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

:cheers:

[Vegas69]

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

[Jim Nilsen]

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 :lol: ) 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]

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 :lol: ) 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

:cheers:

[GregWeld]

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! :faint:


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! :woot: I had to have the poor old Nomad towed back to the shed after that one.

[Jim Nilsen]

Hey! Lean is mean! :faint:


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! :woot: 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]

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]

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

[GregWeld]

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.

:unibrow: You could do like one shop just did (I had to "just say NO") on a buddies car -- they teed the IAC into his power brake vacuum hose....


Yeah -- like that works!

Why is it that when people see EFI -- their brain goes into a sink hole?

[Jim Nilsen]

It's been a long week, the TOB is rebuilt and back in. Started the car back up and checked for leaks and all is good.

I have been talking to Mark and he is looking at my cal and datalogs if I got them to him correctly. I can't thank him enough for helping me.

Lot's of things on the checklist and it will be a long day. I have a friend coming over and we are going to change the brake fluid and get the rest of the car prepped. It's gonna be run what you brung again this year but it will be a big step up from the last time.

See ya all in Michigan !!!

[Jim Nilsen]

The Motorstate was a blast and the car made it there and back on it's own. The PS went out in the 2nd session and made it too hard to steer on the track to be able to recover from a slide, the auto cross was a lot of work but I could manuvere the coarse and finally made a really good run in spite of the engine rteaking up in the high rpm.

I am finally caught up on things at home and am getting to the problems at hand. The rebuilt rack is ready to go in and I am getting a new fuel filter next week to see if it is the part of my rpm problem.

I have 2 weeks to go and the heidt's event will already be here. Steering 1st and then back to the engine problem. I have to be able to get around without the workout and the car runs well enough to make even if i don't get it sorted out.

I am hoping for the problems to go away without a bunch of parts swapping in the ignition.

Now back to the fun of 4th of July

[camcojb]

congrats Jim, sounds like fun even with the problems.

[Jim Nilsen]

After a bunch of searching and going thru the fuel system and finding the clogged filters and then still having the miss I broke down and just got a new dual sync distributor. the Irony of it all is that I ordered the new one at 3pm and by 7pm I had a code 72 which is a cam and crank sensor pickup problem code. So the diagnoses and the timing was as spot on as it could get.

The car runs great now and the rev limiter sounds are actually the rev limiter now. The best thing is that I have finally gotten used to shifting early and I am better at getting to the shift before the r's get to far up. The IQ3 shift lghts have taken me some time to get used to, I have finally stopped looking at the tach for the time to shift. Old habits are hard to stop.

they say the weather is good for saturday and I am really looking forward to seeing how good the car runs when it is running good!!!:thumbsup:

:cheers:

[camcojb]

I have had my go-rounds with those dual syncs............... :lol: Glad you got it figured out Jim.

[GregWeld]

After replacing THREE Dual Syncs --- I switched to batch fire and run a regular MSD 6 Digital box and MSD distributor.... I don't really need the sequential firing mode since I don't have to worry about emissions and or getting the very last .01 MPG out of the pigs.

NEVER once had a problem with anything EFI after that.

[supremeefi]

I hear you guys.

Just to let you all know I have just taken delivery of a newly redesigned Accel Dual Sync for a SBF. The trigger wheel has been revamped as well as the mounting for the sensors. Seems those were the major problems.

I'll let you know how it goes. It's going in a Thruster'd 362 SBF with an EFI'd RPM intake.

[TurboNova]

After replacing THREE Dual Syncs --- I switched to batch fire and run a regular MSD 6 Digital box and MSD distributor.... I don't really need the sequential firing mode since I don't have to worry about emissions and or getting the very last .01 MPG out of the pigs.

NEVER once had a problem with anything EFI after that.

It's not just the last .01 MPG but also duty cycle of the injectors. With bank to bank mode you end up using twice as much duty cycle since the injectors fire twice as many times. The injectors all firing in the rail also make for inconsistent A/F cylinder to cylinder too, since the pulses are all banging around in the same rail.

Sequential is also worth some HP, emissions and low speed drivability. There are many ways that are better than any of the dual sync distributors out there.

My favorite way is a MSD or FAST crank trigger for RPM and a regular MSD distributor modded to be a cam sync. That will have zero problems and the crank trigger is way more accurate in the timing department. This setup will work with most stand alone ecus no matter what the brand.