Hiya gang. I recently had my motor rebuilt after spinning a bearing. It's a 1994 coupe. The parts list:

Eagle 15034L internal balance rotating assembly. (383)
KB197 -12cc dish
GMPP hot cam kit
Sealed Power OE lifters
OE pushrods.
Opti-II conversion
P&P heads
ported intake
OE exhaust manifolds
OE cats
OE cat-back
Centerforce DF clutch and SM Fly (neutral balanced)
PCMforLess computer

The shop I used refuses to warranty their work since I supplied all the parts. The very night I brought the car home she began stumbling terribly, and died. Afterwards, she didn't even turn over. I had her towed to my Mom in Law's garage. I jumped the number 4 and 12 pins on the DLC, and got no codes in return.

I got her running again, and today I drove her home. She runs nicely when cold, and then begins to ping as she gets hotter. The SCR is roughly 10.8:1.

The coolant stays in a good range, about 195 to 210. At those temperatures the oil is running roughly 230-ish. I put in some 108 octane booster to limp her home. I'm also heading out right now to get some 100 octane to see if that quiets her down some. Is it possible that I'm too lean, and as such leaning towards detonation? I'm going to check my fuel pressure in a little while, and will get back to you with that.

I have an FSM, and am trying to work out where and when to look through the diagnostic charts. I'm just trying to gather up some ideas other than mine to look for. Does anyone have a suggestion for a good data reader to do aqcuisition with?

Thanks in advance folks. Free e-beer for all.

-DarkMatter

 

If that is not a typo, then that is your problem. I hope you meant static and not dynamic

 

Errr, yeah. Fix that right now. Typed it in a rush out the door.

 

Fuel pressure at idle is 43 PSI. Not driving and raising the RPM it falls then rises smoothly. I ordered 30lb injectors. For now she's sitting still.

 

Don't let coolant temperature fool you. Often, just a few degrees TOO MUCH ignition timing won't show up as higher coolant temps; in fact sometimes the coolant temp will be lower WITH TOO MUCH TIMING.

Coolant temps are not the answer.

Before I started tearing into the engine replacing this part and that part, I'd verify the initial timing setting.

Far too many people believe that backing down on the initial timing is a BAD THING, but it isn't. Two degree less initial advance can make all the difference.

First see where you're at with the EST disconnected. Let us know what you find.

Jake

 

 

If I understand this post correctly, what you're seeing is a condition we call surging. It can be caused by several different things, most often a vacuum leak.

Jake

 

Well I had originally intended on replacing the injectors when I did new heads next summer. So, If I buy a set of 30lb'ers now, but don't need them, I at least have them.

Now, I just realized that I didn't mention the year in my initial post. I'll go back and add that after I get this up. It's a '94 coupe. Paging through the FSM, I see no listing for "EST". What I do see is "Ignition Control Circuit", and it's a white wire on PCM connector B5. Are these the same connectors? If they are, I'll go ahead and get on that.

I'm not sure if we're on the same page re: surging. What I mean is that when the car is running, having my wife step on the throttle from inside the car, and raising the RPM, there is a corresponding rise in fuel pressure. I thought this was correct. There's only a very small drop in pressuse (2-5 PSI) before it starts climbing with RPM.

Thanks a million for the suggestions and help Jake.

 

Thats what Im thinkin.

 

Fuel pressure INCREASES as engine vacuum DECREASES. So it's normal to see fuel pressure INCREASE when you suddenly open the throttle quickly because the vacuum momentarily drops off.

Many times the problem can be something a simple as a vacuum hose that, over time, has become brittle and is leaking or, after doing some work on the engine , a hose was left disconnected.

Back to ignition timing: If the timing is set too low, you will often see an increase in coolant temp and may even become of victim of the "glowing-red header" syndrome that others have so often written about.

As an engine heats up, it becomes much more sensitive to spark timing. Engine will run great when cold though. Many set their initial timing too high because the engine feels so much more responsive at that setting, but once the car stretches out on the top end, the engine lays down because of too much advance.

You can just use an inexpensive vacuum gauge connected to the engine to check the reading. I use one of the hose bibs on my power brake booster.

The reading should be steady with NO sudden dips or flucuations; the needle shouldn't bounce. The actual number you see on the gauge can vary depending on the engine parts installed, especially the over-lap of an after-market camshaft.

Keep us posted on what you find.

Jake

 

I'm sorry to ask again. Are the "EST" and ignition control circuit the same?? I can't find an "EST" anywhere on the PCM layout. I know I see it referenced as a "tan or brown wire" but I don't know if that's for the older L98s, or if it also applies to the LT1.

Thanks again

 

Sorry I can't help you with that one.

I just bought a 96 LT1 for my son, and working on it will be a whole new learning curve for me. Over the years all I've worked with are L98s and pre-L98 engines.

There's a saying "Ignorance is Bliss", but in this case I don't think that applies. Wish I knew, but I don't.

Someone else will probably chime in with the answer to your question.

Jake

 

Hey, fair enough. It was pretty cool for you to chime in with what you do know, and I greatly appreciate it. I'll look into the vacuum leak possibility as well.



-DarkMatter

 

Found a few small vacuum leaks in and around the EGR system. Patching those up right now.

As far as timing, FSM says that no timing adjustment is possible?? Is this correct?

 

I believe so, but on a 94, I'm out of my element.

Again, someone else will have to confirm this.

Jake

 

Have you called Bryan up and asked him about it? There are some areas around the country we can run hot tunes because of the gas, humidity, temp, altitude.. Prehaps you in one of those areas.

 

Actually, I was going to give you guys a call tomorrow afternoon. I put about half a tank of 100 octane in and she's still pinging bad.

I was going to ask on the phone tomorrow, but hopefully you'll see this now. What kind of data reader can I use to connect to the PCM? I purchased an OBD-II version today, but it tells me It can't connect.

Thanks in advance.

-DarkMatter

 

Theres one I haven' had the chance to use but Bryan has.. Something like OBD2allinone.com or something like that. I use EFIlive and my Matco determinator on the obd2 cars.

 

I dont think you can adjust the LT1 timing without changing settings in the computer

 

The timing on a LT1 is set when the Opti-Spark is installed, it could have been installed wrong?