I have a 95 LT1 with an LE1 h/c package. The opti, wires and plugs are new. It was doing this before the opti was changed. New IAC, new TPS new O2s, new fuel filter and no vaccum leaks I can find. It starts perfect and idles perfect until warm. The car does everything but die. It drops down as far as 300 RPMs at red lights. It is down on power and I am lost as to where to look. The car has no codes stored and the SES is not on. What am I missing?

 

First unplug one of the O2s and see if it runs better even after it warms up. Running that way will eventually set an SES however you're interested in how it runs after it's up to operating temp. You will need to eventually correct the DTC.

If it stays running better after warm up, you know it's a problem in the closed loop control. And I would put money on a burned O2 wire cause of the headers. The very first place to look is the harness overwrapped with foil going down the passenger shock tower down toward the starter. Even though it's overwrapped with foil, the wires get cooked from the inside.

If that's not it keep looking underneath.

 

I never would have thought to look there. I am also going to check my fuel pressure today. Thanks.

 

Update: I unplugged the O2 sensor and it ran better, but didn't set a code or a light. I scanned it with Freescan(Datamaster will not work with my computer) and I have a csv file I will post. It does seem like it starts as soon as it goes into closed loop. The wires to the O2s looked fine. They were clean and as flexible as new wire. I did notice that my ignition timing is jumping all over the place. What causes this? It is even doing it before the idle goes crazy.

http://www.mediafire.com/?4jfxt41jmth

 

To confirm the wiring is ok, watch what the O2 readings look like at running temp. Obviously they should be jumping around anywhere from .100 to .900. If any appear stuck say above .450 then short the black to the purple and the tan wire at the O2 connector. It should now stay near .200. If not you have a broken wire/ bad connector.

Incidentally, when the O2 is disconnected it will take quite a while to set a DTC. You should wait until that time to confirm it is set. Once the connection is put back, it will eventually reset itself.

 

They are both jumping anywhere from .28-.9. I will disconnect it again and try it longer. It really seems like a vacuum leak, but I can't find one anywhere. I checked the intake tract, the intake fittings, all vacuum hoses, the opti hoses and the intake gasket. The fuel pressure is at about 44 with the hose off and 38 with the hose on. While driving it changes with vacuum like it should. I just don't want to throw parts at it. I swear my car is throwing a tantrum.

 

Next thing to pay attention to are the fuel trims. Also an indication of proper running during closed loop. This will give some indication as to whether you may have a partially clogged injector.

Incidentally, you could check the vacuum level with a mity-vac brake bleeder. Chances are if the level changes as shown by the mity-vac when you pull a random hose off and goes back up when reconnected, then it should be considered ok. Expect a level somewhere around 20 inch of mercury(or is it water) I forget, with a normal stock engine. The level is not as important as it changing with the hose off and on.

May also be worth while to lift the injector rails and power up the pump with the fuel pump prime connector and look for dripping.

 

Forgive my ignorance, but what are fuel trims? The injectors are new SVO 30s I installed in February. It doesn't do it immediately after it goes into closed loop, but several minutes later. I am new to datalogging and I don't fully understand the scan I posted. I am afraid to drive my car for fear of it tearing up.

 

You can read about fuel trims or "corrections" on Fred's web site.
http://members.aol.com/InjuneerZZ/Tech.htm

 

Oh, ok. My left integrator is staying at 128 for a while after start up then it fluctuates. It goes as low as 114 and as high as 145. My right integrator starts out steady at 128 and begins to vary also. It gets as low as 107 and as high as 132. Going by the link you posted this shows my car is going into closed loop and the O2s are doing their job. Should they vary this much? The left block learn starts at 131 and dips down as low as 113 a couple times and then goes back around 126-128. The right block learn starts at 137 and gets as high as 152 and as low as 113. They both hit 113 at the same time in cell 7. What function is in cell 7? Sorry for all the questions, but I am learning. What is causing the block learns to dip so low? I am thinking this has something to do with my problem. When my idle starts getting crazy my right block learn shoots up to 148 and stay there a while. Thank you for helping.

 

Either the engine is going lean or it just thinks it's lean. When it goes to 148 what are the O2s showing?

Actually a better question is what do the O2s show before it goes to 148?

FYI I had a burned O2 wire and it showed it was rich all the time (by the O2). The PCM would then pull fuel until it bottomed out and it would briefly pop into open loop, reset itself and go back to closed loop and start the process all over again. The way I traced the problem was to short the O2 harness to ground. When I did that, it still showed rich and I knew it was a wiring problem.

 

The O2 readings drop with the idle. The left one drpps from .08 to .04. The right one drops from .08 to .67 to .044. When the idle drops to 450 RPMs they both (O2s) drop to .23. After the idle problems start the right side gets as low as .13 and stays there for a while. What does this indicate? I think if there is a problem it would be in the right side. On my next day off I am going to ohm them out all the way to the PCM. Maybe this will tell me something. How much of your wiring did you have to replace?

 

The O2s indicate the engine is running lean even after the fuel trims go rich. Since it runs good in open loop, I'm thinking the wiring is an issue. One thing that I've seen a couple of times is the O2's were plugged into the wrong side. Easiest way to check that is unplug one and see if that side goes to about .450. If the other side does, you know the wiring is crossed. If it stays lower than .450, you know the wiring is bad. Start with the right side if you feel that is worst one.

Mine was the right side (albeit the opposite problem) where the wires go down the inner fender. You'll see the bundle over wrapped with foil. I thought that was enough protection from the header heat and it did work for about 2 years. Then they finally burned through. Since I knew the right side was my problem, I just started looking there cause it was the most logical. I simply cut out the bad area of the wiring and soldered in longer jumpers so I could reroute the wires in a safer location.

Since your problem is the right side and it's showing lean all the time, I'de be willing to wager money the problem is those very same wires are burned through and the signal wires are touching the ground wire. You'll know for sure if you unplug the right O2 and the signal stays the same. Or try wiggling the wire bundle to see if the signal changes.

Hope that helps

 

I believe I fixed it. I thought I had a blown intake gasket, but that was not the case. I removed the ground on the front of the engine to get to something else and I noticed some corrosion. I cleaned it off and cleaned the block area and my car is running perfect. I guess it was a ground problem. What do those grounds control?