The nightmares begin.

[rs74]

Starting to try and get all of the issues resolved on this truck. Vacuum lines were masking taped together, grounds not tightened down, just half assed all around. So I have found that I have no wiring for the electronic spark control module. Not sure where it went to. Is there a connector to where it can be taken out?

I peeled back the wiring loom a bit to see if maybe someone had cut wires but nothing yet. I did find this one connector that I don't know where it goes. Truck idles good but wants to start falling on its face when getting into the gas. I assume its because the ESC isnt hooked up along with knock sensor. I also have an O2 sensor broke and not hooked up.

[ChevyTech]

What year truck and which transmission.
Yes, it makes a difference in the spark control.

If it is your 1993 and it has a 4L60E the knock module is built into the PCM.

Is this an engine transplant?

[rs74]

Originally Posted by ChevyTech

What year truck and which transmission.
Yes, it makes a difference in the spark control.

If it is your 1993 and it has a 4L60E the knock module is built into the PCM.

Is this an engine transplant?

Yes this a 93 w/4L60E. A previous owner had put this engine in and I am not sure what it came out of. I had read this morning that the ESC was built into the computer. I did notice the knock sensor wire was not hooked up. Also the drivets exhaust manifold O2 sensor is broke and not hooked up. I need to fix both of those and see how it is timed.

The engine runs pretty good at idle but struggles when you give it too much gas. I fixed a lot of broken vacuum lines and have been rerouting wiring. Found the grounds on the thermostat housing were not tight and one of the eyelets broke so it was not making contact. Is the timing plug to disconnect under the dash or on the firewall on 93?

[ChevyTech]

The timing connector for an 1993 is under the hood near the transmission dipstick.


The location is shown in this thread:
http://67-72chevytrucks.com/vboard/s...d.php?t=358853

[rs74]

Thanks. Just trying to figure out why this engine is running so bad. It has just been a handful of little things that I am fixing along the way. Evidently the previous owner did a butcher job on this when replacing the engine.

[iluvmy72]

I would definitely consider a new harness.

[rs74]

I plugged the knock sensor in and re-timed to 0 degrees. Cap and rotor look good too, Still runs like crap though. Getting ready to pull the broken 02 sensor. Hopefully it comes out easy and doesn't pull the threads with it. Engine revs free in park and neutral. Just stumbles in gear. I haven't replaced the fuel filter yet either. May need to check fuel pressure.

[rs74]

Put new 02 sensor on and fuel filter but no change on startup. I ended up disconnecting battery for 30 minutes hoping for a relearn. Hooked it back up and it ran a lot better. Engine light kicked back on within ten seconds though. I drove it about 30 miles and all was pretty good. It still seems a little sluggish so I might bump timing up to 2 degrees from 0 after I see what code it threw. Making headway.

[ChevyTech]

If it does not run well with the timing adjusted to zero you should test the fuel pressure with the engine running.

The oxygen sensor is not affecting the fuel mixture until closed loop operation, so started cold the oxygen sensor is not being used. If it runs bad when first started cold the oxygen sensor is not the cause.

[rs74]

Originally Posted by ChevyTech

If it does not run well with the timing adjusted to zero you should test the fuel pressure with the engine running.

The oxygen sensor is not affecting the fuel mixture until closed loop operation, so started cold the oxygen sensor is not being used. If it runs bad when first started cold the oxygen sensor is not the cause.

I am still waiting for the guy to come and scan it for me to see what kicked the light on. Someone said to check the EGR but not sure what valve came on it from the factory. I guess there are two different kinds.

[ChevyTech]

A 1993 is a OBD1 system and you can retrieve the codes without a scan tool.

Here is a link to a post, with links to sites on retrieving the code without a scan tool.
http://67-72chevytrucks.com/vboard/s...5&postcount=11

The post is from the FAQs thread here.
http://67-72chevytrucks.com/vboard/s...=445487&page=2

To find many threads on EGR diagnosis you can search my user name and EGR.

[rs74]

This morning the truck was running pretty good. Went over to the next town and back which is about 40 miles round trip with only a little sputtering at about half throttle but it wasn't too bad. Then when I got back it started running like garbage. Drove about another 25 miles to get my 03 that just had the trans rebuilt and had the codes read there. The only thing that showed up was the 43 code which was present last time but the knock sensor was not hooked up then.

When I hooked it up I noticed that part of the plastic sleeve on the connector that goes inside the knock sensor was missing. Also it looked like maybe part of the metal piece inside of it may have been damaged a little bit. So after picking up the 03 and leaving the 93 I went and bought a new pig tail connector that I will put on in the morning. I am also going to throw a tune up on it since I have not done that yet since getting this truck and who knows the last time it had one.

Not sure why all of a sudden it started running like that. We did have a lot of rain today so that thought ran through my head with all the moisture. I will do the connector and see how that goes. If not then a new knock sensor will be bought.

[rs74]

Well I bought a new pigtail connector for the knock sensor and installed along with a tune up and no change. Still has the 43 code so going to go get a new knock sensor.

[ChevyTech]

Once the code 43 sets during a drive cycle the system will run in a backup mode, and there will no electronic spark timing control which will affect the way it runs. Some people notice the difference and some people don’t.

Code 43 can be the hardest code to find the cause of. My first suggestion is to pay attention to when the code gets set. When diagnosing it, it is very helpful to know if the code 43 is being set during the self test, or does it get set driving down the road on acceleration when the system is seeing a ping or something rattling on the engine.

Each time the Vehicle is started and certain criteria is met (coolant temp, MAP reading, engine RPM), a self test of the knock senor circuit is run. The ECM adds spark advance while anticipating a knock signal. If no knock signal is detected during the test a code 43 will be set.

Anything that prevents the knock/ping or prevents the system from detecting it will cause a code 43 to be set. A bad knock sensor, ECM failure, wiring, Timing way retarded or a very rich mixture can cause the code.

What many manuals will not tell you is that a code 43 can be set by something loose rattling on or in the engine. Lifters, cam, rod, crank and piston noises all have the potential for causing false knock signals to be produced.

The Knock sensor contains a piezoelectric crystal which causes a voltage to be produced. Loose components on or in the engine can cause the knock sensor to create a voltage and the system may interpret this as pinging. The system retards the timing because it determines it is pinging.

Loose torque converter bolts can cause a false knock signal to be detected.

Clear the 43 trouble code from the ECM memory. Make sure the key is OFF and removing the ECM fuses for tens seconds should clear the code. You could disconnect the battery to clear the code.
Drive the vehicle and try to determine when it sets.

Does the code set when you are just reaching T/Stat temp?
When you drive it hard?
When driving at freeway speeds?

CT

[rs74]

The code sets within the first ten seconds or less of starting the vehicle. The last three times I have cleared the code the light has come back on that fast every time.

The engine idles fine except when trying to get into my spot at home. It seems like with my foot on the brake and turning the wheel getting in front of my pole barn it wants to die. I took it out last night after the tune up and new connector and still when about 1/3 gas pedal it wants to start stumbling like its losing power. If I try to give it more gas you can hear it sucking air into the throttle body but I am not gaining any power. Kind of like the sound of when you open up the four barrel on a quadrajet carb. It just has that sound.

Now if I quickly feather the throttle a bunch I can get it to build speed to reach highway speed. Once I get there then it is the same thing. If I try to give it more gas then it wants to stumble and there is no power. I am going to try to get to the parts store this weekend and get the knock sensor and see how that goes. When combing through the scanner it did say that a possible cause could be ECM related like you said. I guess this is what I get for buying someones hack job of putting this engine in.

[rs74]

When I was underneath the truck yesterday I did notice a few things I need to address. The previous owners didn't bolt the trans dip down to the transmission and also didn't bolt the metal sleeve that the starter wires run through so it is just laying up against the exhaust manifold. I need to get the wires off the starter and re route the wiring because the ran it the wrong way. Ughh hacks.

[rs74]

Feeling a little aggravated here. New knock sensor is in and the light is off now but still running like crap. No change at all in the way it runs.

[rs74]

So I am thinking either check fuel pressure, EGR valve or maybe the computer.

[ChevyTech]

THE KNOCK SENSOR MUST MATCH THE ELECTRONIC COMPONENT IT IS SUPPLYING A SIGNAL TO!

It is a good thing you got a new knock sensor.

If the knock sensor in the engine was from a vehicle that used a separate ESC module, then you needed to get the correct module for your vehicle which has the module built into the PCM.

Everything is unknown about your engine. You may want to do a compression check.

The computers rarely fail.

Testing the fuel pressure with the engine running would be a good idea because these trucks have several problems that can cause low fuel pressure.

You could just disconnect and plug the vacuum hose to the EGR and take it for a test drive and see if it makes a difference.

[rs74]

I think I need a break from this. I can't even get it to syay running now. It was idling up and down. I took the breather off while it was running so i could get a better look at things. When it wants to die I can crack the throttle to keep it from choking out but it still wants to die afterwards on its own.

The knock sensor I bought is for this truck but I am not sure what this engine even came out of. I am thinking pre 93 because it had the esc module still bolted to the intake bracket. Just getting fed up here a little. Wouldnt be so bad but my 03 just started making a noise and I think its the front output bearing for the front driveshaft on the transfer case. Just cant win right now.

[ChevyTech]

If it seems like it is choking out (to much gas) check the coolant sensor that the PCM monitors.

There are specs & instructions here, in post #7
http://67-72chevytrucks.com/vboard/s...d.php?t=322811

[rs74]

Double checked both. They are hooked up and brand new in the last two weeks.

What about grounds? I noticed my 89 has a ground strap at the front of the block passenger side and one at rear of block passenger side but this 93 doesn't. Could that affect anything?

[54 jimmy]

you need a ground from the block to the frame. one from the block to the body and one from the body to the frame. i had one on my 91 break from the body to the block and caused all kinds of problems.

[ChevyTech]

54 Jimmy is correct that missing or poor grounds can cause all kinds of running problems.

There should be a ground between the back of the passenger side cylinder head and the fire wall. There should be a ground strap and a ground wire that goes into the harness.

The ECM and engine sensors ground at the front of the intake manifold under the front intake bolts/studs or by the thermostat.

A 1993 should have a ground between the negative battery cable and the fender.

[rs74]

Originally Posted by ChevyTech

54 Jimmy is correct that missing or poor grounds can cause all kinds of running problems.

There should be a ground between the back of the passenger side cylinder head and the fire wall. There should be a ground strap and a ground wire that goes into the harness.

The ECM and engine sensors ground at the front of the intake manifold under the front intake bolts/studs or by the thermostat.

A 1993 should have a ground between the negative battery cable and the fender.

I knew about the rear strap from the head to the firewall and font of head to the frame. There is a negative lead coming off of the battery cable that isn't hooked up. The ground wires at the thermostat housing are hooked up after I found they were finger tight and one eyelet was broke. I will have to look for that ground wire in the harness that goes to passenger rear of head. I don't recall seeing one there. I will see if napa has some ground straps in the morning.

I put another throttle body on this morning after I cleaned it really good. It made only a small difference. I tried to set the timing and the closest I could get back to zero before stalling out was about 4 degrees. Maybe some grounds will help. Also I have been getting the crap shocked out of me when trying to turn the distributor by hand. Been using a screwdriver since then. Man that will wake you right up. Lol