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This issue can be on cold OR hot start. But it seems, if I turn the ignition to on without starting then off 3 times, on the 4th i start, I get a good start. weird. I dont know if theres a setting in VEMS where a condition like that would exist. But take a look. Doesnt get too cold here in Hawaii, maybe 55F early morning and high 90F in afternoon. Which is why warm up and start up looks the way it does. One thing I noticed is EGO is always off and in visual graph it shows EGO 100%. I dont fully understand all features yet, so please excuse nooby questions. Thanks in advance -Wayne
my first thought is that you're not getting enough fuel for the first few tries, but by the 4th time there is enough residual fuel on the port walls that it can now start happily.
cold start needs more fuel, but some of that fuel will just settle on the walls of the intake port rather than go into the engine (cold fuel doesn't evaporate very well) so you need more fuel to compensate for that.
my first thought is that you're not getting enough fuel for the first few tries, but by the 4th time there is enough residual fuel on the port walls that it can now start happily.
cold start needs more fuel, but some of that fuel will just settle on the walls of the intake port rather than go into the engine (cold fuel doesn't evaporate very well) so you need more fuel to compensate for that.
i thought that too but that would only happen during start up. After warming up to temp, it should run normal. the problem im having is from start up, until i shut off the engine. doesnt matter if its a 5min from or 45min drive.
BTW, has anyone with VEMS wired in an aftermarket TPS sensor? Im doing the 65mm FORD TB mod and will wire in a new TPS 3 wire sensor. The factory plug is 5 wires. Looking at the VEMS diagram, only 3 inputs are needed. Would like to just splice into factory harness instead of making another one to the VEMS ecu.
Any startup, either hot or cold, needs extra enrichment during cranking. Is there a table to set cranking enrichment?
Yes there is Dave. Will check that out. Thanks. But like I said previously, the stumbling and low idle will stay until I shut down and start up the car again. So even after driving for a long time the issue is still there.
Yes there is Dave. Will check that out. Thanks. But like I said previously, the stumbling and low idle will stay until I shut down and start up the car again. So even after driving for a long time the issue is still there.
Why don't you have an idle control valve? This sounds like a street car, so it would be a very nice thing to have! Otherwise your idle speed will vary depending on engine temperature, accessory load, etc. Plus an ICV will allow a higher idle during the warmup enrichment period, etc . . . . .
While ignition timing and fuel mixture certainly have an affect on idle speed, the main determinant is the amount of air entering the engine. Without an ICV, the throttle body bypass screw is the only thing that controls this when the throttle plate is all the way closed. Have you tried playing around with the mechanical idle speed setting? Are you sure the O-ring on the bypass screw is OK? Any other vacuum/boost leaks? You need to make sure that the mechanical components are OK before getting too deep into the ECU side of things.
All of that said, have you looked at datalogs when the symptom is/isn't occurring? There is a lot of data available with the VEMS or most other standalone ECUs, so a close look at that might reveal your answer . . . .
Why don't you have an idle control valve? This sounds like a street car, so it would be a very nice thing to have! Otherwise your idle speed will vary depending on engine temperature, accessory load, etc. Plus an ICV will allow a higher idle during the warmup enrichment period, etc . . . . .
While ignition timing and fuel mixture certainly have an affect on idle speed, the main determinant is the amount of air entering the engine. Without an ICV, the throttle body bypass screw is the only thing that controls this when the throttle plate is all the way closed. Have you tried playing around with the mechanical idle speed setting? Are you sure the O-ring on the bypass screw is OK? Any other vacuum/boost leaks? You need to make sure that the mechanical components are OK before getting too deep into the ECU side of things.
All of that said, have you looked at datalogs when the symptom is/isn't occurring? There is a lot of data available with the VEMS or most other standalone ECUs, so a close look at that might reveal your answer . . . .
Haven't had a idle control valve for a few years prior to installing vems and was still running a maf and piggyback. Yes it's a street car without Ac.. Car ran fine on vitesse maf and smt6, having a hard time believing that I would need an icv with vems. There's also a few individuals I know who have vems without an icv without my issues. I've logged both conditions, good run and bad run and given them to Peep. However it hasn't shown an answer that he or I can figure out which is why I'm reaching out here. I also thought that it might be the solid state DME relay I have from F9 but it showed issues in 3 spare relays. Beginning to think it maybe the speed/reference sensors. Gonna grab an o-scope from work and check out the signal. Thanks
Btw, can a few of you upload a configuration file so that I could compare settings?i know it will depend on mods, but would like to make sure I didn't mess with an obvious settings. Much Appreciated.
Haven't had a idle control valve for a few years prior to installing vems and was still running a maf and piggyback. Yes it's a street car without Ac.. Car ran fine on vitesse maf and smt6, having a hard time believing that I would need an icv with vems. There's also a few individuals I know who have vems without an icv without my issues. I've logged both conditions, good run and bad run and given them to Peep. However it hasn't shown an answer that he or I can figure out which is why I'm reaching out here. I also thought that it might be the solid state DME relay I have from F9 but it showed issues in 3 spare relays. Beginning to think it maybe the speed/reference sensors. Gonna grab an o-scope from work and check out the signal. Thanks
You could also use a timing light to verify that it's firing correctly. Just use a silver marker or whiteout to mark TDC on the crank pulley and timing cover for reference. Set the idle timing table to 5 degrees in all cells so you know it's not moving around. Check the timing when it's idling good, then check it when it's not idling good.
You could also use a timing light to verify that it's firing correctly. Just use a silver marker or whiteout to mark TDC on the crank pulley and timing cover for reference. Set the idle timing table to 5 degrees in all cells so you know it's not moving around. Check the timing when it's idling good, then check it when it's not idling good.
Thanks will definitely try check timing for both conditions. Haven't thought of that. I don't have a scalloped flywheel. Factory flywheel. It's been consistent with 4th start being a good one.
Update* so after installing a new coil pack and plug still will not start on all 4. Got a hold of Peep and said I blew the ignition drivers for pins 36/34. Gonna scour the island for transistor V3040P.
BIG PROBLEM. After trying to fix stumbling issue, i adjusted some values via my laptop and uploaded therm the next day. Adjusted idle values and ignition firing order. Upload while ignition on and engine off. Upload successful but car now running with only 2 cylinders. I trouble shot and found cylinders 4 and 1 are not getting anyspark. Which happen to be the firing pair on my wasted spark. After trying to swap pins and configuration on VEMS, it seems ECU PIN#36 is dead. I even bought a new coil pack in hopes to resolve problem. Tried pin pairs on 33 and 35, 11 and 12. They do not start engine. Even after configuring " ignition visual outputs". 34 and 36 runs on two cylinders. With anyone running wasted spark care to share their config so that I can compare. But pretty sure at this point my pin 36 is damaged or in-op. Frustrating because all i did was upload a config file. Any help would be greatly appreciated. -Wayne
Update* so after installing a new coil pack and plug still will not start on all 4. Got a hold of Peep and said I blew the ignition drivers for pins 36/34. Gonna scour the island for transistor V3040P.
...
This one below
some time ago I had two fried V3040P
My solution was an additional heat sink.
I'm running wasted spark as well. -->https://rennlist.com/forums/944-and-...l#post14325562
Attached is my current config file. Though it's for a NA and I use the ICV, but Starting/Idle shouldn't be much different.
Unfortunately I can't open your uploaded config file, it seems to be corrupt.
does the VEMS waste spark use an external igniter box to drive the coil pack, or those transistors are it?
those transistors are it, as far as I know and understand.
But you could also use an external ignitor box driven by VEMS to drive the coil pack, but in my case not needed. It depends on the coil pack.
This one below
some time ago I had two fried V3040P
My solution was an additional heat sink.
I'm running wasted spark as well. -->https://rennlist.com/forums/944-and-...l#post14325562
Attached is my current config file. Though it's for a NA and I use the ICV, but Starting/Idle shouldn't be much different.
Unfortunately I can't open your uploaded config file, it seems to be corrupt.
thanks! will try to compare configurations. weird that the files corrupt. i also blew my pin 36 ignition driver. car runs on 2 cylinders, so i believe my 34 pin is good. did you burn both? where did you end up sourcing your transistors? nearest i found is in Texas off Ebay. Mouser doesnt have any in stock until July 2018. LOL. I guess blowing these is a common thing? Is it cause of the output of the coil packs? Would it be better if we move to coil on plug? I also ended up burning the trace from pin 36 to center pin of transistor.
03-07-2018, 03:03 AM
