We were supposed to take the '93 to Bowling Green last week, but at this point I'm actually thankful it DID start acting up. (We got a bunch of wine that never would have fit with our luggage.)

The car has been driving just fine, with a little bit of heating up (never goes over 230) - I looked in at the radiator and it looked a little clogged so I know that's a big part of it. On an odd occasion during idle, it would have a slight miss every once in a while. Not enough for me to be concerned about.

However, the S/O wanted a clean car to go in, so she washed it. No, she didn't wash the engine - she knows better. She washed the wheels, and I had a feeling she might have gotten a squirt up in the engine compartment. The engine WAS hot when we got home, before she washed it, so I suspected moisture getting up in the opti. I didn't have a full (new) opti, just the cap & rotor, so I figured I'd pull it as a last ditch effort and do the vent mod. Pulled the water pump and the opti the night before we were supposed to leave, only to find the opti BONE dry. No moisture whatsoever. The metal divider plate however had some very light surface rust. So I replaced the cap & rotor and put the water pump back in. Same thing.

Here's the odd part - it runs FINE when you start it (though it does start a little hard) for about 2-3 seconds, then poof - it runs terribile. It'll die within 10 seconds or so if you don't give it some gas, and even then, it still runs very rough.

Car has roughly 70k miles, and I recently put an Accel 300+ box on it. I did try a different coil (the one that came with the 300+ unit) and it didn't make any difference. The rough running is inconsistent, i.e. I don't think it's just one plug or wire.) I replaced the coil wire (it did have the corrugated cover on it, which I made sure to replace) and that made no difference either.

I'm going to change the plugs and wires for sure, but wondering if the bone-dry opti needs to be changed, or does anyone think there's a possibility of it being the ICM? Somewhere I also remember seeing where the "puck" on the platinum plugs can deteriorate and create a larger plug gap that doesn't fire as well.

Any ideas? Opti? ICM? Wires? Plugs?

 

Did you use a plug in harness to install the Accel 300 box? If so, I would start by unplugging it, and going back stock. These aftermarket amplifier boxes are known to fail.

 

Also start with the simple things. Throttle body or IAC carboned
up? Have you ever replaced the plugs and wires? Any codes flashing?
Fuel filter? The opti can still fail even If dry.

 

Yea, tried unplugging the 300+ also, same results. Car is new to me by a few months, and haven't had time to work on it. Thankfully it's not my DD so it's not a critical thing.

I have a new fuel filter, plugs, wires, and even a new set of 24# Ford injectors to go in it, just with my job and everything else going on, haven't had time to work on it. Hopefully will have some time this week though.

I did the vent mod to the opti while it was out, but haven't hooked up the hoses (don't have everything for it yet, this was an "emergency" fix I attempted before vacation - gave up and got a rental.)

I'll probably go ahead and get a new water pump, as it's cheap insurance - does anyone have any pics of the weep hole mod where you put a brass fitting and some hose in to reroute the drain?

 

OK, I'm hating life.

I just spent 10 hours replacing the wires, plugs, OPTI, water pump, ICM, and even the coil.

Still runs like complete and utter sh~t.

If I EVER meet the SOB responsible for the complete lack of room for the #8 plug, I'mma kill 'im. Oh, and the SOB responsible for the optispark and it's idiotic placement.

So, after pulling the plugs I noticed they're HORRIBLY fouled out (rich.) I can *smell* it really bad when I start the car. I've shut it off and didn't run it for more than about 30 seconds to avoid fouling the new ones out.

So - one of the things that comes to mind is that I removed the tach filter for the Accel 300+ but I don't have it hooked up right now.

Other thoughts are vacuum leak and/or MAP sensor (which I have a spare and will try tomorrow.)

As before, NO codes whatsoever. Runs fairly smooth for about 3-5 seconds on startup, then BOOM rough, rougher, and dies all within about 15-20 seconds.

Please guys - any ideas?

 

The most simplistic thought I have is the fuel pump runs for 2 seconds as it should when the fuel pump relay activates it. But then the oil activated switch is not keeping the pump going and the pressure falls off and it dies. Maybe the wire came off or something stupid like that. But I would sure would hook up a pressure gauge to see what was going on.

 

You might have a couple of bad injectors. You should ohm them ( 15-16 ohms each or is it 12-13 ohms?). Also could be leaky injectors. Hook up fuel pressure gage to find out.

 

Don't have a pressure gauge yet, will go get one soon. Have a set of extra injectors but need injector filters to go in them.

I don't understand how a lack of fuel would cause the over-rich condition though, hence my thoughts of a vacuum leak or MAP sensor going bad.

Thanks for the thoughts so far. I'm really at wits end since it was running great then BAM! it ran like crap.

 

I think what trackman is getting at is the injectors can be leaking causing a rich condition. Others can chime in and correct me on this, but I think you want to start it up, with the gage on it, then shut it off and see how quickly the pressure drops.
On a LT1 another method is to simply unbolt the injector rails, and lift them out with the injectors attached. Turn the key to on to pump up the system and see if any are leaking. And when im talking of leaking, im talking of not fully seating between cycles and letting gas run into the motor.

 

Ok then. The other side of the coin being to rich could be a defective fuel pressure regulator or vacuum input to it. I would measure the pressure at the rail and make sure it is with in tolerance. If it is to high, it will run rich.

 

I would continue with the fuel issue. You might also want to check the IAC. Clean the air intake and throttle body with Air Intake Cleaner, including the intake for the IAC.

 

OK, bought a pressure gauge this afternoon, and it pumps up to 40psi when I turn the key (but not cranking) and it drops to about 30-32psi when I start and run the motor - before it dies of course. I give it a little gas and it goes up to about 40psi or so.

When I just prime the motor, it stays at 40psi so I don't suspect any leaking injectors.

I also tested the FPR, when I put a vacuum on it (vacuum pump) it drops pressure from 40 down to about 30 or so PSI. Not sure if this is normal pressure or not though.

Also put a vacuum gauge on it, and it's around 15-20" of vacuum, erratic of course because it's running rough.

Starting to wonder if I have bad gas?

 

Vacuum sounds normal and so does fuel pressure. I have not checked it in a while, but I think mine idles in the upper 30s.

Lets move into another area. Off hand at this point it almost sounds like there is an input to the PCM that is making it go real rich.

You need to check the temp sensor in the front of the water pump. Check it for open and any loose wiring connections or corrosion. It has a huge input on the air/fuel mix and would make it run real rich if there was an open in the circuit. You might do the same for the air temp sense also, but it does not have the same impact as the water temp sensor.

 

OK, I'll give that a shot. I guess I should have done that when I did the water pump.

Oh and I already replaced the MAP sensor, had a spare so I figured 'why not' and swapped the spare in. No difference, obviously.

This is driving me nuts.

 

Could it be the o2 sensors? Especially if its running rich after a few minutes. See if you can find someone to hook a scan tool on it and see what it is doing.

 

Probably not the O2 sensors. It has to go into close loop to receive input from the O2 sensors. There are 3 conditions to get into close loop. One is that it has to get to 125*. Until then it is in open loop and fuel air mix comes from the sensor in the pump and the fuel tables in the software in the PCM. There's more but these are some of the basics.

 

There's a sensor in the pump??

 

I was under the impression that we were talking about a 93. If that is not true, I apologize for any misinformation. But on the LT1, the sensor is right on the front of the pump.

 

Oh, you're talking about the CTS sensor - my bad. I'm thinking fuel pump. Yes, we're talking about a '93 LT1 still! Brain fart....

 

Your fuel pressure should stay around 41 psi when running.. LT1's are very sensitive to fuel pressure fluctuations! 30psi is too low!! I would replace the fuel filter (I think you may have already done this) and check the tank sock (and replace the fuel pump since you'll be in there anyhow).

Make sure you gas can is venting like it should and the charcoal canister is purging like it should..

I'm 99% sure on the fuel pressure thing.. But I would like someone to verify and correct me if I'm wrong.. I know at idle mine bounces between 38-41 (I just checked it last week).