Got a bit of a strange one going on with my 383 SuperRam setup in my 91 Formula (speed density setup).

I've got a wideband O2 sensor mounted into my right header. It's right after all the pipes come together on my Tri-Y headers. It typically reads in the high 12's at idle and low to mid 13's while cruising. So it's reporting that I'm running rich on the right side of the motor.

My heated narrow band O2 sensor that drives the ECM is in my left header bank. It's showing a good tune with almost perfect 128 BLM's in the same areas the WB is showing rich.

The first thing everyone is probably thinking is the NB O2 is notorious for reading incorrectly, but I don't think so in this case. I swapped the sensor locations just to check it out. With the NB on the right side, it leaned out the motor to where the WB on the left side was reading 16's and the motor definitely idled bad and wouldn't rev cleanly in neutral. Acted like it wanted more fuel during just a couple of minutes time test sitting in the driveway while in closed loop. By all indications, the right side of the motor is running rich and both O2 sensors are reading correctly.

This is backed up by the fact that I still can't seem to pass the emissions testing here in the Dallas, TX area. I'm getting closer, but still failing. My last test I failed the 15 MPH hydrocarbons (HC) with a reading of 121 (allowed max is 117) and I passed the 25 MPH HC with a 110 reading (max was 114). But my CO was really high at 15 MPH (1.59 while max was 0.65) and at 25 MPH (I had 1.68 with max being 0.63). My NOx was fine at both speeds so I passed that part.

Trying to diagnose the problem further, I pulled all the plugs over the weekend, expecting to see something to point me towards a particular cylinder. Surprise - all the plugs looked great! No black on the porcelain on any of them (just a little on the metal base of the plug threads), and the right side's plugs looked identical to the left side of the motor! Granted the plugs only had 300 miles or so on them of mixed city and highway driving, but I would have thought that would be long enough to show any problems.

To top it off, the car is running great! If it weren't for the verified WB and NB O2 sensor readings and the fact that I'm failing emissions, I wouldn't even know I had a problem. Granted emissions stickers can be "bought", but I want it running correctly and legal. It looks like I've still got a small problem, but I'm at a loss on what to do next. What would cause extra fuel in the exhaust on only the right side of the motor?

I really hope someone can help me decipher this one. It's driving me nuts. I'm spending far too much time underneath this new 383 setup instead of just driving and enjoying it! Plus I need a current inspection sticker before I get a ticket for the expired one.

Can someone please help me out on this? I honestly don't know what way to go next.....


- Vern

 

Try swapping the injectors from left to right and see if the out of balance O2 readings follow.

 

Vern,
Just out of curiousity what type of WideBand are you using? I've been looking into getting one but still can't afford the almost $200 for the sensor itself.

As far as your problem between the two banks I don't have a lot of input as this is a little beyond my reach. But what about your injectors? Maybe you have a few on the rich side leaking but not enough to foul out your plugs? Maybe a blockage in the fuel rails on the other side?

 

I got the TwinTech WEGo kit off ebay for $225. Here's there web site for more info: www.daytona-twintec.com

You'll have to dig some to get past the WEGO II to see the WEGO (which is a lot cheaper). May be in their close outs or specials area....

As for moving the injectors, I could swap them out just as easily since I have a set of LS1's on the work bench, but why?

Do you think a sticking or leaking injector could cause this?

 

I was just thinking that if the injector was sticking it would be dumping slightly more fuel into that side of the engine causing it to be richer than the driver side.

Did that $225 include the cost of the O2 sensor?

 

YEP. Only problem is it won't log data history so you can go back and look at it later. All you have is an LCD panel that shows the current reading whenever you're looking at ti.

 

Interesting because their website says that all models datalog if I remember correctly.

 

That's for the more expensive WEGO II.

The standard WEGO does not.

 

No one else have any ideas?????

Please????

 

One or more leaking injectors on the right bank would seem to be the most likely culprit. Any easy way to check (at least with the stock runners) is to remove the plenum and runners, undo
the bolts that hold the fuel rail to the manifold keeping the supply and return lines at the front of the rail connected, and lift up the whole rail assembly so that it's sitting above the manifold where you can see the injector tips. Then pressurize the fuel system for a few seconds and look for dribblers. I've found two different sets of leaking injectors this way. Car ran fine seat of the pants in both cases.

 

vernw,

Have you seen the info at the link below? If not, see the "split BLM" section. This doesn't directly apply to your application, but you might find it helpful/interesting.

http://para.noid.org/~lj/PCM%20Tutorial/PCMtutorial.htm

HTH

 

In a word...Yes.

 

I agree.
.
Any chance you could borrow half a set of known-good
fuel injectors?

 

I've got a set of brand new LS1 injectors sitting on the work bench, guess I'll try putting them in this weekend and see how that works.

First I think I'll disassemble the SuperRam so I can pull the fuel rail and see if any of the Holley 24# injectors are obviously leaking or dripping. If so, then I'll test the LS1 injectors the same way and make sure they don't leak before I reassemble everything. Unfortunately you have to loosen the runners (which means removing a couple of rockers - a real pain) to get the fuel rail off and get to the injectors.

Doesn't look like I've got much choice though, does it?

Thanks for the replies, I'll post the results of this testing this weekend.

Have a Great Day!!!


- Vern

 

Vern......taking the plenum off is a huge PITA....I've had mine off like 5 times now. I've been able to get my fuel rails out twice now though without loosening the runners.....it's tricky but possible. Also you can get the bottom runner bolts out without loosening the rockers. I used an allen head socket that had about a 5 or 6 inch allen arm on it and was able to get in there without looseing the rockers last time. Huge help so you don't have to reset the valves.
Good Luck!

 

Hope you're right on the not loosening the runners. I had to a couple fo weeks ago when I swapped out the bad lifters, but will try it this weekend w/o loosening first. I hate having to take off all that **** on the passenger side to get the valve covers off....

Sure hope I can figure it out. Any hints?

 

I don't remember exactly how I did it last time. I think I pulled up one side of the injectors first, then the other so they were both just dropped into their ports pretty much. And I think there was enough wiggle at all the connections for the injectors and rails to get it out. You may have to loosen the clamps for the crossrails between the large rails. If you do then replace the o-rings in there and tighten them up when you drop the rails back in. It's a real pain but can be done.

 

I JUST BARELY PASSED ON SATURDAY - the CO was right on the edge but everything else is fine. Except the WB is still reading high for the right bank. I found my hose routing was mixed up on the diverter valve so that I wasn't getting full flow to the cats (was split between it and one manifold, don't remember which one).

Here's the 25MPH emissions test results:

Type______Standard__________Reading

NOx________796______________130
HC_________114_______________58
CO%_______0.63______________0.63
CO2%________-_______________13.5
O2%_________-_______________1.50

Anyone have any idea why these would come out this way? The 15MPH test about the same except the CO dropped a smidge to .58 (whooppee!)

I still read in the low 13's on the WB in the right bank, haven't swapped any injectors (yet).....

- Vern

 

Does the high CO reading and low O2 reading on the right bank WB sensor still indicate a rich condition? Surely someone has seen something like this before.....