Engine "stuttering" under full boost - see dm file

[E.Murray]

The truck was having boost control issues when I got it. No cat and Sportmachines billet impeller worked together to make sure the stock wastegate couldn't bypass enough exhaust, leading to overboosting and wavy control. I got the Forge Billet wastegate and did some port work on the wastegate side of the turbo. It pulls great under part throttle and light boost, but I can't get above 13-ish psi and there's a high frequency "stutter" I can feel when I put the boot in it. I'm hoping some more experienced eyes can pick up any oddness in the datamaster file. Yes, the injector DC is high, but I'm still a bit rich, so I'm not concerned about it. I know I can also crank the spark some, but I want to get the boost straightened out first. Where should I look?

 

[WyoSyclone]

Re: Engine "stuttering" under full boost - see dm file

You may be blowing out the spark (weak ignition). What type of plugs are you running and what kind of shape are they in, and what gap?

Probably pull the plugs and check them (may as well do a compression check while you're there).

I'd also use a multimeter and check resistance on each plug wire..... make sure you don't have a bad wire. Make sure the ends are in good shape and that they're not burned through anywhere.

It's a place to start. Next would be to check fuel pressure and change the fuel filter if that hasn't been done in a while.

 

[Eric Sy GN]

Re: Engine "stuttering" under full boost - see dm file

On that chip, the AFR from the wideband is being displayed in the AFR crank box, which showing 14.3. Not good there.
I agree with Wyo on checking the fuel pressure, especially under boost.
Eric

 

[Don W.]

Re: Engine "stuttering" under full boost - see dm file

Your AC was on, probably won't change things though. Block Learn (BLM) is not working at that point in the graph. You have a code in ECM. Click on the red and it will show you. Figure that out then clear and retest.

But like Rob said good chance it's ignition. Ohm test on the wires is not a good test because you're testing with 1.5 volts and ign is 50,000, or whatever. If the wires are old change them. They could ohm fine but short to ground somewhere under heavy load. Our motors put a lot of load on the ign. Check the plugs as mentioned also.

 

[Peter]

Re: Engine "stuttering" under full boost - see dm file

My vote is also for some sort of spark problem. First check the plug gaps. If any are >.030, reset to.030 or less and see if the stutter goes away. I set mine to .025 and let 'em grow from there. The engine could very well be dropping one or two cylinders due to plug gap being a bit wide on those cylinders.
I don't know about everyone else, but in the 190kpa range, I shoot for 11 to 12:1. I doubt if that is the problem, although too lean there will contribute to KR.

 

[68steiny]

Re: Engine "stuttering" under full boost - see dm file

Wow...I have almost the exact same setup and the exact same problem. 3" open exhaust and forge with blue spring. Part throttle the truck runs great...I put my foot in it and it stutters. I do however, get real rich real fast in boost and I thought that was the problem, but tuning with Code 59 didn't fix any of that.

I will also start going through the ignition stuff now.

 

[E.Murray]

Re: Engine "stuttering" under full boost - see dm file

OK, seems like ignition is the place to check. The wires are quality silicone 8mm with maybe a few hundred miles. They look like new and worked fine before the turbo work, so I wouldn't expect an issue, but I have a spare set. I'll see if that helps.
I just checked compression and was 148-151 across all cylinders. Plug gap is .032. I didn't change that (had set them a hundred miles or so ago). Is that wide?
One issue that I had forgotten about until you guys brought up this stuff: I think my crank pulley has slipped on the damper. When I was adjusting the valves, I just used the timing mark the first time to get things to TDC. I had clatter, though, so I pulled it back apart. This time I ignored the timing mark and watched valves move. Cylinder 1 was at compression TDC with the timing mark at about 6:30 with respect to where it should be... I used some white paint and marked the correct location. Once I put it together, I checked ignition timing and it appears to be a little off (a few degrees) compared to my white paint. I was debating whether to adjust it. The question is whether I trust that it was right before (P.O. said he verified it was 0 degrees) and my paint mark is off a bit. Or do I set it at the paint. I was putting that off for now and had shoved it to the back of my head. But if I have an ignition issue, maybe I need to re-visit. Could that be related? Or is weak/insufficient spark the most likely candidate?

 

[E.Murray]

Re: Engine "stuttering" under full boost - see dm file

Oh, forgot the other thing. I said it was rich based on the new AEM wideband O2 I added. It was showing 10.8-ish under full throttle on the gauge. If AFR crank is the actual AFR in Datamaster, though, I'm lean. I have the same WBO2 feeding both places (pin F14 to ECM for TurboTweak chip), so which is right?
Eric has suggested check fuel pressure before and I got a gauge with the parts truck I just bought. I hadn't had time to put it on, but maybe it's time to verify. I have the gauge, AFPR, Walbro and 50lb injectors and was going to do them all at the same time. My plan was to get everything running from one set of changes before throwing another at it, but the gauge is easy and useful either way.
My biggest obstacle to a great truck is that I have to have a full time job...

 

[dgoodhue]

Re: Engine "stuttering" under full boost - see dm file

The AFR is lean but it maybe is because of the misfire (the spark retard is 0.0)

I would go over the ignition as mentioned above. What brand and part number of spark plugs are you using?

 

[E.Murray]

Re: Engine "stuttering" under full boost - see dm file

So the AFR in the datamaster file is correct over the gauge? Now that I know the crank AFR is something interesting, I checked it. Does this look right?


Also, the plugs are NGK UR5. Thanks!

 

[dgoodhue]

Re: Engine "stuttering" under full boost - see dm file

Are you using 2 O2 sensor (stock and WBo2)? If so the stock o2 130mV is lean like the WBo2. Anyways, I am still not convinced the lean AFR is the root cause, I suspect its the misfire is causing the lean condition.

 

[E.Murray]

Re: Engine "stuttering" under full boost - see dm file

Just using the wideband O2 in a location about 6 inches further downstream from the stock. Stock narrow band is not hooked up.
Since I'm not getting any knock, you may be right on the misfire as the culprit. I'll give the ignition a good once-over tonight.
Is that wavy AFR crank normal?

 

[Don W.]

Re: Engine "stuttering" under full boost - see dm file

Yes, .032 is to wide. Reset as mentioned to .028. If the motor is unmolested stock why did you adjust the valves? TurboTweak chip? Based on the single reference point in each DM posted you're running way lean. Turn up both param 1 & 2. I'd go a little on 2 and quite a bit on 1. Eric can chime in here.

Can you link to the actual file?

I wouldn't trust your method of finding TDC for timing purposes. Use a piston stop. Even a small error can make a big difference. If the damper has slipped what's keeping from slipping more? Hard to trust that it doesn't slip every time the motor starts or some other time.

You still have a code, need to check that.

 

[E.Murray]

Re: Engine "stuttering" under full boost - see dm file

I'll reset the plug gap tonight with the rest of the checks. As far as the valves, I did the valve seals, so resetting adjustment was in order. I'll also crank up the fuel some. Since I was trusting the gauge (which showed rich), I didn't consider the fuel thing. I'll do it in two stages: first set plug gap and check ignition, leaving fuel alone, then (assuming it's still lean) making those adjustments in the TurboTweak.
I agree on the timing thing. That's why I just left it alone. I hadn't had indicators that the timing was out, so I didn't want to mess with it (if it ain't broke...).
I think the error code is leftover from when I started it without the brown wire (when checking timing), but I could be wrong. It's showing "MALF 42: EST Monitor Error".
I don't have a way to upload the actual file.

 

[Eric Sy GN]

Re: Engine "stuttering" under full boost - see dm file

Something is wrong with your wideband reading. I would go over the wiring again. Make sure you are using the correct output wire from your AEM, and that the correct output signal is selected. You are using the AEM gauge part# 30-4100?

 

[E.Murray]

Re: Engine "stuttering" under full boost - see dm file

I just grounded the wideband to the frame, but I saw that some people talked about grounding it at the ECM (pin B9 I think?). Is that acceptable? I'll trace it tonight.

 

[E.Murray]

Re: Engine "stuttering" under full boost - see dm file

Just had time to close up the plug gap to .028 and run before the rain hit. First, though, is the question of whether I should trust the gauge or the datamaster for AFR. During the runs I've made, the gauge has shown around 10.7 while the DM file shows oscillation (regardless of throttle position) between 14 and 17. When I pulled the plugs, they were all black like I had been running rich:

Based on this, I trust the gauge over the dm. Fair enough?
The latest run, with new UR6 plugs gapped to .028 is shown below. I also checked all wires (looked new - only have a few hundred miles on high quality wires) and verified all connections. Note that I had none of the stuttering this time. All the people that suggested looking at the ignition are friggin' geniuses. It ran great, although still felt slow. I suspect it's because my timing could stand some real advance. Note that my boost is up where I want with no adjustment to the actuator (except for the notable spike to 18 psi at the 1-2 upshift). What do you think?

If someone is willing to look at it, I'll try to find a place to upload the actual dm file in the morning. Thanks a million for the time to help me out. I am having a great time playing with this, and have learned more in the last month than in the previous 5 years of wrenching...:tup:

 

[Eric Sy GN]

Re: Engine "stuttering" under full boost - see dm file

Glad you're making headway.
Definitely get the wideband reading fixed up. You are using it to control fuel in the chip, so the chip is getting bad info, which could possibly damage something. I would start by moving the wideband ground to the ECM.

 

[Don W.]

Re: Engine "stuttering" under full boost - see dm file

That plug looks very close to perfect. What I would like to see or have you tell me is... If you look at the ground strap carefully you should see a point where it changes color. A super closeup photo would be nice nut regardless you want that color change to be about half way from the base to the end.

 

[E.Murray]

Re: Engine "stuttering" under full boost - see dm file

They didn't look too bad in the picture, but were notably more sooty and black than the times I'd pulled them previously. Considering that I've driven maybe 3 miles since last time I looked at them, it seemed to me like I had a potential fuel fouling issue. They definitely looked more rich than lean, though.
As far as the timing mark, here's a picture of the new one after my run last night.

As I said before, I could stand to advance timing a bit. The line is after the bend in the strap.
In my very limited datamaster experience, I see two things. First is the overboost at the 1-2 shift. Ideas on how to reduce that? Other than that blip, the boost is a hundred times more solid than before the wastegate and turbo port. The other thing is the knock retard bump at the 2-3 shift. Makes it harder to justify advancing timing... The run was pretty clean, but sloooow. 1/4 mile in datamaster was 15.8...
Eric, I'll re-check my wiring to the ECM and move the WBO2 ground to it before the next run and see what that gets us. The correct amount of fuel should go a long way.