View Full Version : V 8-6-4 problems!

04-15-04, 09:33 PM

i'm a german Cadillac enthusiast owning a 1980 Eldo Biarritz with
the 368 engine.

I'm really glad that i found this useful forum, hopefully someone out there can give me advice to solve the following prob on my engine.

In general i have a good and smooth running engine.
The previous owner disabled the modulated displacement, so i'm running all
8's the whole time.

The car starts well cold, then for half a minute runs okay.
But when i want to leave my garage place into the dense traffic we have here in Hamburg/Germany it starts to lack power and becomes nearly undriveable. I doesn't take any throttle so i have to push the pedal only very slighty. If it gets just a bit too much throttle it starves or fires back though the throttle body. The only way to get it running normal from this condition is to press the pedal in "Neutral" gear very carefull until it reaches a high rpm rate, then at a certain high rpm it appears like someone turned a switch and it runs normal again.

It seems like some engine control component suddenly looses his fault and causes a normal engine run. Feels like a sticky valve or something that is able to move free again if penetrated with high rpm's, as it shows a sudden
change when the engine turns fast for a second.

Also when the engine is parked hot and then started again 5 mins later,
the problem shows up again a little less heavy.

Only pushing the pedal to the floor and letting the engine yell for a second
solves the problem until the next start.

Also sometimes the car idles in waves like crazy.

I tried everything to get rid of this fault. I changed every sensor, O2, coolant sensor, exhaust sensor, EGR, air temp, SM-TX1 (whatever that was!?).

I changed the sparks, plugs, wires, fuel pump, fuel filter.

The throttle body had a small leak so i put on one from a 350 Olds.
I changed the ISC.

But all that had no effect on this problem. This appears in different intensities, sometimes heavy, sometimes bearable.

The car doesn't show a code in diagnosis check, but i'm not shure if the
computer works right on this function.

Did anyone of you had the same problem or can give me advice on this?

Hope to hear from you,

thanks Jan

04-16-04, 08:14 PM
Hi jan!
you're problem might be a bad throdle position sensor
did you use your original throdle position sensor when you
replaced the original tbi unit?
if so you may need a new throdle position sensor
i hope this helps :burn:

05-02-04, 02:16 AM
I also have a 1981 with a 368 motor, but mine is a fleetwood. My throttle positioning sensor started to give me trouble too, was acting a little diferent than yours but similar, I would try that!

05-02-04, 02:41 AM
Think you may be right with the throttle position sensor, it's the
only sensor i did not change yet.

I had no time to work on my cad, but as soon as i put in the new
TPS i'll let you know if he was the culprit!

Thanks and greets from Germany,


05-03-04, 03:09 PM
TPS is a good suggestion...I also wanted to add that water/moisture in the cylinders would also cause the symptoms you described. You might also try removing the spark plugs again and blowing some air in there and make sure it is clean and dry.

07-10-04, 03:49 PM
Thanks alot, you guys out there!

As some of you guessed the TPS was the culprit for my engine trouble.

Unfortunately two different shops specialized for US-cars weren't able to localize this small part as the fault. So they changed everything else they could find, cost me way too many bucks...

I should have come earlier to this forum!



Night Wolf
07-10-04, 05:31 PM
I think thats great that you run the classic Cad in Germany :D.... kudos to you :)

08-04-04, 06:40 AM
Your secondaries might not be opening. Check your linkage. Your carb has two tiny little primaries, and gigantic secondaries. The primaries were just about enough to let the beast idle for an emissions test.

08-04-04, 07:24 AM
how is that thing on the Autobaun(hope I spelt that right) of course they got different speeds in different lanes. It's really cool to se a german person like old cadillacs oh and hope you like the new ones.