from a stop light. All and all, it's a lot of fun and needs tons of cosmetic work. But it runs pretty good. Lots of little things, but the biggest at this point is that it shakes when warm at the idle at a stop light and just starting up.

Checked the timing and the replaced or cleaned the cap, rotors, wires and plugs lately?

Oh yeah. And it's only rough when idling and getting going. Smooth as a baby's bottom the rest of the time.

Are you having to power brake it at stop lights at stuff? Will it run by itself at idle, or will it die if you don't rev the engine a little bit? Check for vacuum leaks. Has the car done alot of sitting? You say the cosmetics are nasty, well if it has sat around, rubber parts like vacuum lines will deteriorate. Do what davesdeville said too, its like 50 bucks worth of stuff.

once the thermostat opens the idling slows down and then after it's been running a lot it gets rough. I was a shop boy at a Caddie dealer in the 70s when these were new, so I know what normal is: a monster while its racing at fast idle and very smooth when running warmed up. As far as the body goes, it was originally burnt orange, now burgandy. It needs minor work on the sheet metal, and all new extensions, which I have, but have not painted or installed. It will eventually be white. I picked it up running from client for $1500 a year ago, had a mechanic redo the heads. It leaks a fluid quite a bit. Not tranny or oil, I suspect power steering. I've since found a new mechanic that does only old cads and can get me parts (owns a caddy only wrecking yard), I'd plug him, but that might not be allowed.

I've had the engine die on me rarely, only at start up. It will diesel if I shut it off while it is still cold and fast idling. I leave it in gear when I shut it down so it won't diesel. I do this out of habit, so the dieseling problem is possibly worse then I know, but I doubt it.

I have the same issue with my 76 Eldo convertible with fuel injection, and so far no mechanic has been able to figure it out. I've replaced the Throttle Position Sensor, the EGR valves, all the vacuum lines, the fuel pumps (2), fuel filters all the fuel lines, all the plugs and wires, and the temp sensors (2). The car also has all new hoses and belts, and the timing and compression all check out OK. I've also been feeding it premium gas with Seafoam gas additive the last few tankfuls,And it STILL runs like crap off the line, and at idle. Once it gets going it runs like a dream, but from a complete stop it hesitates, and threatens to quit. And lately it has developed a new issue. If I shut the car off after it's been running awhile, it doesn't want to start again. It just cranks like it's not getting any gas, which I know isn't true. Eventually, like an hour later, it will start right up again with no problem at all. Weird. So if you've gotten any useful feedback please share it with me as I'm frustrated as hell, and I've already put 4k into this car with nothing to show for it. Thanks!

If it has trouble starting when warm, you might want to check your fuel pressure regulator. That could be leaking. Or, a leaking injector.

EldoradoRich: When the FPR goes, fuel will leak into the cylinders after the key is shut off, effectively flooding them. This is likely why you can't get it started after it has been running for a while: the car has too much gas.

Replace your FPR, and I bet your issues will go away.

Thanks for the FPR advice, it's seems to make perfect sense, and of course it's greatly apprecicated. I just ordered a new FPR, and will let you know how it turns out.

B/t/w, any advice on the hesitation when taking off from a stop? Considering I have new TPS, sensors, fuel lines, sparks, etc...I'm thinking it might be the EGR Backpressure Transducer. Any thoughts on this? Thanks again!

EldoradoRich: We HT4100/4.x engine guys want to help you out. Here's a post from another member from our section regarding your issue (in case you hadn't seen it). I echo the sentiments about kicking the timing up a few degrees, especially on a 1975 500 cubic inch V-8. The spark is retarded when the throttle is abruptly changed; this effect can be magnified by underadvanced timing. Here's what another HT4100 member had to say:

>>
The TPS , as you know is adjustable. This is from memory, so bear with me!! With key on, engine off, slowly rotate the throttle from idle to wide open throttle. You should hear distinct electrical clicks from the TPS. I believe it is 16 clicks from idle to wide open. If the TPS is misadjusted, there will be a fuel delivery delay at tip in throttle. If it were me, I would move the TPS so the first click occured with just a slight opening of the throttle then road test it. Also advancing timing 2 degrees could help. Also the idle speed screw in the front middle of the throttle body can be turned out ever so slightly to slightly raise the curb idle. Locate a manual on this car or the 76 thru 79 Seville which has the same exact system with smaller injectors. Hope this helps. Merry Christmas!!