I'm trying to get my tune in order. I was having trouble in closed loop. Idle was way rich. Blms were pegged at 108 and the o2s were still at 990-1000 mv. I checked and my vacuum fitting on the fpr was bad. I changed it. Raw fuel smell in the hose..
Changed the fpr.
I thought that would solve the problem.
Still pig rich.
Changed it to open loop. Idles great. No more stumble or hesitation.
Put a wideband on it
Idle was at 11:1 afr.
Commanded is 14.7
So I scaled the maf table in that area. It got a little better. It's now at 13.5.
But when I go wot it's lean. So I scaled the maf table up top..a lot.
I was showing around 14.3 now it's 13.3.
What the heck is going on here.
What would cause this? It shouldn't be that far off, should it?
Rich idle, lean up top.
Going to check fuel pressure this weekend. Any other ideas?

Car has a cone filter in place of the stock airbox, Longtubes and 1.7 rockers.
Can't think of anything else that's changed the airflow characteristics of the motor.

 

fuel injectors? new throttle body?

 

Throttle body and fuel injectors are stock factory units. I checked the injectors for leakage and they appear to be good.
I tested the fuel pressure not too long ago, and it was perfect.

Haven't located any vacuum leaks.
Not sure about exhaust leaks. Seems that an exhaust leak would show a false lean through the whole rpm range though

Just not sure if this is normal.
Seems like something is off here.

 

The PCM thinks the car is lean and that is why it's dumping in all the extra fuel.

Any chance you have mistakenly mixed up and interchanged the banks of the pre cat O2 sensors?

Tell us more about what mods are done to the car. Also, what year is it? A signature would be a good idea. Are the mods at the bottom of the first post the only things done to it?

Were the 1.7 rockers recently installed? When did this start happening? Was it running find before vs after any mods? Is the car throwing any codes? Have you had it scanned for codes...a few will not set the SES light.

You may also need to post up a scan log of the car so as to see what it is doing in closed loop.

 

It's running open loop, so the o2s are not the issue.


It was running fine then, I stopped for gas and when I was leaving it started running really bad, stumbling and missing. I got it home and scanned it, it appeared that the right o2 was flaking out. it was reading between 0 and 4mv. I disabled closed loop. the car ran fine. I figured it may be the extension for the longtube.
I then logged the car and saw it reading normal. I re-enabled closed loop, then the pcm started pulling fuel like crazy. and it was running bad, stumbling off idle. once moving it was fine.
Put it back in open loop.
I checked the fpr and found the vacuum elbow was rotted, so I replaced it, I also noticed the hose smelled like fuel so I changed the fpr too. This didn't help. I put a wideband and it showed 11.0:1 afr at idle. This is in open loop, so the o2s should have no effect. I can see them reading high 900s to 1000 though, so I'm pretty sure it's definitely rich.

When I was in closed loop the pcm was pulling fuel, not adding it.
It's a OBD1 94, Don't know why my signature was turned off in the first post. I didn't do that..

I should also mention that I've had issues with closed loop idle ever since the long tube install. I'm actually fine with running full time open loop, I got no cats.

 

I think I understand more of the issue now. I thought you were saying that when going into closed loop you had a problem.

Let me make a comment on your tweaking the PCM....

No need to go tweaking the PCM tune for what you have. The only thing that might need to be tweaked is the WOT AFR to lean it out just a little from how rich it is stock. Nothing else needs to be touched unless you want to tweak the speed limiter, rev limiter, etc.

It's true that changing the air intake will shift the MAF calibration, but in my experience, it will not shift it enough to cause major issues with the fuel trims to require a recal of the curve.

Is that something you can perfect once you have fixed your core problem? Sure, but for now keep the PCM programming stock until you have figured out your fueling problem. Don't introduce more variables into the equation.

Exhaust leaks, vacuum leaks, O2 wiring problems, and ignition problems(misfires) can all cause rich issues. Have you pulled the plugs to see if they are burning fuel properly? Are you sure you have not burned any plug wires?

When did the 1.7 rockers get installed?

 

The very little tweaking I've done so far was to adjust for the 3.42 gears and remove some timing in areas that I was seeing knock. It was running pretty good with the tune. It has had an off idle stumble ever since the long tube install, so idle was set to run in PE mode. It ran a 13.36 at 103 with the tune that way. Just exhaust and an ebay cai as mods.

I had set it back to idle in closed loop and it was running ok, but there was still a hesitation off idle a lot of times. if I floored it it would fall on it's face before taking off. Not always but most of the time. I think when my fpr started leaking it was too much for the pcm to adjust for, since it already was correcting for a rich condition at idlle, maybe that's possible?
It has actually had this problem since the long tube install, even replacing the o2 sensors with new ac delco parts didn't change the problem. Tried tuning for the headers with delay, etc. no help.

Was just surprised to see it so rich at idle and low rpm and lean up top.
adding 9% got me good at wot, but to get idle to around 14:1 I had to lower by about 15%.


o2 wire problems cause a rich issue in open loop?

I thought that a vacuum leak would cause it to run lean in open loop, am I backwards here? I sprayed every vacuum hose and connection with starter fluid, couldn't locate any leaks.

I did foul out the previous set of plugs right when it started running bad in closed loop, but the current ones look pretty good.
haven't checked the plug wires, I'll take a look.


The rockers got installed after I put the car into full time open loop. The car actually drives great, idles good, good acceleration.

 

I think you are think right that vacuum leaks in open loop should cause a lean problem, much of what I mentioned is for closed loop issues.

If it's rich in open loop, I would think that it's either got an issue not burning fuel, incorrect airflow readings(MAF, IAT, MAP issues), incorrect coolant temperature(sensor in water pump), leaking fuel injectors and/or incorrect fuel pressure.

I'd start by getting the programming back to stock and try to chase down the issue from that point.

The reason I asked about the rockers is that mis-adjusted ones can cause all kinds of problems.

Have you got a log you can post of it running in open loop since the trouble started?

How are you locking it into open loop mode?

 

I set the temp to enter closed loop ridiculously high.

I'm wondering if my MAF is jacked up somehow, or maybe the wiring to it. I have had a couple of times when I get a MAF error code, like it's unplugged, though I've never seen it not work during logging.


I used the engine off method to adjust the rockers, 1/2 turn preload.
Coolant temp sensor is new and appears to be accurate.
I'll be checking the fuel pressure this weekend, and it's easy to pull the fuel rail and check the injectors for leaks, so I'll add that to the list.

 

Have a look at this.....I ran across it again today(I've seen it before) and ScannerDanner presents some very good information on how fuel trims can react to ignition and fuel injector misfires.

 

Well. I tested the fuel pressure today. When I turn the key on it jumps to 40psi for a second then I hear a click, like a relay or a solenoid and pressure drops to about 35.

Engine idling is about 32, fpr hose disconnected is 39-40.

I pulled the fpr hose. It's dry but smells of fuel. I think my brand new fpr is probably bad. Figures

Got it at advanced auto. Only one in stock anywhere around here.

I'll probably order one online.

Grrr
The issues never end.

 

i wonder if your pump is weak; being at least 3psi short? does it get worse when you rev it? if so, you'd figure pump... if not, regulator

 

Yeah
That's what I'm worried about. Last time I went to the track my afr jumped to 14:1 at around 6k. Thinking it's not keeping up with demand. It would also explain why I had to fatten the mixture up top to get a good pe afr.

The thing that I don't understand is my idle afr. I seem to be getting a false rich condition. All my googling has yet to turn up anything that would cause this. Narrow band sitting at around 1mv at idle, wide band normally drops to 11:1 or lower when it's fully warmed up. Worse after it's run hard. It had actually dropped down to 10:1-9.9:1. It was just idling away. Not possible. So I pulled the plugs. Here's #7


Rest of the plugs looked pretty good. This was the leanest cylinder.


Wth can cause a false rich condition?




Lean

 

An exhaust leak between the exhaust port and oxygen sensor will cause a false rich condition.

The o2 sensor will see the additional fresh air from the eexhaust leak and will add fuel.

 

An exhaust leak between the exhaust port and oxygen sensor will cause a false lean condition.

 

false lean condition = real rich condition when closed loop trims it out

 

Exactly

mines doing the opposite. the O2s are reading pig rich, not lean.
I let the car idle for a while with the O2s pegged out reading rich, then pulled that plug, obviously not running rich. It's open loop anyway, just trying to figure out what would cause this.

 

I've been reading through the '94 service manual for a rich condition as indicated by the O2.

Here is what the service manual states to check in the below picture....the EGR valve stuck open at idle is one issue I had not considered....



It also makes reference to disconnecting the sensor from the wiring harness, grounding both the O2 signal wires(not the heater wires) and looking at a scan tool to see if the indicated O2 voltage is below 0.35V. This is testing the PCM inputs to make sure they are not somehow locked into a permanent "high". Due to external wiring issues or PCM input failure.

We really need to see a full scan log of what it's doing with close loop enabled.....warm it up in open loop, then enable closed loop and do a full log of the engine inputs and outputs for a few minutes at idle.

 

1.7 rockers aint gonna make it go that rich. He's asking for help not opinions on a PCM with unknown tune. Sounds more like drabble w/o a clue!

 

Well now, from one drabble to another, Merry Christmas to you too cardo0.