Avast, thar be waves on the high seas ye landlubbers!

Anyone know what the hell is going on here? This is very annoying to try to drive at cruise.

 

Cant say i've ever seen anything like this.

 

Me either..

It's worth mentioning that this only happens in cruise. As soon as I increase or decrease the amount of throttle, everything smoothes out.

 

That looks weird. Does it run weird to boot?

 

It runs weird only when this happens. It doesn't always do it, but when it does it's always on the highway when I'm trying to hold a constant speed. I see the wideband display start to wag wildly between lean and rich like a narrowband gauge at idle.

 

Have you thought about the idle valve settings? Just something to check.
I have been playing with my idle settings and the MAP sometimes looks like this when I **** it up, only at idle though not at cruise.

 

I actually just took out my idle valve on Saturday, but it was doing this before I did that.

 

where's your boost source hooked up? your MAPdot starts going crazy.....

 

Given the limited info we have, I'm with Brainey here. Seems like the MAP sensor is either being fed from a point in the system where manifold pressure is unstable, or it's being fed with a line that is so large in diameter and so short in length that it's picking up discrete pulses as intake valves open and close.


I was about to see that this almost looks like an electrical issue, as AFR seems to be tracking PW a little too perfectly for my taste, but I can see that CLT and TPS are both perfectly clean, which kinda rules that out.

 

I'll double check the MAP source today and get back to you, right now all I remember is it's hooked up wherever Ben and/or M2CC thought was a good idea.

 

resonance! maybe you have a vibration causing your map signal line to shake and do that?

 

A vibration like the MMR diff mounts I installed a few weeks ago? That would certainly explain how it begins softly and begins to feed on itself, like feedback. Hmm... maybe I should try zip-tying the line to other things to stabilize it on its way to the firewall. If it's not effective.. at least it's (nearly) free!

Joe, Brain: The MAP source is the 90* fitting coming off of the plenum just in front of the FPR.

 

I always connect to the nipple on the #4 runner that is capped off.

 

Did you check the hose diameter feeding the MAP? That waveform looks like the MAP is reading pulses, which you don't want in this application.

I would either find a smaller diameter hose or find an orifice to install. A quick and easy way is to get a tie-wrap around the hose and pinch it down. Not too much, you still want a signal.

 

I'm thinking more and more that the location of the MAP source isn't likely the culprit, if for no other reason than because it's been this way ever since I got 'squirted and this issue is brand new.

 

I am not referring to the source of the feed but the diameter of the hose to the MAP sensor.

 

Yeah, we were typing at the same time.

I'll try choking it down if holding it still doesn't work, but like the location, the line has been there from the beginning and this is a new occurrence.

 

do a search on this same thing....move it to the back of the manifold, the port neo suggests is perfect. or teeing of the fpr.

 

I looked at the #4 runner and didn't see anything. Is it on the underside or something?

So, I just got back from a datalogging run, tried zip tying the line every 6" on its way to the firewall, and then cinched down as much as I could on the line, neither worked.

Tomorrow I'll try going to a smaller line and see how that does, if that doesn't work, then I'll try shuffling the locations. Really appreciate your help guys, thank you!

 

I had a similar problem a while back. Out of the blue I was getting noise like that. I had it hooked up to the unused nipple on the #4 runner. Matt suggested teeing it into the frp line. After that it was perfect.
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