Engine Starvation / Fluttering

[JThomas]

Within the last month, I have driven my '92 Z and have experienced a situation where the car sputtered/fluttered under acceleration. It almost seems as if the car had bad gas or something. After continued driving, the problem seem to go away.

At the time of the incident, the car had a half a tank of gas (Premium)

After the first occurence, I added an injector cleaner and last night when it happened, I added a fuel additive.

Do you think:
1. Bad gas
2. Injectors going bad
3. Clogged or dirty fuel line
4. Dirty or clogged fuel filter
5. Fuel pump issue
6. Wrong time of day??????

The car continued to drive each time, but it was a noticeable loss of power / acceleration.

Any insight would be helpful.

Thanks. :thumbsup:

[XfireZ51]

So does it drive ok at steady cruise but breaks up under acceleration?

[JThomas]

Somewhat okay at steady cruise, you can sense the difficiency, but more noticeable under acceleration.

After filling the tank today and driving from Lansing to Detroit and back, no problem whatsoever. (150 mile round trip)

[secondchance]

How old is the fuel filter?

[VetteMed]

I was having a similar issue when my fuel pump(s) were dying. Might not be your issue, but worth checking pressure.

[rhipsher]

Any codes set?

[tomtom72]

JMHO Joe.

You didn't mention any SES light flashing briefly or on, so I take it to mean "NO"?

Do you have the OEM injectors? If yes it could be the signal for the end. I don't know all the symptoms. When mine went they gave no warning that I detected. They were fine, I got gas, upon restart they were junk.

Fuel filters in C4's seem to be a bit of a mystery. I do mine every year. Okay, like back in the old days:redface: How is yours? Oh, along that vien. Do you run the gas down really low? I thinking trash in the tank sticking to the sock type of deal? If you know the filter is clean the pressure test is a bit more valid when done, JMHO.

Your narrative about the gas fill ups is/maybe a clue. Runs fine now on this last fill up? It has had the benifit of gas treatment x2...see what I'm talking about? Goes back to the trash in the tank idea.

If it was coils or plugs or wires....it don't fix itself. It's fine now, right?

Just some thoughts for you.

:cheers:
Tom

[JThomas]

Thanks for all of the feedback. I purchased the car last year in April and had to acquire a lot of the vacuum lines under the plenum. (Thanks to this forum) :thumbsup:

I don't know how old the filter is, but I believe it had been replaced while the plenum was off. I will check my paperwork from the dealer. The car now has 101,5XX miles on it. The injectors could be original or old, I don't know. When I got the car it had 97,XXX miles.

No SES lights or anything, just the sputter under acceleration, but again after a full tank, the problem seems to go away.

For now, the tank is full. I'm headed off to Woodward Ave. in Detroit for the annual Woodward Dream Cruise! If you should see a Bright Red '92 ZR-1 with the hood up, that will be me. :mad:

But the back up car will be the '07 Z06! :dancing

Let the games begin!:cheers:

[Jeffvette]

Joe, I'm over in London ONT if you want to come over.

[Ccmano]

Sounds like mine when the secondary injectors went south. The engine would studder whenever I would get into the secondaries. But before you go after that, replace the fuel filter and check the fuel pumps. Ideally I would just replace the fuel pumps. It's just a matter of time for them anyway, especially if they are origninal. Make sure there are no bits floating around the botom of the tank. Haveing said all that chances are good that the injectors are the culprit.
H
:cheers:

[Paul Workman]

Make sure there are no bits floating around the botom of the tank.


Oh, you mean like a red shop rag, Dom????:jawdrop:

My fueling problem may have contributed to a possible valve issue - waiting to see. I didn't seem to have a delivery problem at idle or even under WOT, until the rpm got past about 4500+ or so.

Testing the pumps individually (easily done using Marc H's trick and hot wiring them individually at the pump connector instead of the FSM method) didn't reveal anything under no or light load. But, adding an extension to my fuel pressure gauge and taping it to the windshield allowed me to see what was going on at WOT, exposing a weak secondary pump! (As my luck would have it, one of the new pumps had a bad check valve. So, after installing them once, I was back in there again doing a pressure test to isolate the leak. Can't win for loosin' sometimes!:rolleyes:)

http://i185.photobucket.com/albums/x220/6PPC_bucket/tech%20files/FPtestLarge.jpg

You can measure the resistance of the (hot!) injectors to see if the insulation of the coils is breaking down. You should have ~12.5 Ω Â± .5. Anything in the mid 11s or lower and you have the beginnings of trouble 'fer sher'.

AND...one more thing that fails under heavier loads is ye ol spark! You might (as Jeffvette will tell ya) start simple and replace the plugs. And, you can measure the resistance across each of the coils. If one is more than 3% lower than the rest, I'd put the evil eye on that sucker too!

Or, of course you could get lazy and put a scanner on 'er and run it to see what that turns up. (Best damn tool in the box was that scanner I bought about 5 years ago!)

Maybe you can find something useful here. Hope so.

P.

PS

AH! When I first got my Z I had some serious stumbling and bogging at WOT which turned out to be my accordion-snorkel tube collapsing. Marc H has some cute lil wire hoops that keep that from happening. Or, do like I did and make a sleeve out of aluminum sheet metal and line the tube with that. (Some say it smooths the air flow - working at least as well as punching the TB out. I :dontknow: about that, but it cured one of my stumbling problems instantly!)

[rhipsher]

If Jeff is close enough then take it to him. He will be able to diagnos and fix the problem quicker than you can.