Help with Air/Fuel management all sugestions are welcome

[Modjoe]

Hi,

I have a SilverTop 20V and it runs like crap, it barely does one single burnout, I checked compression and is fine, replaced Spark plugs now with denso Iridium, still runs terrible.

According to a friend of mine who has a Wideband meter, he told me that the car has the Air/Fuel ratio with an extraordinarily rich mixture thus the car is not able to burn it completely causing back fires and lack of power. the car constanly back fires and can barely perform a single burnout.

So, based on internet research and consulting a couple of mechanics, I think I may have a failed AFM. I started another post to make sure if the AFM on the 20v and the 16V is the same. Sadly I had no replies. So at this point I'm looking forward to replace that AFM and use a different engine management system.

I have seen 2 possible options:

1.Run the ST with the BT ecu (ECU, harness adapter, and other sensors) But I have no idea of which possible technical challenges this might present

2.Install a MegaSquirt or other aftermarket ECU. But in My country, this will be near to impossible to achieve and extremely expensive.

I really need a hand to decide wheter I can get that engine running properly. Any suggestions are welcome.

[mooreofit]

have you checked you temp sensors?. speaking of theres other little things you can do to change the air fuel ratio like adjustible fuel pressure regulators and modifying sensor input circuits like adding a potentiometer in the iat or clt circuits

megasquirt is fun.

[Modjoe]

have you checked you temp sensors?...

I declare my self a complete ignorant on the subject, I'll consult a tech ref guide to see If I'm able to locate/diagnose those sensors

... speaking of theres other little things you can do to change the air fuel ratio like adjustible fuel pressure regulators

I'm currently looking for one, just been unable to find any reference on differences between aftermaket (AEM, OBX, etc) or generic regulators to make sure if they have performance differences.

... modifying sensor input circuits like adding a potentiometer in the iat or clt circuits

I don't have a single idea of what those circuits are, but I'll do my homework and check

megasquirt is fun.

I have heard that but based on my location and the lack of parts/labor I cannot do, also I'm not sure I'll be able to perform the installation/tunning myself without a Dyno and assistance.

[mooreofit]

megasquirt is not easy. it is but when it comes to diagnosis things get a little tricky. if you are new to a soldering gun and assembling circuits i would just leave it to the pros. diy only charges 100 dollars more for assembly. if you study the manuals msextra manuals especially tuning will become fairly simple. but if your setup is similar to made in the 80's im sure he would send you his msq.

[dr.occa]

i'm leaning more towards suggesting running a BT ecu & harness. most if not all sensors would be the same with the added MAP but minus the AFM.

[Modjoe]

i'm leaning more towards suggesting running a BT ecu & harness. most if not all sensors would be the same with the added MAP but minus the AFM.

This weekend things got worse, my car started to run in 3 cylinders and there was a lot of smoke, for my luck it was unburned fuel. After some phone calls I was able to meet the only 20V specialized mechanic in my entire country. Went to my place and find out that the O-rings on the injectors where leaking so the combustion chamber was getting soaked in fuel but there was a larger issue.

The fourth cylinder was not behaving properly, the spark was right but the injector triggering was completely lost. sometimes it was working properly some times it doesn't even worked. After swapping the ECU with a known good, problem solved. I also find out that the MAF has been altered so it is not working properly.

At this point Dr.occa's recommendation is the best strategy since I'm not crazy about spending a lot to go back to MAF. My mechanic has done the BT ecu conversion before and he has the MAP valve and other parts, I'm only missing the BT ECU and the BT O2 sensor.

Do you think that someone around here might have a BT ECU for sale??

[dr.occa]

unfortunately, bt ecu's are not as common as 16v gts ecus. while you're hunting for one from an individual, give ebay and jdm engine importers a try as well.