arec2001

I've been trying to figure this problem out for a long time on my 87 GTA (350 stock internals), and here's the latest:

At startup o2 will read 1024 or so for the first few minutes (integrator gets stuck at 70), run real real bad, then it will do a few hundred cross counts and settle around 0 - 200. Then the BLM's will shoot up to 160 and stay there, running real rich. It does this at all cells. It's a new 3 wire o2 sensor, and I did verify that the heater is working (draws 1.8 amps). Maybe i wired it wrong? 2 like colors (white) i used as heater and gnd, the black wire i used as signal.

Changed fuel pump, pressure is fine at 45psi, 38 w/ vacuum. TPS is fine, MAF tracks with RPM, although idles at 6 - 10gps (600-1000rpm, idles real rough) Is that too high?

All other sensors seem working fine. No trouble codes, except for the VSS, because it's disconnected 'cause I haven't made the t-56 speedo work yet. First things first.

Any ideas?

Car is stock except for no cat, edelbrock headers, flowbastard exhaust, and a t-56.

vwdave

I might seem to be Captain Obvious and also just be talking out my *** with this. When my TBI started acting up, the 02 sensor was reading extremely lean. In fact, the car was running rich as hell. The 02 sensor tells the computer how the mixture is and does the opposite. (Lean reading, it richens the mixture.) But when it richens, the sensor picks it up and leans it back out.

Turned out, my headers melted the wire, and only 1 strand was left. So it was getting a reading, but a very inaccurate one.

*Reads post again*

Ehh, I guess there was not much point to this post. Hope something in there helps ya out.

Damon

Oops! Back up for a second. 160 BLMs indicates it's running LEAN, not rich. The ECM is fattenting things up to the limit of it's ability to do so (160 is as high as it goes). So you're running lean for sure- and I bet you have already suspected this for some time. What you're seeing is the ECM trying to compensate for the lean condition and failing becuase it's too far to go.

Last time I saw a "160-pegger", as I like to call it, I found out the car had 24# injectors where the chip was burned for 30# ones. Woops.

You're on the right track now. I screwed up in exactly the same way on exactly the same issue a few years ago. once I understood what the numbers meant everything started to make sense.

AND.... it was on an 87 GTA! I think I would take this as "a sign." You sure someone didn't use some old 19# 305 injectors instead of the 350's larger 22# units? Or install a chip designed for bigger injectors but not install the larger squirters? MAF-equipped cars freak out real bad when the injector constant doesn't match the atual flow rating of the injectors. Surprisingly, my car wouldn't throw an SES light hardly ever despite behaving exactly like yours does- pegged 160s for extended periods of time and a lousy cold start/idle

Don't worry about what the BLMs or Integrators are reading before the O2 comes up to temp (lots of cross-counts). THey're almost meaningless.

10 g/s MAF reading at idle sounds within the bounds of sanity, depending on engine size and idle speed.

arec2001

I wish my problems were that simple. I am aware that 160BLM means that the ecm is trying to richen things up - which matches my o2 readings - but the darn thing is running so rich it makes your eyes water! The only time it runs "a little better" is when the computer is reset and it starts out at 128blm - then it doesn't run "so rich".

The injectors, ecm, and cal are factory. The sad thing is that the whole thing was running fine before it was rebuild (freshened up, it had 225k). Compression test showed all cylinders within 5psi (195 - 200).

To make matters worse, every once in a while, usually when it's real cold outside (well, 45 degrees, Florida cold), it'll run fine for a few seconds, then go back to its crap mode! That's how I know it's nothing mechanical, just something electrical. I'd suspect the distributor but it's only a few months old. Cap, Wires, and plugs are new.

The only thing that changed during the rebuild was the factory exhaust. Got replaced w/ edelbrock headers. So I thought it was the o2 and i went to heated o2....but it wasn't it.

the MAF burnoff relay was bad for over a year (replaced it recently) so maybe the MAF is dirty? I'm going to clean it tonight.

vwdave

From reading that, I am 95% sure that you messed up your vacumn connections.

Damon

That really still sounds like the syptoms I expereinced when I had a problem very much like this. It wasn't my car but the owner kept claiming that it ran "rich"- he could smell the gas. Nope- so lean that he was getting an occasional misfire that would dump raw fuel into the exhaust and you could really smell it (especially with a gutted cat).

Also, I had the same experience with a computer reset- would run better for a short time then get worse. I think it's because the ECM was running in open loop and slightly richer fuel maps until the O2 came up to temp the first time. As soon as the O2 came on-line it would peg 160 in a matter of seconds and things would get rough real quick. That one mystified me, too, and I still don't know why it ran like that.

FYI- When pegged at 160 the "learn mode" would turn on and off from time to time, too. Again, not sure why but it wouldn't do that once the fuel curve was within the ECM's ability to control it.

Just as a test you might try bumping fuel pressure up to 55 PSI (vacuum line off) and see if it has ANY effect. if you're really lean this big bump in fuel pressure might get you back in the ballpark where the ECM can achieve a 14.7:1 mix. Not saying that's the solution. Just a diagnostic test for now.

arec2001

I bumped the pressure up to 55psi two weeks ago and it ran even richer. When I first started diagnosing this problem I thought it was fp or injectors for sure but now I don't know.

I probably won't get the time 'till tomorrow or thursday to check out the stuff Vader recommended. I'm also going to disconnect (plug) every vacuum line to make sure that vacuum isn't a problem.

The only thing that leads me to believe it could be something related to vacuum is that for some reason the passenger intake seems to slightly puddle with oil. Never the driver side. Also, when I last had the runners out (when I sent the injectors out to be cleaned), the passenger side runners were real oily.

The cause of that could be the the jb weld having run off the huge hole I had to cover on the rear water jacket of the intake manifold. It corroded there so much that water and oil started to mix. That's why I originally rebuilt the engine, thinking the head gasket was blown! All it was was the intake. Had it not been for that the engine would still be running fine.

Darn engine had 225k on it and bearings looked like they had 50k of normal wear...

arec2001

Well, I changed the spark plugs & wires (one of them was burnt), also changed the ignition module (I had a no-start one day and the scan tool was showing no reference pulses), and it runs slightly better. The "big" miss is gone.

However, the o2 still reads rich all of the time; now the thing even goes to open loop at times . I plugged all the vacuum lines to be sure it wasn't a screw up on my part - there was no change

Interestingly, I did a vacuum check, and sure enough, the vacuum fluctuates between 11-15kpa at idle. I'm assuming that it should be more solid than that. What is a typical vacuum reading on a stock 350 TPI? By how much should it deviate? Maybe it's leaking around the intake. I'm pulling the intake tonight.

I also have an idle problem, where sometimes after a while the idle goes higher and higher (computer commanded = 550, idles at 800, then 900, then 1100, up to 1600). Idle motor sticking? Weird thing is that if I shut the car down and restart it the idle *usually* returns to normal. Is that because the computer commanded the motor to park? How can I tell on the scan tool that the computer has sent the iac motor to its most closed position (what is the iac count #?). I was originally suspecting the EGR, but it idled up with the vacuum disconnected from it - unless it begins to leak after it warms up. How can I rule out the EGR?

arec2001

Well I pulled off the intake and all of the cylinder ports looked oily. The intake manifold bolts seemed undertighened so maybe that's where the oil leak to the top of the intake was.

The strange thing is that all runners look black *except* for cylinder #7. The port is clean. This is the port that had the spark plug that seemed it hadn't fired in a few months (I think the wire was bad - i already replaced it). Why would it be clean, though?