Accel Gen 7 start up and high rpm problem

[Jim Nilsen]

I am currently having a problem with the car starting up and idling, I have to push the pedal when it is firing and it will rev up and then idle, otherwise it dies. I also have a miss /breaking up at 5500 and above.

I had a bad backfire and it has been a problem since. The IAC was whistling on start up much more than it ever had. Everything else seems to be good and it has a lot of power thru the whole range until it gets to 5500 or more. It varies a bit and somtimes goes higher and will go to 6400 at times.

The springs, pushrods and ignition have been checked and a new rotor and cap were also installed.

I think the IAC was maybe damaged from the backfire?

I sent Mark Remmel a private message to see what he thinks and am also looking for other thoughts as to what might be the problem.

The car was running great and would pull to 6400 and go the rev limiter at 6850 with no problems and ran really strong, now just before the Motorstate it is acting up.

Thanks for any help , Jim

[Vegas69]

Check all the basics. Timing, Fuel Pressure, Plug Wires, Connections..

[Jim Nilsen]

Originally Posted by Vegas69

Check all the basics. Timing, Fuel Pressure, Plug Wires, Connections..

Yep , did all that before I posted. Been thru this before and knew I had to eliminate all the basics. With all of the data logging I have and gauges to monitor vitals it makes it a lot easier to eliminate potential problems.

The IAC is what seems to be the problem on start up and it also acts as the acceleration modifier thoghout the whole rpm range. The car runs good after it starts and it only has the problem on the top end.

I am going out today to get some datalogs done to review what is happening now that I have fresh parts to eliminate any questions as to their input to the problem.

Thanks for reminding me because it can be something simple when you are doing it for the 1st time, unfortunately I have been thru the school of hard knocks with this system and it seem more like a fire drill than an emergency.

[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.

[supremeefi]

Originally Posted by Jim Nilsen

Yep , did all that before I posted. Been thru this before and knew I had to eliminate all the basics. With all of the data logging I have and gauges to monitor vitals it makes it a lot easier to eliminate potential problems.

The IAC is what seems to be the problem on start up and it also acts as the acceleration modifier thoghout the whole rpm range. The car runs good after it starts and it only has the problem on the top end.

I am going out today to get some datalogs done to review what is happening now that I have fresh parts to eliminate any questions as to their input to the problem.

Thanks for reminding me because it can be something simple when you are doing it for the 1st time, unfortunately I have been thru the school of hard knocks with this system and it seem more like a fire drill than an emergency.

Just an FYI for everyone, although you could say the IAC calibration can effect tip in therefore acceleration, in reality the IAC and acceleration modifier are not directly related in any way on any system, Accel or not. 2 different things.

[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.