Bizarre: 2G 6 bolt running on 2 cyl.

[KFred 513]

So I know this problem has been covered many times, but solutions are rarely posted. The few people that follow up with a solution fixed their problem with something that has checked out in my car.

I have had the car for less than a week and on day 3 it started to studder/hiccup unpredictably. DSM link never logged a misfire. The miss was independent of any factor I could control (RPM, throttle%, AFR, etc.) The tach would also skip around with the studder. We swapped in a working power transistor with no effect. The problem only occurred after the motor was fully warm. The miss went on for a few days and then disappeared for 2 days.

Yesterday while cruising in 5th gear the car stuttered worse than ever and never recovered. After a quick examination I had to continue to drive the car home about 10 miles. At a friends garage We quickly realized the car was only running on cylinders 1&4.

I thought the motor was toast so we started a compression test. The compression checked out at ~150 across the four. Then we tested spark. All four plugs have spark. A noid light showed that all 4 injectors get signal. We checked the timing, and of course, the crank jumped a few teeth. We corrected the timing, but no change. I pulled the valve cover to make sure the rocker arms were all in place, they were.

Tonight we swapped in a working CAS, with no change. We also tried spinning the CAS rotor by hand with it plugged into the harness.One thing we did notice was That on my buddy's car, every 1/4 turn caused an injector to fire. On my car every 1/2 turn caused an injector to fire. This was using the same CAS.

I am really at a loss here. The problem only happened yesterday but we have spent a good amount of time on diagnosis with no change. We know that 2&3 aren't firing because both injectors can be unplugged with no change.

Sorry for the long post, but here is the mod list so everything is out in the open. I'm just pasting it from the craigslist ad.


Engine:
90' 6 bolt stock block w/ Wiseco rings and ACL tri-metal rod bearings
97' head (6 bolt converted)
94' black top CAS
BC 272/272 cams
Fidanza Cam Gears
ARP Head studs
ARP Exhaust manifold studs
Balance shaft delete
A/C delete
Quad layer metal HG
Fluidampr harmoic balancer

Ignition:
Coil on plug (Intrepid coils)
MSD DIS-2 high output ignition amplifier
NGK BPR7ES plugs

Intake:
Q45 90mm Throttle body
JMF street intake manifold
Magnus heat barrier gasket
FP 4in intake
ETS 10.5 street intercooler and piping (anodized black core, black piping/ couplers)
Tial 50mm BOV
PTE HP5857 billet ball bearing turbo (oiled from head with in-line earls filter)
K&N filter

Exhaust:
RRE 3" Downpipe (V-band)
Full custom SS 3in ID piping
FP race manifold
Punishment racing 02 housing (recirculated)
Tial MV-S Wastegate (water cooled)
Megan Racing Muffler

Suspension/ Handling:
Ingalls rear camber kit
Tokico Illumina struts
Tokico 1.7 inch lowering springs
Energy suspension bushings
-front upper control arms
-front lower control arms
-rear trailing arms
-rear upper control arms
-rear Knuckles
Prothane motor mounts
Megan racing front strut tower bar
RRE rear strut tower bar

Brakes:
SS brake lines
Brembo Calipers (Evolution 9 powder coated black with white lettering)
Evolution 9 rotors
KMV adapter plates
.
Drivetrain:
Fidanza 8lb flywheel
Fidanza 6 puck V.2 clutch and pressure plate
Extended slave cylinder rod
Energy Suspension shifter bracket bushings
Full length SS clutch line
Skateboard bearing shifter bushings
95' LSD rear differential

Fuel:
Walbro 255lph HP fuel pump (rewired)
F.I.C. 1000cc Injectors
Fuellab mini FPR (w/ gauge)
Fuelab in-line filter
-06an ss/cloth braided#line from tank to FPR
F.I.C. fuel rail

Management:
DSMLink V3 (Speed Density, NLTS)
AEM Wideband gauge
AEM Tru Boost gauge and controller
AEM Oil pressure gauge
AEM Water Temp gauge
AEM Volts gauge
AEM 3.5 bar MAP sensor
GM IAT sensor
Greddy turbo timer
ECMtuning V3 GM MAF harness

Cooling:
Koyo aluminum radiator
Maradyne 12" fan (pusher)
Mishimoto 12" fan (pusher)
JM Fabrications overflow tank

Miscellaneous:
CF Hood
Evo 9 Enkei rims
Battery relocation (trunk)
Shaved valve cover (6 AN fittings)
JM Fabrications Deluxe catch can
Jay Racing Alternator relocation
Vibrant vacuum block
NRG steering wheel quick release
NRG steering wheel hub
No name steering wheel
Imperial power steering cooler
Non-cruise control cable

 

[Arthris]

Its pretty simple. 2/3 are the same coil. So assuming this check the coil. check the Transistor block. All connections to these and then check the wire coming from the ecu to the transistor block. If you search for a wiring diagram it will tell you witch pin it is. Also the ECU will not log a misfire. I believe in order to use link you have to use a 95 ecu correct? they where a OBD 1.5 to say the least. Pretty much a bastard OBD ecu. OBD 1 do not detect misfires. they where pretty dumb and only checked all sensors for faults.

 

[KFred 513]

Its pretty simple. 2/3 are the same coil. So assuming this check the coil. check the Transistor block. All connections to these and then check the wire coming from the ecu to the transistor block. If you search for a wiring diagram it will tell you witch pin it is. Also the ECU will not log a misfire. I believe in order to use link you have to use a 95 ecu correct? they where a OBD 1.5 to say the least. Pretty much a bastard OBD ecu. OBD 1 do not detect misfires. they where pretty dumb and only checked all sensors for faults.

Thanks chris, I'm not sure about the ECU but DSM link does detect "random misfires". A misfire code popped up today but I'm not surprised about that. I'm not sure if you read my entire post, but all four coils are producing spark. I'm running a home made Intrepid COP setup. All 4 coils have been tested with brand new replacements with no change.

I have also replaced the transistor with a known working transistor. If this were my problem I would assume there would be a no spark condition.

I do plan to swap in a stock ignition to rule out a failure of the COP/ MSD setup. I should also mention that the MSD ignotion can be easily bypassed, and we have done so. The condition remains with the MSD bypassed, so I can assume that is not my problem.

 

[dsmrollerz90]

It could also be the ignition control module/ ignition transistor. They are very common to act like a bad coil and cause the car o run on only 2 cyl.


Never mind already beat me.

 

[KFred 513]

Thanks roller, and yeah we have tried everything that commonly causes this issue. After a lot of reading last night I found that oil/water sitting in the spark plug well can cause spark to arc through the coil/wire boot to the wet area on the head. This would prevent the spark from getting inside the cylinder. That is the first thing I will check today although I am doubtful it will be the issue.

I feel like it is so weird that an electrical problem occurred at exactly the same moment as the car jumped time. In my mind it makes more sense that an electronically caused misfire resulted in the crank jumping time. Does that sound reasonable?

 

[Talon virgin]

Have you checked the injectors themselves?

I had cylinders 1/2 go out on me from clogged injector screens. the PO apparently had never changed the fuel filter.
if they are... a slow spray of carb/choke cleaner could be the solution

 

[delta448]

A noid light showed that all 4 injectors get signal.

All 4 are firing? -Or all 4 have power, but only 1&4 are ever grounded by the ECU to fire the injector?

on my buddy's car, every 1/4 turn caused an injector to fire. On my car every 1/2 turn caused an injector to fire. This was using the same CAS.

Check the wiring harness you're using for the 1G CAS swap.

Have you tried to set the base timing or moved the CAS adjustment since you got the car?

Can you post up a log?

 

[KFred 513]

Talon, yes we did check the injectors and they are all working properly. We swapped #2&3 with 1&4 but the car continued to run on only cylinders 1&4.

Delta, I was actually inside the car cranking the starter but the guy that used the noid light is the head mechanic at my buddy's shop. I would assume he was getting a blinking light, especially since a few guys were watching the test, I would think one of them would notice a solid light rather than a blinking light.

Last night while poking around with a shop light I noticed a small loom of wire tucked down near the passanger axle by the CV joint. It took some tugging to get the wire out of where it was, since it was pinched in between the axle and Transfer case. When I got the bundle of wires into view, I could see that the loom was torn apart, one wire was shredded in half, and another was near breaking .
I traced it back directly to the coil/injector harness plugs. I soldered these back together and the car purrs nicely on all four cylinders again

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I think its safe to assume that the studder/hiccup I experienced was directly related to the wires shorting as they slowly got torn apart. It makes me wonder how many unsolved "studder" cases are caused by a bare wire somewhere in that harness.

Thanks to everyone that chimed in and offered advice!

 

[trillatl]

This happen to me last year... Check to make sure the plug going into the mass air flow is all the way plugged in. That will make the car run like crap and jump a tooth... I took it to a shop and they told me to buy a new one. Pulled the plug out and sprad it with cleaner and plugged it back in tight... Problem fixed...

Sorry just seen that you already fixed this issue....

 

[abrekel]

Try going into DSMlink then go to dtc and disable the missfire dtc.

 

[Dayonaise]

I had the exact same issue and my dsmlink wasn't logging anything at first but cylinders 2 and 3 would drop out once the cargot warm, anyways long story short it was the # 55 pin on my 1g ecu i am not sure but i think #26 on a 2g ecu I'm probably wrong.
Either way it controls the 2&3 cylinders and it was actualy a fault in the ecu, i sent it to Thomas at ecmtuning (dsmlink) and they fixed it and shipped it back. How i found out was by plugging in a multimeter to that pin output and it did not register a voltage so maybe try that cause i pretty much changed everything you have already before i found the issue
If needed i can dig up the link to my old thread to be more clear