I bought a 96' suburban, used w/65k on it' about a year ago. It ran beautifully at first. After about 3 months it started running poorly. I bought a scan tool and found it was generating two dtc's (P0172 & P0300). I've replaced the plugs and wires and the cap and rotor. I also replaced the fuel filter I've checked the O2 sensors (seem OK), MAF (seems OK), MAP (seems OK), checked for intake leaks and found none. Now looking at coolant temp. sensor and fuel inj. sys. Need suggestions HELP.

 

Welcome to the Chevrolet Forum. The first one says bank 1 is too rich and second indicates random or multiple misfire. Might be injector problem. Try running a couple of bottles of Techron thru it.

 

Thank you for the reply, I have run some fuel injector cleaner through the system. I think it was STP or Gunk. Is that what Techron is? I've never heard of it.

 

Techron is a branded product. Sold at most auto supply stores. Unlike STP, et al, it actually works.

Here's what it looks like: http://www.chevron.com/products/ourf...tives/tcp.aspx

This is the concentrate. They also have a regular that's a little cheaper.

 

Thank you Sir, I'll give it a try and let yiu know how it works. I do believe the problem is in the injection system. I guess if this doesn't work my next step is to visually inspect the poppets?

 

Hey Shark, I put 4 bottles of Techron in my tank the last time I filled up. We're about 3/4 the way through the tank and still have the same trouble. According to my scan tool, when it goes into closed loop testing is when everything starts going south. Any ideas?

 

Bublfunk,
I just fixed my misfire issue yesterday. Only thing is that my code was a P0302, so I knew which cylinder was having the issue. Have you gotten any other P030# codes? At first all I had was the P0300. I disconnected the battery and let it sit for 30 mins. I had to drive for a while for the code to come back. When it did, it came back as a P0304. The last number represents the cyclinder. So cylinder #4 was my issue. It was running rough and had no power. After reading what others did and everyone getting inconsistent results, I decided that I would not replace any plugs, wires, rotor, or cap.
I removed the plenum (upper intake) to get to the spider assembly. I then completely removed the #2 and #4 injectors from the spider assembly and the intake manifold. I then swapped them. I put #2 in #4 place and vice versa. Put it all back together and cleared the computer by disconnecting the battery. When I test drove it, the error came back and of course it idled like hell. This time the code was P0302. The problem had followed the injector. I bought a new injector. Cost $60.99 at Autozone. I don't like Autozone, but they had the cheapest price, I had a $20 card, and the brand was the same as other places. I replaced the injector, and no codes and it has power and idles smooth as silk. Anyways, this is some extreme troubleshooting as it is a crap load of work. But, I used the info from many others who have spent a lot of money and got the same results. I just don't have that option. Good luck and let me know if you have any questions. I have taken that plenum off 5 times now and have gotten good at it.