

 

Do a compression check on #4. I bet its really low.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by wreckedmyteg &raquo;</TD></TR><TR><TD CLASS="quote">Bad cap?</TD></TR></TABLE>

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tegra &raquo;</TD></TR><TR><TD CLASS="quote">replaced the following:
Cap
Rotor
Plugs (twice)
Plug wires
Fuel filter
Etc.

</TD></TR></TABLE>

 

There's only a few things that can affect ONLY one cylinder.

Sparkplug, wire, & cap. You've changed them.

Injector. What happened when you swapped them? The problem stays at #4?

Wiring for that injector? Sounds kinda unusual, but ??? Have you checked it at all?

I think the valve clearance has to be WAY off to cause this?? Burned valve? Bad rings on that cylinder? Compression & leakdown might tell you something.

 

Figured out what it was after taking muckman's advice and doing a compression check. Compression was 0, so I pulled the head and this is what I found:


...Hmmm what seems to be the problem?



At least nothing was damaged in the cylinder, but are the valves supposed to be white like that?




Modified by Tegra at 9:24 PM 8/22/2004

 

I love being right.

And yes exhaust valves are usually whitish/tan as all the hot gases travel around them, burning off any carbon, etc.

 

Ok, after having the new head on for a few days I have determined that cylinder #4 is still running rich. I pulled the plug today and seen that it was black again (fuel black, not oil).

After swapping injectors, and now the head itself, I am thinking it HAS to be ignition related. As stated earlier, I have replaced cap/rotor/wires/plugs etc. I have not replaced the igniter or coil. The igniter has 4 wires coming from it, so I am assuming that it uses one for each cylinder to fire? If that’s true, could just one connecter fail in an igniter and possibly cause this condition?

Another odd thing that seems to be related is that the engine is idling high (1,000-1,500). I have cleaned the iacv and fitv, and checked for vacuum leaks (none). Maybe the engine is increasing idle in an effort to increase ignition output?

Edit:
I did pull the plugs on cylinders 3 and 4 to watch them spark side by side. #4 appeared to be weaker and less frequent.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Tegra &raquo;</TD></TR><TR><TD CLASS="quote">... The igniter has 4 wires coming from it, so I am assuming that it uses one for each cylinder to fire? ...</TD></TR></TABLE>No. The ignitor & coil fire repeatedly, exactly the same way. The ONLY thing different from one spark to the next is the position of the rotor.

I don't know the details of signal processing for the CYP, CKP, & TDC sensors, but maybe there's a point knocked off one of the star-wheels on the distributor shaft? So maybe at ONE position the waveform from one of these sensors is weak? I'm kinda guessing, but that's the only other thing that's different.

 

So what do each of the wires do on the igniter?

 

I'd have to check, but probably something like this...

1) Power
2) Signal from ECU
3) Signal to coil
4) Signal to tachometer
(Ground thru mounting bolts?)

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Tegra &raquo;</TD></TR><TR><TD CLASS="quote">I did pull the plugs on cylinders 3 and 4 to watch them spark side by side. #4 appeared to be weaker and less frequent.</TD></TR></TABLE>Do this again but swap the plugs or use new ones. Since your #4 plug has more soot, I'm just wondering if that's the only reason it's spark looks weaker.

 

You should replace the spark plug on #4 after the new valve.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Muckman &raquo;</TD></TR><TR><TD CLASS="quote">You should replace the spark plug on #4 after the new valve.</TD></TR></TABLE>Yeah! I figured you did. Also, how's the compression? How do we know the new/fixed valve is working properly? Same head, or did you swap in a different one?

 

looks like your running pretty lean

thats a bit TOO white

i'm guessing #4 got so lean that it burnt the exhaust valve, and chipped it
and then your not getting any compression. so the gas isn't gonna really burn, and be sure rich and just dump the air/gas mixture into the exhaust

 

Ok, I guess I should clairify a bit:

I replaced the entire head with a new head(cams too).
Compression numbers were something like 178, 185, 190, 190 (with #4 being 185)
I am guessing the reason the other valves were so white is because the O2 sensor was picking up all the gas coming from cylinder 4 and trying to lean back the mixture. I was throwing a fuel supply code at the time (before replacing the head).

I used a clean plug to test cylinder #4 today, and the plug that was fouled was brand new 2 days ago.

I currently have no ecu codes, just a mildy high idle, and black soot coming from the tail pipe.


Modified by Tegra at 11:33 PM 8/26/2004

 

Bump...

 

bump cuz i have the same problems 2, changed distributor, spark plug , spark plug wire. etc buts its on the #3 cylinder

 

Bump..

 

Update:
I took some quick pics of my plugs tonight. The strange thing is, plug 4 seems to have developed a white tip, where the carbon use to be. It is still obvious that it was fouling, but do the plugs look like they are running lean? I am not getting very good gas mileage (27mpg +/- 2) and have been noticing that my car has a weird hesitation during acceleration. It's not quite like surging, but more like someone is flipping a switch on and off for my fuel (it's not really that noticeable). Dunno, could be way off on that one, but it's the best I can describe over the net.





Add .orig.jpg for detail.

 

can you try replacing the distributor with a known working one? this one is strange. interested on what the outcome is.

 

Unfortunately, the only other dist. I have access to is an obd1. My car is obd0, so unless someone lives near Kansas City, MO, then this is not an option.

 

This is a puzzle alright! Well, I had a similar problem, except it was like you said,but from ALL cylinders. Basically I solved it doing the following: CHanged cap and rotor and advanced the timing. Now plugs are running clean. Also, I went from 25 to 31 MPG city/highway. Best of luck!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Tegra &raquo;</TD></TR><TR><TD CLASS="quote">... because the O2 sensor was picking up all the gas coming from cylinder 4 and trying to lean back the mixture...</TD></TR></TABLE>Remember that the O2 sensor does NOT measure gas. It measures oxygen. So when you get misfiring the O2 sensor picks up the 'unused' oxygen & thinks you're lean. Unless the ECU 'knows' about the misfiring (OBD-2 CKF sensor?) it'll probably correct by trying to go rich.