96 GMC Jimmy black smoke, backfires, Timing?

[corhey88]

I still have the Duralast cap and rotor and wires, I did Replace the Plugs to AcDelco. I do believe that did help it a bit.. I can try putting AcDelco cap rotor and wires... Would that really make that big of a difference? I have never had trouble with buying that brand before on other vehicles. I will have to ask about what the specs where on the Fuel System.. Thanks

[old_master]

There are several threads on AF where members have installed Duralast secondary ignition parts on their 4.3 engines, (do a search). They have experienced problems either right away or shortly after the parts were installed. This includes all GM vehicles with the 4.3 "W" & "X" engines, not just Blazer & Jimmy. If you were to put the vehicle on a scope, you'd see immediately if the problem was caused by a fault in secondary ignition. But, since a scope is not a piece of equipment found in the average DIYer's garage, it's another important reason to use quality parts. I'm not saying your parts are faulty, but it's a possibility. I would suggest starting with an AC Delco cap and rotor, and see if you can get the fuel pressure and leakdown results. Might not be a bad idea to add a fuel pressure gauge to your tool box They're like $20

[corhey88]

I reinstalled the EGR valve today.I also disconnected the battery to reset the computer. And just for the hell of it i started the jimmy in the driveway and let it run for about 15 min. It actually stayed running the whole time. But it began idleing higher than normal. Anyways...I plugged in the OBD2 Scanner And i got new Codes ! ! they are
-P0300 multiple cylinder misfire
-p0134 O2 Sensor circuit No activity detected
-P0146 O2 sensor circuit no activity detected
-P0152 O2 sensor circuit High Voltage
-P0753 Shift Solenoid "A" Electrical
So, has the computer detected a bad O2 sensor?? and how can i tell wich one, i think there are Four on the jimmy
Thanks,

[old_master]

DTC's must to diagnosed and repaired in the order that they appear. Then after the repair, clear all DTC's from the memory, and perform a drive cycle to confirm the repair. Disconnecting the battery will turn the SES light off provided there are no hard faults. It will not remove the DTC's from memory, that must be done with a scan tool.

Whatever caused the P0300 to set, likely caused the other DTC's to set also. After diagnosing, repairing the cause of the P0300, clearing the memory, and performing a drive cycle, it's quite possible the other DTC's will not return.

P0300 is almost always caused by a fault in the secondary ignition system: Spark plugs, spark plug wires, distributor cap & rotor, and ignition coil however, it can also be caused by low fuel pressure.

[corhey88]

I am sorry but u have no resaon to believe i have a fuel pressure problem. I have Replaced the Fuel pump, the Fuel filter, And i just replaced the Fuel regulator, and the "Spider". And my mechanic already looked at my fuel system... My battery had a drain on it untill three days ago. This was causing the computer to continusily be reset.. Therefore it could never save codes... And Yesterday was the first time since i owned the Jimmy that the truck actually ran long enough to heat up.. I believe that the vehicle must warm up in order for the oxygen sensor to have set a DTC. I Have also replaced every single part in my secondary ignition system.. Even the ECU ! coil, ignition module,.So i Am eliminating that as an option as well. So that leaving me to the last option.. being a Fault in my Emissions system, and i have already cleaned my egr valve, bought a new map sensor and maf sensor. And the fact that i do have DTC's for Oxygen sensors.. I am going to buy the oxygens sensors.. TO be honest .. I have replaced everything else that could be causing this problem.. its change these are its goin to the junkyard. I have listed all the parts i replaced in all my messages i posted. And i found the sensors for 20 bucks each on ebay. Thanks for the help

[old_master]

You've replaced a ton of parts and spent a ton of money, and the problem is still there. Now would be the time to diagnose rather than guess. I am assuming that since you used a Duralast distributor cap, you most likely used an Airtex fuel pump, (Autozone sells both of those). The reason I suggest checking fuel pressure and leakdown is that Airtex fuel pumps are known to have low fuel pressure and leaky check valves.... right out of the box. Just because a part is new, is no guarantee that it's good.

[corhey88]

I got my fuel pump from Auto Value...
I Fixed the problem yesterday! My friend suggested because of the backfire to check my Firing order... Turned out two of my spark plug wires needed switched around. I started it up, and it runs Excellent. At least i know i have a ton of new parts...
Thanks for the help

[Mbcomp]

hahahahahahahahahaha i'm sorry but all that for a firing order! common always start at the basics! Nice try though old_master

[old_master]

Originally Posted by corhey88

....I Fixed the problem yesterday! My friend suggested because of the backfire to check my Firing order... Turned out two of my spark plug wires needed switched around. I started it up, and it runs Excellent...

In your very first post you mentioned that you replaced the cap and wires... Let me guess, you switched #1 and #3 in the cap? It's a common mistake and also the reason to replace wires one at a time Anyway, glad you got it going.