It is a 96 Lt1, obd1. Stock motor other than headers and exhaust and Moroso CAI. Stock program.

I pulled the plugs and they were black. I have been using Freescan and PCMComm. I am seeing BLMs always below 128. Cruising they are 108, the lowest they can go. I thought that BLMs were stored and when the car goes to a particular cell, it uses those stored values. I am noticing that if I am cruising and they go to 108, I can hit the throttle and send it to another cell. Once I go back to cruising, the BLMs start at 128 again.
If I slightly accelerate, the BLMs will go down. So it seems like fuel is being pulled everywhere.

I have disabled all emissions controls via Tunercat and removed equipment.

The car will stumble after after reaching operating temp(160) under load and low rpms. Also, it has slightly popped back through intake only twice that I can remember. The car runs great at WOT above 2k and the motor is in good condition.

I have yet to check fuel psi but I leaning towards a stuck closed fpr or sticking injectors. I had problems with them when I first tried to get the motor running. I had to tap on them because they were locked up. BTW, anyone know of an injector cleaner that actually works?

Thanks in advance, Mike

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The only injector cleaner (I know of) that actuall works is Techron, or is it Techtron. I can spot the bottle a mile away, it's black, and usually retails for around $6. Someone posted a Consumer Reports type ad a while back that showed this was the ONLY injector cleaner at most auto parts stores that actually works.

 

Thanks, I will pick some up tonight. Worth a try.

 

Tried the cleaner but it did not help.

Also, checked fuel psi and it was good. Any more ideas?

 

Both sides? Man, 108 at cruise is really bad. You check for an intake or vacuum leak?

Hal

 

Is it only stumbling after it warms up? If so, there is a chance that your O2 sensors need replaced.

They may be falsely sensing a rich condition and pulling the fuel is making you run lean, etc.

When was the last time the sensors were replaced?

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Solomon
What's life all about?
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Learn the basics of tuning your OBDI LT1 PCM!

 

As for the intake leak, I thought the Blms would be higher than 128 if that was the case.

It progressively gets worse as the car reaches operating temp. I replaced one sensor 7k miles ago and they are both pretty close to each other so I figured the sensors weren't the problem.

 

I am having the same exact problem. My car runs smooth as can be, but then as soon as it hits about 160 degrees or so, it starts missing. It is a slight miss that you can only really feel on a smooth road. I've tried a few things also, but can't come up with anything. Just recently though, my car is hard to start. I wonder if it is a problem with the injectors. Someone on another post mentioned that they had trouble starting the car because the injectors were actually leaking a little when the car was shut off. Then, it would flood a little when trying to start it. I wonder if our injectors are actually leaking a little while running at a low RPM. Mine pulls great until I'm going about 60 with about a 10 percent TPS.

Sorry about the long post.

Todd

 

As long as you have injectors that still have their retaining clips on I believe you could check for leaking (svo and others don't allow installation of the clip so don't try this with those). Just pop the rail up a little and turn the car to run (not start). I believe the clips will not let them pop out of their sockets (pull on them to make sure before you try this). I have never tried this so just blip the key to the run position then check.

Hal

 

Also, one thing that strikes me as odd is that the tables should correct themselfs and go to 128 after block learn corrections. If this is true then why does it stay at 108?

Hal

 

Yes you can do that with the fuel rails, and it is in the service manual as well.

I thought the tables remain constant and the blms just compensate for what is needed. I don't know for sure though.

Anyway, I think I am going to replace the Opti, coil, wires and plugs and see if that cures the problem.

 

I have the same exact problem... here is my LT1 Tech post on it...

I have already tried a new Opti, coil, and new plugs. Wires are next on my list, even though they are visibly OK... they aren't burned, no arcing... they are Taylors, I may have cracked the core wire trying to get Opti boots on .).

And of course that may not fix it either... Just letting you know it wasn't my Opti (*hint* try a few other things before the damn Opti!)

I don't think its ignition related though. I've tried checking for exhaust leaks, sometimes I hear a little something... but I don't see anything.

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FormulaV8.com · 1994 Formula · A4 · 3.23
13.45 @ 102.5 MPH w/ 1.9 60' | 267 rwhp | 307 tq/lbs | 3535 lbs
"I know for a fact he is NOT an Easter bunny"

[This message has been edited by stevil (edited September 08, 2002).]

 

I finally fixed my slight miss at 60 mph and my hard to start problem. It was my adjustable fuel pressure regulator. It was actually leaking fuel through the vaccuum line. When it was running, it would allow it to run a little rich. When I shut it off, the pressure would bleed the fuel through the vaccuum line into the engine and let it flood. I've been fighting this since I got the car running, and now I've just got the stock regulator on it. The bad one was an Aeromotive, but don't know if I'll put one of those back on it. I know there are other alternatives to Aeromotive.
Todd

 

Yeahhh! Replaced the optispaz and coil wires and it fixed the problem. It is fun to drive again!

 

Call Aeromotive on that bad AFPR. I bought one myself & had the same problem. They fixed mine for free & told me they had changed the type of rubber used in the diaphram. They will try & blame it on Alchol in your fuel at first. I had mine on the car for only a month though. I did a search on this site using "Aeromotive" as a key word & found other posts of the same problem.