Car has bad miss

sm6989 · Jul 9th, 2007, 06:52 PM

Alright..I got a g20 with a sr20det swap, My car is currently haveing a bad miss when you try to get on it, if you just stay normal and give it light gas, its not that bad, but when you go to give it more it barely goes anywhere thats how bad it is...My ecu is pulling two codes, one is the Maf sensor and the other one is the knock sensor..I've replaced both but still same problem. Only way I can get the problem to clear up for a bit is if I unplug the plug from the maf sensor while the car is running then plug it back in...then it'll run nice for awhile then just go right back to what it was doing...Can anyone help me out and tell me what the prob could be? Its just a stock 91 g20 maf, could it be too small since im boosted?

**wes** · Jul 10th, 2007, 10:05 AM

Quote:

Originally Posted by sm6989

Alright..I got a g20 with a sr20det swap, My car is currently haveing a bad miss when you try to get on it, if you just stay normal and give it light gas, its not that bad, but when you go to give it more it barely goes anywhere thats how bad it is...My ecu is pulling two codes, one is the Maf sensor and the other one is the knock sensor..I've replaced both but still same problem. Only way I can get the problem to clear up for a bit is if I unplug the plug from the maf sensor while the car is running then plug it back in...then it'll run nice for awhile then just go right back to what it was doing...Can anyone help me out and tell me what the prob could be? Its just a stock 91 g20 maf, could it be too small since im boosted?

It is related to the MAF. First of all what fuel system and managment are you using? Second how much boost and on what turbo? The MAF is likely not suited to support the power you want to make, but that will not cause it to run bad when not in boost. Hell the car will rip even with the MAF that is too small up until it leans out and you start blowing shit up.

sm6989 · Jul 10th, 2007, 08:06 PM

No fuel management, I think its a garret t28, im only doing about 8psi.. everything done to the engine is as followed..

Avenir(sr20de) engine
FMIC
all hard IC pipeing
3 inch DP
greddy type-s BOV
300z injectors
300zxfuel pump
300zx fuel filter

**wes** · Jul 10th, 2007, 10:17 PM

Quote:

Originally Posted by sm6989

No fuel management, I think its a garret t28, im only doing about 8psi.. everything done to the engine is as followed..

Avenir(sr20de) engine
FMIC
all hard IC pipeing
3 inch DP
greddy type-s BOV
300z injectors
300zxfuel pump
300zx fuel filter

So you are using what ECU the avenir? Why did you switch injectors if you are using an avenir motor?

sm6989 · Jul 11th, 2007, 05:30 PM

I dont know. thats how I got the car..the ecu just says on it sr20det..so i take its just a stocker or something

**wes** · Jul 12th, 2007, 10:00 AM

You need to do some serious troubleshooting. I have 4 things I would check right away.

1. Boost Leaks- do a pressure test of the IC piping tomake sure it is not leaking. Visual inspections are NOT enough, unless you are pressure testing you are wasting yoru time.

2. Check the timing!

3. Check the MAF voltage!

4. Check the fuel pressure and make sure it is where it is supposed to be.