Rough running

[Hog]

Originally Posted by Billy Mild

Tonight I did a little more driving with my old school Snap-On MT2500. I set the lights for Closed Loop, Port Throttles closed, and Knock detection. For the the first time since this started I have a common thread, when the stumble occurs after decel, when the car is around 2000ish RPM and I give the car 30-40% throttle, the knock light goes ON, and the car stumbles, the secondaries appear to open as well. Very interesting IMO. So I believe it is due to a knock being detected, now I don't know if there really is a knock.

Unfortunately I don't have a stock chip anymore. Would it be worth test driving with a stock 91 chip to see if anything is different?

Mr Mild, you say you are getting some knock sensor activity when you open the throttles suddenly?
I wonder if you are getting some "Burst Knock"? Burst knock usually occurs during heavy throttle transitions. Some calibrations will pull ignition timing advance in these areas to avoid the real knock.
Could also be some lean knock with all the extra air rushing in with the sudden opening of the t-body throttles and Port throttles opening up quickly. In this case some extra Acceleration Enrichment could help?
Just some brainstorming on my part.

[XfireZ51]

Originally Posted by Billy Mild

Tonight I did a little more driving with my old school Snap-On MT2500. I set the lights for Closed Loop, Port Throttles closed, and Knock detection. For the the first time since this started I have a common thread, when the stumble occurs after decel, when the car is around 2000ish RPM and I give the car 30-40% throttle, the knock light goes ON, and the car stumbles, the secondaries appear to open as well. Very interesting IMO. So I believe it is due to a knock being detected, now I don't know if there really is a knock.

Unfortunately I don't have a stock chip anymore. Would it be worth test driving with a stock 91 chip to see if anything is different?

Port Throttle at 2000rpm open at ~ 34% TPS for stock cal.

There is a brief interval where secondaries do not come on to give time to the secondary throttle plate to fully open. If you are in decel w DFCO enabled, its going to take a bit to get fuel to the chambers when you get back on the pedal. Need to look at the knock counts to determine severity of the knock and its duration.

[Billy Mild]

Originally Posted by Hog

Mr Mild, you say you are getting some knock sensor activity when you open the throttles suddenly?
I wonder if you are getting some "Burst Knock"? Burst knock usually occurs during heavy throttle transitions. Some calibrations will pull ignition timing advance in these areas to avoid the real knock.
Could also be some lean knock with all the extra air rushing in with the sudden opening of the t-body throttles and Port throttles opening up quickly. In this case some extra Acceleration Enrichment could help?
Just some brainstorming on my part.

Never heard of burst knock until your post. This is an interesting thought.

Originally Posted by XfireZ51

Port Throttle at 2000rpm open at ~ 34% TPS for stock cal.

There is a brief interval where secondaries do not come on to give time to the secondary throttle plate to fully open. If you are in decel w DFCO enabled, its going to take a bit to get fuel to the chambers when you get back on the pedal. Need to look at the knock counts to determine severity of the knock and its duration.

DFCO is on with a stock tune correct?

Haibeck enabled his "Anti-Backfire" mode on my chip.

When I get my OBD1 Bluetooth adapter back I will be doing some more datalogging to hopefully get those knock counts you are talking about.

Another thought I had is maybe one of my coils was having issues that clears up once in a while. Is there anyway to test for a bad coil without pulling the plenum?

I have to say thank you in a advance for giving any kind of advice. I finally figured out how to use TunerProRT to review my datalogs which is really freaking cool.

[Billy Mild]

I noticed for a cold start that smoke pours out of the exhaust. It smells like the engine is running really rich when cold. Is this behavior normal?

https://youtu.be/xxOwdnuKfD8

https://youtu.be/Dj1_KrkSAYs

[Billy Mild]

I took old girl out for some driving today. I think I have figured out what causes the stumble. It appears to happen around 2000-2400 RPM. It occurs in decel with no throttle input, as soon as I start to open the throttle again it seems to almost stumble like its struggling to breath. When I open the throttle open further 30% or more the secondaries kick in and it cleans up.

Could it be the transition from closed to open secondaries? I am going to see if they are being requested but not opening.

[mhobtr]

Originally Posted by Billy Mild

I noticed for a cold start that smoke pours out of the exhaust. It smells like the engine is running really rich when cold. Is this behavior normal?

Mine smokes like that and then clears up but I don't get that black spray on the floor.

That spray looks like water condensation in the exhaust which blows out when you start it.

[jss06c6]

Billy,

Don't know what your outside temps are, but this steam is normal for cold start. It should go away when the engine warms up.

Sent from my XT1585 using ZR-1 Net Registry mobile app

[Billy Mild]

Tonight I finally got a SES light. Codes 55, and 64 popped up. After I had my scanner on I cleared them and 55 stayed. It appears that this might lead to a fuel pump issue. That would make sense.

How big of a job is replacing the fuel pumps on this car?

Similar issue:
http://zr1.net/forum/showthread.php?...acement&page=3

Where is the secondary port solenoid switch at?

[Billy Mild]

I replaced the fuel pumps last night and the car overall runs better. Smoother idle, feels like more power up top. The stumble still remains.

Conditions when it happens, decel from 3000+ RPM slow down to around the 2000-2200 RPM range and give it just a little throttle 10-20%. It will stumble. I noticed while on decel the left side INT drops drastically from 120-125 range to 64, while the right side stays around 120-125ish maybe 113. I notice the lower INT on the left side the worse the stumble is. If I got WOT the stumble stops right away, but I think that has to do with it is enriching the mixture immediately and ignores the sensors. This stumble happens with power key ON or OFF

So on the scanner I'm not sure what side of the engine is the left vs. right side. Could this be an exhaust leak, O2 sensor issue, or something else?

[XfireZ51]

You have headers and exhaust. In decel, you have high vacuum and basically with the increased breathing the exhaust provides, it could be necessary to richen up the AE pumpshot at lower TPS% changes.
Again, Billy it would be helpful to see what the % TPS change is at the time of the stumble, plus are the secondaries kicking in or is this happening w just the primaries.