Cold running motor

Hu Ryde

Hu Ryde

Donating Member
Here is the issue, I have a 160* thermo and the EGR system plugged in the lower intake and UR6, (1 step colder plug). So I virtually have no excessive heat in the motor, it runs fine, but is there a chance that the motor could be running too cold? Should I step back to a 170* thermo or even a 180*? My only issue is after driving and come to a stop light I have a hesitation when I begin to take off, like it's loading up, or leaning out. Could by any chance the top end of the motor be too cool or am I crazy? DM shows a drop of the o2mv levels to 0 then back up. Upon this back up climb on the 02mv is when it comes out of the hesitation. Motor has just had top end, heads ported, polished and all new gaskets, no vac leaks and new IAC, new wires, cap and rotor, everything is right, timing is 1* retarded. any ideas?
 
ed hess

ed hess

race or get outta the way
yep, I wll let you know after tommorrow if its your fuel pump. after i do mine in the morning. But when i changed injectors some of that hesitation went away.

ed
 
Hu Ryde

Hu Ryde

Donating Member
My injectors were just flow tested and cleaned so they are not the issue. Not sure about the pump though.
 
ed hess

ed hess

race or get outta the way
I wasnt trying to be funny or kidding when i told you i would let you know tommorrow. But i get that one to and their isnt much lef for me to do. Fixed ground problem today. goota write about it. post it tonite.
ed
 
J

just a 6

R.I.P MyClone
Re: Cold running motor

I have the exact same problem with my Sy, and i did the same mods that you did except i installed Speed Pro pistons and L35 rods and Iridium plugs at the same time. I tested 160, 180 and 195 t-stat no differens, but i discovered that if i raised the fuel pressure from 40 to 50 it went away for a couple of weeks, now i have the fp set at 60psi and it's very rare that it stumbles from a stop. I too have the injectors flow tested and i start to belive that maybe that company did not do a good job with that, i used the same company as you did. I notice on my DM logs that the O2 reading is kind of slow, i might have a lacy O2 sensor? I also notice it's more stumble with A/C on then off, the O2 reading is slower with A/C then w/o. Sitting on idle in gear there is a 5-7 second time between lean and rich reading on O2 sensor, i thought they were suppose to be faster respons then that? At least my old 91 Eclipse AWD had a faster reading between lean and rich, and they both use OBD-I pcm's (ECU). Keep me updated if you find the problem, ok?

I'm running Walbro 255 HP fuel pump, no differens compare to the old 190




Hu Ryde said:
Here is the issue, I have a 160* thermo and the EGR system plugged in the lower intake and UR6, (1 step colder plug). So I virtually have no excessive heat in the motor, it runs fine, but is there a chance that the motor could be running too cold? Should I step back to a 170* thermo or even a 180*? My only issue is after driving and come to a stop light I have a hesitation when I begin to take off, like it's loading up, or leaning out. Could by any chance the top end of the motor be too cool or am I crazy? DM shows a drop of the o2mv levels to 0 then back up. Upon this back up climb on the 02mv is when it comes out of the hesitation. Motor has just had top end, heads ported, polished and all new gaskets, no vac leaks and new IAC, new wires, cap and rotor, everything is right, timing is 1* retarded. any ideas?
Click to expand...
 
Hu Ryde

Hu Ryde

Donating Member
What thermo do you have? What about a DM of this stumble, do you have any? And while I'm at it how about a DM of the idle to compare with mine. Here is my DM of the problem:

Hold shift and click: http://www.huryde.com/images/stumble.uni

As you can see in frame #0 - 57 my tps is at 0%, me sitting at a stop sign. 02mv @ about 600 or so. At frame 58 I begin to take off from stop o2's ok for a couple of frames but then pow, they drop to 0mv, a complete lack of gass lean condition and this is where the stumble/hesitation is. This cycle is repeated several times though out the drive.

THe same happens arround frame # 980 when I do a light run to see if I get similar results. Does anybody see anything here that I'm missing or anything of that sort?
 
Hu Ryde

Hu Ryde

Donating Member
ed hess said:
I wasnt trying to be funny or kidding when i told you i would let you know tommorrow. But i get that one to and their isnt much lef for me to do. Fixed ground problem today. goota write about it. post it tonite.
ed
Click to expand...

Poor or faulty grounds may also cause funny acting truck.
 
J

just a 6

R.I.P MyClone
It looks like you have a bad O2 sensor, it looks like it's stuck on center. They are suppose to go from lean-center-rich-center-lean if you look at it with a scan tool. You O2 is mostly in the center part of the 0-1volt range, if all your O2 sensor connectors are ok i suggest you try with another O2 sensor, maybe you damage it when you rebuild your engine. If you got some antifreeze or cleaner or something in your downpipe, that is enogh to ruin a O2 sensor. If you think oyu got a bad ground, try to put a jumper cable between the down pipe and battery ground just to make sure your O2 is grounded.



Hu Ryde said:
What thermo do you have? What about a DM of this stumble, do you have any? And while I'm at it how about a DM of the idle to compare with mine. Here is my DM of the problem:

Hold shift and click: http://www.huryde.com/images/stumble.uni

As you can see in frame #0 - 57 my tps is at 0%, me sitting at a stop sign. 02mv @ about 600 or so. At frame 58 I begin to take off from stop o2's ok for a couple of frames but then pow, they drop to 0mv, a complete lack of gass lean condition and this is where the stumble/hesitation is. This cycle is repeated several times though out the drive.

THe same happens arround frame # 980 when I do a light run to see if I get similar results. Does anybody see anything here that I'm missing or anything of that sort?
Click to expand...
 
Hu Ryde

Hu Ryde

Donating Member
What all can a bad o2 indicate, will that through off all fuel settings and such? To my guess it would but I'm not sure. Probably. Do you think this could be the prob with the stall? Hopefully, I'll try a new one.
 
J

just a 6

R.I.P MyClone
You got mail, do you have any WOT logs from a really hot day after you did your rebuild, i'm curious about your IAT on a hot day and WOT. I have about 120 degree going down the highway here in Texas when it's about 95 outside, when i stop and then take off in a WOT the IAT climbs rapetly up to 148 degree. I like to see your DM log on a WOT on a hot day, you got any? I think i have a bad heat exchanger?



Hu Ryde said:
What thermo do you have? What about a DM of this stumble, do you have any? And while I'm at it how about a DM of the idle to compare with mine. Here is my DM of the problem:

Hold shift and click: http://www.huryde.com/images/stumble.uni

As you can see in frame #0 - 57 my tps is at 0%, me sitting at a stop sign. 02mv @ about 600 or so. At frame 58 I begin to take off from stop o2's ok for a couple of frames but then pow, they drop to 0mv, a complete lack of gass lean condition and this is where the stumble/hesitation is. This cycle is repeated several times though out the drive.

THe same happens arround frame # 980 when I do a light run to see if I get similar results. Does anybody see anything here that I'm missing or anything of that sort?
Click to expand...
 
Hu Ryde

Hu Ryde

Donating Member
Unfortunately I do not, all the summer time was spent rebuilding the top end, I know that my upper intake never gets hot to the touch anymore like it did before. I'll dig arround and see what i have that is with the new top end. I'll get back to ya. Thanks for the e-mail, good stuff, going through your files now. Thanks again.
 
Hu Ryde

Hu Ryde

Donating Member
Nice, here goes $130 out the window...... whosh, it's gone!!! ? Thanks again, hopefully this might clear something up eh?
 
Falco

Falco

Donating Member
Guys,

Sorry to rumble in, but are you sure you don't have a vacuum leak around your FP regulator. My hesitation, stumble was caused by a vacuum leak directly at the regulator.

Peace,
 
ParTyBoy

ParTyBoy

New member
Hu Ryde said:
Actually only $72.73 shipped through GM parts direct. Not too bad but still.
Click to expand...

Jesse... stock AC Delco 02 sensor is just a Bosch sensor with a AC Delco number added on for cross refferencing... Just go to autozone and get Bosch part number 13077.. List price is $58.99 .. couple years back they were $45... :-?

13077.jpg
 
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