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thanks for all your replies. Sorry I haven’t replied recently I have been on holidays and haven’t been able to do any more diagnostics on the mazda. Also sorry for the long post.
I bought a new fuel pump and installed it. Fuel pressure now sits steady all the time and doesn’t fluctuate. Idle when warm is now really smooth and it is a lot easier to start when cold. But the bucking hasn’t changed. But still may have been a contributing factor but at least that is fixed.
While on holidays I started doing some research into engine management systems and what options I have out there. I am still researching and deciding at this point on which way I will go. a lot of it will come down to price and whether I can tune it by feel to get it running as the closest shop to me that can do dyno tuning is a little over 300km away for me. And I would prefer to install a system that I can get a basic tune out of for testing before towing it 300km to get it dialled in nicely.
But in the meantime I decided to get a wideband now, as I will need one with the aftermarket ECU for better quality tuning and they are always handy to have anyway. So I flew home yesterday for work and had a few spare hours before my lift arrived to pick me up, so I went ahead and installed the Wideband sensor and gauge. I bought the MTX-L innovate as it has wideband and narrowband outputs and datalogging capabilities.
After I installed everything, I calibrated and set it all up and fired the mazda up for the first time with the wideband. From everything I know about AFR’s on petrol vehicles stoic is approx. 14.7:1 and anything higher is lean and any number lower is rich.
I am getting numbers that don’t seem right to me. Which may be another contributing factor but I am still looking for a set of AFR maps for the stock computer just to compare to for now. After the engine starts, from cold, AFR is sitting around 11.2:1 with slow variations of 0.1 up and down, as I let the mazda warm up, just idling, the AFR slowly increase to 13.0:1. I left it until the thermo fan kicked in and engine was at running temps, and the AFR sat nicely between 12.92:1 and 13.11:1 at idle. I understand the richer start up is to help with firing the engine from cold and to help the engine warm up and keep idling.
I then took it out for a quick drive on medium acceleration the AFR would drop to 10.1:1 and would drive really well. come off the accelerator and the AFR would shoot up to off the scale which is 22.4:1 for this gauge, and when back at idle it still stays at 13:1. On hard acceleration and pulling boost the AFR would drop down to as low as 9.3:1 and that is around where the bucking/loss of power starts.
As I only had a short time before I left for work that is all the testing I have done so far, I will do more and more in depth when I get back home, as I only got 5 minutes of actual drive time.
But to me those figures seem WAY too rich, the last turbo I helped build the richest we were getting was 11.2:1 with a heavily worked engine.Once I do decide and get the money spare I will get an aftermarket ECU for it, But could the higher compression engine be tricking the stock ecu into dumping in too much fuel and could this cause bucking from the torque loss from too much fuel in the air/fuel mix in the cyl’s? And also I only run 98 octane fuel from a reliable station. which I believe is the equivelant to 92/93 octane in the states.
thanks for your help and any more that can be offered
thanks for all your replies. Sorry I haven’t replied recently I have been on holidays and haven’t been able to do any more diagnostics on the mazda. Also sorry for the long post.
I bought a new fuel pump and installed it. Fuel pressure now sits steady all the time and doesn’t fluctuate. Idle when warm is now really smooth and it is a lot easier to start when cold. But the bucking hasn’t changed. But still may have been a contributing factor but at least that is fixed.
While on holidays I started doing some research into engine management systems and what options I have out there. I am still researching and deciding at this point on which way I will go. a lot of it will come down to price and whether I can tune it by feel to get it running as the closest shop to me that can do dyno tuning is a little over 300km away for me. And I would prefer to install a system that I can get a basic tune out of for testing before towing it 300km to get it dialled in nicely.
But in the meantime I decided to get a wideband now, as I will need one with the aftermarket ECU for better quality tuning and they are always handy to have anyway. So I flew home yesterday for work and had a few spare hours before my lift arrived to pick me up, so I went ahead and installed the Wideband sensor and gauge. I bought the MTX-L innovate as it has wideband and narrowband outputs and datalogging capabilities.
After I installed everything, I calibrated and set it all up and fired the mazda up for the first time with the wideband. From everything I know about AFR’s on petrol vehicles stoic is approx. 14.7:1 and anything higher is lean and any number lower is rich.
I am getting numbers that don’t seem right to me. Which may be another contributing factor but I am still looking for a set of AFR maps for the stock computer just to compare to for now. After the engine starts, from cold, AFR is sitting around 11.2:1 with slow variations of 0.1 up and down, as I let the mazda warm up, just idling, the AFR slowly increase to 13.0:1. I left it until the thermo fan kicked in and engine was at running temps, and the AFR sat nicely between 12.92:1 and 13.11:1 at idle. I understand the richer start up is to help with firing the engine from cold and to help the engine warm up and keep idling.
I then took it out for a quick drive on medium acceleration the AFR would drop to 10.1:1 and would drive really well. come off the accelerator and the AFR would shoot up to off the scale which is 22.4:1 for this gauge, and when back at idle it still stays at 13:1. On hard acceleration and pulling boost the AFR would drop down to as low as 9.3:1 and that is around where the bucking/loss of power starts.
As I only had a short time before I left for work that is all the testing I have done so far, I will do more and more in depth when I get back home, as I only got 5 minutes of actual drive time.
But to me those figures seem WAY too rich, the last turbo I helped build the richest we were getting was 11.2:1 with a heavily worked engine.Once I do decide and get the money spare I will get an aftermarket ECU for it, But could the higher compression engine be tricking the stock ecu into dumping in too much fuel and could this cause bucking from the torque loss from too much fuel in the air/fuel mix in the cyl’s? And also I only run 98 octane fuel from a reliable station. which I believe is the equivelant to 92/93 octane in the states.
thanks for your help and any more that can be offered
cheers again eric. I have been on forums talking to people who have done the same work as I have done and most of them are still running stock ECU without any issues. I will go aftermarket if I have to just a money issue atm lol.
I have been monitoring my fuel pressure since i last posted, and I am thinking that I may have a dodgy fuel pump, but not sure. I have installed a pressure gauge onto the FPR. I set the pressure to 40psi with engine off, when I start the engine up it drops to 32-33psi, all this is as per WSM. pressure is steady and needle holds quite still, but after driving it until the surging starts if I check the fuel pressure again it has dropped and the needle is bouncing all over the place from 20-30psi. If I wind the pressure back up to correct levels it keeps bouncing. I have to let the car sit for 2-3 hours before i can start it back up without pressure fluctuations. It is a brand new fuel pump, but i have had a few dodgy new parts for this car since the rebuild start. could this be a sign of a dodgy fuel pump? before i spend a lot of money on a new ECU? thanks agincheers again eric. I have been on forums talking to people who have done the same work as I have done and most of them are still running stock ECU without any issues. I will go aftermarket if I have to just a money issue atm lol.
I have been monitoring my fuel pressure since i last posted, and I am thinking that I may have a dodgy fuel pump, but not sure. I have installed a pressure gauge onto the FPR. I set the pressure to 40psi with engine off, when I start the engine up it drops to 32-33psi, all this is as per WSM. pressure is steady and needle holds quite still, but after driving it until the surging starts if I check the fuel pressure again it has dropped and the needle is bouncing all over the place from 20-30psi. If I wind the pressure back up to correct levels it keeps bouncing. I have to let the car sit for 2-3 hours before i can start it back up without pressure fluctuations. It is a brand new fuel pump, but i have had a few dodgy new parts for this car since the rebuild start. could this be a sign of a dodgy fuel pump? before i spend a lot of money on a new ECU? thanks aginHi. thanks for your reply.
We have a brand new fuel pump, filter, hoses and fuel pressure regulator. fuel pressure is set to factory manual specs, and flow is better than the manual states. when we rebuilt the motor we installed brand new O-rings and seals for the injectors, I just bought bungs this morning to block off the vacuum ports and start troubleshooting one line at a time to see if it is a vacuum component or line causing the low vacuum, I did find multiple small exhaust leaks where the manifold bolts to the head this morning, I popped the manifold and turbo off and found that the exhaust gasket and heat shield had been installed in the wrong order. They had the heat shield against the manifold and not the head. installed new gaskets and shield and looks like the exhaust leaks are gone, I haven’t road tested yet, but this could have been one of our issues throwing the O2 sensor out of whack. Let you all know once I have road tested and looked more into the vacuum side. vacuum was at 16inHg this morning when doing the exhaust leak, it holds fairly steady and has a very slow movement between 16 and 17, not jumping or anything just slowly moving. if I snap the accelerator open close vacuum goes close to 0 and bounces back up to 23inHG before idling back down to 16/17.
Hi. thanks for your reply.
We have a brand new fuel pump, filter, hoses and fuel pressure regulator. fuel pressure is set to factory manual specs, and flow is better than the manual states. when we rebuilt the motor we installed brand new O-rings and seals for the injectors, I just bought bungs this morning to block off the vacuum ports and start troubleshooting one line at a time to see if it is a vacuum component or line causing the low vacuum, I did find multiple small exhaust leaks where the manifold bolts to the head this morning, I popped the manifold and turbo off and found that the exhaust gasket and heat shield had been installed in the wrong order. They had the heat shield against the manifold and not the head. installed new gaskets and shield and looks like the exhaust leaks are gone, I haven’t road tested yet, but this could have been one of our issues throwing the O2 sensor out of whack. Let you all know once I have road tested and looked more into the vacuum side. vacuum was at 16inHg this morning when doing the exhaust leak, it holds fairly steady and has a very slow movement between 16 and 17, not jumping or anything just slowly moving. if I snap the accelerator open close vacuum goes close to 0 and bounces back up to 23inHG before idling back down to 16/17.
Thanks for all your help.
WYSETECH – as soon as I find a GT being scrapped or parted I will grab the heatshields and install them, they are pretty rare where I am so has been taking a while to find one. When it first started the bucking we thought it was boost cut system kicking in, so installed a boost gauge to monitor boost and it holds steady at 7psi even when the bucking kicks in, sorry should have mentioned that in my first post.JS – I am not running the MSD controller just the ford TFI coil and still using stock ignitor. the coil has been mounted further away to help prevent heat soak in case that was a contributing factor. looks like I might have to start researching into aftermarket computers. I tested the WG today as per the WSM, applying 8psi of air pressure to the vacuum/boost line and opens and closes smoothly with the pressure being applied and removed.
I did notice today while checking the WG that my vacuum level has dropped since first started this project. Not sure if this is contributing but have read today that these motors are very sensitive to vacuum performance. It was at 19InHg now it is at 15InHg. I hit all the hoses and connections with starter fluid and couldn’t identify any leaks with that, when back home I will start tracing and pulling vac lines to see if I can find where I am losing vacuum. I also checked compression to check it wasn’t mechanical and got 145, 147, 147, 150
Thanks for all your help.
WYSETECH – as soon as I find a GT being scrapped or parted I will grab the heatshields and install them, they are pretty rare where I am so has been taking a while to find one. When it first started the bucking we thought it was boost cut system kicking in, so installed a boost gauge to monitor boost and it holds steady at 7psi even when the bucking kicks in, sorry should have mentioned that in my first post.JS – I am not running the MSD controller just the ford TFI coil and still using stock ignitor. the coil has been mounted further away to help prevent heat soak in case that was a contributing factor. looks like I might have to start researching into aftermarket computers. I tested the WG today as per the WSM, applying 8psi of air pressure to the vacuum/boost line and opens and closes smoothly with the pressure being applied and removed.
I did notice today while checking the WG that my vacuum level has dropped since first started this project. Not sure if this is contributing but have read today that these motors are very sensitive to vacuum performance. It was at 19InHg now it is at 15InHg. I hit all the hoses and connections with starter fluid and couldn’t identify any leaks with that, when back home I will start tracing and pulling vac lines to see if I can find where I am losing vacuum. I also checked compression to check it wasn’t mechanical and got 145, 147, 147, 150
Hey eric thanks for your reply. After we first got the car running after its rebuild it was running quite well and the surging only started about 2 weeks later, it started as a random buck every now and again when accelerating and slowly deteriorated to all the time once warm, we replaced the leads (which were already brand new) and plugs (also new) with the 8.0mm leads and it still bucked once warm, just a more rapid buck, then we did the coil upgrade and changed the dizzy cap and rotor again, and it still bucked just behaved slightly different when it bucked. when the bucking starts under acceleration I have to release the accelerator for it to stop as it wont pull any faster, but sometimes if I only use enough throttle to just slowly accelerate I can pull past the buck zone without it bucking and will keep revving smoothly.
Also with the ecu and the age of the car from what I have read I can’t get the ECU remapped I have to swap up to aftermarket. The injectors are the standard GT ones for the car and are good for up to 200HP thereabouts. I am pretty sure I am not that high on power.here is a quick video I took of the taco when the surging happens, you can see it when I accelerate at 00:20 to 00:30
[video]http://www.youtube.com/watch?v=s9r5MDuP3Fg[/video]thanks for all your help
Hey eric thanks for your reply. After we first got the car running after its rebuild it was running quite well and the surging only started about 2 weeks later, it started as a random buck every now and again when accelerating and slowly deteriorated to all the time once warm, we replaced the leads (which were already brand new) and plugs (also new) with the 8.0mm leads and it still bucked once warm, just a more rapid buck, then we did the coil upgrade and changed the dizzy cap and rotor again, and it still bucked just behaved slightly different when it bucked. when the bucking starts under acceleration I have to release the accelerator for it to stop as it wont pull any faster, but sometimes if I only use enough throttle to just slowly accelerate I can pull past the buck zone without it bucking and will keep revving smoothly.
Also with the ecu and the age of the car from what I have read I can’t get the ECU remapped I have to swap up to aftermarket. The injectors are the standard GT ones for the car and are good for up to 200HP thereabouts. I am pretty sure I am not that high on power.here is a quick video I took of the taco when the surging happens, you can see it when I accelerate at 00:20 to 00:30
[video]http://www.youtube.com/watch?v=s9r5MDuP3Fg[/video]thanks for all your help
Cheers grg88. It is unnerving seeing it glow red on easy driving especially with the bucking issue I am having. It just had me worried because the last mazda turbo we had would only start glowing if you were feeding it and spooling up the turbo for extended periods. But if you are right but those exhaust temps that makes me worry a little less lol. And wysetech I suppose it would hear up more from it bucking and probably throwing fuel into the manifold heating it up even more.
Cheers grg88. It is unnerving seeing it glow red on easy driving especially with the bucking issue I am having. It just had me worried because the last mazda turbo we had would only start glowing if you were feeding it and spooling up the turbo for extended periods. But if you are right but those exhaust temps that makes me worry a little less lol. And wysetech I suppose it would hear up more from it bucking and probably throwing fuel into the manifold heating it up even more.
Just to be sure I will double check all grounds again in the morning. All fuel lines are at the back of the motor and exhaust is at the front and wraps down under the motor. There are no heat shields on the exhaust manifold or turbo as they were missing when I got the car.
Just to be sure I will double check all grounds again in the morning. All fuel lines are at the back of the motor and exhaust is at the front and wraps down under the motor. There are no heat shields on the exhaust manifold or turbo as they were missing when I got the car.
thanks heaps for your quick reply. greatly appreciated. I also forgot to add when it surges/bucks it will not accelerate further usually in the 2500 – 3200rpm zone, and have to release the pedal, if I hold the accelerator at around 20-25% I can pull past the buck zone without any bucking, but the extreme exhaust temps have me worried.
We went through and have checked all the grounds and installed new earth cables from battery to chassis and engine. Also have buzzed out every wire from the ECU to their location and all have full continuity. Has me stumped lol technically with what I have it should run. Engine has 155 PSI compression across all 4 pots.