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Discussion Starter #1
I scrounged the forums a bit yesterday, and after some testing, thought I'd isolated my dead cylinder problem to a bad injector, but this seems not to be the case. Here's the situation: a while back the car started randomly missing on cylinder #4 (the furthest aft one, I assume the numbering starts with #1 in front....). It would be running fine, then it would start running rough. Pulling the plug wire on #4 didn't change RPM or anything. Then at one point it stopped doing it, and was fine for some time (just brief runs in the garage, however, as I'm doing some other work to the car and have had it parked for weeks). Now #4 is totally dead, never fires.

Here's what I've done:

1. I've verified that I've got juice coming to the #4 plug, and I've cleaned and gapped the plug. I also tried swapping it with the plug from #3. I can hold the lead close to the plug tip and get a nice strong arc, also I've managed to inadvertently zap myself a couple times......so I'm 99% sure spark is not the problem.

2. If I pull the plug on any other cylinder, RPM drops, so they're all good.

3. I hooked a light up to the #4 injector harness and it glowed low around idle, and got brighter as I added throttle and RPM picked up.

4. I hit the #1 injector with 12 volts very briefly while the engine was running, and momentarily the engine seemed to smooth out after a second or so and RPMs increase for just a bit...obviously the cylinder quickly goes too rich, but it verifies that I've got fuel pressure going to #4. After this test I was thinking I may just have a bad injector, but......

5. I just tried swapping #4 and #3 injectors, no difference whatsoever. #4 cylinder is still dead, #3 still burnin'. I didn't mix the injectors up either, as I labeled #4 after removal, before I ever touched 3#.

6. Back when the problem was intermittent, I usually heard a rather loud electrical-sounding clicking from the engine area when #4 would fire up again, sorta like a really loud injector (but it didn't sound like it was coming from an injector, more centrally located on the engine). I noticed the same thing a couple times last night when I hit the injector with 12 volts and got #4 (apparently) firing....though it didn't happen necessarily when the injector got voltage, just when #4 started working again. It sounds like when you hold the spark plug lead above the plug and it arcs.

7. I tried moving the spark plug leads around to rule out cross-fire, though these are brand new leads (had the problem before replacing the leads, I was hoping that would fix it).

8. If, while the engine is running, I disconnect the #4 injector harness, RPM actually goes up a little....presumably because the engine no longer has to churn unburnt fuel out of #4?


I'm leaning towards a valve problem, but that doesn't exactly make sense either. Also I don't see why flooding it with fuel (when I hit #4 injector with 12v) would fix it. I'll probably pull the valve cover tomorrow night, but I don't really know what to look for. Any ideas what sort of valve issues might cause these symptoms? Or should I be looking somewhere else entirely?
 

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Cap-n-rotor in excellent condition? (no cracks, corrosion, burn marks, etc)

'Really loud clicking' type noises are sometimes caused by arc where there's a short in the ignition circut. (spark crawling down the cap to wherever or plug tower to plug tower jumps for example)

Have you tried running the engine in complete darkness and looking at everything from coil to dizzy to wires to plugs?

What happens if you swap the injector plugs between #3 and #4? Is 4 still dead, or does 3 die instead? (engine doesn't care which injector harness wire goes to which injector, just that it reaches where it's going)

Is the #4 plug all wet when you remove it for inspection?

A compression and leakdown test should let you know if it's a valve issue.
 

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Discussion Starter #5
Thanks for the responses, guys. I tried some stuff tonight but it looks like the nature of the problem has changed....now it won't even run. AT ALL. :mad:

Yesterday before going to bed, I swapped the #3 and #4 spark plug leads, just to see (double-checking to ensure I don't cross them up). Tonight I tried starting the engine....nothing. All I can get is an occasional fire, I would guess maybe 3 or 4 in a row at most, then back to just cranking. But even this is extremely rare. I guess this rules out it being strictly a problem with cylinder #4. Between the clicking noise I mentioned previously, and the apparent inability for the car to even fire on ANY cylinder despite having fuel, I was leaning towards an ignition problem.

I pulled the distributor cap to inspect and clean.....the contacts and rotor looked pretty good, but I went ahead and hit them lightly with a Dremel wire brush anyway to clean off the minor buildup present. I put everything back together...upon turning the engine over, apparently the distributor had been loose and finally gave, because it started to turn and I found the plug leads twisted a little by the distributor body turning...!!! Sooooo I got out the FSM, hit the forums here, and went through the procedure to set timing (making sure to torque that clamp down really good). I was hoping a loose distributor had been my problem all along. Tried starting...no difference. So I've pulled the entire distributor to inspect it. There's a bit of turning play in the shaft, virtually no side-to-side play. How critical is this?

Anyway the distributor and cap look good...no cracks, no burn marks, no evidence of arcing or anything like that. I'm curious as to how this system works though....what is the center conductor (inside) on the cap made of? I thought it was corroded metal at first, but after scratching on it a bit I realized there was no clean metal down there to get to, it just keeps coming off in particles like a rock or something. That doesn't seem very conductive........am I missing something?

Also, I tried measuring across all spark plug terminals on the cap vs the center terminal for the coil, and turning the rotor shaft (with the distributor out of the car but reassembled)...never got a reading. Is this correct, does the center terminal and/or the plug lead terminals work strictly by arcing, without physical contact?

One other thing....I remember a few weeks ago when I'd run the car, if I held one spark plug lead near the plug, it would jump quite a distance in a big white spark. The other night (when the engine was still running) it seemed like I had to hold the lead closer, and it wasn't as bright. I noticed tonight, while cranking, if I disconnect the coil lead from the coil and hold it close to the coil, it has to be really close to make the jump, and it's not white...it's combination of blue and orange. I chalked this up to the fact that there's not as much voltage available during cranking....but then isn't the coil basically just a big capacitor? Shouldn't it discharge the same amount of juice every time?

I did look some more at the intake system, been able to give it a pretty good going-over during all this. I have a cracked line going back to the "secret compartment" on the passenger side, but it's been that way since I got the car...I fixed it temporarily with electric tape and the car ran fine (actually ran with the leak, but idles better with it fixed). Also the line going from the bottom of the oil separator to the dipstick is cracking, just found that the other day...again, temporary fix with electric tape (this isn't part of the vacumn system anyway is it?).

I took ghnl's advice on the connectors and just had a look at the AFM, both flywheel sensors, the CTS, and the #4 injector connector: no problems.

Is there any way to definitively test the coil? I really don't want to spend $85+ on a new coil, only to find that wasn't the problem.
 

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There's a bit of turning play in the shaft, virtually no side-to-side play. How critical is this?
That depends. (it's not great, but not terminal either)

If you set up timing so that the last direction you move the dizzy body is toward advance (anti-clockwise) the slack will be taken up in the correct direction. (you'll take that play out so the timing will at least be unable to retard itself by however many degrees)

You'll want to rectify it before too awful long though as any side play will just get worse til the rotor ends up buzzing and wobbling more and more severely which will eventually lead to really horrific running up until the point where it simply blows the cap to pieces. (likely it'll quit running by that stage though, unless you're big on keeping the revs spooled all the time, in which case it might even happen while you're out scratching backroads)

Any significant rotational play may eventually cause the pin between the drive and shaft to shear and then you end up with a dead dizzy and the problem of how to get the drive out once the dizzy body comes out of the block without it. (not really a common occurence at all actually, just one of those sick twist of fate things that can happen instead of winning the lottery that day)

what is the center conductor (inside) on the cap made of?
It's more of a carbon rod rather than an actual metal. (think alternator or electric motor brush material) You may have even noticed the filings/dust looked like pencil lead powder.

...scratching on it a bit...keeps coming off in particles
You didn't make any chips in the rod did you? Chips lead to cracks, cracks lead to failure.

Also, I tried measuring across all spark plug terminals on the cap vs the center terminal for the coil, and turning the rotor shaft (with the distributor out of the car but reassembled)...never got a reading. Is this correct, does the center terminal and/or the plug lead terminals work strictly by arcing, without physical contact?
The only physical contact between the cap and rotor is at the center pole.
The outer part of the rotor that goes by the plug terminals is an air gap. (a very specific one at that. The wrong cap matched to the wrong rotor can cause all sorts of havok. Always replace both as a matched set and don't mix manufacturers/brands)

I disconnect the coil lead from the coil and hold it close to the coil, it has to be really close to make the jump, and it's not white...it's combination of blue and orange.
White or very bright it should be, and usually accompanied by a rather volumous 'crack' noise as it arcs. Though it's not really a good idea to do it to often or for very long lest it damage other components. In fact the manuals kinda frown on it. (it never stopped me from trying, nor do they take into acount that it can happen outside of 'test conditions', like when the wire pops off or you get a great honking splash of water on it while you're tooling down the road. Still, it's not good to make a habit of testing it that way)

I chalked this up to the fact that there's not as much voltage available during cranking....but then isn't the coil basically just a big capacitor? Shouldn't it discharge the same amount of juice every time?
Not neccisarily. If there are issues with the internal winding or the oil inside has somehow leaked, it'll start to break down the coil until it simply won't throw any kind of voltage anywhere.

Also the line going from the bottom of the oil separator to the dipstick is cracking, just found that the other day...again, temporary fix with electric tape (this isn't part of the vacuum system anyway is it?)
Technically no, it's not. Just a return line for the seperated liquid oil to get back into the engine. Though if the seperator is clean and completely devoid of oil in the canister, it can leak air back into the induction. (not overly likely, but certainly possible)


Is there any way to definitively test the coil? I really don't want to spend $85+ on a new coil, only to find that wasn't the problem.
Yes:

With all wires disconnected from coil using a multimeter set to ohms resistance, check resistance from the negative post to the positive post which should be 0.6 - 1.0 ohms and from the center tower to the negative post which should be 3K - 5K ohms.

While you're at it, look at that little plug looking bit on the top near the center tower. It should look intact, dry and pretty much smooth. (if it's damaged or missing, chances are fair that the oil has leaked or boiled out and the windings have burned down roaching the coil, which at least would give you an idea why it failed the above test, which it very likely would)

Now with all this no fire and such suddenly occuring, are you absolutely sure that you're getting at least 10.3 volts through the system? (multimeter or voltmeter at the battery terminals, not the leads or cable clamps, during cranking)

Any less and the system won't 'wake up' and get the ECU and ICU operating.


******

Add on edit side note:

A weak ignition signal from the coil may potentially send a weak, intermittant, or no signal at all to the tachy relay in back.

If that's not working quite right, then the fuel pumps may not run, or be intermittant, along with the injectors getting spotty due to thier relay acting goofy because it's getting a goofy trigger signal from the pump relay.

Loosely put, if the coil is weak or bad, then it can pretty much take out a whole bunch of stuff with it, not just fire at the plugs.

Worst case scenario:
No coil = no fire
No fire = no trigger signal to tachy relay
No trigger signal to tachy relay = no pumps and no signal to injector relay from tachy relay
No signal to injector relay from tachy relay = no spray from the injectors (that don't have fuel pressure anyway because the pumps didn't run)
 

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Discussion Starter #7
Just checked....from positive to negative terminals, I'm getting 1.4 ohms. Is this high enough to cause a problem? From center to negative it's right at 4k. :/

I don't see a plug on the top of the coil....there's a little tube area sticking up that looks like a plug could go there, but it appears to be quite closed off further down (like at the height of the rest of the coil's top surface).

Fuel pump runs fine during starting.

I'll check that starting voltage tonight, and also get a pic of the top of the coil (on lunch break right now).
 

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Discussion Starter #8
Pic time!

http://www.theplaceofcoolness.com/pics/alfa/coil1.jpg

http://www.theplaceofcoolness.com/pics/alfa/coil2.jpg


Yes, I have the wires reversed in these pics......somehow I ended up with the positive and negative on the coil swapped a few weeks ago, though the car ran fine that way at the time. I did try swapping them back the right way just now, no difference....still get a weak spark. As I understand it this shouldn't actually make any difference.

I checked starting voltage at the battery...at no load, it's around 12.5 volts right now (been doing a lot of cranking since this problem came up). During cranking, it drops to about 11.2 volts. I did have to check at the clamp hold-down screws since I didn't have anyone to help me and the alligator clips I'm using won't fit over the actual battery posts, so this means my reading is actually low, IINM.
 

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That depends.
Any significant rotational play may eventually cause the pin between the drive and shaft to shear and then you end up with a dead dizzy and the problem of how to get the drive out once the dizzy body comes out of the block without it. (not really a common occurence at all actually, just one of those sick twist of fate things that can happen instead of winning the lottery that day)
Oh, holy hell. I thought that might have been a mechanical advance feature on the dizzy. So to tell me, does 30 degrees of "rotational play" mean time for a new pin? This explains alot for me!
 

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I chalked this up to the fact that there's not as much voltage available during cranking....but then isn't the coil basically just a big capacitor? Shouldn't it discharge the same amount of juice every time?
No. An ignition coil will output only enough voltage to fire the sparkplug. At idle, the voltage required is only about 7kV. Under high load conditions, the voltage required can be 30kV+.

Yes, I have the wires reversed in these pics......somehow I ended up with the positive and negative on the coil swapped a few weeks ago, though the car ran fine that way at the time. I did try swapping them back the right way just now, no difference....still get a weak spark. As I understand it this shouldn't actually make any difference.
Yes, it does make a difference. Although the coil will still produce a spark with the wires reversed, the available voltage will be reduced by some 50%. Coil primary terminals are labeled positive and negative for a reason.

Two questions;
When you switched the #3 and #4 sparkplug wires at the plugs, were the wires also switched at the cap?
Has the vacuum hose from cylinder #4 to the brake booster been eliminated as a possible cause?
 

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So to tell me, does 30 degrees of "rotational play" mean time for a new pin? This explains alot for me!
If you have 30 degrees rotation on an L-jet dizzy shaft, something is very wrong! Should be almost nil. I'd pull the dizzy and check both the drive and the pin.
 

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If you have 30 degrees rotation on an L-jet dizzy shaft, something is very wrong! Should be almost nil. I'd pull the dizzy and check both the drive and the pin.
Bosch motronic, not L-Jet, still being computer controlled I wondered why it had mechanical advance, I guess it shouldn't!!! What type of pin is this, is this a roll pin, anyone know the size of it?
 

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Bosch motronic, not L-Jet, still being computer controlled I wondered why it had mechanical advance, I guess it shouldn't!!! What type of pin is this, is this a roll pin, anyone know the size of it?
Pardon the slip. The L-jet and the Motronic dizzy's are basically the same as the ignition system used in the L-jet IS Motronic (meaning it's digital).

Don't know what type of pin it is but I'll guess about 5mm diameter and 20mm long.
 

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Pardon the slip. The L-jet and the Motronic dizzy's are basically the same as the ignition system used in the L-jet IS Motronic (meaning it's digital).

Don't know what type of pin it is but I'll guess about 5mm diameter and 20mm long.
Thanks! Hopefully this gent will be able to figure out where is problems are occuring as well.
 

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Discussion Starter #16
No. An ignition coil will output only enough voltage to fire the sparkplug. At idle, the voltage required is only about 7kV. Under high load conditions, the voltage required can be 30kV+.
..........

Yes, it does make a difference. Although the coil will still produce a spark with the wires reversed, the available voltage will be reduced by some 50%. Coil primary terminals are labeled positive and negative for a reason.
Hmmm ok, that may explain why my spark during cranking is even weaker than before, now....I'll have to swap again and verify. Last night I noticed there is almost no spark now, though I have the wires hooked up the right way. I'd just assumed whatever is causing the problem, was getting worse. Quick question: how does the coil "know" how much juice to put out? It looks to me like the green-black wire on the positive terminal is the voltage source, and pin #1 on the ECU grounds the negative terminal when the coil needs to send a charge to the plugs. I don't see any way to adjust output.

Two questions;
When you switched the #3 and #4 sparkplug wires at the plugs, were the wires also switched at the cap?
Has the vacuum hose from cylinder #4 to the brake booster been eliminated as a possible cause?
Yep, switched #3 and #4 at the cap, and have since removed and reconnected all wires many times in the process of trying to fix this. Not sure what you mean about the vacuum hose.......it doesn't go to any cylinders, it goes to the intake plenum. It is on the #4 end of the plenum, is this what you mean?
 

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As an afterthought, I suppose I should mention that while that hose will affect the vacuum in general, it won't be quite as specific to #4 as the old style would be.

Granted #4 will get more of an effect than the other 3 simply because of proximity, but as it's not connected directly to that intake port, it'll create issues with the other cylinders also.

More along the lines of a false air leak rather than a specific cylinder killing thing.
 

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Discussion Starter #19
Whew!!!!!

OK, back to square #1 on the misfire, I think. I guess I was a bit premature in my assumption that I had good fuel supply, I was basing this on the wet injectors and plugs.....I guess they were just still a bit damp from when the fuel supply had been ok. Anyway, after noting rather dry plugs tonight, and pulling the filter and pump, I discovered I was getting no pressure to the pump. Turns out there's a filter in the trunk area just above the gas tank, and it was TRASHED with junk (looks like rust particles). I shook it a bunch and got it cleared out for now.....I think a POR15 tank treatment is in my future. :)

Just curious, is this supposed to be here or is it an add-on? I don't see it in the FSM. I know the guy I bought the car from replaced the pump, and this filter looks new as well, so I'm thinking it's something he added. Glad it's there now, it kept all that crud from wrecking the pump.

It's late and I didn't want to run the engine much (populated neighborhood....) but it sounds like the miss is still there. However, in the process of diagnosing the no-start problem, I finally did a compression check, and cylinder #4 is about 20 PSI lower than the others. Gonna run some more checks and then probably check/set valve clearances all around. I hope that's all it is. The other cylinders seemed a bit low (around 150) but I forgot to hold the throttle open, so I'll run a more accurate check tomorrow when I have more time to dig into this. Also I'm using a cheapy Walmart compression checker..... :rolleyes:
 

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First off, your compression is likely to read a bit low due to the VVT not kicking the intake cam to advanced, so it's not moving all the air through the cylinders. As in you're looking for balance more than astronomical pressure numbers.

If you've got the mechanical type, the engine won't crank fast enough to activate it. If you've got the electronic type, you won't see the oil pressure instantly come up high enough to rotate the cam while cranking. (mabe on the last crank or two, but certainly not the first several)

150 isn't super bad though actually. Some of the VVT engines run as low as 120-130 across all 4 cylinders.

Those that don't have VVT seem to be in the 170-180 range IIRC.

You did have the throttle WFO while testing didn't you?

Also, you can see if it improves by adding around a couple teaspoons of oil into each cylinder and re-test. If the pressure goes up significantly, you've got a ring issue. If it only goes up a couple pounds, then things aren't so bad on the bottom end.

**

The filter thing:

Right off I'm gonna say 'PO aftermarket add on'.

The in tank pump has it's own little clip on filter sock that lays down in the very bottom on the pickup end of things (looks kinda like a fish tank net AFA material)

From there fuel goes through the pump through a very short run of stepped hose (which can fail and lead to goofy things happening when there's less than 1/2 a tank of fuel) into a metal line past the fuel gauge float assembly and up out of the tank.

Once out of the tank, a soft line to the side of the trunk where it transitions to a hardline that carries across the front of the trunk, which bends down to go through the trunk pan over the diff on the right side.

A short 3-4 inch run of soft line, then back into a hard line where it weaves around the suspension and chases the shape of the chassis, then soft line to the underchassis main fuel pump.

Soft line from there to the main filter, and out off that with another bit of soft line that ties into a hard line that chases up to the firewall.

Once at the firewall, soft line again to the rail.

The return line takes about the same route and has hard stuff in about the same spots.
 
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