pikez35

I have a 93 lt1 auto. It has a rebuilt engine with forged pistons and i believe a cam. Thats what the previous owner told me. I confirmed the forged pistons when i had to replace the head gaskets. I've had replaced the tps, iac, knock sensors, icm, coil, water pump, cts, optispark, put new msd 8.5 wires on. I replaced the optispark connector harness today. the old one had some corrosion in it. after i did that it seemed to run better but it still has a back fire and a lil bit of a miss. I rand the obd and i get a code 15, 22, and 43. 15 is the cts this is a new code not sure why happened after i replaced the opti. 22 tps low voltage. I have already replaced the tps, ive had the tps plugged in and out. i heard someone saying that it will come back into adjustment after driving a half a dozen driving cycles with it plugged in. 43 knock sensors open circuit. I replaced both knock sensors already and have checked the connections and they seem tight. only thing im thinking is it has something to do with the fuel injectors maybe the fuel filter. i haven't replaced those. when i check for pulse on the injectors with a screw driver to my ear on each they seem to be pulsing fine. It seems like im getting good fuel pressure to but haven't checked it with a gauge just pushed in the relieve valve once and alot of pressure came out. I have an appointment with a shop to clean the injectors out in a machine and to check them. He said he'll do it for $70. doesn't seem to bad. Do you think this is the problem or what else should i look for to possibly figure this out and save the $70.

STL94LT1

Make sure you didn't damage or forget to reconnect the Coolant Temp Sensor. The CTS is located on the front of the water pump.

marcwb

Dont ever replace parts without confirmation of them being bad. The best thing to do is have some engine data to see whats going on such as maf, coolant temp, 02, fuel trim and other sensory info. Try checking the maf sensor for hot, ground and 5 volt reference with key on. You will not be able to check airflow reading unless its a bosche. the delco requires a scanner.

1963SS

Has the miss been there since you got the car? Someone with dyslexia has posted the firing order wrong on one site. I'm looking for it but I just printed out the pic when I went to wire mine.They have the 5-3 wires reversed and that's just wrong. I had a bad miss that seemed to get better as I revved it up but I was getting random ((every minute or so, maybe) popping into my intake. It would still drive.

If you're getting a popping the spark is not getting where it needs to be at the correct time. On a 93 the opti can go in wrong. It just takes a little more pressure. I'd want to know that it correct and that the plugs are firing in the correct order. It just takes a few minutes to check it.

toptechx6

A lot of good advice posted so far, I'll post something that should help check firing order and wire routing.



Seems that many chase exotic solutions for misfire on these cars only to discover it is a simple ignition problem. Always best to start with the basics and do the diagnosis by the Factory Service Manual to isolate the problem before replacing parts.

pikez35

Thanks for all the replies. I went and replaced most of the sensors because most of them where broke off or missing. I put the opti in correct and thats actually the same picture i went off to do the wiring when i replaced the wires with the msd ones. I'm leaning towards its more of an injector problem cause it will miss intermediately and is worse once it warms up. This shop down the street from me said he has a tester and cleaning machine and will do it for $70 so worth a shot.

cleon123

Hi

Did you find the issue on the missfiring?

/Cleon

pikez35

pm sent. It was most likely my crappy stock delco injectors which i replaced with bosch III's. I have replaced the opti, msd wires, and all sensors though as well. Doesn't hurt especially if your car has higher miles

littlesk8cracker

in my experience and many others on this site, the msd wires are absolute garbage! watch the engine running in the dark and see if you can see and wires arching. i put msds on mine and they sucked, replaced with taylors

pikez35

Its all on what you like i have the super conductor msd wires 8.5mm and they run good. I also researched the forums and many members used these and liked these the best If its arching somewhere you have a break in the wire. Most cases not the wires fault but from melting on the header from it not being routed properly. Even with my old mallory wires that were on there i never had an arching problem. I doubt this is the problem in your case. but doesn't hurt to check.

littlesk8cracker

no problem now. my msd were not arching, just was suggesting that as something to look out for. no the problem on my msds were first that they would not make a solid clicking to lock onto the plugs. i kept having them fall off the plugs and opti. then when i went to remove them, 2 of them just ripped apart. and i used the silicone stuff so they werent stuck on

pikez35

maybe you just got some defective wires. mine stay on good and have never had a problem.