Tom M'Guinn

Where are you? Maybe we can't point you to a mechanic who is more familiar with these cars....

Often times, when a car runs fine off boost, but stumbles under heavy throttle, it turns out to be a weak ignition. You are not describing a classic case of weak ignition though, and it's hard to know whether your FQS changes fixed an unrelated problem, or masked another symptom of the same problem. With a classic weak ignition, the stumble will normally occur shortly after the boost first hits (so lower then 5200), and it's rarely at the same rpm every time like you are describing. That said, it's still the first area I'd check.

Could be a million other things of course (fuel starvation, terrible AFR for some reason, rev limiter set wrong, bad dme/klr, etc., etc.), and it still would be useful to see a video showing the problem happening a couple of times. People familiar with these cars may notice clues you are missing.

fejjj

I am not sure what you will see on a video. I would be accelerating hard with my iPhone in 1 hand and you would see the tach hit 5200 and the sound is going to be the same sound as hitting the Rev limiter.

The ECU is brand new (Rogue) and it did it prior to installing.

Maybe I should change out the plug wires, cap and rotor?

raleighBahn

Fejjj, don't take the following the wrong way. If I didn't wish you well, I wouldn't care if you pour your money into a hole. Just making sure you don't read a negative tone in the following.

Tom is one of the real bright guys on here and is just asking for you to take a video. You are pushing back on the suggestions and instead asking which part is bad. Advice on the board is free. The quality of that advice is directly proportional to how much you're willing to do on your end. If it were me and Tom said take a video, I'd be taking that video and posting it before he lost interest. The video will not solve your problem, but it may cause someone to ask you to do a more specific task based on it. Imagine your car wouldn't start and someone asked you to send a video. Why would you video the tach if it won't start? Ah, but is there tach bounce? Now that tells us something. Accept the possibility someone may see something that isn't readily apparent.

You can replace your ignition wires, cap, and rotor, and maybe it will work. Maybe it won't and now you've got a new FPR, damper, plugs, water temp sensor, cap, rotors, and wires - but still a stumble at 5200 rpm. Throw in a TPS and new a DME, it's only money. You should instead buy a nice multi-meter, fuel pressure gauge, noid light, ignition tester, and etc for little money that will give your ROI well into the future. These are really simple, cheap, and quick tools to give you some idea of where your problem is or is not. This is not nearly an exhaustive list, but if you had them you for sure would not have replaced anything you've replaced yet.

I would recommend following the test plan in the Turbo Workshop Manual, like the set you have been posting for sale, starting on page 28-16 (Vol 6 Turbo Manual). You can check a whole bunch of things in that list with the multi-meter - almost anything that doesn't ask for an oscilloscope. Do the simple checks from that guide too - it is showing you where the important plugs are to make sure something didn't just fall loose and making you chase your tail.

Put together the blink code tester and see if you get lucky on the things it will pick up. Lindsey tells you how to build this and how to run the test.

In principle, a cut-out usually means one of the following is not there: air, fuel, or fire (what you need for combustion). That could be due to a basic reason (ie something that delivers one of those three elements has failed, like a fuel pump or ignition wire), or a complex one (the computer making decisions about how much fuel, air, and fire is making incorrect decisions).

Step 0: Post Tom's video

Step 1: Go to Turbo Manual Test plan, 28-17 (test point 1) and verify all of the plugs are plugged in. This costs nothing. Given you have M-Tune, you will not have the AFM plug. Check to the best of your ability, that grounds (including where ground strap ties into firewall) are clean and tight. You won't be able to reach the one on the back of the block.

Step 2: Get some of the basic tools above, or tell us what tools you do have, and the group can help you check some things around air, fuel, fire, and failing that, the DME and sensors it relies on to make good decisions.

Step 3: Build that free blink code tester and follow the instructions to see if you get a lucky hit on something.

JacRyann

You can watch the boost-gauge to determine if boost stays flat.

In your original post, you said AFR was in the 10s. You must have a gauge that you can watch when it stumbles.

I suggest you mount a camera over your shoulder and take a video as Tom recommends. This will allow us to examine your gauges and have more data to analyze than what you have given us.

fejjj

My son went for a ride with me tonight and he took 2 short videos for me.

Cut happens just before the 3 second mark.

fejjj

Tom M'Guinn

Well, the backfires suggest you have fuel that is not igniting in the motor but is instead burning in the exhaust. That doesn't necessarily mean your ignition is cutting out, but tends to point in that direction. If you just smoothly rev to redline with the boost gauge around 1 or less, does it rev nicely to redline without any issues whatsoever?

fejjj

If I rev it very slowly, it will go to redline.

I am thinking ignition as well.

I ordered a new cap and rotor just in case as they are an easy swap.

If I was getting a weak spark, would that also cause the car to be running rich (13.5) under cruise?

Tom M'Guinn

Not really, but when it misfires the AFR readings won't be accurate at all. Is your car running rich at cruise? I thought the only remaining issue was when it cut out at 5200? After it's al warmed up and idling at a stop light, what are the rpm's at idle and what does the wideband read?

Are you still planning to take it to a mechanic?

If the ignition is due for a refresh, you should pop in new plugs (they're cheap) and wires. Plugs can get fouled from all the cutting out, and wires are a common source of ignition problems (even when they "look" great, etc.).

fejjj

Warm idle is around 900RPM and AFR 14.2-14.8

Cruise AFR is around 13.5

Plugs were just replaced BPR7's gapped to .026

Wires less than 2 years old.

I am still planning on taking it to a mechanic.

My plan was to change out the cap and rotor and see if that solves it and if not, do the wires.

Auto_Werks 3.6

Which coolant temp sensor did you replace? I think there are actually 2 and oNE is more important to ecu function than the other.

fejjj

The front one with the Blue collar.

fejjj

Ok. My friend helped me make a Blink code tester and it did not pull up any codes.

Next step is to replace the Cap and rotor and if that doesn't solve it then we are going to follow the Test plan in the Turbo manual.

raleighBahn

Good deal. Just make sure you checked the codes after the drive, without turning the car off (no memory). when the tester is in and you don't see blinking, you can verify your test port works by pulling the TPS plug while the car is running (the tester will start blinking until you plug tps back in).

fejjj

Yes we followed the procedure listed on the LR site.

We also verified the voltage to the test port.

Changing the Cap and Rotor tomorrow and will report back.

Thanks again!