Engine hesitates bad on accelleration

#1

Hey Folks,

I’ve got a 1990 325i that is bone stock w/ the exception of a split second air fuel controller.

I am totally perplexed with my current situation. I cracked the cylinder head a while back, replaced it with one that was decked and pressure tested, and the car hasn’t run right since. First off, if I disconnect the battery, let it sit, and try to start, the engine will start, then immediately die. I have to have the gas at about 2/3+ when turning over, and then it’ll go. Next problem, The engine idles fine but when I step on the gas it boggs down hard, and will sometimes even backfire. I pulled a code using a scan tool and got “07” which is the Air Flow Meter. Replaced that but I’m still getting the same code. I have a Split Second Air/Fuel controller hooked up, but it came with the car so I know little about it. The car ran like a champ before the cylinder head went on me.

The Following Things have been done…
Compresssion test- All cylinders w/in Bentley parameters
Leakdown test- all cylinders w/in range
Fuel PSI Regulator- about 6psi off, replaced
Coolant temp sensor- Tested SAT
Crank Position sensor- W/in resistance range
Valve clearance- All w/in range
Fuel pump relay- all terminals tested sat
Fuel Pump pressure- Spiked and held at 60psi w/ outlet hose clamped
Fuel Injectors- Recently cleaned/flow benched/new seals
Ignition Coil- Barely out of resistance parameters/replaced
Spark Plugs (bosch +4)- They were new when I installed the head but were super fouled and stank of fuel/replaced w/ OE bosch plugs
O2 Sensor- Tested SAT, had a spare so I replaced it anyways
Vacuum Test - around 10-12" holding constant

Soemthing else of note. I completely removing the heating system and all associated wiring, w/ the exception of one wire that looked like it went to the computer. I also Remocved the car stereo, speakers, and all associated wiring. Would this affect the engine management system in any way?

I am at a complete loss. How long does the computer need to reprogram itself? I can get the car to cruise at about 15-20mph, but if I give it any gas at all it totally bogs down and hesitates real bad. With that being said though, it’ll rev (slowly) as high as I want and stay constant when in neutral (havent tested under load) Has this happened to anyone?

#2

Double check your timing belt/timing?

#3

Doh! Stupid double post!

#4

Steve, Kevin is right. #1 - Constant 10"-12" suggest a valve timing issue. #2 - Backfire is usually a lean condition under sudden acceleration or retarded timing. 1 tooth off on your belt timing can get the same result plus lack of power… :slight_smile:

#5

The only reason the split second controller is installed would be to convert to a mass air flow sensor. I know BMP Design sold a kit with a maf and split second arc-II. Someone could put one on but it wouldn’t help unless it was to solve a problem caused by another upgrade. I would start by removing the split second controller. They aren’t cheap so you might even get a couple hundred for it.

#6

Thanks guys, my boy at the shop where I work on my car said it wouldn’t be idling right being one tooth off, and I put the car back together in a hurry so that might be it. I’ll find out when i get off work in a few days…