Rough Idle and other problems.

Now I know that the rough idle problem has been addressed in other threads, and normally I wouldn't post a new thread, but there are some other symptoms alongside this that I have not seen mentioned in other posts.

I have a rough idle, and rarely, like once every one or two months, the SES light comes on. I am very busy, and haven't been able to pull a code with the light on. The idle shakes the car and the tach needle fluctuates slightly.

In addition to the idle, when I am in park and revving the engine, even just up to 1500, and trying to maintain that speed, it will drop about 500 rpm, and then slowly go back up to 1500, and then repeat.

Also, when I am up at say 2500 or 3000 RPM and let go of the throttle, the engine rpm will go down in steps, like 2500, 2200, 1500, 1000, 700, 650. This takes about a second and a half or more.

I haven't been able to take the plenum off to check for washing due to a stripped torx screw that some idiot in a shop messed up, but when I get some money, I plan on checking (just need to buy some tools).


Any help in this area would be appreciated, and thanks in advance to everybody.

You can still pull the SES code if the light isn't on.. the computer stores the codes... swing by autozone and ask them to check your codes... and don't let them tell you they can't do it on a '95 vehicle.. they do mine all the time.. (it's a '95)

since this is intermittent I'd guess your egr valve is sticking.. which is a symptom itself of the dreaded fuel injector..

Mine did that same kind of behavior before I replaced my fuel injector.. and cleaned out the egr valve.

Get the codes read.

No one is that busy not to take 10 minutes at AutoZone or Advance to get the codes read.

Okay, okay i got the codes read at school (good thing i'm in auto shop). My only code is a P0131 Low voltage in sensor circuit bank 1...


Any help here? one of my classmates thought it might be an o2 sensor.

Your O2 sensor is not getting voltage it requires or the sensor itself iffaulty.

That code is for the O2 sensor before the cat.

i have a 93 blazer 4.3 vortec v6, and i sorta had the same problems, the only code i had was EGR...... on mine, it would idle REALLY rough, same as your with the tach fluctuating and whatnot, plus when i would drive it would be funning fine then just start suddering...... on my exhaust system it was rotted into the muffler upto the cat.... i put a new exhaust system on it, still shudders and spudders..... so i changed the distributer cap and rotor, plugs, and plug wires, the plugs were ok, but the carbon buildup on hte dist cap was TERRIBLE, plus the rotor was rusted onto the pin....., so i cleaned everything up, and it ran GREAT.... and has been for about 4 monthes... i was pretty proud of myself..... hah, but yeah, if that replaceing that o2 sensor doesnt help it, i would reccomend replacing the distributer cap, and along with me putting a new dist cap on it was allowing the engine to get a full burn which burnt off the carbon on hte EGR valve, so it was kinda a win win situation, well sorry for writing a novel, all the best with your blazer...

Jake

thanks for the information. I removed the EGR valve and checked it, and there was carbon on it, but it was functioning fine. I plan to change the O2 sensor soon, and then might get the cap and rotor checked out as normal maintenance anyways.

How old are they and how old are the plugs?

sorry i haven't been on in a while. The plugs were just changed about 2k mi ago. I didn't have the cap and rotor done at the same time, however (god i know i'm gonna get yelled at by BlazerLT for that) I just started a new thread, because i recently tried to smog the thing, since it hasn't been showing the SES light for a while, and it came back with high NOx emissions, but nothing else was high. I've heard that it could be the EGR, but that it isn't the O2 sensor because other emissions would be high as well... any more tips?

just posted to a reply to your newest post on the failed emmissions test. definetly sounds like an EGR problem. see that post for more info

sorry i haven't been on in a while. The plugs were just changed about 2k mi ago. I didn't have the cap and rotor done at the same time, however (god i know i'm gonna get yelled at by BlazerLT for that) I just started a new thread, because i recently tried to smog the thing, since it hasn't been showing the SES light for a while, and it came back with high NOx emissions, but nothing else was high. I've heard that it could be the EGR, but that it isn't the O2 sensor because other emissions would be high as well... any more tips?

NOx would be high combustion temperatures from an EGR plugged up a bit or a lean fuel mixture cause by maybe a plugged fuel filter.

I would change the cap and rotor seeing new plugs won't do a damn thing seeing the cap and rotor are the same. It is a chain, one wink link and it all fails.