LarryD

Ok, this is my 92 with about 40,000 miles on the current engine rebuild.. Everything has purred fine with the engine with not even a miss, until tonight. I brought it home on a tow truck. I was cruising freeway at 60 mph when all of a sudden the engine just died instantly. The tach dropped straight to zero.. I looked in the rear view mirror to get over to the side of the freeway and saw a big bunch of sparks flying out the back of the car.. It reminded me of molten metal and/or something dragging on the pavement.. The engine still cranks over fine and even tries to start if only briefly.. No visible damage and no fluid loss on the ground.. Temps were normal and no rattle.. I didn't hear any ping but I am hard of hearing so probably wouldn't hear it anyway... I had just filled up with gas and was maybe 5 miles down the freeway when it happened. Its midnight and I just got it home so haven't tried a compression check yet that will have to wait a day or two.. The sparks were a bit spooky. Could that have been the catalytic converter and if it blew out would it cause the engine to die suddenly? I am hoping this is a catalytic converter problem and not something like a melted piston... It was dark so I couldn't tell if there was oil smoke as well as the sparks....

maroe624

Sounds ignition related to me. Coil maybe ? This is a 3.1 right. Pretty bulletproof . The sparks out the back of the car is weird. Could point to internal damage .

LarryD

That was my first thought since it was like you turned off a switch. Thought it could be the ignition module inside the distributor but sparks out the back are unusual unless it dumped a bunch of fuel into the catalytic converter and took that out. There wasn't any sound to it. It has a 94 3.4L in it but basically the same engine as the 3.1 since it has the original 3.1 cam, bolt on stuff, and ECM.

LarryD

Well, internet research says the Cat can overheat, melt and even through sparks... (Maybe wishful thinking here)... The overheat is usually caused by excessive fuel hitting the Cat. Possible causes are listed as 1) Bad Plugs, 2) Bad Exhaust Valves, 3) Bad O2 Sensor, and 4) Bad Fuel Injectors. A bad ignition module or coil cutting out would also add fuel down the line but the car wasn't missing. I have been having the ghost EGR error for some time now but not sure that is related. So, I plan to check for codes first but suspect I will only see the EGR code. Then I will check for spark and unbolt the Cat to eliminate any back pressure to see if it starts without back pressure. If that doesn't work, then I will pull the plugs and inspect them followed by a compression check on all six cylinders. If all good there, I will pull the injectors and send them out to be checked and cleaned. After that, I am at a loss.

Another thought crossed my mind. I am approaching 40,000 miles on the rebuild 3.4L. Could this be a longer term problem (again wishful thinking that it is the Cat). The stickies on this 3.1L to 3.4L swap say have you change the injectors to those from the 3.4L to add fuel flow for the additional (all be it small) amount of increased cylinder volume. I did that change so I wonder if this is a mistake that causes excess fuel going to the Cat? However, I did change the whimpy air intake can near the fender well to the dual snorkel style over the radiator to increase air volume in at the same time that the 3.4L injectors were installed...

LarryD

So, checked last night and I didn't get any spark. Hopefully then the ignition module or coil quit allowing raw fuel to hit the catalytic converter causing all the sparks flying out of the back of the car as the Cat overheated quickly.... At least that's the theory at this point.. Picking up a new ignition module, cap and rotor for the dizzy. Also, putting on a new coil at the same time... Will see if it runs after that. If it does, then I need to decide if the Cat needs to be replaced.... The only OBD code I had was the code 32 for the ghost EGR...

LarryD

Good news!!! I changed the ignition module, cap, rotor, and coil... Car started right up and seemed to run fine.... Sooooo, guess it loaded the Catalytic Converter up with fuel when it quit and blew sparks out the exhaust when the Cat overheated... Now I just have to see if the Cat needs to be replaced or not...

maroe624

So you put the 3.1 cam in the 3.4 ?

LarryD

I didn't use the cam out of the original 3.1L but you can. The 2.8, 3.1 and 3.4 cams all fit the 3.4 block. However, the 3.4 uses a cam position sensor that is not needed in the 2.8 or 3.1 so when I ordered a new cam, I ordered one as a 3.1L without the cam lobe for the position sensor. The grind was slightly more aggressive in performance than the stock cam.