Same here, problem seems to go away with a new fuel filter and injector cleaner.... for a while. Not as frequently now after the opti, but I'm thinking a faulty injector.

 

OK, i just found this thread, and have read through it... I too have this problem of the car hesitating just below 2K RPM. It seem to be from around 1750-2000 RPM its doing it. Unlike most of you guys, my car is doing it cold and hot engine temp.

Where should I start looking to fix this?

 

Well I guess I will add to the list. My problems is similiar to some and different than others.

My car acts up more when cold than hot. When I first fire up my car it will idle up and down 400rpms +/- and sometimes almost stall. I also have had my low coolant light recently coming on and off tho my coolant is full. I thought my trans was slipping but they said a hesitation was keeping it from shifting properly. So I took it in a had diagnostics ran.

No codes
No vacuum leaks

The MAF snesor was reading 70hz low according to the mechanics but they werent sure that was the problem. I purchased a slp 85mm Z06 MAF for lt1's and when I first fired up the car and drove it it seemed good for a couple days. I also had reoiled my K+N at the same time.

Well now the surging is back and I am starting to hate my car. It normally is worst when first fired up and runs pretty normal most the day. Every once in awhile if I am holding speed my car will all of the sudden feel WAYY FASTER..

I have had all of the following replaced in the last 20000 miles
Opti
Wires
Plugs
MAF
Knock Module
Coil
Fuel Injectors cleaned

I am currently extremely broke and cant afford to guess.... this blows

I am going to try cleaning the MAF sensor in case the K+N was over oiled after that I am thinking TPS?????

I also haved started smelling burnt plastic/coolant kinda smell when the car heats up...... but just an occassional whiff. If I stop the car and smell around I cant smell it. The car is running about 10-15 degrees hotter than it used to. Right around 215 it never use to top 200 and almost always ran at around 185.

ALL SUGGESTIONS WELCOME PREFERABLY FREE OR CHEAP ONES

 

One more thing I forgot. I do have a backfire sometimes on start-up since the problem started. I also have noticed more popping and cackling when lefting off the gas on the freeway than what was normal........

 

turn your atmosphere controls OFF....i can feel an obvious studder and slight loss of power when my climate controls are on at any position other than totally OFF. this often happens right around 2k. i can actually watch my A/C voltage with the scanner and see it change at the point in question like it "kicks on" at 2k or something. now this is when the climate **** is set on mid level vent...not only A/C..and happens when the temp **** is in any position. when the turn it off all together...the voltage makes NO change.

next you need to get a scanner and log some runs. i have a scanmaster installed on my car and every once in a while i will get sudden knock retard. it will go from "0" to "9" in a split second and watching my scanner, i can feel a change in the car the instant i see 9 degrees of knock retard.

the problem could be many things but these are some that i have noticed with the help of a real time scanner.

 

I personally never use atmoshpheric controls ..... 100 degrees out and sticking to the leather...roll down the window. 30 degrees and freezing my **** off..... create more body heat. Creature comforts are something I never have gotten use to having. They didnt work well on my 68 Nova or my 72 Nova so I never used them. Kinda habit not to now. If I let my car sit you can hear it surge bad. Thanks tho
Shawn

 

Wow back from the dead. Its amazing how many people have the same problem and have no clue what it is.

Here is my fix it list. You might wanna try some of these things. It kinda sucks that I have done all of this and my car still has a low rpm stumble and high rpm miss.

*Replaced*
plugs- tried different gaps
3 Different types of wires
opti
o2's
fuel filter
fuel injectors
Blocked EGR
Intake manifold gasket
coil
fuel injectors

*Checked*
Relocated ICM
IAT
voltage on knock sensor and resistance
fuel pressure
coolant temp sensor
engine ground
Unplugged MAF
Exhaust leaks- I don't think I have any too big that would make a difference
Made sure nothing was banging underneath the car

*Cleaned*
seafoamed whole engine several times.
tbody
MAF
MAP

 

i also have a smell, but i only smelled it after my new hooker catback was installed, it was REALLY bad the first 1.5 weeks, then it went away mostly but sometimes i can still smell it. i'm almost certain its something in my catback cause i never smelled it before then.

i got my car hooked up to a tech2 and found that cylender 4 was acting wierd in a cylender load test... with 60k miles, we're assuming its not a compression problem (eventually this will be confirmed), the plugs and wires were changed, so the fuel injector will be replaced next. i cannot seem to find any fuel injectors locally but i did get a used fuel pressure regulator from a guy and will be installing that soon. after i replace that and my fuel injectors i'll have a whole new fuel system, and a whole new ignition system up until the wiring harnesses and the ignition control module.

and so if it aint ignition, and it ain't fuel... gotta be compression i hope not

 

94greenz28,

does your car try to stall at 5100 rpm or is it ONLY one mis??

if your car falls on its face at 5100 and doesnt recover then id suspect it is running out of fuel. from the looks of it..you have already replaced EVERY imaginable part except for the FPR. it is cheap and relatively easy to replace. ever tried hooking up a gauge to monitor the fuel pressure??

 

Wouldnt a fuel problem be more constant? Most of my problems are really random and normally(mainly on start up or around 2000rpms. I have also replaced my fuel pump and my fuel filter but I have not checked the FPR yet.
Shawn

 

I have been having the same problem....Just recently it started acting weird. Especially in the mornings car will even turn off on me at times while I am at a light..I been trying to figure out this problem for 1 week now, still messing with it...If I find something I will make sure to let you guys know.....Vice Versa, It's really pissing me off...

 

I took my 1997 Z28 to a good Chevy dealer where I used to work and after Me and my buddy who is a ASE Certified mechanic went for a little ride. He said stop the car and pull over. He unhooked the vacuum to the EGR Valve and when I pulled out. I could believe it NO HESITATION. JUST PLENTY OF RAW POWER it felt like it was brand new. He saw I needed to replace the EGR Valve and Possibly the EGR VACUUM SELONOID>Pardon me if I misspelled words.

 

I just replaced my EGR valve not to long ago though. Is it possible that it could have gone out in only 25,000 miles???

On another note, I cleaned my MAF today, and air filters just because. Also to see if it would "improve" my hesitation situation. Nope... Just letting everyone know. Probably has no relevance to the situation.

 

so disconnecting the EGR vacuum will disable it as if it was blocked off?

where is this vacuum tube, i wanna try this. i know it'll throw a code, i can live with that.

 

It cured the hesitation on my car!!!! which is a 1997Z28. EGR Valves are bad about getting a lot of carbon build up so 25,000 miles will surely do it because these car run rich anyway. You probably wouldn't even get a code because the EGR Valve are not linear which means they are not electronic like the ones on the LS1 Cars. Just make sure you block of the Suction so it wont suck in dust into your motor. Try it it can't hurt!