When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I remember having this conversation with FAST about a year ago... the lead tech, forgot his name, told me the best place for there O2 to be was at the collector.
Remember... The above is for a more factory system with a cast ram exhaust manifold and 1-2" pipe. The exhaust gasses in this setup stay much hotter all the way out.
Us/me on the other hand, run 1 7/8" ceramic coated headers with 3" free flowing mandrel bend exhaust with X-pipe,,, thus the heat is dissipated more quickly///
Thus the bung on the collector.
My system is similar to yours with 1 7/8" ceramic coated headers but with a 2 1/2" mandrel bend exhaust with X-pipe. I installed but O2 sensor just a few inches from the collector to sample exhaust from more of the whole bank of cylinders rather than more from the cylinder for the header pipe closest to the O2 sensor (as recommended by FAST at the time I intalled EZ 1.0).
This picture was taken before FAST EZ, but the O2 sensor is installed in middle of the straight section of the pipe adjacent to the header flange (upper right corner). Hopefully heat loss isn't significant across that distance. My money is on a sensor heater electrical problem that I test tonight.
I remember having this conversation with FAST about a year ago... the lead tech, forgot his name, told me the best place for there O2 to be was at the collector.
You want the WBO2 as close to the engine as possible to reduce the time lag for the reading. The closer it is to the engine, the more 'current' the reading is, letting the EFI react faster.
But there is a risk of overheating the sensor when it's in the collector. Happened to me.
You want the WBO2 as close to the engine as possible to reduce the time lag for the reading. The closer it is to the engine, the more 'current' the reading is, letting the EFI react faster.
But there is a risk of overheating the sensor when it's in the collector. Happened to me.
I measured 12V from pin 3 of the 6-pin O2 connector (orange wire) to vehicle ground (engine), but I only got 11.48V when I measured between pin 3 and pin 4 of the O2 connector (sensor heater ground, white wire). That's not a large drop, but it might be enough to impair the heater.
I traced the main positive and negative wires back, I have the red wire on the battery terminal, but the ground wire connects on the cross member just below the battery box where the battery ground connects to the heavy cable to the engine ground. I learned from the CPG Nation/FAST forum that FAST "uses the battery as a filter." I might have noise in the circuit from something else that shares the negative connection.
There's another ground wire there (other than the FAST ECU) too. Tonight I am going to run both small ground wires up to the battery post like the FAST instructions say and measure again.
Connecting the ground directly to the battery terminal fixed the ~half V drop to the O2 sensor, but now there seems to be an ECU connector plug problem.
Now, when I turn on the ignition, the ECU rarely starts up (i.e., blue light does not come on). I took the ECU off its mount and reseated the plug CAREFULLY several times. No improvement. Whenever the ECU fails to start, I only have to touch the plug gently toward the back of the ECU and the ECU starts. If I simply shut the ignition off, let the ECU power down (blue light goes out), and turn the ignition on again, the ECU fails to start again but starts with a light touch again.
All the pins in the ECU look perfectly straight. The hollow pins in the plug don't see perfectly straight but they can't be straightened because they are not rigid. If you push a pin to align with pins around it, it just moves back into its slightly-off position. Perfect pin alignment was apparently not a priority.
Is there any trick to get better contact between the solid pin in the ECU and the hollow pins in the connector? Do I need to replace the harness? Yikes!
I just explained the problem in a FAST "Send Us A Message" contact and asking them they recommend to fix the fickle connector switch and what my options are.
I hope they respond soon.
What else would I need to replace other than the ECU to switch to XFI? What are the benefits of XFI over EZ? Still self-learning?
I just explained the problem in a FAST "Send Us A Message" contact and asking them they recommend to fix the fickle connector switch and what my options are.
I hope they respond soon.
What else would I need to replace other than the ECU to switch to XFI? What are the benefits of XFI over EZ? Still self-learning?
It will give you data logging of EVERYTHING... and tables to tune,,, much better unit, And yes, it is also self learning,,, but you will have to learn a bit more also... not that hard.
They will give you a train in for your other ecu, so the price is more reasonable... maybe around $250 if i remember correctly... it IS WORTH IT... if you are going to keep your car... otherwise your always guessing....
The below graphing in recorded real time is what it looks like.. BUT, they are only graphing 5 ... you can graph as few or many as you like.. There are like 20 different inputs you can graph individually or in any grouping you like, as in below 5.
I just found the following post on the CPG Nation/FAST forum:
" After months of rough running and various weird problems, 2 new o2 sensors, new map sensor, new tps sensor. numerous phone calls to tech support and endless frustration I have what was causing my problems. On my last set of troubleshooting I did an 02 sensor harness wire trace. I had to unplug and unbolt the ecu for this. It all seemed to be working again but i noticed as soon as i moved the ecu even slightly things went haywire. I kept checking and after re seating the plug i noticed any pressure would make it go south... idle stumbling, rich etc. I called tech support and we tracked it down to a missing retainer in my ecu plug. There should be a clear plastic piece on the end of the gray connector. without it pins can come loose and or touch each other occasionally. So, it can present itself as any number of problems depending on what pins are getting knocked around, come and go etc. The support rep made it sound like this was a pretty common problem, people think the retainer is a shipping protector and pull them off. The rep told me that it was not an available part and that I would have to buy a $200 harness... F that. I pulled the connector apart and got a Delphi part number. Tracked down the line sheet and bought it from Mouser for 2 bucks. So if you have been having numerous odd problems I suggest you look at the connector. The delphi part number is 12110488. You can get it at mouser." Missing retainer in ECU plug
I've been considering a Fast to replace an Accel unit (for a Jet Boat project, I love the Tri-power on my 68), if that's how they support the product I'll be re-thinking using a Fast. Good to know you found the part though.
The connector cap was definitely missing as the without-with pictures show.
Without the connector cap With the new connector cap
I was very careful to get the hollow pins centered in the connector cap before I pressed it on all the way. I was optimistic about plugging the connector into the ECU, but that optimism was extinguished immediately.
The ECU behaved with the connector cap the same way as without the cap, including the ECU starting when the connector was twitched. Then it got worse. The ECU wouldn't even start (based on the blue light not coming on). I used a tester to check pins in the connector, especially the battery (#31), 12V switched (#4), and the 2 power grounds (#10 and #28). All 4 pins tested correctly, so I tried the connector in the ECU again.
Still no indication that the ECU was running EXCEPT that the O2 sensor got hot (which just needs switched power, so the relay is working) and the handheld worked with correct ATS, CTS, etc. but no values for engine-running parameters.
My guess is that the ECU is not working. I will call FAST tomorrow and see what they say.
Does anybody have any other ideas about what could be wrong?
The connector cap was definitely missing as the without-with pictures show.
Without the connector cap With the new connector cap
I was very careful to get the hollow pins centered in the connector cap before I pressed it on all the way. I was optimistic about plugging the connector into the ECU, but that optimism was extinguished immediately.
The ECU behaved with the connector cap the same way as without the cap, including the ECU starting when the connector was twitched. Then it got worse. The ECU wouldn't even start (based on the blue light not coming on). I used a tester to check pins in the connector, especially the battery (#31), 12V switched (#4), and the 2 power grounds (#10 and #28). All 4 pins tested correctly, so I tried the connector in the ECU again.
Still no indication that the ECU was running EXCEPT that the O2 sensor got hot (which just needs switched power, so the relay is working) and the handheld worked with correct ATS, CTS, etc. but no values for engine-running parameters.
My guess is that the ECU is not working. I will call FAST tomorrow and see what they say.
Does anybody have any other ideas about what could be wrong?
A. if it is the ECU, trade up to a XFI sportsman.... Hell, do it anyway... it makes trouble shooting much easier as you can see monster and graph ALL input sensors,, ALL...
B. if you do not get 100rpm pulse the ECU will not start, period.
Check your crank trigger... no blue light blinking, but other lights on... that is your problem
I've been considering a Fast to replace an Accel unit (for a Jet Boat project, I love the Tri-power on my 68), if that's how they support the product I'll be re-thinking using a Fast. Good to know you found the part though.
Its a good unit if you do everything correct, and do not have engine issued like oil in the cylinders.. I have seen issues from all makes.
Its a good unit if you do everything correct, and do not have engine issued like oil in the cylinders.. I have seen issues from all makes.
I agree. When it was working, the GM 350 HO was running better than advertised.
The oil and air leak from the valley problem is fixed and ground is fixed too. Everything I know I didn't do correctly has been corrected. I'm out of ideas other than some basic ECU or harness problem.
I have a VERY patient buyer waiting for this car, but winter is coming and he's got to get it home before the snow flies.
A. if it is the ECU, trade up to a XFI sportsman.... Hell, do it anyway... it makes trouble shooting much easier as you can see monster and graph ALL input sensors,, ALL...
B. if you do not get 100rpm pulse the ECU will not start, period.
Check your crank trigger... no blue light blinking, but other lights on... that is your problem
It was late last night when I finally shut the lights off in the garage. I didn't even check this thread then because I wouldn't have done anything about it then anyway. I just read your reply a couple hours ago. (I didn't know the ECU was waiting for a 100 rpm pulse!)
I threw everything together and took it for a 50-mile test drive. It runs like it should now! It's back to being an over-achieving GM Performance 350 HO again. It idles (but sometimes stumbles a little when coming to a stop), it accelerates (WOW!), and throttle response is fantastic!
I owe Paul Dana special thanks for his help solving these FAST EZ-EFI problems.
10-29-2018, 03:41 PM
