Here are the mistakes that people are most likely to make with MegaSquirt^® EFI Controller, based on +30K messages, not on anyone's experiences in particular:

10. Worrying about the timing of fuel so that injection happens when the intake is open. This is intuitively important, but practically of little consequence.

Solution or www.megamanual.com/seq/index.htm

9. Blaming MegaSquirt^® for other problems. Make sure your engine runs well before converting, do not try to use it as a 'fix' unless you already know exactly what is wrong. Some people have spent a lot of time, effort, and anxiety sorting through the entire universe of MegaSquirt information, only to find that their problems were caused buy a weak ignition coil, bad fuel pump, etc.

Solution

8. Not purchasing the stimulator. This will let you sort problems in your harness (frequent) from problems in your MegaSquirt^® (rare), as well as help you to understand the MegaTune software, etc.

Solution

7. Not using the stimulator (or vehicle power) when trying to update the embedded code. MegaSquirt^® needs to be powered by the stimulator to do this.

Solution

6. Mixing up the stimulator and MegaSquirt^® (and/or relay board) DB37 connectors. These must be the right way around.

People have tried to fix this by using a 'gender changer'. This WILL NOT work, as the connections will be 'mirrored' relative to the intended pin outs. The correct solution is to replace the connectors with the correct ones in the correct locations.

5. Inadequate wiring, connectors, splices, etc. have been responsible for a number of problems. These are VERY difficult for someone else to diagnose over the list. A good multi meter, test light, and a lot of patient testing is often the only way to sort the problems. The best advice is to be extra careful when you are putting your harness together, and check everything as you build it (before it is buried under the dash, etc.).

Solution

4. Not using a ground wire with the relay board. Pin 19 on the MS to Relay Board cable needs to connect to terminal 19 on the 20 position terminal strip to ground the sensors.

Solution

3. Using a power source for MegaSquirt^® that supplies 12 volts at RUN, but not during cranking. The engine simply won't start, since MegaSquirt is turned off during cranking. It may cough a few times (because the prime pulse has supplied some fuel, and the ignition isn't affected, but only a very lucky set of circumstances will start the car! (Enough priming pulse to start the car combined with very short cranking times). This appears similar to the next problem...

Solution

2. Mis-wiring the TPS. A surprising number of starting problems are eventually traced to a mis-wired TPS that invokes the flood clear mode, preventing starting. The engine coughs a few times if the priming pulse is large enough, then dies. There are instructions for checking the wiring of the TPS in the manual, or you can check that the idle count is below 175 in the TPS calibration in MegaTune.

Solution

1. Not reading the documentation. It's amazing how many people don't read the MegaSquirt^® site, the MegaManual, or the FAQ before asking a question.

Solution

Honorable mention goes to:

• installing the stimulator or MegaSquirt^® LEDs backwards. (stim assembly guide)
• not connecting XG1 to XG2 for testing on the stim (see step 54 in the assembly manual).
• not having a shop manual for the car you are trying to convert. This will save many headaches when you try to connect MegaSquirt^® EFI Controller, and is especially important if you are trying to convert a later model vehicle.
• installing the stim transistor incorrectly (the flat side should face the TPS pot)
• installing one or more of the polarized caps (or diodes) backwards.
• installing the CPU 'upside-down'.
• not understanding the conditions for EGO activation, and assuming the O2 sensor is broken/miswired. (see step 56 in the assembly guide)