Car is running after rebuild but developed a problem. Cold it runs fine but As the engine warms up and after 3500 rpm getting increasing missfire to the point of backfire. Timing has been checked and looked over on the files. It returns to normal on a restart.

I'm not seeing wires to or the sensors touching engine. Another clue might be the vvt only responds by going from min. to max. It does happen when VVT is unplugged. .

The suggestion is to check cam sensor and crank sensor.

Help is appreciated.

What is the gap on the Trackspeed crank wheel ? I had to tap and add sensor on the crank and my notes from last year don't tell me gap.

What to check on sensors prior to buying others?

This is a 2001 vvt engine with AEM EMS-4 and built from scratch wiring in a kitcar. ebay GM truck coils

Along with this I am still getting a random problem of the EMS not working after shutting down and trying to restart. It will not work until it " cools down" ( some time passes and it works fine, 5 seconds to 30 minutes) . The EMS just got redone so the car must be doing something to it. Starter, fuel pump, and separately switched and do not go thru box. thank you for suggestions

 

I generally put about a credit cards thickness between teeth on the trigger wheel and the crank sensor.

Where is the AEM located? Can your laptop connect to the AEM during the times that it does not work? Have you checked that it is getting 12v?

 

When the box won't hot restart, if you unplug the EMS box and plug it back in, does it fire back up?

FYI, I have an EMS-4 VVT map that works now. There's one important tweak from Series1 to Series 2 that needs to be made.

 

Wow, having same issues with my motorcycle and have not found a solution yet. Hoping this thread might give me some insight. I've replaced plugs, wires, coil and ignition control......Still missfires and bckfires after 15 mins of driving and then cuts off until it cools down then repeat till I get home.

 

Shuiend - ems will not connect when it does its work, no spark, no response. Thank you for gap. Savington - tried unplugging from box. ( have it located under the steering wheel now.) Box was just changed out again yesterday with latest updates, It is less often shutting down, but... . With VVT plugged in unable to alter other than full on and off so something is not right. Any idea's on what is overheating and changing or skipping timing? Can't see how the ebay coils could change timing.

 

When the car will not start, are there any lights on the AEM to show that it is getting power or anything? Is it possible for you to unplug it and check to make sure it is getting 12v then?

 

no lites on the AEM but I will check on the 12 volt, hmmmm. A fuse that is iffy, wire that is bad ?! good thought. The box has not worked with just unplugging it and plugging back in.

I will check fuses and unplug it and check r power next time it goes out and I do have an extra LED lite I could install inline thanks

 

I mean I have not ever used an AEM, I am just throwing out ideas of what would cause this. For some reason it seems like it is not getting power or something. At least that is why I would think that you could not connect to it during that time.

Also what happens if you try to push start the car while it is in the cool down period?

 

do you have a IAT? did you look at intake air temps when the car is missing?

don't know about AEM, but I had a similar issue (running MS2) and found that IAT temps were unreasonably (and unprobably) high at the time. Good calibration of the IAT took care of it.

 

Simple problem and solution. On the 2001 I had to tap and bolt in the crank sensor and it was moving. I had used silicone on mounting and as rev's increased the sensor must have been rotating away from crank.

 

You should not have had to tap anything to fit the crank sensor on an 01.

 

No tapping required on an 01, you would know better than I. On this engine I had to tap, perhaps I have a different year 02, or this part of the oil pump which was upgraded. ? I did install a lite on dash showing power to ECU and redid two sensor connections and engine has started each time since then. Shuiend thanks for your help
Next steps is to get VVT setup, dyno tuning, shaping aluminum on an english wheel for a hood. Autocross at a local airport first weekend in June.

 

I am not sure what combination oil pump and block you ended up that had to be tapped, but whatever it all works now for you and that is what matters.