Need Help, hesitation

**ESBdieselcam** · 10-08-2009, 05:49 PM

He all. I've had my car now about 2 mos. 99' z with 66k on the clock. More often than not, the car hesitates and stumbles like an s.o.b. from about 2000 rpm-3000rpm. Otherwise it runs well. Ocasionally I will throw 2 codes, both for rear o2 sensor low voltage (lean?) that usually only happens when I'm on it hard. Gonna test the fuel pressure i guess. Any other Ideas? Thanks!

**Spaz** · 10-09-2009, 07:23 AM

Originally Posted by ESBdieselcam

He all. I've had my car now about 2 mos. 99' z with 66k on the clock. More often than not, the car hesitates and stumbles like an s.o.b. from about 2000 rpm-3000rpm. Otherwise it runs well. Ocasionally I will throw 2 codes, both for rear o2 sensor low voltage (lean?) that usually only happens when I'm on it hard. Gonna test the fuel pressure i guess. Any other Ideas? Thanks!

your cats might be clogged or a 02 might be taking a shit on ya...

**blue02Z** · 10-09-2009, 11:01 AM

a dirty maf can make em act funny like that on accel. you mite have 2 different problems and the o2 code just be a coinkadink

**0rion** · 10-10-2009, 09:10 AM

what about above 3k rpm? Kinda makes me also think it could be MAF related. Get some MAF cleaner at a parts store and clean your MAF real good.

**pajeff02** · 10-10-2009, 09:18 AM

Also MAF related -- has it been ported or do you have an aftermarket unit? Ours was ported and de-bladed and we had an off idle stumble. Replaced the MAF with a new GM unit and all is well.

**ESBdieselcam** · 10-10-2009, 06:30 PM

The car is completley stock. I'm gonna try cleaning the MAF and hopefully soon, get rid of the cat (full exhaust) how can I get around not having cats? is there a o2 fooler? Thanks for the help guys....I'm a diesel junkie turned onto LS1's. Sooo, I'll have a lot of questions. Thanks

**pajeff02** · 10-10-2009, 06:45 PM

Originally Posted by ESBdieselcam

The car is completley stock. I'm gonna try cleaning the MAF and hopefully soon, get rid of the cat (full exhaust) how can I get around not having cats? is there a o2 fooler? Thanks for the help guys....I'm a diesel junkie turned onto LS1's. Sooo, I'll have a lot of questions. Thanks

There are O2 sims and you can also delete the rear sensors with a tune. As far as emission inspection, I am uncertain what NY requires. In our area of PA, I could easily hollow out a converter and get away with it. Or, if I wanted to be crafty, install a converter shell around a non-catted Y so it would pass visual inspection. Not that I would ever encourage anyone to break the law...

**35th-ANV-SS** · 10-10-2009, 06:54 PM

Originally Posted by pajeff02

There are O2 sims and you can also delete the rear sensors with a tune. As far as emission inspection, I am uncertain what NY requires. In our area of PA, I could easily hollow out a converter and get away with it. Or, if I wanted to be crafty, install a converter shell around a non-catted Y so it would pass visual inspection. Not that I would ever encourage anyone to break the law...

You Sir are wise beyond your years.

This is why I love Indiana.

**ESBdieselcam** · 10-10-2009, 07:16 PM

Yeah, I'm pretty lucky. Where I live in NY, we don't have emissions testing, beyond "is the check engine light on". Thank you. I plan on waking up in the am and heading out to find MAF cleaner. I hope this is the problem.

**ESBdieselcam** · 10-11-2009, 09:55 AM

Thanks guys for all the help. I cleaned the MAF, and now I remember why I bought an F-car. WOW! what a difference

**DaddySS** · 10-11-2009, 10:45 AM

Glad you got it solved.

**blue02Z** · 10-12-2009, 08:28 AM

**99RTA** · 10-13-2009, 06:10 PM

I had the same symptons and it was rust in the fuel system. Finally clogged the injectors so bad it stopped running.

**0rion** · 10-14-2009, 07:17 AM

Originally Posted by 99RTA

I had the same symptons and it was rust in the fuel system. Finally clogged the injectors so bad it stopped running.

must've came from the gas station you buy gas at because 99+ f-bodies had plastic tanks. I'd look at buying gas somewhere else from now on.

**99RTA** · 10-15-2009, 06:07 AM

naa it was the fuel lines and fuel rail. GM has a tech bulletin about it. They are bare carbon steel and if you use fuel with ethanol in it the lines slowely rust inside. Cost me over 3k to fix it ast the dealer. Crazy thing is the new parts from gm are not coated, about 3 years after that repair i had the fuel rail pulled to inspect the injector screens and sure enough the fuel rail was starting to rust again. I use a fuel additive now so the lines don't rust as quick.