FirehawkNS

iTrader: (3)

Got an issue that popped up a few weeks ago on my 99 Z28 (mods: 115k miles, Lid, Headers, ORY, Corsa, TR-6 w/ >8k miles, tuned about 6 or 7 years ago, fuel filter has about 5k miles, new rear)

I cranked the car up and was letting it warm up and the car started to stutter and cut off, but caught itself and reved up and back to idol. About 2 minutes later it did it again, but couldn't recover. Turned the key and it fired right back up and ran fine.

On the way to work it stuttered like that about 4 times while either on throttle a little (like holding speed up a hill) or just holding speed/rpm. It would feel like the car was hitting invisible walls going down the road 3 times on the 25 minute drive.

If I happen to be pulling to a stop when this happens the car will cut off unless I can catch it when I feel it start and rev it up.

This happens in Neutral/park or while driving. When it happens all gauges look fine except the "Check Gauges" light starts flashing. I have two Volt meters in the car, neither show any drop in voltage except when the car actually cuts off. Oil pressure is fine, temps stable, RPM's look stable.

In an hour drive it might happen 1-2 times on average. In a day running around it might happen about 4-5 times. I was thinking fuel pump, a buddy is thinking Throttle Position Sensor (which was replaced around 30k miles) or MAF.

To me it's like the car quickly looses fuel or spark. I thought maybe bad fuel which it still might be. I had a little less then a half a tank and went ahead and filled up again at a different place. It may or may not have helped...I thought it had, then about 45 minutes later the car cut off. lol

Although I doubt it has anything to do with it, the newest change to the car is I put in a new rear end about a month and a half ago. Stock rear out of a 2001 WS6 and had the speedo recalibrate for the new gears at PCM for less. I didn't touch any of the other harnesses except for the brakes, but just in case I am throwing the info out there.

anthony.fatica

iTrader: (10)

My guess based on experience with a similar problem is the MAF or rear O2s. Goto autozone and see if you kick any codes? My SES light wasn't on all the time and yet it still kicked O2 codes. While you're there pick up a $4 can of MAF cleaner and follow the instructions...

Sykokilla

iTrader: (4)

https://ls1tech.com/forums/generatio...m-stutter.html

FirehawkNS

iTrader: (3)

Not kicking out any SES lights (not throwing any codes, I wish it was). I cleaned the MAF back in October, but have been meaning to do it again just to be safe. I was running a K&N most it's life, but have been on paper since early last year.

No rear O2's since I don't run Cats (they have been tuned out).

FirehawkNS

iTrader: (3)

I guess it could be the Bank 1 o2's, but I have never had them go out without throwing a code. They were replaced back in 04 or 05 I believe. I do expect them to go out due to the headers so maybe I should go ahead and look into that.

anthony.fatica

iTrader: (10)

Hmm. IDK then, having the O2s tuned out and the MAF solved my problem...maybe fuel filter?

bdplays

Fuel filter? If it has not been changed lately it is worth a few bucks to eliminate it as a possibility eh?
The other thing that comes to mind is a crank or cam position sensor...

FirehawkNS

iTrader: (3)

Now you guys are seeing my issue. I replaced the Fuel filter about 5k miles ago. lol

I figured the crank/cam position sensor would throw an SES. I am going to research the MAF first. Replace it with a friends and see what happens.

anthony.fatica

iTrader: (10)

flux capacitor?? lol

mark21742

Try plugging your MAF and running the car...this will throw a MAF code, but bypass the MAF to eliminate it as your problem...if your problem goes away then try cleaning your MAF and if cleaning it doesn't help then replace it

V68Sweep

Up until about 1 week ago I was running with 3 bad O2s. I had codes for Bank 1 sensor 1 and 2, and Bank 2 sensor 2. I was driving like that for a year. Not a single sputter, caugh, or complaint.

I am not as experienced here as many people, but I would venture to say that this sounds like a fuel thing. Try the fuel filter and hope for an easy fix Good luck!

FirehawkNS

iTrader: (3)

Update...sort of...

The car has gotten worst. It has started to cut off while driving and taking up to a minute before it will crank back up. The motor isn't getting fuel when this happens as far as I can tell as the motor sound when trying to crank is exactly the same if I try to crank with the Fuel Relay pulled. I have replaced the relay.

Going forward I plan to go ahead and buy an Electric Fuel Pressure gauge to replace the Nitrous gauge I currently have (took the Nitrous off a while back).

I am also going to try to rig up a way to make sure voltage is still reaching the pump when it happens by tapping onto the wires at the harness at the back of the car above the rear. Anybody know which wire I could tap to do this idea?

Past that I have some friends that run a shop that I was going to drop the car off and see if they can drive it with their big scanner plugged in to see what it is doing when this happens. bad thing is Sometimes I can drive and it not do it at all, other times it will do it every 3 or so miles. Frustrating.

I still think Fuel Pump! A family member said pressure regulator on the fuel rail maybe.

This thread probably should be moved to fueling section.

FirehawkNS

iTrader: (3)

Forgot to mention, I tried this and it didn't help.

mark21742

I want to say the in tank regulator runs around $45 at the local auto parts store....if your not losing power to the pump, and your pressure is fluctuating is try that before a new pump.

One of my friends cut an access door in the floor over the pump so he doesn't have to drop his tank

FirehawkNS

iTrader: (3)

I thought that regulator was apart of the pump? Just like the one on the fuel rail looks to be part of the fuel rail.

BIG_MIKE2005

iTrader: (116)

Just order the Racetronix direct fit pump from WS6store without the hot wire kit. Put it in your stock bucket with the stock regulator in place which is also locater in the top of the bucket. I was having a very similar issue, replaced about $700 in parts tracking it down before I hooked up a fuel pressure gauge to the rail & discovered I only had 15# instead of 58-60#

The regulator is a little part in the top of the bucket housing. You can replace it but usually they only go bad is the little o-ring gets out from the regulator housing getting egg-shaped. But thats a easy fix as well. Go to Autozone, get a black o-ring the right size, replace & add a hose clamp around the regulator to keep it from getting egg-shaped.

I'd say its a pump & not voltage, mine is a 99' as well & voltage was perfect, pump just finally took a dump at 166k miles. And the little thing on the rails isnt a regulator, its a pulse thingy, LOL. I forget the actual name but its supposed to even out the fuel delivery between the rails basically. And if your not shy about cutting the access door is the way to go, I did my entire pump swap in about 1.5hrs taking my time. The hardest part was getting the lockin ring off the pump to get it out of the tank.

FirehawkNS

iTrader: (3)

I think i am going to move ahead with this idea. Are there any good directions showing exactly where to cut? I plan to look this up, but figured I would ask as well. I remember it being posted years ago when people started doing it.

*EDIT* - Always go for the stickies! lol

http://www.gonicd.com/intankinstall/...mpinstall.html

FirehawkNS

iTrader: (3)

Well more fun, my 01 Blazer started doing pretty close to the exact same thing this week. Difference is it hasn't cut off yet while driving, but this morning started having the feeling on throttle like it was hitting a speed bump (3 times in a 20 minute drive). Also it will not crank on the first key turn starting this week no matter how long you hold the key. turning over, just not firing up. Release key and try again and it will fire right up. Maybe there is something in the gas around here killing my pumps? I have three places I usually fill up at and the Z has been through several tanks from different places.

So I have a fuel pressure gauge now, but missing an adapter to install it, so waiting for that to come in, and I have a new fuel pump. I want to see the pressure when the car cuts off before I try the pump.

Frustrating.....

BIG_MIKE2005

iTrader: (116)

Well you also gotta think these pumps are over 10yrs old now too. Its about time for them to be crapping out.

With the issue I had I knew as soon as I turned the key to "on" that it was fuel related once I had the gauge. It should be close to 60# with the key just turned & at idle. If its not without the car even started its definetly delivery related which is pump/filter issues.

FirehawkNS

iTrader: (3)

Yea that's true. The Z is going on 115k miles and the Blazer is close to 160k. Just funny that both start similar issues within a month of each other. The Blazer concerns me more since my niece had it a couple of weeks ago when the radiator split and she ran it to red line on temp before she called and I got her to pull over. Sort of paranoid about what that high temp could have done.