Hello I'm new here but frequent the site fairly often for advice to see if someone is experiencing the same problems I am. Anyways to get down to it. 2000 chevy blazer started running rough idling rough and backfiring like crazy. Changed plugs and wires it didn't help. Changed cap and rotor and no backfiring and seemed to be running alot better. Now my problem is it's still running a little funny. Will be fine then a little rough it goes back and forth almost like a fuel issue. Any help??

 

Do you have any codes? Which cylinders are misfiring?

George

 

I dont have any codes bc I haven't been able to drive it. Before I changed plugs wires cap and rotor it would stall and almost completely die when put in gear and backfiring pretty bad. I read that I shouldn't drive it very far with the CEL flashing as it could damage something that I don't have money to fix atm. I had checked the CEL before 2 yrs ago and it said cylinder 3 was misfiring. Cap and rotor are united motor product plugs are ac Delco and wires are ngk but I wouldn't think that would matter to much 🤷‍♂️

 

You dont need to drive it to get codes. Here are some cost effective ways:

https://blazerforum.com/forum/2nd-ge...lazers-103424/

Backfiring is usually timing. Sounds like the dist cap and rotor helped but you still check cmp retard.

A shade tree diagnostic that might help is to mist the engine in the dark at idle and liik for arching.

Also look for vacuum hose issues, Christine has write ups.

After you get code reader and live data capability we should look at fuel trims and O2 sensors

Make sure that you have clean gas and a new fuel filter

What did the old plugs look like?


George

 

I haven't changed fuel filter but was thinking it could be an issue as most everything is original except what I've replaced/changed. I also thought maybe maf or iac or tps sensors. Possibly even the spider injector which im not looking forward doing myself on that. 😓 thanks for the info George ill definitely be doing fuel filter soon and try to get some codes for ya
Old plugs didn't look to bad and they didn't have any gas or oil smell to them just smelled old 🤷‍♂️ and had some corrosion that looked like from wear and tear/weather

 

I have a cheap reader similar to this and like it. Works on all my cars. If it told me any more than the basics I wouldn't know how to fix it anyway!

edit: One of the problems with the plug-in types is the receptacle terminals can get messed up, maybe from plugging the OBD in crooked. That happened to me and I had to replace the receptacle, $18. So from that standpoint, wireless might be better.

 

Ok so I bought a cheap reader for 20 at Walmart a hyper tough. Gave me code P0303. I have changed plugs wires cap and rotor. Plugs are ac Delco the rest are not. I've read that anything can cause the misfire on cyl 3. Ig im back to throwing parts at it to get it running right. Fuel filter along with sensors including O2s 🤷‍♂️

 

Scroll down a little and there are some related threads. Also, maybe something here will help https://blazerforum.com/forum/search...archid=4346049

 

Double check that the spark plug wires are connected correctly.

It is easy to mix up Cylinders 1 and 3. The passenger side order is 2-4-6 whereas the driver's side is 3-1-5

If I recall correctly, checking the wires is the first step in diagnosing backfires according to the service manual. The book also says to check that the wires are not in contact with any metal or each other along their length.