Carpokes Porsche Forum

Two weeks ago I was playing with a guy on a motorcycle on a tight twisty road in the country. I was right on his tail until we hit a straight away. He nailed it and I nailed and I passed him. About 1 mile down the road my ignition cut.

I had this happen a couple of years ago and it was caused by the stock coil. I replaced it with a MSD Blaster and the problem went away.

This time I recognized what had happened so just coasted down a long hill for a few minutes and then it started up and I continued. My AFR after re starting was high 11’s at idle and very light throttle and low 11’s under light boost. I was driving to our lake house so when I arrived, I shut it off. I waited 20 minutes, restarted and my AFR’s were back to normal.

Yesterday I was coming back from the lake and after a hard boost run about 40 minutes into my trip, I looked at my AFR while cruising off boost and it was back in the high 11’s again. I did boost it just to see what the AFR would do and it did NOT go below 11.2. I did not have an ignition cut this time but did have the rich AFR cruising and part throttle.

Any help would be greatly appreciated.

How do you know it was your ignition and not, for example, your DME relay, injector harness, speed & ref sensors, ignition switch, etc.? Did you happen to notice what your boost gauge read when the car was coasting? The boost gauge is a great way to see if your DME/KLR is getting power or not.

What is your AFR normally when you are on full boost?

It's probably something simple (TPS?), but your story makes me wonder about solder joints inside the KLR (or DME). @Crazy Eddie had a cracked solder joint in his KLR that would trigger the WOT signal intermittently. His car would idle perfectly for a couple days, then randomly get all lumpy and run super rich. After lots of testing and parts, we found cracked solder joints in the KLR. We soldered those up (for free, which he loved) and it's been fine for years now. If your KLR has cracked solder joints, it could be doing that AND interrupting the ignition signal from time to time.... I'd rule out the more obvious stuff first, but something to keep in mind....

I don’t know for sure that it was my ignition but whenever I have had a boost cut, I don’t lose ignition. The care just goes into limp mode for a few seconds. My car lost all ignition and all gauges looked the same as when the car is not running.

The ignition cut under full boost.

My AFR under full boost is normally 11.2.

I have a Rogue Tuning/ftech DME but the stock KLR.

Tom wrote: Mon Oct 11, 2021 6:36 pm How do you know it was your ignition and not, for example, your DME relay, injector harness, speed & ref sensors, ignition switch, etc.? Did you happen to notice what your boost gauge read when the car was coasting? The boost gauge is a great way to see if your DME/KLR is getting power or not.

What is your AFR normally when you are on full boost?

It's probably something simple (TPS?), but your story makes me wonder about solder joints inside the KLR (or DME). @Crazy Eddie had a cracked solder joint in his KLR that would trigger the WOT signal intermittently. His car would idle perfectly for a couple days, then randomly get all lumpy and run super rich. After lots of testing and parts, we found cracked solder joints in the KLR. We soldered those up (for free, which he loved) and it's been fine for years now. If your KLR has cracked solder joints, it could be doing that AND interrupting the ignition signal from time to time.... I'd rule out the more obvious stuff first, but something to keep in mind....

Lol
The only way I was able to get a hint as to what it was even after all the testing , was I had removed the passenger seat and had the DME and KLR boxes out on the floor … I noticed when I moved the box the problem would correct itself for a few mins …
Yes free is always a winner
Thanks Tom

Fejjj951 wrote: Mon Oct 11, 2021 7:03 pm I don’t know for sure that it was my ignition but whenever I have had a boost cut, I don’t lose ignition. The care just goes into limp mode for a few seconds. My car lost all ignition and all gauges looked the same as when the car is not running.

The ignition cut under full boost.

My AFR under full boost is normally 11.2.

I have a Rogue Tuning/ftech DME but the stock KLR.

Did you get a big backfire? I had an intermittent ignition cut-out issue, and it would always make a huge backfire when it would cut-out under boost. Keep in mind, there are several things that can kill the motor -- speed/ref sensors, injector harness, key switch, dme relay, etc., etc.

But.... if your car is normally at 11.2 at WOT and is randomly running at 11.2 when not on WOT, then it might be worth looking at the KLR. Do you have a spare to try and/or are you familiar with the look of cracked solder joints?

Do you have any onboard logging where you might get some clues?

No backfire.

LR injector harness, LR speed and reference harness, Ftech SS DME relay.

I have been having long cranking on cold starts which I know can be bad fuel pump check valve or leaky injector. I still have the original fuel pump and fuel filter so was going to change out the pump and filter tomorrow.

Can a leaky injector also cause an ignition cut?

I don’t have a spare KLR and not familiar with the look of cracked solder joints.

I do have the Rogue logger but have to hook up to computer to log.

Original fuel filter??? Probably not related, but ya gotta change that.

Leaky injectors would not kill the ignition. But a frayed wire inside any one of the injector connectors will shut down all 4 injectors and shut down the motor just like losing ignition. The rich thing is a clue though -- and could be unrelated. How are your grounds? I'm happy to look at your KLR if you don't mind the car being off the road a while.... Might be worth hooking up that logger in case the TPS or MAF or something else is sending bad signals....

Fejjj951 wrote: Mon Oct 11, 2021 7:03 pm I don’t know for sure that it was my ignition but whenever I have had a boost cut, I don’t lose ignition. The care just goes into limp mode for a few seconds. My car lost all ignition and all gauges looked the same as when the car is not running.

The ignition cut under full boost.

My AFR under full boost is normally 11.2.

I have a Rogue Tuning/ftech DME but the stock KLR.

Do you have a Rogue Tuning chip, or just the Rogue Tuning DME with the stock chip? I wonder if you're hitting the DME overboost feature. That wouldn't explain the rich AFRs but it's possible you have multiple things going on. But I don't know if the Rogue chip still has the DME overboost protection.

Tom's advice about the KLR is great, but before you go checking the solder joints, here's how you can check if it is actually going into wide-open-throttle mode when it shouldn't: look at Section 9 (page 20) in the DME/KLR Test Plan[1].

Check the voltage between terminals B and C on the test socket (there's a pinout near the start of the document). If it shows 0v when you're seeing an AFR of 11 at idle, it means you're in WOT mode, and there's a problem with either the TPS, the TPS harness, or the KLR. This wouldn't explain the hard engine cut, but it's worth checking anyway. As Tom said if there are bad solder joints, then the KLR could easily cause both issues, since the ignition signal has to go through the KLR before going to the coil.

[1] https://jhnbyrn.github.io/951-KLR-PAGES ... t_Plan.pdf

I have full Mtune and not hitting over boost protection as boost is set to 17psi and boost gauge shows 17psi at WOT. Over boost protection is set to 22 PSI for E85 which is what I run.

That is a great suggestion regarding the test port and will try that next time it does this. Keep in mind that I only had the ignition cut the first time followed by the rich condition. The 2nd time I only had the rich condition.

Tom’s offer to send my KLR is a generous 1 and I will likely take him up on that. I am in the northeast and the car will be going into hibernation for the winter in a few weeks so I would pull the KLR then. Thank you Tom!

Tom,

Grounds were all cleaned about 2 years ago but definitely worth double checking!