Rough idle, engine miss at medium throttle

Hi saintmarysjohn, Welcome to 2carpros

Lack of acceleration,chugging,hesitating,jerking,bogging,misfiring etc. could be caused by one of the following below: I know its a long list to check, what makes it hard there's no CEL, no starting point-But you can try the TPS and MAP sensors and the fuel pressure for a starter

This guide will help us find it

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Please run down this guide and report back.

Just replaced all of the o2 sensors and exhaust gaskets. Because it had a p1133 code truck runs good with a rough idle when coming to a stop I have not replaced the timing yet. What could cause that idle to go 880 rpm to 920 rpm with no vacuum leaks.

How did you look for vacuum leaks?

I hooked up the vacuum gauge to the power boosters and saw that I was at 22 in of mercury. And then I sprayed wd40 over vac lines, and did not find any engine conditions changing. Hooked up the fuel gauge to fuel rail, and found that I had 39psi to the fuel rail at key on engine off. and Then hooked up the t-gauge to where the fuel flitter was, and found that I had 30psi to it.

I have never seen it done that way one way is to watch the fuel trim on a scan tool and spray carb spray all over watching the fuel trims.the best way to find even the smallest leaks is with smoke.

why is my truck idling rough after i have changed the spark plugs and the altenator

Engine running rough or misfiring can be cause by the following:

1.Defective spark plug.
2.Inadequate spark/coil,defective spark plug wire.
3.Lack of compression
4.Vacuum leak
5.Fautly fuel injectors.
6.Insufficient fuel pressure.
7.Contaminated fuel.
8.EGR valve that is leaking.
9.Oxygen sensors.

I have a 96 chevy s10 truck with the 262 4.3 vortec engine. I had it put in the shop for a burnt valve on the number 1 clinder and lifters knocking on the #2 and #6 cylinder , so i had the heads reworked on it. Now the engine runs fine at idel but when you get the rpm's up to about three grand the #6 lifters start knockin and the engine sounds like it wants to quit the whole time unless it's at an idel. it has no power at all and it will not climb a hill period. And my quetion is what do you think is wrong with this engine.

Sounds like you need to have the camshaft checked if the valve lifters are replaced and the rocker arm nuts are torque to specs-camlobes could be worned

depending on how loud hte knocking is it may be activating the kock sensor andit's cutting the power back. check the oilpressure by manual gauge. Make sure the rockers are adjusted though as well.they may notbe.

I just bought the truck for 400 dollars, it was missing on cylinder 4 so the person that I bought it from said. I went and changed out the plugs and wires along with the coil that was not already changed. The missing is not there any longer. When I take off it bogs way down unless I give it pretty much all the pedal. Is this because of a compression problem or is it a simple fix

Inspect and test all the following listed below and get back with some testing results we start here

Oxygen sensors.
Catalytic converter.
Fuel injectors dirty/sticking.
Mass airflow sensor/Airflow meter.
Throttle position sensor.
Manifold absolute pressure sensor.
EGR Valve
Fuel pressure regulator leaking or defective fuel pump.
False air leakage.
Fuel contamination.
Foul/defective spark plugs.
Open spark plug wires.
Ignition coil/Coil packs defective.
Incorrect ignition timing.
Cap and rotor.

I've had the truck for about 7 months. Rough idle since I got it. Found several vacuum leaks and fixed them. Replace the EGR, plugs, wires, cap, rotor and MAP sensor. Cleaned the TBI and replaced all gaskets and pressure regulator diaphragm and spring. Replaced the PCV and have blown out all vacuum ports and lines with carb cleaners and have not found any blockage. Lately, the truck has gotten worse and will hardly idle until it warms up and now, there is no power during acceleration until fully warmed up. Works better when I manually shift thru the gears allowing the engine to get higher RPM's. When on the highway, it would get up to speed but seems to take more time than at first. It doesn't have any power to pass other traffic on inclines in the mountains.
During idle, running very rich and can smell fuel.
Any ideas?
Jarrell

check fuel pressure with a gauge may below . if that is ok then it may be the injection unit has gone bad if it's cpi injection. if throttle body injection check for a vacuum leak at bottom of tbi unit they like to blow gaskets there.

Hello, I have a 1993 chevy S10 blazer with 102,000 miles that idles very rough at a stand still, but under power runs okay. I have replaced the fuel injectors, replaced the oxygen sensor, cleaned the egr, cleaned the throttle body, cleaned the plantum, cleaned the idle air control (that was very dirty), checked the charcol canister for fuel in it , it was okay, check spark plug wires for arching they were fine, put blazer on a scanner and came up with a rich fuel code which was a 44. No engine light or codes other than rich fuel. You can also smell a strong fuel smell especially when you first start the blazer then it seems to clear up. Im stumped. would greatly appritiate your advice on what you think could be the problem

Check the fuel pressure and get back with the readings

Hi, Im not able to get the fuel pressure readings the guy who has the tester is in the hospital. could the problem be the cataltic converter. It has a very strong fuel odor, I did have replace all the fuel injectors if that helps.

Could be disconnect the exhaust pipe on the exhaust manifold and hang it aside and try it again and see if it goes

my truck has been idleing rough for about a month now. it has gotten progressivly worse. it used to run rough only when the a/c was on but we replaced the idle control and the problem was solved for about 4 months. here's the first problem- now it runs very rough when i am stopped or with no foot on the gas at idle speed. almost stalls when you come to an adrupt stop. when you do a steady speed the truck runs perfect. second problem is if the a/c is on,still runs rough but the a/c will quit blowing completly when you try to pass someone or stomp the gas, then resume cold when you let off or maintain speed. to let you know something else-the truck has ALWAYS had blue smoke on start up. the temp gauge reads even and no problem lights come on, no other signs or symptoms that i can make you aware of. the truck runs the same rain or shine, hot or cold weather.

You have a vacuum leak in the A/C vacuum supply line! This is the black line that goes thru the firewall, trace it to either the break, or the check valve and reserve tank, that could be cracked. Fix the vacuum leak and both a/c and idle will improve, the blue smoke is burning oil. if only at startup, it's probably valve stem seals.

I have owned my truck for 12 years. This my third engine and I have been chasing down this problem all the while. Despite different engines (new ones) there has always been a skip/miss at all speeds. It runs good and gets 20 mpg. but I just cant seem to find the problem. This new engine from Jasper was installed with all new stuff and it still does it! I suspect it may be an issue with the HEI system (fine tuning or upgrading) , a timing issue or maybe its just typical of this engine. If so are there any changes, upgrades or fine tuning that can be done to remmedy this issue. I am a pefectionist when it comes to my ride so please help this is driving me crazy. PS- Ive been through about 4 exhaust manifolds over the years. Why do they keep cracking?

Have you checked the MAP sensor , EGR valve and EGR contoller?

[quote:2dd5c480c9="mcferrance"]Have you checked the MAP sensor , EGR valve and EGR contoller?[/quote:2dd5c480c9]


Never replaced the MAP sensor (not sure how to check it), EGR replaced with new engine, not sure about the EGR controller

i was going to say check egr. i had a trick bag one years back when i worked at chevy. it had been to several dealers and what i found was the problem is that the egr adapter had the wrong gasket installed causing a lean misfire. this would answer the question of why manifolds are cracking. **i think we are onto something here. disassemble egr and the mounting to make sure the right gaskets are installed. you can try sspraying a little carb cleaner around intaqke and see if it smoothes out,(lean miss). get back to us.

[quote:8474f9f042="mastertechtim"]i was going to say check egr. i had a trick bag one years back when i worked at chevy. it had been to several dealers and what i found was the problem is that the egr adapter had the wrong gasket installed causing a lean misfire. this would answer the question of why manifolds are cracking. **i think we are onto something here. disassemble egr and the mounting to make sure the right gaskets are installed. you can try sspraying a little carb cleaner around intaqke and see if it smoothes out,(lean miss). get back to us.[/quote:8474f9f042]

Ill try that. What is the correct gasket? Thanks man

My workhorse truck finally left me on the side of the road after 15 years. The power steering pump bracket broke in half - belt came off. drove the truck back home without the belt - replaced the pump bracket and replaced the serpentine belt. Now the truck wont start...barely turns over, runs rough and makes terrible noise for 30 seconds - then upon trying to restart. nothing. Runs fine without the serpentine belt - but when installed - wont run . Is the timing belt maybe out of sync when the pump bracket broke? Worked fine - now cant drive it with the belt on. Thanks for any help.

[quote:fe1452c045="jason pierce"][quote:fe1452c045="mastertechtim"]i was going to say check egr. i had a trick bag one years back when i worked at chevy. it had been to several dealers and what i found was the problem is that the egr adapter had the wrong gasket installed causing a lean misfire. this would answer the question of why manifolds are cracking. **i think we are onto something here. disassemble egr and the mounting to make sure the right gaskets are installed. you can try sspraying a little carb cleaner around intaqke and see if it smoothes out,(lean miss). get back to us.[/quote:fe1452c045]

Ill try that. What is the correct gasket? Thanks man[/quote:fe1452c045]

Check to make sure none of the pullys on the belt drive are locked up. the 4.3 has chain driven timing, and that has nothing to do with the accessory belt anyways. I get the feeling one of the accessories locked up: the belt drive does have the ability to keep the motor from turning in these trucks.

i forget exactly but i remember that when you take it apart you will see that there is a space not covered by gasket that should be causning basically egr operation at idle. there are 2 different style gaskets, i so you have a 50 50 chance of getting the right one. these gaskets are always reused when doing engine work but at some point someone replaced it. my problem came to after a head gasket was installed.

My S10 Blazer has intermittently developed a rough idle that sometimes clears up after running the engine at high revs for a bit. Seems worse with cold weather. Engine trouble code is 33. Have already replaced the MAP sensor, seemed to fix, but problem came back.

With colder weather now, it is constantly in rough idle. Will stall if left at idle. If throttle is opened wide, engine will run fine until gas pedal released and goes back to idle.

1. I am trying to find the ECM module to see if there is a connection problem in it - web says it is located under glove box, is this right??

2. Any other ideas as to what the problem might be as it is not a faulty ECM.

Thanks

Check the wiring harness and connector for the MAF. Also you might want to pull the EGR and clean the pintle a small chunk of crud can hold them open enough to cause the rough idle.

Ok, will do that- where is the ecm module located?? The web pages indicate it is behind the glove box, but I have partially disassembled the dash, and I don't see it yet.

The ECM is behind the glove box area mounted vertical.
If you remove the glove box liner you will see it mounted there.

Hi, my pickup that is having rough idling issues and hesitation while accelerating. The problems only occur after the truck has warmed up and the acceleration issue only happens when I try to quickly accelerate. I am also noticing a decline in fuel economy as well as an increase in the smelly of my exhaust. I have pulled a spark plug thinking that they might be fouled or just gaped improperly but they looked fine.

Hello,

It sounds like you have low compression in one or more of the cylinders this guide should help us. It could have a bad injector.

https://www.2carpros.com/articles/engine-vibration-at-idle

Please run down this guide and report back.

i have a blazer and it was doing kinda the same thing. get it warm and see if there is a knocking in the distributor cap. that should help narrow u down a little. I got a rebuilt distributor and new plugs and wires the truck runs great!

My 89 Chevy S-10 has 71,000 miles.
The engine runs good when it is cold, but
when the engine warms up it seems that the idle lowers and the engine starts to run rougher than when I first start it up.
The engine begines to run so rough that it acts like it's going to stall but does'nt. I've replaced the Air idle controll valve,new ECM,new plugs and wires and an O2 sensor. The EGR valve seems to be OK. I've had a vacuum check done on the valve (EGR) and it seems to be operating properly, but i'm unsure if it could be bad. When I hook up a vacuum gauge to it the idle does change. If I do it while it is could it starts to run as it would when it warms up. What would be the problem is there something that I might be over looking? What might the problem be?
PLEASE HELP!!

Try this, remove the EGR and check to see if it is plugged with carbon. Let me know what you find. Also, make sure the intake isn't plugged with carbon where the EGR mounts. Also, check the hoses going to it to make sure they are not plugged.

Let me know what you find. You should also check the valve when it's off to make sure the valve is moving and sealing when closed.

Ive Checked the EGR valve to see if there was any carbon build up. The area where the EGR valve seats seems to be fine. I don't see a whole lot of build up.
I've checked all the vacuum lines to see if they were plugged. They seem to be clear. I've also checked all the vacuum inlets going into the throttle body for any heavy build up. I found that the line for the PCV valve had some heavy build up, but was able to clean it out with some throttle body cleaner. ? would a worn pcv valve cause this problem. The reason i'm asking is because when I pull lose the pcv valve line off the throttle body the idle seems to smooth out quite a bit and the idle comes up just a hair. How would I know if the electronic vacuum sensor is working properly?
I've taken some throttle body cleaner and sprayed the surrounding areas of the EGR valve really good and also cleaned inside where the valve sits. The inside of the throttle body behind the EGR valve did'nt appear to have alot of carbon- just minor amounts. I sprayed throttle body cleaner into this area just incase there was. I also sprayed the area around where the injectors spray and around the IAC
valve and just about any where else I thought that minght be effecting the vacuum air flow. It's still idling rough when its warm but seems to be trying to run a little better that's why I was asking if the pcv valve might have a part in this. That's why I'm also asking about the electronic vacuum sensor. You pull the vaccum lines off and I've got vacuum on one side but not the other. Oh! the egr valve does seem to be moving fine but, it does make a slight rubbing sound.
I'm working at it little by little but, I know that the issue will be terminated eventually.

The PCV can cause a rough idle. Are you sure it is working properly? Also, did you check the intake for leaks? The intake gaskets on these vehicles have a history of leaking.