pologreen97z

Hey all-

I brought an 77xxx mile '97 Z28 M6 to Texas from California last year. This car was originally sold in California. I have noticed lately that it seems kinda sluggish off the line and doesn't seem like it has near the oomph it should have in the low to mid RPM range. As far as I can tell, it has the original plugs(have all service records from new). The only mods to it are a skip shift eliminator and K&N filter charger. Other than that, it is bone stock. The only repair I have done to it is a new fuel pump(ouch) due to running it out of gas(stupid no low fuel light).

Questions:

1) Would the fuel pump issue have caused some sort of plug fuel fouling, resulting in the sluggishness?

2) Are there things on the California cars that are robbing me of power? I had an almost identical car back in '98 and it seems like it was much quicker than this one.

Thanks for the help

Fatdog2

Nice stone driveway.Anyway,the original calif cat is very restrictive and when I get some more money I'm with a magnaflow or catco cat like I had on my old 1993 bird.I blew my cat to pieces,literally ,it broke up inside around 80,000mi or so,.Some of the pieces ended up in the muffler,so I replaced the cat and the muffler at that time.Anyway,I would clean the kn filter first,then replace the gas filter(not on that driveway please).At night close your garage door and aim the car at the garage door and with headlights on rev the engine and see if the lights flicker(not steady bright).If the lights don't stay steady,then I would replace the coil(coil wire to).Hope this helps.Also make sure all the plug wires are on tight.

Injuneer

He has dual cats, so it's not reasonable to compare them to your single cat 93. How did you determine that the cats on a CA car are more restrictive than 49-state cats? Just curious.

I bought my 94 brand new in CA, and the M6 cars were 50-state compliant - no difference between CA and any other states. On the other hand, 95 A4 cars included less restrictive dual cats w/ the CA emissions package, while the M6 cars kept the single cat.

Chimera96

[QUOTE=pologreen97z;6969024Questions:

1) Would the fuel pump issue have caused some sort of plug fuel fouling, resulting in the sluggishness?[/QUOTE]

if you have a "fuel pump issue" did you check fuel pressure with a gauge?

One that has a hose long enough to tape it to the windshield so you can test drive at SUSTAINED WOT to see if FP holds. If it drops than you do have a "fuel pump issue"

not clear on how you determined you have one.

Injuneer

He already replaced the pump. I think he is asking if the problems with the old pump could have contributed to the problem of low power - for example could it have caused the plugs to foul?

The answer would be "unlikely". If the pump burned out due to running out of fuel, it's likely that there was little operation of the vehicle with a faulty pump. If, on the other hand, the pump was already on it's way out a while before it totally failed, it may have suffered from reduced capacity. But that would cause the engine to run lean, the PCM would see the lean condition on the O2 sensors, and would increase the injector pulse width to deliver more fuel.

But, never hurts to check the fuel pressure.

Can't see anything as a result of the earlier fuel pump problems that would have caused fouled plugs.

If you have an 18 year old car, with the original plugs, wires, coil and ICM, it's possible that you could have ignition issues. Particularly the plug wires, that will crack over time. Do you sense a misfire when you hit the accel pedal with the engine at low RPM in a numerically high gear? That's when a weakness in the ignition system would show up.

You might also want to clean the MAF sensor, and check the air inlet elbow for cracks.

What trans do you have - A4 or M6? If it's the A4, which rear axle gears do you have - 2.73 (GU2) or 3.23 (GU5)? The 2.73's would make is seem sluggish, I would think.

pologreen97z

Yes, pump was replaced less than 500 miles ago, The car is an M6 with 3.42(GU6) and limited slip (G80). It occurred that the fuel filter may have never been changed. I am not seeing it in any of the documentation from the previous owner who was meticulous with his records.

Honestly, it just seems to me that it is lacking some of the seat of the pants feel gunning it from 2nd and working through the gears.

Hopefully, this makes sense.

Thanks for the help.

ACE1252

That is a nice looking '97.

I'd get it on a dyno or to a track and post up the numbers to us. That will tell us it's state of tune.

The Service Engine Soon(SES) is not on is it?

For a stock LT1 M6, you should expect 8.9-9.1@80-81mph in the 1/8th mile. This also depends on how well you get off the line. Regardless of the time, the MPH should give us a good clue on how strong the motor is performing.

Best I could get out of mine first time out(as in my first time on a drag strip ever, 1/8th mile) was 8.9@80mph. The car had a K&N filter(not the CAI...just a K&N filter in the stock airbox) and Flowmaster catback system. Everything else was stock.

pologreen97z

Thank Eric-

No SES light. Though, the coolant light keeps coming on for a reason unbeknownst to me.

Good idea on the Dyno pulls. I will work on getting that done.

shoebox

4th Gen LT1 F-body Tech Articles

Fatdog2

I just thought all the single cats where restrictive (for the early years) because I blew mine to pieces.Never heard of that before.I forgot the 95's had dual cats.

ACE1252

I think I have an old Motor Trend article where Jon Moss mentioned that the change in the Y-pipe for the dual cats was responsible for the 10hp bump from 275 to 285 for the F-bodies in '96. So in reality, the dual cat CA cars in '95 got the hp bump early, Chevy/Pontiac just didn't advertise it until '96.

If I remember right, '95 was the first year for the 3800 series II V6 as well, but it could only be had with an auto. That forced me to wait until '96 to order my Y87 5M.

Not Dave

Nice car. I too am a new owner of a 97 though mine has 140,000 on it.

I'd change the fuel filter. It's easy and inexpensive. Changing the fuel pump may have sent some debris through the fuel line. Even if not and it's the original filter it was due to be changed over a decade ago.

I recently changed the drivers side plugs and wires. The wires were Packard so probably original. The plugs were very worn AC Delco so may have also been original or maybe replaced well over 50k miles ago. The car now idles smoother and seems to run a bit stronger.

Your cats may have some blockage adding more restriction. Mine seem to be okay but each car is different. If yours is like mine it'll take a lot of rust penetrant to get the Y pipe off. Might do other, easier things first.

Not Dave

BTW mine has the same chrome wheels though my car is white. Yours is looking good.

Injuneer

The chrome wheels were optional (RPO N98). Cost was $500 on a Z28, more on a base car. They were installed on 10,288 cars.

Trivia courtesy of the Camaro White Book.

pologreen97z

First dyno run today. 271 RWHP with 306 lb/ft. Air fuel was dead on. Clearly running strong I just need that extra oomph. I want to keep it basically stock so I may just do a Cat back and shifter. The tech said it was the cleanest/smoothest LT1 he has ever had on his dyno.