Accel Gen 7 start up and high rpm problem

[GregWeld]

I ended up replacing the TPS on the Nomad after it caused a backfire - that backfired so hard it bent a pushrod... Seems it was "breaking down" and the ECU didn't know where the throttle was. That part went south quite quickly though, once it went. That was 4 or 5 years ago and that part has never given me trouble since then.

I also had trouble (several times) with their Dual Sync distributors.... (I was an early adopter - too early as it turns out ) which was the major reason I stopped using Accel and switched to the non cam signal EZ EFI... Seems that OIL can get up inside the distributor and cause all manor of issues -- PARTICULARLY if you have laid the distributor on it's SIDE after it's been installed etc - so it has oil on it.... A simple disassembly and cleaning was all it needed and bingo - it was fine again.

[Jim Nilsen]

Originally Posted by GregWeld

I ended up replacing the TPS on the Nomad after it caused a backfire - that backfired so hard it bent a pushrod... Seems it was "breaking down" and the ECU didn't know where the throttle was. That part went south quite quickly though, once it went. That was 4 or 5 years ago and that part has never given me trouble since then.

I also had trouble (several times) with their Dual Sync distributors.... (I was an early adopter - too early as it turns out ) which was the major reason I stopped using Accel and switched to the non cam signal EZ EFI... Seems that OIL can get up inside the distributor and cause all manor of issues -- PARTICULARLY if you have laid the distributor on it's SIDE after it's been installed etc - so it has oil on it.... A simple disassembly and cleaning was all it needed and bingo - it was fine again.

I didn't think about the tps getting hit with the shock wave of the backfire and throwing it off. I will have to reset the values and see if it changes ? Could be as simple as that or I need a new one?

I got to talk to Mark today and he is going to look at my datalogs for clues and it was also discussed that the map sensor could be scewed also.

After going thru some of my datalogs I found that there is a spike that happens when I shift that goes to 17.25 a/f which isn't good. Last for a blip of a backfire it seems if all is just right.

Good thing is it still starts and runs good to 5500.

I'll keep you posted as to what happens. Another time at bat and I hope it gets better just like it did last time. If it was in the cards I would put a Fast or Holley EFI on it and let it self tune itself but i just am not up to the whole change over yet.

Thanks , Jim

[GregWeld]

Originally Posted by Jim Nilsen

After going thru some of my datalogs I found that there is a spike that happens when I shift that goes to 17.25 a/f which isn't good.

Hey! Lean is mean!


I've not had to replace a MAP sensor... and it was my TPS that was bad that caused my backfire! It was just a bad one... and would get heated up and break down. Started crapping out -- then would be fine -- then would momentarily loose the throttle... When it finally went it caused a backfire in a drive thru at a McDonalds! It scared the woman behind me so bad she backed out of there and left! I had to have the poor old Nomad towed back to the shed after that one.

[Jim Nilsen]

Originally Posted by GregWeld

Hey! Lean is mean!


I've not had to replace a MAP sensor... and it was my TPS that was bad that caused my backfire! It was just a bad one... and would get heated up and break down. Started crapping out -- then would be fine -- then would momentarily loose the throttle... When it finally went it caused a backfire in a drive thru at a McDonalds! It scared the woman behind me so bad she backed out of there and left! I had to have the poor old Nomad towed back to the shed after that one.

Thanks for the follow up on the rest of the story of the tps. I am holding off on any new parts until Mark reads the datalogs, if things are not right it should show up there.

I pulled my distributor cap last night to see how the new rotor was doing and it had made it's way loose again, it can actually rock a bit on the shaft which could cause a spark scatter at high rpm possibly? The low end shouldn't be effected but it is still something that shouldn't be the way it is. I have gone 9,000 miles with it and it can work but when it has problems it makes you wonder WTF quality control was doing that day.

talk to ya later

[supremeefi]

Hey Jim, as mentioned send me those logs and we'll check it out.

Your lean spike is because of your VE, it's all over the place and makes no sense as I mentioned to you yesterday. Normally it's not the ECM that's the problem but that's what almost always gets the blame.

As far as self tuning, the Accel makes doing it yourself much easier than most. You simply datalog it and drive it like you would anything else. Then come back and do a "Fuel Overlay" that will tell you where you just were on the VE tables. Take the cells and correct them accordingly, either individually or in groups. Normally takes less than an hour and you can customize your map as well for extra lean cruise etc, can't do that with the EZ stuff.

And don't forget the benefits of total spark control, and from cold to hot running. None of the self tuning stuff has that either.

[1Bad68Cat]

Originally Posted by supremeefi

As far as self tuning, the Accel makes doing it yourself much easier than most. You simply datalog it and drive it like you would anything else. Then come back and do a "Fuel Overlay" that will tell you where you just were on the VE tables. Take the cells and correct them accordingly, either individually or in groups.

Can you explain how to do the fuel overlay. I would like to eliminate the lean spikes I am seeing in my setup. Thanks.

[supremeefi]

Easy, set your datalog for 20 min or so, remember it registers in seconds.
Use these parameters,
RPM
TPS
MAP make sure you pick the same one as your tables, i.e. KPA, % etc.
O2 Feedback
O2 correction
Timing

Make sure you've set your rpms in the tables (F2, F3, F4) to reflect your driving. No sense in having tables that go to 6500 if you're not going to run it there, you're wasting resolution. Store your existing cal, put your Acceleration modifier at 1.0 across the graph. Enable the Datalog, drive the car making an effort to accelerate smoothly and with no excessive pedal movement. hold for a second or two at various loads and rpm's. When the datalog is done it will automaticlaly store it by dating it, i.e. 06132011 etc.
Then open your cal, press F2, go to "Overlay". Click on the datalog you just did. All the cells that you hit during your drive will be highlighted in blue. Down on the bottom it will tell you the actual O2 and correction as well as the other parameters you picked for the log. By pressing the page up or page down keys on your computor keyboard it will move the cells around the graph in the order they were stored. Correct them accordingly and send to the ECM. When you're done then address your transient fueling, the acceleration modifier, TPS ROC, and Tau. Make sure you've set your air/fuel table to the values you want where and when you want them beforehand. And obviously make sure it's up to temp, timing is good and there are no other modifiers in use.
Once you do it the first time it gets easier, you can do different parts of the map, full throttle, cruise etc all at once.
Then fine tune from there, air/fuels, spark timing etc. And remember all fueling calibrations are taken from the VE, if you change that you change other areas, that's why you do this, the "Steady State" stuff first.

When done right I'll put the drivability of the Accel up against anything, even systems that cost twice as much.

Hope this helps.
Mark