ls1charged

iTrader: (8)

So i got a 99 SS a little over a week ago, 75k miles, super clean! The car feels like its being held back.... hooked up HP Tuners and sure enough, it seems like its down roughly 40 hp!! We also noticed that after scanning each individual cylinder, we got multiple misfires in Cyl 1,2,6 and 7!! Since ive had the car i have done:
Tr6 plugs
Fuel Filter
Remove AIR and EGR
Seafoam
Lucas Fuel Treatment
Both upstream O2 sensors

Now everything has been detuned as far as AIR,EGR and rear O2's, but the car feels the same after all of the above! Also we threw it up on the lift and noticed that the previous owner put in a flowmaster muffler in place of stock and also removed only the drivers side CAT!!!?? After scanning we pulled #1 and #7 plugs, #1 looks fine however #7 looks lean, white as a ghost! Any input would be greatly appreciated! Thanks

RockinWs6

How would hp tuners tell you its down on hp? Is it pulling timing?

I would suggest a compression test followed by a leak down test. Then I start looking at intake gaskets and possibly valve lift. Might have a worn cam etc. Partially blocked cats?

ls1charged

iTrader: (8)

Cut off the cat yesterday and welded in a pipe, car feels better but still not great.. Gonna try to swap mafs with a friend and see if that's another culprit

Sinister_Z28

Dirty maf can do that. What about plug wires? CRC Maf cleaner is like six bucks at auto zone. What air filter are u running?

ls1charged

iTrader: (8)

I cleaned the MAF but still feels weird, it has a K&N in it from when I bought the car, I did plugs but not wires

Tbird232ci

iTrader: (4)

Plugs are only as good as the wires they connect to.

Funny story. Years ago, I bought an 85 Dodge Shelby Charger from a buddy of mine. He told me the list of stuff he did to it, and mentioned he put Iridium plugs in it. When I got to the car, I pulled the plugs out, looked at the part number and then looked them up on Advance Auto's website since Iridium plugs just got popular. They were 11 dollars a piece! I looked at the brand/part number on the wires...they were the 8 dollar a set cheapie wires. I put a custom set of MSD wires on it, and put regular copper core plugs in it, and it ran significantly better.

ls1charged

iTrader: (8)

so after logging tonight we found out that the drivers side of the engine is running more lean then passenger side, also the O2 sensors dont seem to be switching as quickly as they shoud be, they are brand new! Do i have an electrical issue??

LS6427

iTrader: (2)

Probably just a bad NEW 02 sensor........happens all the time.

.

ls1charged

iTrader: (8)

The new O2's dont seem to be switching any different tan the old ones though......

LopeyZ

iTrader: (2)

A quick and dirty O2 sensor test is to swap them bank to bank and see if the problem follows the sensor.

jimmyblue

iTrader: (11)

If your plugs are telling you about a cylinder-cylinder
fueling imbalance then chase that down ASAP. There
seems to be a lot worse problems on #7 and #8 cyls
(whether from air distribution imbalance in the manifold,
or fuel injectors at end positions catching all the silt,
dunno in this case - but have seen the latter on other
cars).

bank-controlled EFI depends on some assumptions, one
being that all the cylinders are acting the same. With
fueling skewed, the O2 sensor feedback has to work with
the average and you get one lean, 3 pig rich to comp it,
and the lean one goes pop someday - after driving your
knock learn factor all the way to low octane table.

You might just pull all the injectors and get some
'01-'02 OEM larger ones pretty cheap, swap the table
and call it good if they're virgins. Or send your stock
ones out for service, but they're no prize to begin
with. Sometimes guys who do injector service will
give you a good deal on refurbed ones they have
lying about, too.

ddnspider

iTrader: (26)

The O2's are not the issue. See the attached picture of both banks switching. There is no way that BOTH brand new O2's were bad out of the box. The switching looks the same with all of the mods done as it did when it was picked up from the dealer with no mods. I unplugged the MAF and the car did seem faster, so we swapped a MAF on it and it seems a bit better as well, but it still seems to struggle and the O2's obviously look like crap. My hit list:

1) verify fuel pump voltage at WOT
2) verify fuel pressure at WOT
3) check grounding

If it still feels off at that point, then it may be a good time to swap injectors and rails and see what it does.

Jimmy,

Have you ever seen O2's look like the posted picture? If so, what were the symptoms/issues? I've never seen O2's look like this.

Bullitt117

iTrader: (1)

I'd replace the plug wires if I were you. I was chasing down a miss and fuel trim problems for a month once and it turned out to be a loose plug wire lmao.

ls1charged

iTrader: (8)

Thanks for all your input guys!!! I did end up doing plug wires to eliminate that variable, feels the same... After doing some searching to fix a lights pulsing issues, I came across a thread talking about checking all your grounds in the engine bay... Last night I located all major ground wires, unbolted them and ground down the idiot factory paint they bolted them too and voila, the car pulls smoothe in every gear, doesn't bog down in 2nd and my cruise control isn't shutting off randomly!!! Now I just need to log it and see how it really looks but it feels hella better!!!

ls1charged

iTrader: (8)

So today we checked voltage to the fuel pump, everything checks out! also swapped injectors from the cylinders that were misfiring to other cylinders hoping to follow a problem but some of the same cylinders still misfired as well as the cylinders that were not previously! Any thoughts?

nascarnate326

iTrader: (1)

What is your fuel pressure?

Can you post a video of the car running?

Have you tried a different MAF? I only ask because I cleaned mine and it got better but when I replaced it I got the full power LS1 feeling back.

Compression check?

ddnspider

iTrader: (26)

Fuel pressure is ~60psi at idle. Didnt check it at WOT.

Per my last post, we did swap MAF's with no change.

Did a compression test on some of the cylinders and they were within a few psi of each other.

We don't have video, but I have logs showing the specific cylinders showing misfires randomly.

redbird555

iTrader: (14)

Does the car actually feel like its mis firing? I've seen that misfire counter in hptuners be wrong multiple times on several different cars. According to it every ls1 car I'd've put it on had multiple misfire on random cylinders yet all ran fine.

Also checking fuel pressure at idle is useless you need to check it on the road under load at wot. This outs a demand on the pump and anything under 58psi will cause issues. Also have you put its on a Dino just to see what it makes I don't mean to take a stab at you but it may be all in your head

ls1charged

iTrader: (8)

The car doesnt feel like its misfiring, one thing ive been noticing is from time to time in 4th gear at 50mph ish, the car feels like its surging almost.... i also have a really bad interior/exterior light pulsing issue, i dunno if that has something to do with whats going on, the battery always seems to be putting out plenty of power so im not sure whats causing that? weak alternator??

Cole Train

iTrader: (30)

Could be false misfire readings. How is the KR when it feels like its bogging down? Have you checked the coil harness or injector harness for breaks in the wires? I've seen a harness cause issued with this. Also check in pitch black if youre getting any arching off the plug wires. Seen this before as well. Itll feel like its bogging down at half to WOT and you'll chase is down and its never what you think it is. Just humor me and check under the hood with no light in the area and no headlights and see if you're getting any arching from the plug wires... Rev it up and stuff just to see.