marc1130

LT1 wont go above 4k rpm, after Fuel Filter replacement, no SES

Symptoms:

[LIST]will not go to redline, craps out at 4500 rpms[LIST]

possible cause:
It just starting doing this severely yesterday after fuel filter replacement, I put the old one back on, symptoms still present. I used a pint of seafoam with the old filter, and today I put the new fuel filter back on.

I have visually inspected the coil to optispark wires, and insured all spark plug connections, I just did a tune up 15k ago with plugs and wires.

No SES light is present. Seems to misfire and struggles to reach 4500 rpm.

Clogged injector?
Bad Fuel pressure regulator?
Fuel pump seems to be giving enough pressure,
bad optispark?
bad iginition coil?

Any ideas, it was almost like someone turned on a switch and the problem happened.

rclearyiii

I am not familiar with seafoam. Is it safe for oxygen sensors?

marc1130

if anything it will help clean the o2's

ghost stripes

i used sea foam one my 3rd gen the told me the only way to do it was through the brake booster tube did you do it that way ....and yes it is safe for 02 sensors

RamAir95TA

Maybe it's totally unrelated, but perhaps your cat(s) is/are clogged?

kumho

My 1993 Z28 had about the same symptoms last year after I added a can of seafoam to the tank. Turned out that my fuel pump went bad. I think the seafoam may have loosened up rust in the tank and killed it.

marc1130

symptoms actually started before the seafoam. I'm gonna check the fuel pressure sometime this week.

marc1130

Update: 7-26-09

Fuel Pressure Tested Okay.

• W/ ignition on, engine off, reads 41-42psi, then drops to 39 psi after ignition off.
• (spec calls for 41-47psi with no more than a 1-2psi drop)
• w/ignition on, engine on @ idle 34-37psi (spec says it should not drop more than 3-10psi from the reading w/ ignition on, engine off)
• WOT under full load 41-42 psi (spec says it should hold at 41-47 psi)
• No fuel coming out of the vacuum line on the fuel pressure regulator.

I replaced a intake tube going from the MAF to the throttle body. I have a 2002 ws6 ram air setup on my 95 LT1 Trans Am. And now acceleration seems to be constant and will not misfire at high rpms, in fact it will stay and hold at redline.

I also unplugged the inlet and outlet optispark vacuum tubes from the throttle body and air box and ran clean compressed air through the optispark with the car on and off to see if any debris or moisture buildup would escape or loosen up anything in there causing problems, nothing came out.

Car is still struggling power wise.

I think I have a clogged catylitic converter, its a single style cat placed in line after the collector, and y pipe, seems to be shaking alot and impeding exhaust flow??

MikeGyver

Do u smell sulfur? clogged cat.

marc1130

Thanks RamairTa and MikeGyver. I had an air-intake leak after the MAF and a clogged cat. Long story short, I unclogged the cat, sealed the intake leak and the car feels far more powerful than before the problems started. Thanks everyone!