My 4ac is missing/sputtering?

[BlackStar]

Not sure which word to exactly discribe it by. (6/9/13) After my last fail, I had my carb rebuilt and tuned, and ask the re-builders to set it up to have a better chance to pass smog. Unfortunately, I think they overly leaned out the carb. With the engine running, it sputters slightly, and the fuel in the bowl is below the bottom mark. When i rev the engine over 2k rpms, it beginnings to sputter more, and the revs decrease. I checked the plugs, they are in the good range, and maybe going to the lean rnage.

I did some more work (6/17/13)

I still have my problem. I adjusted the carb's float, it is now between the bottom and top notches in the float bowel. At idle, it feels like it has a missfire, it doesn't feel smooth. Not really rough either, since according to the tach needle it is constant and strong. Revving the engine, from 1k to 2k, ti revs fine. 2K and above(though mainly between 2k and 2.5k) it does the same miss tendency. For example, say if i rev the engine to 2.5k rpm, and hold it, the rpms will fluctuate, go down, then trying to go back up to maintain. even if it does go back to 2.5rpms, it will still fluctuate.

The plugs are a year old. The rotors is maybe 6 months old. The rotors also shows no signs of damage, same with the rotors cap. I changed spark plug wires to the originals my car had, and noticed the missing worsened. The wires I am running currently I found in good 'looking' condition at the pick a part. it could be my problem. However, The car never ran like this before with the wires.

The only part that has changed in any way since when it was running fine till now was the carburetor rebuild. Either the wires'went bad(though unlikely) while the car was sitting, or I am looking at the work system. I also don't want to start throwing money at it till I have a good idea on where to focus.

Could it be the 91 grade fuel I am running in it? Before, I only used 87.

[dr.occa]

Maybe your mech fuel pump is going bad.

Is it timed properly as well?

[BlackStar]

Yes, timing is correct, right at 5.

[BlackStar]

Bumping this, made a video

http://youtu.be/DkO2227CVLY" onclick="window.open(this.href);return false;

bass sound warning. However, te sound to listen for is the 'popping' sound. Also, when i reenter the car, notice how the tachometer moves up and down while a I rev. The popping noises are present at idle(slightly) and between 2k and 3k rpms. Fuel, ignition?

[BlackStar]

gonna give this a bump and update. I replaced the wires with new denso wires, and i still have the same problem. The cars sputters while revving, and pops at idle. Maybe its a fuel problem(either carb tuning or octane). New fuel filter btw. As i said before, i don't remember the car doing this at all before having the carb being rebuilt and adjusted to run lean(the spark plugs do confirm the car is running lean) tomorrow i'll do a number of tests, maybe i messed up the engine some where. Maybe I should try to rich-en the car up a bit?

[morgan]

Lean could = what Jonas mentioned...fuel pump

[BlackStar]

I actually going to be doing a lot of tests tomorrow, check the fuel pressure is on the list! I hope it is the fuel pump, easier then a burnt valve!

[daveskatesallday]

if needed i have a fuel pump lmk

[BlackStar]

update. I'm going to have to tear into the engine

compression:
cylinder 1 110-120
cylinder 2 140ish
cylinder 3 155
cylinder 4 135

burnt valve probly, I'll have to get it machined

vaccum at idle is between 15-17, since the needle twitches.

[BlackStar]

You know, I should bump this. I did a leak down test, if anything, i have a large amount of leaking in the rings. I'm not sure if its because they did not seat, haven't seated yet,(I am seeing leaking range from 43% to 35%, the engine maybe has 3 miles on it) or are fubard. Also, some cylinders will leak into each other, like 1 leaks into 2. yet, when doing the test on two, it did not leak back. I could use some advice before I do anything drastic. I got a better vacuum reading at the base of the carb, and it holds a fairly steady 18 inches. sometimes it will go 17, and the needle twitches ever so slightly, yet it does not fluctuate to a different number. /after a readjust of the valves, the popping at idle is almost gone. I am tempted to try seafoam or marvel mystery oil, good be some gunk on the valves and rocker assembly giving me trouble.

However, i am more worried about the compression and leakage numbers.

[dr.occa]

So is this a freshly rebuilt motor then?

[BlackStar]

yeah.



Another thing that struck me while talking with a friend, is that the rings could not be seated yet. I guess i'll drive it around, and rev up the engine with load. I really haven't done that, and i doubt it will hurt anything. The vacuum reading is too good to be a bad headgasket.

[dr.occa]

When seating rings you have to load up the engine. Open your throttle hard in 2nd, 3rd and 4th gear but don't go any faster than 65mph then decelerate hard (not brake hard!) by lifting and shifting down through the gears. Make sure there aren't cars behind you when doing this. The feeder at light traffic times or a little to no traffic street nearby would be an okay place.

You want short bursts of hard acceleration AND deceleration.

[BlackStar]

I'm gonna be doing that shortly, I'm actually kind of excited to do it to, feel those 80something horses run! I'll probably do it early in the morning on the day i bring it to smog, do a quick oil change and then get the car smogged. Get the car nice and warm, and broken in. My friend is putting the idea of autocross in my head!

[BlackStar]

Made a few observations today. No popping back through carb. half throttle and WOT, I have no pops or misses at all, and revs willingly. It only light revving that will give me a pop. It really is starting to sound like a too lean air fuel mixture. My guess is above light acceleration, the jets take over and supply the fuel. The idle circuit, which is too lean, doesn't give enough fuel for the light revving and idle, causing the pop.

Just my noob guesses, welcome to opinions. I have been in contact with the shop that rebuilt my carb, they suggested turning it out 1 full turn(I did ask them to make it lean for smog reasons, guess it is too lean). I'll work up slowly to that when I get time to work on the car tomorrow.