10:1 AFR's, stumbling, help!

[SevenMKIII]

I've been reading threads for days, no one seems to have the same problems as what I have.

First and foremost, I just finished a rebuild and some key parts I'm using that may help diagnose my problem are:
Denso 550s
HKS VPC/GCC
EGR! CC! VSVs!
Stock fuel pump and FPR, there is vacuum to the line
AEM UEGO
HKS MHG
ARP head studs

I've checked for boost and vacuum leaks, couldn't find any at all
Pretty sure all of the grounds are connected

Only code is the coolant temp sensor, which is a broken wire I haven't gotten to yet. NO other codes at all.

I'll start the car up, it runs okay (good AFRs, around 14.5-15) for about 15 seconds and then it slowly richens itself to 10.0:1 and just stops there. You can smell the gas and see a bit of smoke. When I blip the gas the AFRs lean out to a more reasonable level around 13-14. Also, the throttle response is horrible, I'll tap the throttle and you hear a swoosh-BOG-rev?

I'm running out of ideas! It all seems to lead to a vacuum leak (leak=bad throttle response and running pig rich) but I cannot find the problem for the life of me!

Checked timing, right at 10*, everything was triplechecked during the rebuild, there can't be something simple I overlooked.

Only thing I can think of that I may have done incorrectly was the vacuum manifold. I ran a larger vacuum hose off of the throttle body nipple (large one that runs to the brake booster) and installed that on one side of the manifold, my 6 hoses going to misc. things, and the other side of the manifold is plugged into where the factory brake booster line goes.

ANY help, I want to get this running ASAP I've been without a car for literally 6 months...it sucks.

-Chris

P.S. If someone with Supra experience lives around central IL I would be more than happy to pay for your gas or lunch or something if you come check it out and help me fix my car!

 

[steven89]

check to see if your cam teeth are off by a tooth or so, mine were during the HG change and it cause the car to run horribly...

I'll tap the throttle and you hear a swoosh-BOG-rev?

sounds just like mine was when mine were off..

 

[SLO-MK3]

Only code is the coolant temp sensor, which is a broken wire I haven't gotten to yet. NO other codes at all.




I'm running out of ideas! It all seems to lead to a vacuum leak (leak=bad throttle response and running pig rich) but I cannot find the problem for the life of me!

Try fixing your coolant temp problem. With that not working correctly, the ecu wont operate in closed loop, and will switch to deault rich mode to protect the engine, which is more than likely your problem.




A vacuum leak would cause a lean condition becase you're pulling in more air than the afm is measuring.

 

[antman]

What he said..

 

[SevenMKIII]

Originally Posted by SLO-MK3
Try fixing your coolant temp problem. With that not working correctly, the ecu wont operate in closed loop, and will switch to deault rich mode to protect the engine, which is more than likely your problem.

I had no idea that /\ would effect it at all! I just thought the stock coolant gauge wouldn't operate. I'll try fixing that soon, the wires are broken off in the sensor though. Anyone have the plug they could cut off their harness? lol

I'm 100% sure the timing is correct. When I was rebuilding it I checked it to the tenth power, rotated the crank a few times while checking to make sure it all lined up perfect, which it still does. And I adjusted the timing the other night before posting this so I know that is still at 10* too.

I'll see what I can do about the sensor and try to fire her up again. Thanks! Keep the advice rolling if you can think of anything else I'm forgetting.

-Chris

 

[SevenMKIII]

As per this picture I do not have the "1 green and 1 brown wire for the ecu temp sensor" plug on my harness. My guess is this is why it's running like crap. I have the other single wire, the yellow with green strip. Any way I can hardwire it into the ecu? Where would I find that plug at to run my own wires from it?? I have a field harness for my VPC so it wouldn't be a problem tapping into it. Let me know what you guys think!

-Chris

edit: Nevermind, the sensor I had was on a JDM motor's water neck. I had the correct plug. I just switched the plugs from that to my usdm motor, cleared the code, and started it up and it does the same thing. Except it doesn't stutter when you hit the gas now, it revs freely. And I guess it doesn't smell as rich at all, but it still smokes and my wideband jumps over to 10:1 after about 10 seconds. Think there could be something wrong with the UEGO?

 

[Fletch124]

edit: Nevermind, the sensor I had was on a JDM motor's water neck. I had the correct plug. I just switched the plugs from that to my usdm motor, cleared the code, and started it up and it does the same thing. Except it doesn't stutter when you hit the gas now, it revs freely. And I guess it doesn't smell as rich at all, but it still smokes and my wideband jumps over to 10:1 after about 10 seconds. Think there could be something wrong with the UEGO?

How close is the sensor to the turbo? What angle is the sensor at?

 

[SevenMKIII]

I was sort of confused on where to put it as everybody seems to place the bung right after the turbo. The instructions said 36" after the turbo, so I guesstimated and it is probably 25" down the downpipe at about a 15-20* angle toward the transmission. Would that matter? I'm sure it wouldn't set me back too far if I had to change it.

-Chris

 

[SevenMKIII]

Anybody else? AFRs are still dropping to 10:1 and staying kaput there.

-Chris

 

[Bondango]

HKS VPC/GCC - using the correct VPC chip?? everything wired as should be?
checked that the VPC temp and MAP sensor are connected and operating?

 

[SevenMKIII]

Yep, the 550cc chip is in the VPC. They're all just plugs and harnesses, MAF and AIT sensor both are only one plug, I haven't missed anything. It's just finicky because when the car is idling and I'll lean it out via the gain and idle knobs, the idle gets a little more rough but the wideband still says 10:1?? It seems to work fine when I'm on throttle, if I rev it or anything it leans out to about normal levels.

-Chris

 

[BillyM]

Yep, the 550cc chip is in the VPC. They're all just plugs and harnesses, MAF and AIT sensor both are only one plug, I haven't missed anything. It's just finicky because when the car is idling and I'll lean it out via the gain and idle knobs, the idle gets a little more rough but the wideband still says 10:1?? It seems to work fine when I'm on throttle, if I rev it or anything it leans out to about normal levels.

-Chris

Note that the AFR's may be substantially richer than 10:1 if it's stumbling, regardless of what the wideband says. Most widebands stop at 10:1 due to exceeding the sensor's range any lower.

Check the voltage outa the VPC pressure sensor, instructions on how-to are in the VPC installation or users guide, dont' recall which. Let me know if you don't have them and I'll post them up later tonight.

--billyM

 

[Bondango]

To check VPC sensor voltage...

http://www.alltrac.net/manuals/vpc7.jpg

Can you get a loan of another wideband? im saying this cause ive personally came across a UEGO that was bad outta the box, always read 10.1

Also worth checking the VF from the stock oxygen sensor.

 

[SevenMKIII]

I've been updating the original problem as best as I can. It doesn't stumble like it did before, and I can't smell the gas as much as I could before. Also when I blip the throttle it doesn't try to die like it used to, it freely revs. So at least half of the problem is figured out. Still though, the w/b reads 10:1 (which like you said it may be more rich) but I thought if it went more rich it would just read - - -. I think I have a website at home with the VPC instructions, but not 100% positive I can find it again, it was a while ago.

-Chris

 

[SevenMKIII]

Bondango you beat me to that last post heh. That's the site I had favorited before, thanks! Unfortunately nobody in this little town is much into cars and off the top of my head I cannot think of anyone that has one. Right now I don't have the cash to buy another either... Is it possible that running it that rich for short periods of time bugged up either the stock or the w/b bosch sensor?

-Chris

edit: When I start the car it is about 15:1, then 14.4:1, then 13.5:1, decreasing (increasing fuel) slowly till it comes to 10:1 and stops. It's not always on 10:1.

 

[quake]

first unhook the gcc run just the vpc make sure you have the chip installed correctly it only goes one way tap into te1 and vf1 in the diag port of the car with a volt meter do a search on vf data. next check the sensors do a search on testing the map sensor from the vpc. if all goes well then install the gcc car should run fine with just a vpc i had a problem with the chips from hks when i first installed it went through 2 chips none of them would run the car properly then i had a chip burned custom but first check everything else i said if you still have trouble let me know.

 

[SevenMKIII]

I'm at work right now. The VPC came with the car and the chip was working fine on the old motor. When I get home tonight I'll go buy a hand vacuum pump (minyvac?) and check the pressure sensor and the temp sensor. After that I'll post up my findings and see what you guys say. The kid I bought the car (with the VPC) from gave me a box of parts and a spare MAP sensor but the harness clip was cut off of the end of it, just the wires are hanging out. I wonder if that one went bad?

-Chris

 

[WeDgE]

Mine does the same thing...I did a compression test and it came back horrible...your rings could be gone.

 

[SevenMKIII]

I just rebuilt the motor, new rings hand filed on every piston...shouldn't be the case but I'll test that tonight too while I'm at it. My only feelings on that is that since the motor isn't broken in yet the rings will not be completely seated so my compression may read a bit lower than normal.

-Chris

 

[WeDgE]

My motor only had 25k on it...

Have your injectors tested?