Help! Missfire / Stuttering Problem

[1SlowV]

Hey guys, I was wondering if I could get some help from someone on a small problem I have run into with the car.

1st thing- Under a load, say 5th or 6th gear at lower rpms, if I get into the throttle a little bit to pick up speed, the engine will stutter or miss a little bit until I get up into higher RPM's.
It also does it if I drop down a gear to make a pass, at 3/4 throttle or so. Almost like when you get bad gas in the car, likewise symptoms. I have ruled out bad gas though, BC I have been
through several tanks at different stations and the problem has continued.

Im wondering if its a bad spark plug? dirty/bad injector? MAF sensor problem?

Also, occasionally the car will idle around 2000 RPM's while coming to a stop. Then, after Im stopped for a couple seconds, it will drop down to around 1000 where its supposed to be. Holding in the clutch
helps a little, and will only allow it to go up to around 1500 RPM's before it drops down. The weird thing is, it only does this every now and again. But when it does, it will do it consistently for a while.
Also, on startup, it will idle perfectly every time. It only does the high rises after its been put into gear and driven above 2000 RPM's.

MOD's on the car
Texas Speed Torquer V.2 Cam
Ported intake and throttle body
cold air intake
upgraded springs
valves
pushrods
timing chain
High flow oil pump
High flow water pump
1 7/8 long tube headers
X-pipe
Dynomax Bullet mufflers
06-07 rear end
adjustable groundforce lowering kit
skip-shift eliminator
Ls7 clutch
lightened flywheel
short throw shifter
creative steel transmission mount
and aftermarket shifter bushings

Any ideas?

Thanks a ton for the help guys!

 

[Tuna]

My first thought is to put a scanner on it and see if any codes are set and if the scanner can point to a bad plug or wire or bad MAF. No need to throw parts at it without getting a good scan first.

I'd also get a can of "BG 44K" and put it in the tank. This is a fuel system cleaner and it works very well. If the injectors are a little sticky or clogged up, BG 44K will clean them up. Red Line makes a fuel system cleaner that works pretty good also but BG 44K is my #1 pick. I put a can in my cars each year just to keep ahead of fuel system issues.

Clean the throttle body and make sure the Idle Air Circuit is clean.

That's my 2 cents. Now it's somebody else's turn to speak up.

 

[1SlowV]

My first thought is to put a scanner on it and see if any codes are set and if the scanner can point to a bad plug or wire or bad MAF. No need to throw parts at it without getting a good scan first.

I'd also get a can of "BG 44K" and put it in the tank. This is a fuel system cleaner and it works very well. If the injectors are a little sticky or clogged up, BG 44K will clean them up. Red Line makes a fuel system cleaner that works pretty good also but BG 44K is my #1 pick. I put a can in my cars each year just to keep ahead of fuel system issues.

Clean the throttle body and make sure the Idle Air Circuit is clean.

That's my 2 cents. Now it's somebody else's turn to speak up.

Hey thanks for the tips / advice! I appreciate it!

I need to get it on a scanner like you said to help narrow down my problem. Also, I will the BG 44K a try to see if that helps at all aswell. Read up on it on a couple different sites
and it sounds like it gets a lot of positive reviews, which is unordinary for bottled fuel system cleaners!

Again, thanks for the tips!
Ill let ya know what codes are being thrown once I get a chance to get a scanner hooked up.

 

[Tuna]

Back in the days before computers and fuel injection, tracking down a stumble or miss under load or at idle was a lot easier. These days a scanner is a required tool. Even with a scanner, some fuel system issues escape the scanner. Let us know what you find.

In the meantime, a can of BG 44K can't hurt.

 

[1SlowV]

Got a scanner hooked up over the weekend, and it was throwing a MAF low circuit frequency code.

Cleared the code, picked up some MAF sensor cleaner and sprayed it down, as well as both the plugs and no more stuttering problem or high idle!
Hopefully it will stay that way and was just a dirty sensor or connection.

Bad news, got a right front flat on saturday. lol


Always something!

Thanks for the help guys!ave:

 

[Tuna]

Flat! ?

PITA if you don't have a spare and even if you do.
Hope you weren't on the side of the road too long.

Glad to hear that the engine is running good again.