Rough start? Possible contributing factors?

I've noticed that my 95 has recently started to exhibit a "rough start" that seems to have gotten a bit more pronounced over the last few months.

Once started the engine runs and idles fine, although it isn't perfect and one can feel a slight vibration here and there sometimes. I chalk that up to being 20yrs old, still needing some attention like vacuum lines, etc. But generally the engine runs smoothly once running.

I just replaced the plugs and wires (ACDelco both) but this exhibited itself prior to that.

When I say a "rough start" I don't mean it is hard to start, as the engine turns over and starts right away and again runs smoothly after. But what I do mean is that when I turn it over, it doesn't start smoothly like a well sorted engine does. It turns over and then sort of shudders for a fraction of a second then smooths out. The shudder is pretty pronounced, and definitely isn't normal.

What would be suggested to look into that might cause a hard start scenario like this?

Thanks,
Al

I should add that I think my SC coupler rattle tends too enhance this experience .... and that probably makes it sound a bit more serious than it really is.

It is possible that is most of the issue.... "perception", although the engine still seems to "catch" (from an ignition perspective) a bit and start versus just spin up and start.

Does the car act differently when warm or cold?

Have you had a "real" Injector cleaning like a BG Fuel Injection service?

The coupler will make it appear worse than it is, yes. The engine misfires slightly at idle by design. A worn out coupler gets apparent at idle because of the irregular spinning of the belt. The crankshaft slows down enough to create fluctuations in belt speed, thus allowing the coupler to "knock" from the momentary loss of pressure against it. That's also why a coupler knock doesn't have a consistent rhythm to it like say, a rod knock. It absolutely could sound like or amplify a misfire.

Do you have access to a scanner that can monitor the PCM's built in misfire counter? Seeing that alone can verify a minor misfire(s) that might slowly becoming a concern. The engine can misfire all day long without setting an SES light, as long as said misfires are still within "spec".

Paying attention to this one, seems to describe how my car seems to me.
I'm a new Riv owner & Love the car can't wait to be happy with all aspects!
My Regal is smooth & almost can't tell its running at idle, the Riv shakes & accelerates with a little vibe, got a new FPR I plan to install this weekend cause what I've read made this seem suspect..
Jbird

Not sure on the warm versus cold question honestly. I usually have several hours between drives, but I'll try to keep an eye out.

I'm sure the SC coupler is amplifying the perception, rattle and some vibration. And in fact, that may be the most of it *shrug*. That is low on my list right now though to repair, but who knows that may be the bulk of it.

And no, no injector cleanings. Sending them out to Mr. Injector is also on my list in a month or two. Maybe I'll get a new FPR then since I'm in there.

Replaced the FPR Saturday, it may have helped the start, but the idle is still a little shaky at times.
It doesn't seem to be heat related, just kinda random.

[quote="Abaddon"]Have you had a "real" Injector cleaning like a BG Fuel Injection service?

What does "BG" stand for?
Who could I trust to do this properly, Dealer only?
(seems hard to trust any shop anymore to do things right)

Jbird

Have you changed the fuel filter lately?

Have you put a fuel pressure gauge on the fuel rail? I would have done that before replacing the FPR. They don't typically go bad. You should still see if the fuel pressure is correct. (50 PSI at idle with the vacuum line disconnected and plugged, pressure usually drops when you connect the vacuum line). Also, if you have a FP gauge, you can see how quickly the pressure bleeds down after you turn off the key. It should hold pressure somewhat when the pump is off. If not, fuel is leaking back somewhere. Usually it's injectors that don't close, although on rare occasions it has been the fuel pump itself allowing backflow when it's off (it's usually the injectors).

Fuel injector true 'service' is not usually a dealership kind of thing. I prefer to remove the injectors from the car and send them to a place to be cleaned and flow tested on a bench machine. That kind of service costs about $80-$100 if you remove the injectors yourself.

Most fuel injectors of this age really need a bench cleaning. Some shops have a machine that can push some kind of solvent directly into the fuel rail, I'm not completely sold on that - and it depends how badly the injectors are leaking.

New (cleaned) injectors made a huge difference in my car. Smoother idle, easier starts, no more 'popping' or sputtering at idle (too much fuel going into one of the cylinders), etc.

Fuel filter is next in line, probly should have been first, but in my search I had read these FPR's were "notorious" for failing...
I do not have an FP gauge, I may see into aquiring/borrowing one to look into it further.

I would like to have the injectors serviced that way, sounds ideal, I would prefer to do that at the end of the season though. (just got it out of storage, my first season with the car)
The car runs well, I'm not worried about reliability, just would like to see it run as I think it should.

Thanks for the inputs!
Jbird

I wouldn't say notorious. It does happen, but it also doesn't necessarily fit the problem you are describing, unless your fuel pressure was off. In which case, a fuel pressure gauge ($20 bucks maybe?) would have saved you the wasted regulator.

I'm a big believer in "find the actual problem before replacing any parts" whenever possible.

yes, a better philosophy for sure.
Never had a FP gauge & would not have expected the "tool" to have cost less than the part...

I'll check the FP this week(end) as suggested.

The fuel pump is a new Delphi unit (1 yr, 25k miles new), and I've replaced the fuel filter twice over the last year since the car sat for a while.

I do plan to pull the injectors and send them to "Mr. Injector" this summer.

Al