TR348 TDC Sensor Issues

This came across my desk and should be of interest to TR/348 owners experiencing poor idle and/or missing that alludes diagnoisis or repair:

All Magnetti TDC sensors that are currently on the shelves have internal problems and display backwords patterns on a scope. The problen has been traced to reversed polarity of the TDC sensor itself, sending faulty sine waves to the computers. The result is engines that burn out cats, idle poorly and miss throughout the rpm range.

JR,

Does this pertain strictly to "new" sensors ?

Joe, from the info that I just became privvy to, the story goes, ALL "new" sensors that are in the market place (on dealers shelves) are Faulty, mis-manufactured from Marelli. From what I gathered this means all replacement TDC Sensors manufactured over the last year at least and likely longer (I'd guess much, much longer). So anyone that has replaced a TDC Sensor for quite some time past has recieved and installed a faulty sensor.

I'd post the entire story from a credible source but it's copywrited. It's from an International Technicians Forum I'm a member of.

Hello JR,

Good info.

Reason I asked is, I got a buddy with a 1990 Mondial t. The car basically runs but (recently) started to vibrate more at idle, very much like it feels running on 6-7 cylinders. We pulled all the plugs and they're all firing.

It's got a really strange vibration, hard to describe.

It also rattles in the flywheel (I know the sound, my cousins 348 did the same noise...fix...was a repacking of the flywheel.)

Thus, thanks for the info because TDC sensors did cross my mind as well. I know now to tell him NOT to buy one without investigation first.

But, we still don't know what the problem is.

Joe, how many miles on the Mondial T ?

plus one thing that is easy to check are the fuel pressure regulators...I've seen a few lay down causing simular symptoms. Pull the vacum hoses off the port on the FPR's and see if there is any raw gas present. When the internal diaphrams go bad, they leak raw gas into the intakes via the suction from the Intake Manifold.

Hello JR,

The car has about 35000 miles on it.

I will definitely check the FPR's when my friend comes up. He's coming the weekend of June 20th. That'll be the first thing I do.

I also checked out some Exhaust Gas Analyzers today on the net. 2 gas starts at $2499 and 5 Gas around $4999 (real man's tool that's for sure).

I must be living in the dark ages. I thought a 2 gas would run about $600 or so. I could of swore at one time that's what they cost, maybe when I was in high school

I called the guy who does my smog checks and he said he can do it, so we'll probably take the car there.

When I do, I'll email you the readings and we can take it from there.

Appreciate the help. I'll be owe-ing you one.

Joe,

while anythings possible, your friends Mondial T problem just doesn't quite sound like TDC sensor imo.

Of course it's hard to get a real 'feel' for the problem like this, however I'd be looking for a vacum leak or incorrect Fuel Pressure problem first, before swapping out parts and if those searches turn up nothing, bad ground connections and/or loose or bad harness connections, then I'd spec out the MAF sensors.. All the above are far more likely failures and could cause the symptoms you describe.

HTH's

Hello JR,

I've put together a list of things to go through, then,
if that fails,
I'll go get the CO and HC readings.

We'll set aside the probability of TDC sensors until otherwise.

Great help.

You may be our only hope to getting this thing right. (nobody else has been able to fix it)

It's been running like poo since January.

Joe,

another common problem with the 348 series is bad grounding of the Oxy Sensors. For some reason the Oxy sensors loose their ground and an additional ground strap needs to be attached to the outer sensor housing to solve this issue. I've seen cars from the dealers that have a ground strap secured to the sensor bodies with a hose clamp.

Also you mentioned someone nearby that would check exhaust gas for you, it would be a good idea to check the EG pre-cat (at the seperate capped test ports) to help establish if there's a problem and if so, which bank it's on. On a 355 FI, with a wierd miss recently, I was able to trace the probelem right to the 1 cylinder that was the problem just using a Gas Analyzer and the test ports.

These types of problems need a careful methodolgy to help track them back to the source. It's sorta like reverse engineering...first you find the symptom, then which areas are effected, then whats is effecting that area.

Regards, JRV

Hello JR,

Great info.

You see, I had added o2 sensors to the list of things to check. But all I was going to check was output voltage when connected (between 0.0v - .9v) and when disconnected (.45v).
I wouldn't have known about the ground problem, thus, thanks again.

Best regards,
Joe