Still Trying.. (One Last Shot pt2)

[blackty]

Re: Still Trying.. (One Last Shot pt2)

Matt, Did you ever try modding your ecm to use both banks for the injectors? Is it possible that you are trying to get more out of the ecm that one bank can handle? Does this make any sense to the smart people? Just brainstorming...Jim

 

[BoostedSUV]

Re: Still Trying.. (One Last Shot pt2)

Matt, Did you ever try modding your ecm to use both banks for the injectors? Is it possible that you are trying to get more out of the ecm that one bank can handle? Does this make any sense to the smart people? Just brainstorming...Jim

Jim that's an excellent though however when I re harnessed the truck a month or so ago I made the change on the harness to utilize both banks for the injectors. I thought the same thing and tried it but no dice....

 

[djwaggoner]

Re: Still Trying.. (One Last Shot pt2)

Batt ground to frame yet?
Ground-weirdness does strange things...

 

[WyoSyclone]

Re: Still Trying.. (One Last Shot pt2)

Hmmm, on your first post Matt you say the problem only happens:
1. When it warms up - OK when cold.
2. Only does it when cruising - not while under boost or WOT.

These two conditions would indicate it only does it when in closed loop...when it goes to closed loop (warmed up, or not WOT/boost) it's relying on a sensor. It's OK in open.

You say that when it's cold it idles fine, but when it's warm it idles OK but the O2 and WBO2 readings bounce all over the place. How badly are they bouncing?? The PLX gauge gets its info directly from the O2 sensor. I assume you've got the PLX wired into the ECM and that the ECM is using the signals from the PLX box... see where I'm going here?

Maybe a bad PLX control box? Could you list exactly how and where you have each wire of the PLX connected?

EDIT: Especially, where is the power supply ground for the PLX box grounded at?

 

[BoostedSUV]

Re: Still Trying.. (One Last Shot pt2)

Hmmm, on your first post Matt you say the problem only happens:
1. When it warms up - OK when cold.
2. Only does it when cruising - not while under boost or WOT.

These two conditions would indicate it only does it when in open loop...when it goes to closed loop (warmed up, or not WOT/boost) it's relying on a sensor.

You say that when it's cold it idles fine, but when it's warm it idles OK but the O2 and WBO2 readings bounce all over the place. How badly are they bouncing?? The PLX gauge gets its info directly from the O2 sensor. I assume you've got the PLX wired into the ECM and that the ECM is using the signals from the PLX box... see where I'm going here?

Maybe a bad PLX control box? Could you list exactly how and where you have each wire of the PLX connected?

EDIT: Especially, where is the power supply ground for the PLX box grounded at?

I see where you're going with this but the PLX is wired as an independent unit. It is ONLY wired to the ecm for datalogging reasons. I still have the factory O2 in place. The WBO2 has only been in the truck a few months and I added it in as a "second opinion" to verify what the O2 was doing. I also ran the truck with the O2 unplugged which forces the truck to run in 'open loop' and that made no difference. I also burned a chip that displays O2 counts but leaves it in 'open loop'.

The problem is engine temp related and not closed vs open loop related as near as I can figure with the tests I have done. At idle once the truck warms up it will idle at 14.5-15 on the wbo2 display then creep to like 16.5 and "miss" a little then bounce back to normal. Engine temp definitely effects the problem the most.

 

[WyoSyclone]

Re: Still Trying.. (One Last Shot pt2)

I see where you're going with this but the PLX is wired as an independent unit. It is ONLY wired to the ecm for datalogging reasons. I still have the factory O2 in place. The WBO2 has only been in the truck a few months and I added it in as a "second opinion" to verify what the O2 was doing. I also ran the truck with the O2 unplugged which forces the truck to run in 'open loop' and that made no difference. I also burned a chip that displays O2 counts but leaves it in 'open loop'.

The problem is engine temp related and not closed vs open loop related as near as I can figure with the tests I have done. At idle once the truck warms up it will idle at 14.5-15 on the wbo2 display then creep to like 16.5 and "miss" a little then bounce back to normal. Engine temp definitely effects the problem the most.

I'm confused... if the PLX is wired into the ECM (B9 and E14), isn't the ECM using the signal from the PLX? If you're using both I assume you have two bungs welded into your downpipe. Why would you not be using the wideband since you are running 3-Bar?

Can you disconnect the power from the PLX just as a test... Even if you burned a chip for open loop there may be some kind of crosstalk going on between the PLX and the narrowband O2.

Alternately, you could use the narrowband output of the PLX and eliminate the second O2 sensor.....

....just some thoughts.. HTH

 

[Aeroking]

Re: Still Trying.. (One Last Shot pt2)

the wideband "controls" nothing in the tune correct? its just a tuning reference?

The ECM doesnt monitor the O2 sensor until closed loop, then running an open loop tune eliminates the o2 sensor from the list of potential problems.

 

[WyoSyclone]

Re: Still Trying.. (One Last Shot pt2)

running an open loop tune eliminates the o2 sensor from the list of potential problems.

One would think that would be the case, but if there was a wiring problem in the connection of the PLX, or interference coming in on those lines it could affect the ECM even though the BIN isn't using the reference.

But, I think Matt said this problem existed before the PLX install....so.......


We're still seeing what looks like an issue that only appears during closed loop, possibly via a sensor/sensor wiring. The O2 fluctuating at idle when the car is warm is another clue. I would let the truck sit there idling with the O2 bouncing around and start disconnecting every sensor, one at a time and see if one could be isolated as the cause. I'd do the same with every vacuum connection/branch.

 

[SloGN]

Re: Still Trying.. (One Last Shot pt2)

ok guys

If it's temp related maybe it's possible that there is a coolant sensor going bad? What does the air temp sensor show?


Also could be having a leak in then EGR passage way when the intake get hot it could be making the leak worse. Is the EGR passage way plugged on the lower half of the intake or do you just have a plate over the egr port on the upper half. the gasket could be leaking around the metal crush ring on the gasket. What is your low throttle kpa readings like? do they seem to be in the 50-60kpa range or higher/ lower .


Also when the lean issues start what is the block learn #'s doing they should be pegging @ 160 indicating a lean condition. well that would be long term fuel in the 749 ecm.



Does the tps seem to remain constant during the break=up events?


At this point i would put the entire truck back to stock and start there to rule out any of the mods.

 

[turboj91]

Re: Still Trying.. (One Last Shot pt2)

This problem goes way back. So many things have been changed without results and things keep getting revisited. I know there is a TON on info in two long threads but.. I am going back to the beginning and please Matt correct me if I am wrong.
Stock engine rebuilt and installed (was an actual 2nd rebuild), battery moved to the left side, engine compartment cleaned and painted, and Bam, problem appears. Problem is hidden with some tuning but is never completely gone. Heads changed to Vortec's and intake changed as well. Problem still there. I think something happened at the time of the #2 rebuilt engine install. If only I knew what it was???????

The "hidden" problem reared its ugly head again (became more prominent) when the wideband was installed.

We have had many suggestions from many different point of views. Some have made sense and some have not. There is an abnormal amount of info in the two threads and I don't expect anyone to absorb it all but maybe if we think back in time to what may have happened at the time of the engine install.

I certaintly have not figured this one out. Had some theories but none of them have played out. Only my injector theory made a change in the running but it was only a change and not a cure for the problem.

I am stumped for now until I know what the tail pipe says. Matt, if possible when you go for your emissions test, see how indepth the guy can get beyond the standard State test. The more info you pick up the better (for all of us). If only I could get Dr. Brown's car and go back in time to the day of install of #2.

 

[djwaggoner]

Re: Still Trying.. (One Last Shot pt2)

Problems started when the batt was moved.
Ground that sucker to the FRAME w/ a 2ga wire & Healthy bolt, so you have that variable covered.

 

[WyoSyclone]

Re: Still Trying.. (One Last Shot pt2)

This problem goes way back. I think something happened at the time of the #2 rebuilt engine install. If only I knew what it was???????

Do you remember a wire harness getting pinched or stretched or cut?? That would be the worst cuz it would be hard to find..... putting the battery back to it's stock location, temporarily, would be easy.

 

[turboj91]

Re: Still Trying.. (One Last Shot pt2)

Do you remember a wire harness getting pinched or stretched or cut??

I have had this thought on my mind from the beginning. I would assume that if Matt had known something was stretched, cut or pinched me would have taken care of it. I think something happened that he is unaware of. He replaced a harness but I think it was the injector harness not the underhood harness. Someone have a spare they can send his way?

 

[yar]

Re: Still Trying.. (One Last Shot pt2)

Do you remember a wire harness getting pinched or stretched or cut??

I have had this thought on my mind from the beginning. I would assume that if Matt had known something was stretched, cut or pinched me would have taken care of it. I think something happened that he is unaware of. He replaced a harness but I think it was the injector harness not the underhood harness. Someone have a spare they can send his way?

I sell new GM underhood engine harness' $350 + $25 shipping
Ray

 

[BoostedSUV]

Re: Still Trying.. (One Last Shot pt2)

Pat the EGR is blocked off with a plate but I never plugged the ports on the lower intake. I did have it off and replaced the gasket but I didn't see any leaking.

Jim you are right on the money with what started the problem. Only other things done when it started was I added a boost gauge and an A/F gauge wich I recently replaced with a WBO2.

DJwaggoner I will try to add a ground from the battery to the chassis. Can't hurt anything.. I did at a ground from the engine to the chassis but I will move it.

Rob, I replaced the engine bay harness so would eliminate a pinched wire from the install and removal. The battery is wired up exactly the same as it was in the stock location, I just moved it because the RPM a2a required it. It would make more sense that I pinched a fuel line baceause I know I had trouble getting the motor into place because of the fuel lines against the firewall. Pressure is good even under boost so I don't think it's volume related.

 

[MikeRenz]

Re: Still Trying.. (One Last Shot pt2)

Pat the EGR is blocked off with a plate but I never plugged the ports on the lower intake. I did have it off and replaced the gasket but I didn't see any leaking.

if you have vortec heads then the egr is useless becuase those heads don't have provisions for them. Most people weld the thin egr port of the lower intake shut whenever they weld the intake to mate up to the heads.

 

[qbnkiller]

Re: Still Trying.. (One Last Shot pt2)

what plugs are you using?

 

[BoostedSUV]

Re: Still Trying.. (One Last Shot pt2)

if you have vortec heads then the egr is useless becuase those heads don't have provisions for them. Most people weld the thin egr port of the lower intake shut whenever they weld the intake to mate up to the heads.

Waller did the heads and lower intake for me so he may have sealed the head side of the lower intake. Its been a while and I don't remember looking. I haven't had the lower intake off since I put the motor together.

what plugs are you using?

NGK TR7IX's (tried gap at .022, .025, .035) and I tried a set of TR55's (gapped at .028). I also tried a set of autolite 103's a while back but I don't remember what gap...

 

[qbnkiller]

Re: Still Trying.. (One Last Shot pt2)

OK...do me a favor...take a brand new clean plug (virgin). Put it in #1 cylinder. Warm the truck up and try and hold it at the particular point it is missing/spitting. Keep it there for a couple seconds, and shut the truck off immediately - dont coast down or anything - OFF. Pull that plug out, put in another one and get back home.

Cut the plug open and take a very good hi-res pic of it and post it here. I would be very interested in seeing the color of the plug, timing on the strap, and fuel ring in it.

 

[BoostedSUV]

Re: Still Trying.. (One Last Shot pt2)

Quick update... I'm taking my motor out of the truck this week and swapping it into another TY. When swapping everything else fails, swap trucks! :tup: