Roughs idle

No check engine ligh is not on. This vehicle does not have a distributor its a diesel engine not a gas. All filters have been changed

Already tried that all 8 inj have been replaced and when I remove injectors like you say it make a little difference but engine still rough and smoking but when I accelerate it goes away but smoke still present. Smoke is white

99 Blazer 130,000miles 4.3L V-6

I have been beating my head against the wall on this one. Over the course of the past few days I have dumped just over $300 dollars into parts and nothing has changed. No Codes other than a P0452 Evap low code(been getting this one for a while, but hasn't created any drivability problems.) The problem started while I was driving. The truck would run fine down the road then when I let off the gas to stop it would die. It always starts right back up. In two days it went from dying a couple times, to dying everytime I stop. I have replaced the IAC, EGR, and the MAP sensor, problem worse now. Used a fuel pressure gauge on the fuel system and pressures are good. Used a scan tool to check other systems, MAF, IAT, TPS, etc, everything looks good. Heres the odd thing though. The new MAP sensor is giving some really strange numbers, same thing the old one did. Haynes book says 1.5-2volts at idle and 4.5 full throttle, I get 1.70v at idle. As I depress the gas pedal, the voltage goes down, not up. The more pedal I give it the more the voltage goes down, never higher than 1.0 volt and as low as.5volt. I'm going to try to swap out the new MAP sensor for another new one and see if I happened to get a bad MAP sensor, but the old one acted the same way. I have no idea what to look at next. PCM? I have replaced all plugs and wires, cap and rotor, and the fuel pump within the last year. Put a new MAF on it about 2 years ago.
Any help would be greatly appreciated.

Hello, I have had this truck for 5 years with no problem. A friend borrowed truck to haul equipment 1000 miles away. When he brought it back, he said it will not idle and would barely stay running. (Nice friend). So here I am with a problem. I changed all plugs, wires and rotor. Flushed radiator, changed oil, oil filter, new power steering fluid, new brake fluid, and cleaned air filter. I pulled off intake and sprayed carb cleaner. I added marvel mystery to gas and filled tank up. With all that being done, it still has a rough idle around 400 on RPM gauge. Oil gauge fluctuates around 40. Headlights are dim, but when accelerator is pressed they go bright again. I definitely here a ticking under the hood. Fuel module in gas tank was replaced around 6000 miles ago. I also replaced the fuel filter about a month ago. Please help, I am confused. Could it be IAC, MAF or what?

This is the CSFI vehicle. The SES light does stay on all the time (3+ years now). I am a girl however I love to work on this thing. So should I go ahead and take the intake off and get started on the poppets? Would this make the truck have a missing sound almost like a tappet sound? The belt definitely needs to be changed.

I recently changed motors I have a 1998 chevy ext cab 5 speed well ichanged it to a 700r turbo automatic and put a motor out of a 2002 gmc sierra 1500 well I putit all together now it idles rough when u give it gas it dies I put it on computer and it gave code po118 n po115 help please

MY 1997 with 133,000 miles chevy pick up has a rough idle. After the vehicle warms up and it starts about 30 seconds after comming to a stop. I put new plugs in and it seemed to help a little but has not solved the problem. Any suggestions would be greatly appreciated.

Chris, old plugs looked good. Dist, wires & rotor changed @ 75000. Think maybe Oxygen sensor? Check engine light stays on for days and then goes off for a day or 2.

Have changed plugs, wires, aic valve, egr valve, cleaned mass airflow sensor and throttle body. Still Idles very rough and a lot worse when in gear. Much better when accelerating. Please help.