Alfa Romeo Forums banner

21 - 39 of 39 Posts

·
Premium Member
Joined
·
26,739 Posts
Did you try swapping out those two ignition amplifiers on air cleaner mount with your other car. OH, I guess you did that already I see in some posts back.

Also maybe as last resort you need to swap out ECU for FI system.

Have you checked RPM/Timing sensor 3 prong Bosch connector for crumbling bakelite and possible cross talk between pins?

Myron's front knock sensor and RPM/timing sensor connectors turning to dust sometime ago and I had to piece connectors back together and taped together.
 

·
Registered
Joined
·
5,288 Posts
Discussion Starter #22
update~!

Ok car got progressively worse running -- missing for sure on one cylinder (really could not definitively tell which one) but I thought it was in the rear bank. I was fiddling with it tonight in the dark looking for anything -- and saw what I thought was a dim flash just aft of the big round connector. So brief (and my vision not too good either) I wondered if it was real.

So I got out the big flashlight and started looking around in there-- the harness from the big round connector to the coils and injectors is right there-- hmm --the outer insulation jacket is cracked/missing/brittle (193 k miles) and some wires are visible, but I poke and prod and dont see any breaks/voids/ etc. So figuring I have some time before wife and kids get home, I pull the plenum off (AGAIN) and remove the whole upper harness. get it on the bench under some good light and my magnifiers.

GUess what? ON the underside on the white/red wire on coil (feeds #3 cylinder). insulation is melted, wires exposed, and discolored! So I fix this up with some solder, heat shrink, insulation and for good measure, replace 2 of the injector connectors that had broken over the years. Put the harness back in, replaced the coil on 3, replaced ignition module controlling #3, fired her up and --- no misfire!

Let see if this holds though. Seems like a cascade-- insulation wore, or ignition module fails in hot mode and wire decided to breach right there. Smoked coil (see earlier in this thread). I diddle around there and replace coils and ign modules, and slightly move the harness. Problem gone. Problem comes back again, I move stuff around, and change coils and modules again after all the previous stuff. Remember, every time I remove plenum, I pull off coolant line to throttle body and some coolant spills right down there. White/red was shorting out to ground intermittently I believe and at times, it was pretty constant, other times it was just a hair away frm the short.

Lets see if this really is the CAUSE or the SYMPTOM~!! I am hopeful that I finally tracked this bad boy down -- but hold the Dom and Cohibas for a while---
 

·
Registered
Joined
·
1,765 Posts
It certainly sounds logical to me... That is, you have found a logical cause for all the maddening symptoms and component failures. I'll be keeping my fingers crossed for you...

-Alex
 

·
Premium Member
Joined
·
26,739 Posts
Me too! Now if we can just get power back to our Alfa house. Bad storm yesterday much of VB without power. Bobb got here just after storm with my new to me 164S.

We all had to come down to our beach house for the night as it had power.

Looks like to be a nice car but being really dark and car is black all I got to do last night was ride with him to beach house.

Don't know the extent of storm damage but sirens, power co trucks and no traffic lights everywhere.

Lots of tree damage to power lines. I am sure compared to all area with floods and tornados we will get off lucky here.

Again I say Bob hope you found the trouble in that harness wiring.
 

·
Registered
Joined
·
1,007 Posts
Bravo. Glad to read that the possible cause has been found. Keep us posted.
I appreciate you documenting this. I will look at my wire harness today.
 

·
Registered
Joined
·
410 Posts
That sounds interesting! No matter what, fixing the wires is definitely good. I hope that you finally found the root cause for this.
 

·
Premium Member
Joined
·
15,437 Posts
People forget just how hot these engine compartments run at and stay. The excessive heat bakes and cracks plastic, it ruins wiring insulation, rubber fittings and belts, fuel and coolant hoses, overheats bearing grease, etc. Over the span of many years, as we are running these cars at, these components have to be checked for such degradation.

I try to keep a check list for each of our cars to stay on top of them. Still, once in a while...you end up not knowing what the problem is because there can be so many problem sources. It just takes time to diagnose the failure characteristics to point you in the right direction. I've disliked these newer really high powered direct ignition systems. Too much to handle, many car manufacturers were not up on the required insulation/emf protection when they were introduced.

I hope you got the problem fixed.
 

·
Registered
Joined
·
5,288 Posts
Discussion Starter #28 (Edited)
OK I am going to close this one out

Maybe a bit premature, but I hope not. Time will tell.
Steve, maybe this thread should be in a STICKY with title "24V misfire troubleshooting -- GENERAL" -- can you do this?
If you have rough running at idle, its 99% sure its not a AFM issue -- AFM is out of the picture at idle. Could be a wonky Idle Air Controller tho. If Idle is OK but at speed you have misfire its prbably good to go thru this guide to rule out any of this stuff

Lessons Learned

1. First thing is check injectors- -- put long handled screwdriver onto each injector and other end to your ear, You should easily hear CLICK CLICK CLICK on working injectors. All 6 have to be clicking!. Then , check for leaking air coming in where it shouldn't-- use brake cleaner and spray all around a warm (not hot) engine, the intake runners top and bottom, the air hose, throttle body, idle air controller, vapor separator, etc -- if you hear the engine beat change when you spray this volatile around those areas-- you have a tramp air leak that needs to get fixed.



2. If you know injectors are good, and one cylinder is missing,LISTEN for SNAP SNAP of coil arcing (bad).Bad coil usually gives a SNAP SNAP when it arcs, SNAP should be right on top of the misfire Pull front coils and plugs, check for oil in the plug well, and verify plug gap 0.025". Put back in and start car in the dark- watch for flashes around the coil -- if you find one, replace that coil. Once fronts are known good, if still SNAPPING, swap them into the rears and check verify rear plug gaps). A coil can also be bad without any SNAPPING-- its just fried! I verify coil resistance across 2 outside coil lugs as <1 ohm or so, inner one OPEN to both of the outside ones!!(its the secondary coil) ; or, you can pull a plug, ground the end of it, , pull the fuel pump relay, and have someone crank the car with the plug exposed -- you should see the spark plug sparking!

3. No snaps and still missing? VERIFY TIMING IS CORRECT (search the BB on 24 v timing)

3 and 1/2 = Timing good ? - Now swap the ignition modules connectors to see if the bad cylinder moves positions -- rear most module is for rear bank, front module for front bank. If the missing cylinder moves-- get a replacement ignition module (Located on the side / under the air box right above the ABS pump)


4. Check your fuel pressure and fuel flow. Easy to do -- for pressure, Tee in a gauge on the pass side fuel rail and start the engine -- we want about 42-46 psi. Turn engine off, and see if fuel pressure holds. If it does, proceed to step 5. If not, and it bleeds of quickly (ie < 2 minutes to below 35) then TANK DIVE to replace in-tank fuel lines that are split/leaking.

5. Jumper the secondary of the fuel pump relay to make the fuel pump run. Have it pump into a container -- if you get a full beer bottle in about 10-15 seconds you are in good shape. If not, find the blockage and fix it.

6. Still running rough? Check all 4 ground -- 2 each on intake plenum passenger side, one from throttle body to rear valve cover, and one from harness to valve cover right underneath the big round connector-- make sure that 13mm cap nut has a bunch of washers under it and the cable ground!

7. Remove rear plenum and then start checking continuity from each spark coil connector back to the big round connector. See if there is an open. Also, check each for isolation from ground and each other wire. Refer to the service manual electrical diagrams for wire colors and connectors. Then check continuity from the big round connector back to the ignition modules, check isolation too from ground and each other wire.

7, Still running rough? Time to remove the upper wiring harness from the car and examine it closely, looking for insulation breaks, etc. My break was right where the harness rubs on the water line clamp area/cam angle sensor connector mounting bracket just aft of the big round connector. Could not see it from the top, had to remove the upper harness (carries signals from big round connector to coils and injectors) and turn upside down to find the insulation breach.

8. Still running rough? Post on the 164 forum and we'll give it a good think and get back to you!
 

·
Premium Member
Joined
·
15,437 Posts
Ok, what I've found is first of all, all injectors were clicking away as they should.

I did find that one sparkplug was not firing, since when I pulled the wires from each coil of the front bank one at a time, it made no difference at the sparkplug closest to the filler cap. The idle dropped at the other two plugs. When I pulled that coil and shorted out a spare plug in it, there was no spark.

When I then switched the tri-wire connectors at the power modules, pulling the wires from the front bank of plugs dropped the idle at all three plugs. When I switched the tri-connectors back at the power modules, pulling the wire to the coil of the far right plug once again made no difference in the engine idle rpm. Pulling the other wires did.

I am now assuming that a power module has started to fail, at least for one sparkplug. I know it is not the wiring going to the plug coil, as that far right plug worked when the power module connectors were switched.

I did go through and clean and relube every electrical connection for the modules, coils, injectors, big round connector, etc.

I guess I'm in the market for two new modules, to change them both.

Does this sound correct?
 

·
Registered
Joined
·
5,288 Posts
Discussion Starter #30
Del this differential diagnosis sounds correct to me. The spark coil should be good since you verified that it indeed provided spark when you switched the ignition module connections.

I'd hunt around for a second source (I think evgeny164 had some ideas) rather than pay the big $$ for alfa parts.

bob
 

·
Premium Member
Joined
·
15,437 Posts
thanks, bob.

Yeah, I've starting my search. Hopefully this is the problem, since the car starts and sounds as it should, revs nicely, EXCEPT for the missing cylinder.

Any used LS power modules out there?
 

·
Premium Member
Joined
·
26,739 Posts

·
Premium Member
Joined
·
15,437 Posts
Thanks, was looking at that. Maybe the way to go, just buy a couple for the glove box, lol.
 

·
Registered
Joined
·
5,288 Posts
Discussion Starter #36
I sent to him already mounted to heat sink using artic silver 5 compound.
 

·
Premium Member
Joined
·
15,437 Posts
Just look up heat sink grease on the web. I saw it for sale at the home improvement stores, Radio Shack, on the web, Autozone, etc. It is just a tube like a toothpaste tube, well labeled. Can't guarantee it is the better stuff. Seems when I bought the first little tube of it, there were several grades of it, some pretty darn expensive.

I need some, lost the old tube I had. Arctic Silver 5, huh. Will look for that to use if it is better than the ordinary stuff. I do assume it is if you use it.

Ah, yes, I see it at Frye's for instance, top rated. The picture looks familiar. Maybe that's what I bought years ago.
 

·
Registered
Joined
·
5,288 Posts
Discussion Starter #38
Really any thermate paste will be fine as long as you are diligent in cleaning the mating surfaces. When mounting to an AL heat sink it should be absolutely flat and free from al oxide. To do this get some 6-800 grit emery paper and a glass plate and work in figure 8 pattern until the entire mating surface is shiny. Do the same with the amplifier being careful to ground yourself with a wrist strap. Clean with acetone and apply thermate paste sparingly across the whole surface of the amplifier quickly before al oxide forms ( a few minutes). Clamp em together and clean up the excess with acetone or Etoh. Tighten to spec (the spec is justa-- justa little bit tight)
 

·
Premium Member
Joined
·
15,437 Posts
Thanks, will pay attention to these details if I mount any of these on the old heat sinks. Have mounted electronic units before, so have done it before.
 
21 - 39 of 39 Posts
Top