gravyhound

Hello all, I have a 1992 base model Lt1 350 auto. 159000 mi. that had got hot and had a blown head gasket, the eng. has been swaped out 3 weeks ago with an Lt1 350 out of a 1995 caprice wagon that has 100k mi. on it and it is a good one the compretion is 180 on all cylenders but it needed a tune-up do to a missfire, I have changed the plugs and wires and it ran a little better but still had a slight missfire so I figured the opti spark needed to be changed next being that it has 100k mi and all original, so I ordered a new one and for the 3 days it took for the opti spark to get here I drove the car around town as my daily driver (100 mi.) being that it only had a slight missfire and then on the 3rd day I went to go somewhere and the motor would not start, I checked to see if it was getting fire to the plugs and it was not. Next I has the ignition module checked and it was good so than I changed the opti spark and then got it all back togather and it was hard to start and runs like crap (on 4 cylenders), after jacking with it all day I have discovered that the lift side injectors do not have power to them so my Q. is should I go ahead and change the ecm?

Hooked on Vettes

In the fuse panel on the passenger side of the dash.
Inj1 fuse provides 12 volts to one side of the injector coil for injectors 1,3,5 and 7.
Inj2 fuse provides 12 volts to one side of the injector coil for injectors 2,4,6 and 8.

The ECM grounds the other wire of the injector coil to turn the injector on.

Inj1 fuse could be blown if you have no 12 volts on the driver side injectors.

If the fuse is blown, you need to unplug the connector from all of the injectors on the driver side and measure the resistance of each injector coil. Should be around 12 ohms. Since the four injectors are in parallel, one bad coil can cause problems for the other 3.

gravyhound

sounds good but I do not understand what you mean buy coil or injector coil, is that the harness or are you refureing to injector coil as the injector ??????

aminnich

Injector coil is an internal part of each injector. If a coil has gone bad you just replace the injector. It does sound like you have a blown fuse. A friend had that happen on his 92 and just replaced the fuse and no more problems.

jaa1992

mine blew the INJ2 fuse and ran like crap.
Looked at the wrong fuse for weeks before I got my head on striaght and checked the correct fuse

gravyhound

thx for clearing that up, terms like injector coil from all you HI-TECH mechanics mess us do it your selfers up lol!

ch@0s

I know what you mean. I needed a two filament electronically actuated vacuumed resistor once and had a very hard time finding one.

gravyhound

Ok thx for the help guys but it seem I have more than 1 problem I changed the fuse and the injectors work now and has fire and will start but barley runs, if I start it and keep it running for say 20 secondes all the 8 pipes on the headers are equily hot and if you open the throttle about 20% the rpm will come up to about where it should idle but runs rough and if you give it any more throttle it runs worse and wants to die. I have changed the TPS and MAP sensors and still the same anyone have any ideas? thx again guys

aminnich

Might be as simple as a clogged fuel filter.

jaa1992

Change the fuel filter - its probably the original from 1991/1992 so its what 20 years old at least???

If it still runs like crap then its time to dig in and figure out the issue.
You'll need a fuel pressure gage - unfortunately I had a hard time finding one I could "borrow" from the major parts places. Wound up buying one from Harbor Freight.

Attach it to the schrader valve on the fuel rail (looks like a metal valve stem, has a plastic screw on cap).
Key on - whats the pressure?
Key off - whats the pressure?
Key off an hour later - whats the pressure?

This will get you started

gravyhound

Ok I forgot to say the fuel filter has allready been changed and the fuel pressure has been checked and is fine. I got ahold of a snap-on scanner and got some good info. go a code 28-Quad driver module faults 2 and 3 I have no idea what that is ro what it means. it also has a code 33-map sensor or circut too high but I think that code is just cause it is running the way it is and cant be a bad map sensor cause I just changed it and it did not help. Also under the the troubleshooter it said to check the IAC and I dont know what that is eather.

aminnich

IAC is the idle air control mounted on the passenger side of the throttle body by two torx head screws. It can be rest by simply turning the key on without starting for 10 seconds, then key off for 10 more, then go ahead and start the engine. Otherwise take it off and check the plunger, it could be slugged up.

gravyhound

doesnt the AIC only come in to play at idle or just low rpm cause this thing will on rev past 1000 rpm, I can open the the throttle 50% or 75% and it just will not rev at all, it just blubers. Also I took the cat off just to make sure it was not a problem. but Ill go ahead and check the AIC anyway. Anyone else hav any other ideas????? thx all

gravyhound

Ok I just through anouther $75 at it for that IAC, was not the problem nor was the MAP, fuel filter, cat, TPS. although it does idle a little better but same thing as soon as I crack the throttle open it stalls and stumbles and dies. Now the scanner did say there was a code 28 (QDM) quad driver module: quad driver 1. fault-no quad driver 2. fault-yes quad driver 3. fault-yes so does anyone know what this means? what is it? what does it do? where is it?

Cliff Harris

There are several quad drivers inside the ECM. They turn on relays and solenoids for various functions. You will get a quad driver fault if one of its outputs is shorted to ground. Each quad driver has 4 outputs.

In the '80s ECMs there is one error code for both quad drivers, so there is no way to know which one is bad. In later years (I don't know exactly when -- somebody with more knowledge will have to contribute) there were separate codes for the quad drivers so you can tell by the code which quad driver is having a problem. I believe later ECMs have more than 2 quad drivers.

You need to figure out which quad driver is setting the fault and then determine what that quad driver's outputs do. Then you can look at those circuits and find out which one is bad.

Also, try resetting the ECM to make sure the error code is legitimate and not something that just popped up by accident.

jaa1992

Do you have a factory service manual?
If not get thee one ASAP before you spend another dime changing parts.
It will be the best $100 you spend.

gravyhound

Why cant someone just tell me whats wrong with it LOL!! It idle's rough but stable and soon as you crack the throttle open it just stalls and stumbles and when you let off it takes a few seconds it goes back to that stable rough idle.

jaa1992

Because your answer lies within the FSM. Troubleshooting trees in the books will save you lots of headaches and tons of money.

Hooked on Vettes

You said you had no spark. Installed a replacement Optispark.

Was it a rebuilt Optispark?

Engine started but ran bad. Found a blown injector fuse for one bank of injectors. Replaced fuse still not running properly.

So the replacement Optispark is still suspect.

It is possible to install the Optispark wrong which would
cause the timing to be incorrect.

Here's a thread that has a link to another thread.

http://forums.corvetteforum.com/c4-t...ng-issues.html

Are you sure the plug wires from the Optispark are going to the
correct cylinders?

Are you getting a strong spark at each spark plug wire?

I believe on a 92 you can verify what the computer thinks the engine temperature is by pressing the Gauges button on the Driver Information
Center until you see Coolant displayed in the Dash Cluster LCD.

Have you cleared any ECM codes by disconnecting the battery cable
and verified there are no new codes?

If you're not comfortable using the Snap on Scanner,
you can short pin A to Pin G on the diagnostic connector above
the drivers knee. Turn the ignition On. Any codes will be
displayed on the dash cluster LCD. Module 4 is the ECM.

Since the engine was replaced, are you 100 percent positive all
of the ground wires were reattached at the bell housing stud
on the driver side and the ground wires above the oil temperature
sensor by the oil filter?

gravyhound

The eng is a 1995 so the opti can only put on one way being it has a key way and not splined like the 1992, and firing order is right. the opti is a remanufactured unit. It is not giving any new codes but it does have 26 and 28 quad driver faults and Ill check the grounds in a min. good tip!!