Stumble during start

On a 2006 BRM I've done a bunch of work on, the engine stumbles and shakes for a split second during start but runs and idles nice and smooth. Is this a common cam wear symptom? The chamfer is gone on a few of the lobes when I inspected it. Original cam at 102k miles.

Bump.

Weak battery.

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It has a new battery.

A new OEM battery or Napa/Duralast/Motorcraft? In my experience the difference couldn't be greater. My "diesel spec" Napa battery started smoothly for a few weeks before the car started to shudder and buck harshly for that split second before it started. Long story short, it lasted less than 3 years. I didn't even bother with the pro-rated replacement and went OEM from the dealer and wondered why I hadn't done it sooner. Smooth, quick, powerful starts every time and that's with a 300 RMS sub in the trunk. IMO alternator/starter/battery are things that need to be OEM for factory performance. Of course there's no sense replacing a new battery that does the job, but getting one from the dealer should be considered when the time comes. It's money well spent. I would also say the EGR or wiring harness should be looked at, but you say it runs fine otherwise.

For reference my cam has some wear on the #1 exhaust lobe, torsion @ -0.5, no EGR.

It's an Interstate battery. It looks much different than most Interstate batteries. I can't remember the model number but it seems to crank the engine over good.

It does have an EGR code and I plan to replace the EGR valve when the owner is up for it. But yes, it runs good otherwise.

Could be the starter. I had intermittent hot start problem. Brought the starter in to be tested....and it tested fine. Replaced a couple of different parts only to come back to the starter. It was the starter all along. Replaced with same Bosch original from Idparts....problem solved. These cars require a certain cranking speed or RPM to properly fire...
BTW - I have the Interstate 730 CCA (Cold Cranking Amps) Part # MTP-48/H6....and it works perfect. Interstate makes a great battery.

His starter is most likely ok. Notice he says it starts right up, but there's a quick stumble before catching. No problem starting overall. I experienced the same symptoms and also thought the starter was the issue. So I pulled it, disassembled it, cleaned the commutator, greased the bushings etc. It was fine and a new OE replacement battery fixed the issue; for a while at least. Now it's completely smooth with OEM.

This car is now experiencing a no-power condition and it barely idles. It was fine when parked and now is acting up. I only had a couple of minutes to look at it yesterday. He will barely idle and hardly changes RPM when the go-pedal is pushed. It smokes quite a bit and is stumbling. It will idle for nearly a minute then stumbles and dies. My first thought was the cam as it shoed wear when I inspected the car several years ago when it as purchased. I also thought maybe the turbo VNT actuator was bad or the vanes were froze up. I ran a turbo boost test and watched the rod cycle perfectly. I also removed the intake hose from the air cleaner and it sounds very smooth without any popping. The cam is on the agenda in the future but I don't think it's causing this problem now.

It has two codes that set constantly:

2 Faults Found:
000257 - Mass Air Flow Sensor (G70)
P0101 - 000 - Implausible Signal
Freeze Frame:
Fault Status: 01110000
Fault Priority: 0
Fault Frequency: 3
Reset counter: 255
Mileage: 196916 km
Time Indication: 0
Date: 2000.00.00
Time: 17:18:01
Freeze Frame:
RPM: 1533 /min
Speed: 60.0 km/h
Temperature: 47.7°C
Absolute Pres.: 1071.0 mbar
Mass Flow: 17.07 g/s
(no units): 2.59
Temperature: 87.3°C
000305 - Oxygen (Lambda) Sensor B1 S1
P0131 - 000 - Signal too Low - Intermittent
Freeze Frame:
Fault Status: 00100000
Fault Priority: 0
Fault Frequency: 4
Reset counter: 255
Mileage: 197130 km
Time Indication: 0
Date: 2000.00.00
Time: 16:32:39
Freeze Frame:
RPM: 1008 /min
Speed: 5.0 km/h
Load: 84.7 %
Mass Air / Rev.: 185.0 mg/str
(no units): 0.20
(no units): 0.0
Bin. Bits: 10001001


The weird thing was that the boost pressure didn't change at all during the VNT test. That as really odd to me. It was sitting at 28 psi constantly. It was almost acting like a plugged exhaust but I don't think that is the case as smoke flows pretty freely out of the exits. The torsion value is at 0.0 so the computer may think it's out of range. I replaced the timing belt myself a couple of years ago so I doubt there is an issue there although I plan to check the timing with the proper tools when I get the car to my house.

At this point it almost seems like an engine wiring harness issue. I'll be inspecting that as well.

Do you guy's have any other thoughts?

Bump.

The problem with this car was the EGR valve. It was not closing all the way and choking the engine out. Sorry for the late follow-up. I just noticed this thread.

So did you ever change the cam out?

I should say that the EGR valve fixed the poor running condition. Thebatumble at start was there until the car ended up getting wrecked. It was probably the starter or something.

I did change the cam. But only because the lives were boogered up a bit. The lifters weren’t fished out or anything yet. I feel it ran slightly better with the new cam.

The fix for this problem that I ended up having again with my personal BRM is the starter. A new Bosch SR0496X fixed all starting issues. Sorry to bring up the old post but I wanted to post the solution to a past issue for those that actually use the search function.