Intermittent No Injector Pulse

[ProTouring442]

Here's a weird one for you.

2010 Camaro L99/6L80E combo in a 1959 Impala installed using a Speartech harness and tune.

Starting over a year ago, the car would intermittently not start. Cycling the key and and trying again would, perhaps after a few tries, make the car start.

It continued to get more and more frequent, and taking more and more tries before it would start, though frequently it would start and run on the first try.

It seemed to happen more often after taking the car for a drive, then letting it cool down for a while.

Eventually, it simply stopped starting at all.

Tests revealed we had spark, fuel pressure, power to the pink wire on the injectors, but no injector pulse.

When it stopped starting at all, we purchased and installed a new ECM (from Speartech). Upon installation, it cranked and immediately started.

It's run fine for about a month, but is now starting to do it again.

Any ideas on where the hell to start?

[Shrek]

It is always helpful to post your tune, when asking such questions.

Speartech (and other wiring harness companies) often sell the Corvette APP (accelerator pedal) for use in LS conversions. This APP is not always compatible with the other components that make up the Electronic Throttle Control system.

Sometimes the ECM tunes will have select Electronic Throttle Control system DTCs disabled, but often after enough drive cycles, the "background" diagnostics (like the second ECM core) will start to shut things down.

This may manifest as a sporadic or intermittent issue, or as a dead pedal, or as a no start.

Until you post your tune, and list your Electronic Throttle Control system components, there is no way to know if this is indeed part of your issue.

[ProTouring442]

It is always helpful to post your tune, when asking such questions.

Speartech (and other wiring harness companies) often sell the Corvette APP (accelerator pedal) for use in LS conversions. This APP is not always compatible with the other components that make up the Electronic Throttle Control system.

Sometimes the ECM tunes will have select Electronic Throttle Control system DTCs disabled, but often after enough drive cycles, the "background" diagnostics (like the second ECM core) will start to shut things down.

This may manifest as a sporadic or intermittent issue, or as a dead pedal, or as a no start.

Until you post your tune, and list your Electronic Throttle Control system components, there is no way to know if this is indeed part of your issue.

I hadn't pulled the tune as it's just whatever Speartech did.

So far as I know, the pedal we got came out of the Camaro (we had the yard send all manner of stuff).

[ProTouring442]

Here's the tune.

59 Impala stock Speartech tune.hpt

[Shrek]

OK ... the calibrations (ECM & TCM) are for the same 2010 Camaro.

As long as the APP is from a Camaro, and the connector is pinned for a Camaro, then you can rule out a mismatch in the Electronic Throttle Control system - as being the issue (or one of the issues).

[ProTouring442]

OK ... the calibrations (ECM & TCM) are for the same 2010 Camaro.

As long as the APP is from a Camaro, and the connector is pinned for a Camaro, then you can rule out a mismatch in the Electronic Throttle Control system - as being the issue (or one of the issues).

99% sure it is. Looking at pics, it's definitely not a Corvette unit.

Any ideas on what to look at? I am freaking stumped.

[ProTouring442]

OK ... the calibrations (ECM & TCM) are for the same 2010 Camaro.

As long as the APP is from a Camaro, and the connector is pinned for a Camaro, then you can rule out a mismatch in the Electronic Throttle Control system - as being the issue (or one of the issues).

We have an aftermarket cruise control system installed. Could that be messing things up? How would I check?

You mention the "core" gets "confused," would disconnecting power reset that for a bit?

[kevin87turbot]

Check the switched 12V wire feeding the ECM, that's powered by your ignition switch. If it drops below the min voltage threshold during cranking, it'll certainly cause a no start condition.

[ProTouring442]

Check the switched 12V wire feeding the ECM, that's powered by your ignition switch. If it drops below the min voltage threshold during cranking, it'll certainly cause a no start condition.

Could it cause spark with no injector pulse? But I will give it a look-see.

[Shrek]

We have an aftermarket cruise control system installed. Could that be messing things up? How would I check?

You mention the "core" gets "confused," would disconnecting power reset that for a bit?

The second ECM core (write only) of the E38 or E67 ECM is the "watchdog" for the Electronic Throttle Control system.

It does not get "confused" - as it is not a living thing - and I never used the word "confused" in my post. Its purpose is to constantly check and crosscheck all of the components that make up the Electronic Throttle Control system.

If the aftermarket Cruise Control that you are using is an interceptor module - which connects inline between the APP (accelerator pedal) and the ECM - then Yes, this could cause issues - most often a dead pedal, but could cause a no start in some rare circumstances.

The best option for Cruise Control in a Gen 4 (58x) LS conversion is an E67 ECM - which has internal Cruise Control capabilities.

[ProTouring442]

The second ECM core (write only) of the E38 or E67 ECM is the "watchdog" for the Electronic Throttle Control system.

It does not get "confused" - as it is not a living thing - and I never used the word "confused" in my post. Its purpose is to constantly check and crosscheck all of the components that make up the Electronic Throttle Control system.

If the aftermarket Cruise Control that you are using is an interceptor module - which connects inline between the APP (accelerator pedal) and the ECM - then Yes, this could cause issues - most often a dead pedal, but could cause a no start in some rare circumstances.

The best option for Cruise Control in a Gen 4 (58x) LS conversion is an E67 ECM - which has internal Cruise Control capabilities.

Yes, I understand you never said confused. That was just my spin on things.

I did find a voltage drop issue, and have rectified that, so, fingers crossed.