Weird Hesitation/Stutter

[tpilews]

Okay, first things first. '98 z28, 81,000 miles, M6.

I have a weird hesitation/stutter around 3,500-4,000 rpm ONLY in 5th gear. It's almost like someone is hitting the brakes quickly and one or two times per second. I can hear the exhaust tone quiet like the engine shutting down, but comes back on because I'm in gear and rolling. It really jerks you a bit. I've taken it to 5,000+ RPM in 3rd and 4th gears with no problems. Any ideas of what I should look at first? Car runs great. No pings/knock at startup. Engine sounds great.

[ESBdieselcam]

I had a similar issue when i first joined this site. Everyone told me to clean my MAF with MAF cleaner spray. Cleared the problem right up, car runs like a top. Donno if you have the same problem, but it's worth a shot.

[EVIL-LS1]

I had a similar issue when i first joined this site. Everyone told me to clean my MAF with MAF cleaner spray. Cleared the problem right up, car runs like a top. Donno if you have the same problem, but it's worth a shot.

What he said and try cleaning the Throttle body also see if there any black stuff built up on the inside of it.I had a buddys car doing the same thing and he cleaned the MAF/Throttle body and it fixed his problem.

[Cutlass]

If its a really abrupt jerky misfire, I'd be looking at plugs and plug wires. Maybe dirty fuel injector. I don't have a lot of experience with dirty MAFs, but I can't see that being it if it runs perfect otherwise.
Either that or stop driving so fast. 5th gear 4000rpm is 111 mph

[ESBdieselcam]

I'm gonna stand by my MAF comment, however a check of the rail pressure wouldn't hurt. Maybe she's starving out on the top end?????

[tpilews]

If its a really abrupt jerky misfire, I'd be looking at plugs and plug wires. Maybe dirty fuel injector. I don't have a lot of experience with dirty MAFs, but I can't see that being it if it runs perfect otherwise.
Either that or stop driving so fast. 5th gear 4000rpm is 111 mph

Haha, yeah I guessed on the RPM, but was gonna say 115-120 mph. It's only happened a few times when I had a WRX "following" me. Oh and some black guy in his fart canned Eclipse.

Anyway, thanks for the suggestions guys. I'll take it easy until I get some time to take a look at it.

[cammed goat]

When I had my radiator installed a few weeks ago, my car began stumbling as I left the shop. I turned around and went back to the shop and they hooked up a scanner and found a MAF code(dirty MAF) and sprayed it, took it for a run and the car is running like a top now.

[luvmyz28]

just a thought so dont bash me.
sounds like maf but speed limiter maybe?
just a thought. I dont know how long you've had the car or whats been done to it. speed limiter will cause those things too.

[phoenix05]

wth does this maf you speak of look like. I have this stuttering problem upon acceleration sometimes and it seems from some post i read throughout this general help forum that a maf clean plus fuel filter replacement may get the job done.

Now i drive a 97 TA so im sure the placement is diff but i just need to know wth this thing looks like.

[tpilews]

Okay, a bit of an update. I failed to mention the SES light was on. I got a scanner and read the codes. This reads history as well as current.

P0171 - System Too Lean (bank 1)
P0174 - System Too Lean (bank 2)
P0452 - Evaporative Emission Control System Pressure Sensor Low Input
P0803 - 1-4 Upshift Solenoid Control Circuit Malfuntion

So, looks like the previous owner pulled the skip-shift solenoid instead of using the resistor bypass. I assume this is nothing to worry about.

Anyone have any info on the others? The previous owner said there was a "mild tune" done to the car, whatever the hell that means.

I cleared the codes and will see if any return.

[tpilews]

wth does this maf you speak of look like. I have this stuttering problem upon acceleration sometimes and it seems from some post i read throughout this general help forum that a maf clean plus fuel filter replacement may get the job done.

Now i drive a 97 TA so im sure the placement is diff but i just need to know wth this thing looks like.

[tpilews]

Okay, a bit of an update. I failed to mention the SES light was on. I got a scanner and read the codes. This reads history as well as current.

P0171 - System Too Lean (bank 1)
P0174 - System Too Lean (bank 2)
P0452 - Evaporative Emission Control System Pressure Sensor Low Input
P0803 - 1-4 Upshift Solenoid Control Circuit Malfuntion

So, looks like the previous owner pulled the skip-shift solenoid instead of using the resistor bypass. I assume this is nothing to worry about.

Anyone have any info on the others? The previous owner said there was a "mild tune" done to the car, whatever the hell that means.

I cleared the codes and will see if any return.

Well, to partially answer my own question and for others who are interested, System too lean (bank 1&2) is a MAF issue. Cleaning it should take care of that. If it doesn't, could be a vacuum leak.

Code P0452 appears to be a fuel pressure problem. Anyone have any insight on this? I did a search, but this issue has never been brought up on ls1.

[Spaz]

Well, to partially answer my own question and for others who are interested, System too lean (bank 1&2) is a MAF issue. Cleaning it should take care of that. If it doesn't, could be a vacuum leak.

Code P0452 appears to be a fuel pressure problem. Anyone have any insight on this? I did a search, but this issue has never been brought up on ls1.

my best guess for PO452 would be to change the fuel filter... they should be changed every 3rd oil change anyway...

[Badass WS6]

wth does this maf you speak of look like. I have this stuttering problem upon acceleration sometimes and it seems from some post i read throughout this general help forum that a maf clean plus fuel filter replacement may get the job done.

Now i drive a 97 TA so im sure the placement is diff but i just need to know wth this thing looks like.

I had the same issue(randomly over the course of a month) with my '99 z around 7-8 months ago, I took it to my mechanic and he said more than likely it was my fuel pump going out but to go ahead and buy a new fuel filter and see if that cures it. It did, for about a month. Then one day I went to start my car to go home from work and nothing. Wouldn't start. Bummed me out. Had to have it hauled to my mechanics and sure enough it was my fuel pump that crapped out on me. I replaced it and have had no problems since.

[Wesman]

Okay, a bit of an update. I failed to mention the SES light was on. I got a scanner and read the codes. This reads history as well as current.

P0171 - System Too Lean (bank 1)
P0174 - System Too Lean (bank 2)
P0452 - Evaporative Emission Control System Pressure Sensor Low Input
P0803 - 1-4 Upshift Solenoid Control Circuit Malfuntion

So, looks like the previous owner pulled the skip-shift solenoid instead of using the resistor bypass. I assume this is nothing to worry about.

Anyone have any info on the others? The previous owner said there was a "mild tune" done to the car, whatever the hell that means.

I cleared the codes and will see if any return.

A common issue that tends to cause system too lean codes is a vacuum leak. However, a vacuum leak in itself will not cause the stuttering you are describing. A bad MAF can cause studdering, but you have no codes for a MAF malfunction, which is unusual. Usually the ECM will know there is a problem in the circuit and throw a "low input" or "high input" code.

My best guess would be you have a fuel problem. Either a clogged filter (as Spaz mentioned) or your fuel pump is on its way out. First thing I would do is change the filter and see if that fixes the issue. If not, get a fuel pressure gauge, connect it to the shrader valve on the fuel rail, and see what your pressure is at with the engine running. It should be 58-60PSI. If its lower than that, time for a fuel pump.

[tpilews]

Anyone think this could be a push rod issue?

I've got some vibration in my shifter stick. Well, not vibration, it's more of a shake. It'll idle fine, but there's a small shake every 2-3 seconds. Most noticeable when idling, seems to go away when I increase rpm's. I still notice it until about 1500 rpm.

I don't remember my old '98 T/A doing this, but that was so long ago. I was reading in another thread where a guy over-revved his car and bent a push rod and had the symptom of a shaky shifter.

[Danger731]

never heard that before

[tpilews]

P0171 - System Too Lean (bank 1)
P0174 - System Too Lean (bank 2)

O2s need to be changed?

[cammed goat]

O2s need to be changed?

See, that's the thing. Our cars have 4 O2s. I dunno what the life expectancy is of the O2s in our cars. Plus ya have to narrow it down to either the pre-cat O2s or the after-cat O2s.

[Cutlass]

O2s need to be changed?

cleaning the MAF didn't fix it? Have you checked the fuel pressure? Low fuel pressure can cause lean codes