Hotwire

(94 LT1/4L60-E, custom programming, !air, !egr, !purge, headers, exhaust, etc) Water pump just went out, truck ran funny, figure it was the usual pump/opti deal. Truck isn't running right at all, no current codes, history code #43, Ignition module failure. Won service manuals on ebay, but haven't got them yet, please help.

I have replaced plugs, wires, FULL opti, and am at the end of my strings. #4 cylinder is dead, 5 & 7 were fouled bad.

I have a crane HI-6 and LX-91 coil to install on the motor, but need to get it running right before I can do anything, and I can't STAND to see this thing sitting!!!

Anyone w/ experience or service manual, please let me know what the procedures are for fixing this thing, or point me in the right direction for diagnosing it.

Thanks,

Jeff

Injuneer

You're using the wrong code list, or you have a scanner that gives you the "generic" versions. In an LT1, DTC 43 is "knock sensor failure".

If you aren't getting a spark to just a single plug (#4), its got to be a problem with the wire or plug... not something common to the entire ignition system. If #5 and #7 are badly fouled, could be cross-firing, or you might have a "false lean" loading up the left bank..... causes could include misfires (yes, a misfire really screws up the entire bank), leak in the exhaust system before the O2 sensor, faulty O2 sensor, wiring or ground.

For a decent list of DTC codes, try my ScanMaster writeup.

Hotwire

well, it's a friend's autoxray xp240. it says code 43 electronic spark module failure. trying to find any info on this off of the autoxray site, or outright on the net sucks. all i am getting is crap and advertisements.

I can fire the motor, it runs, but you can hear it missing pretty good. Shut it down, touch all the primaries (ceramic coating) all of them will pull fingerprints off except for #4, it's warm, but nowhere near hot.

It ran completely fine before the water pump went out, that's why I changed the whole opti unit, but it turns out that wasn't it. I understand about all the ignition components being random until the distributor, I tried a different set of wires and changed the plugs w/ no difference, then changed the distributor cap and rotor, expensive non-fix, then the opti part itself, another expensive non-fix. I am declining to change any of the other ignition pieces till I trouble shoot it. I absolutely dispise plug and play troubleshooting, too expensive and no learning.

When you fire up the xp240, it asks for the 8 digit in the vin, year of vehicle, then asks for the 4th digit, tranny type, and some other things, so i felt it was accurate info coming out. Now, trying to find the code specific to it on the net, or anywhere else, good luck. I am going to call their tech support tomorrow.

Preciate the info.

shoebox

Electronic spark control is the knock sensor circuit.

Injuneer's list is accurate and here is another.

96ZRDR

If you happen to figure out your problem, let me know. I am going trough the same difficulties.

Code 43 is knock sensor. Has one wire going to the knock sensor, and you need a knock sensor specific to a 94 Lt1. Do not put any type of sealant that what it already comes with, as it may prevent it from grounding to the block.

Mine had that too, I fixed it, but still did not solve my problem.

Good Luck

Hotwire

are your symptons the same? running rough, missing, etc? I haven't had a chance to pull all pass side plugs.

1,3 looked good, little carbon, 5,7 were about fouled out, these plugs only have about 2-300 miles on them. Changed out opti, plugs that i got to so far, and all wires, no difference. going to try ignition module, ground strap on motor, and coil sometime this week, also getting service manuals, going to look for flowcharts to follow, may be pulling valve covers and checking lash while I am at it. All this is much easier w/ the motor sitting in a s-10 engine bay.

I moved my knock sensor to the driver's side and extended the wire due to clearance problems with a motor mount. I don't think that the knock sensor going bad would cause me all this grief, but I have been plenty wrong before.

Will keep everyone posted.

Thanks,

Jeff

96ZRDR

My symtoms include:
Huge loss of power - 100hp
Rough Idle - Stalls out at times under load
Hard Starting after running a while
Fouls Plugs in minutes
It seems to burn the JET Hot Coating of some header primaries.
Has a huge lag.
Runs very rich at idle.
I can tell that cylinder #1 is not complety firing. i can tell because I after I let the engine run for 5 minutes, I then use a water bottle to spray water on the primaries. On every primary but that one the water quickly burns off, . On #1, the water kind of takes al little to evaporate.

The problem is worse once it goes into closed loop. Power dropff is even more dramatic.

Things I have done.
-Replace Opti with new GM piece.
-Replace Opti Wiring harness
-Replace Coil Wire
-Replace Coil
-New Plugs
-Wires are OK, Taylors are like 2 months old.
-Switched between 22# and 30# injectors.

I dunno, I am replacing my O2's, ICM, checking all my grounds, possibly ground the block like you say,.

Well, I will update my finding too.

Good Luck

Hotwire

my god man, sounds i-dentical!

I have carbon marks in my garage where I have fired it up and hit the throttle a couple of times, thought I had a blown head gasket, wasn't happy.

Have you tried the igntion module, or swapping ecms with someone that has the same year car? just q's I am trying to widdle down, hopefully when I get the service manual it will be a forehead smacker.

try your battery cables running beside the a/c - power steering pump, have seen where a lot of people have had problems w/ the belt rubbing through.

I won't have time tonight to get on it, but will let you know if I find anything.

Thanks,

Jeff

Hotwire

welp, icm and ground didn't help out, neither did adjusting the valves. oh, and thanks gm engineers who thought that not finishing the inside of the head would be a problem, lol, my freakin thumb looks like a slice of bologna...

i'm about done with it, either going to sell it or pay someone to fix it. it's really pissing me off. 7 cylinders are burning rich as hell, one is not. I'm going to pull #4 tomorrow to look at it's condition, wondering if i'm getting fuel to that cylinder, but you said you changed your injectors. I watched the rockers as i cranked the motor over, getting all kinds of action off of them.

might pull some plugs and do a compression test as well. it runs, but i can still hear the miss and when i blip the throttle it will try to choke out and sometimes it's backfiring through the intake. might be the head gasket...

any gm people heard of the head gasket going prematurely on stock motors?

think i figured out code 43. moved knock sensor to driver's side, they said to keep wiring away from ignition system otherwise it will pick up noise and give false readings. lol, i have it coming around under the plug wires and running up into the harness where the coil and ecm are...

jeff

96ZRDR

Have you changed anything internally to the engine? changed cams? I was wondering that maybe you did not line up your timing points on your gears properly.

Just a thought.

Hotwire

no, it's completely stock internally. mods are headers, free flowing exhaust, Ion Soltan (madwolf) programmed the ecm, k&n filter hanging off the maf, and a air foil I just purchased recently. everything else is untouched.

the damn miss just showed up one day, and i saw the water pump was leaking, so i assumed the opti was gone. turns out i just wasted $300, should have checked everything.

Could a knock sensor be causing all this? I know it retards the timing, but how far will it go? Are you showing any codes? I watched it when i fired it up last night and it seems to be pretty active, I may reroute the wire to see if it makes a difference, but why would it change after putting about 500 miles on the truck? The o2s are reading around 430-470mV after I ran it for a couple seconds.

The truck will run, but it bogs down like hell and backfires through the intake if you get funky w/ the gas pedal. It sounds a lot stronger since i adjusted the valves, they were noisy ever since we fired the motor.

it was in a 94 camaro, wrecked, was pulled in early 02, got it on easter of 02, wasn't ran until dec/jan this year, ran strong as hell, but every once in a while you were wondering if it was running right, thinking maybe fuel pressure or something, then noticed it stumbling, looked around, saw water pump leaking, and here i am.

so far have:

*replaced water pump
*plugs
*wires
*adjusted valves
*ignition module
*opti
*cap & rotor
*regrounded motor
*ohmed out coil and anything else ignition related

Going to go home here shortly and check the knock sensor and maybe pull the plugs, AGAIN, and do a compression test. I know it's something, just being a PIA, and with the wife looking at the check book and over my shoulder, it's turning into a nightmare.

Haven't put the pump back on, so changing the knock sensor won't be that bad. but I am going to ohm it out an check power first.

If anyone can check gm database for similiar failures and fixes, i would greatly appreciate it.

96ZRDR

Are you reading your O2 volts with a scanner? It is normal to see the O'2 mvs around that number at startup. The cpu provides them the voltage until they get hot enough is what I have been told.

Mine start at 450, but end up around 700-800mv when fully warmed up and under closed loop conditions.

My Long term blm on my left side say it is running way rich and cannot adjust anymore, my right side is ok. I know my car runs very rich but it only seems to do so in idle, more so under load.

But when cruising things seem to be normal other that the fact that my computer adds fuel due to the 22# injectors not being big enough.

My car seems to idle without load Ok, but but it does have a hint that it is missing. Under load, it is real evident that it is.

This thing just continues to lag, I really do not want spend money anymore.

Hotwire

yes i am running the scanner to tell the voltage, i didn't run it long enough to warm up, water pump is still not hooked up.

checked my knock sensor, it is the wrong one, it measures 100k ohms instead of 3300-4500 ohms that obdi sensors should. obdii sensors read from 97-107k, this might be a small part of my problem. reckon they smashed it pulling the motor from the camaro, and just stuck another on there, one more thing to replace....

here is what #4 looks like after firing it up about three times and taching it up to about 3k.



this is a brand new plug. it smells of gas too. from the ashy color, I would guess that indicates a lean mixture?

Do you have anyone local to you that you could swap pcms with to see if that changes anything?

I have eliminated all my electrical sources, and not getting any codes, and #4 still is missing. The only thing that tells the computer what cylinder it's on is the low resolution signal coming off the opti. Does the computer have different banks for firing each cylinder? I wouldn't think so, just thinking outloud. i might borrow a ocilloscope from work and put it on the signal wire to the ignition module to see if i'm getting all signals coming through.

i am sick right now, will probably do compression test later this week or this weekend.

Hotwire

Just talked to a friend of mine that used to be a gm mechanic.

Does this sound like a leaky intake gasket to anyone? I was messing w/ the intake bolt that holds the alternator bracket when I was having trouble blowing the alternators.. it is right about the #4 intake runner.... coincidence?

96ZRDR, have you checked your intake gasket? the rich on one side might be trying to compensate for the one runner getting extra fuel... everyone is asking me if the elbow is leaking, or vacuum source, no it isn't and all vacuum sources are good. that would lead to lean all the way around, and not just one cylinder...

I did mess w/ the intake bolt that holds the alternator bracket when i was first putting the truck together and kept on blowing alternators cause the volt. reg. was wired straight to +12..... and that bolt is reaaalllly close to the #4 intake runner...

What ya think?

96ZRDR

If you have a 94 engine (Mass Aif Flow) then an intake leak would make your car think it is running lean becuase of the unmetered air that is going though. The PCM will compensate by adding more fuel that is unnessary. If you have a complety internally stock engine, use a vaccumm gauge to dianose if you have a leak or not.

Or you could use my cheap method by pouring a little soapy water where you think the leak might be. just a little.

Your plugs look just like mine, but I do not think it is because of lean condition, but from a overly rich condition. Those plugs are carbon fouled, and seem to be wet of fuel.

If the needle fluctuates up and down then it most likely means that you have a intake leak/vaccum leak. Gauge is about 25-30 $$, and could at least give you an idea if you have to embark on a intake gasket change.

Good Luck Man