Rough Running Engine

My 99 Silverado starts ok when it is raining or high humidity but runs rough until it warms up. then it runs fine, its like the dampness in the air is causing the problem. what can it be? thanks.....binko

Next time it runs fine, try spraying a mist of water over the cap and wires to see if it acts up. Start with the wires. IF it does, replace them.

does a bad ignition switch cause my 1998 silverado to run rough when it is cold, truck starts fine and runs good when engine warms up

Try cleaning out the idle air control valve and see what happens

My 96 vortec 350 is running poorly I have changed fuel pump, fuel filter, cap, rotor, plugs, wires, egr valve, maf sensor. My fuel pressure is ok @ 66 lbs.Here's the deal, my cam timing is running @ -11 degrees on the cam. Is this indicative of the engine needing a new cam chain and sprocket? I know the older engines had a fiber sprocket and we would replace them with a steel, double gear type. I Took the truck to a mechanic and he checked the fuel pressure for me and that's when he told me about the cam. He said that the cam timing should be 0-2 degrees negative or positive, either way. Please help. Thank you.

same problem here and the distribtor gear needed replaced it was wore out but the truck timing has to be set between -2&2 to alighn the cam sensor and crank sensor so it will fire and inject fuel at the right time.

I just got this truck 2 weeks ago, it has a 5.0 l in it that has just been rebuilt. The truck cranks up fine every time but it will run rough for a few seconds then smooth back up and run fine. I haven't had a lot of free time here lately, so unfortunately I haven't been able to drive the truck or mess with it that much yet. I'm trying to figure out is it a fuel problem or electrical problem, what do you think?

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.False air leakage.
5.Faulty fuel injectors.
6.Insufficient fuel pressure.
7.Contaminated fuel.
8.EGR valve that is leaking.
9.Oxygen sensors.
10.Throttle position sensor.
11.Manifold absolute pressure sensor

Chevy 1996 k-2500 5.7L Vortec. The truck was running very rough and was low on power. The rotor cap was damaged as well as the distributor cap. Replaced both. The truck was still running rough. I Pulled the distributor and it had a ton of vertical play in it. I Replaced the distributor and the truck is still running the same.

have an engine scan done on this. it might be a vacuum leak or something else. also check the fuel pressure. most auto parts do scans for free.

Rebuilt Motor with over 1000 miles, just installed new distributor, new MAP Sensor, new Idle Air Control Motor, new Cap and Rotor, TPS is working,disconnected battery for over 30 minutes and recycled ignition 6 times. Service Engine Light is on, Timing has been set, idles smoothly in Park or Nuetral, throttle response is good! But when I shift into Reverse or Drive the motor dies. When I put it back into Park it starts right back up. Code 22,34 and 42 are what shows up on the tester. What is the Fuel Cut off Relay Circuit and where is it located? And any other ideas that might solve the problem?

Codes-
22- TPS signal voltage low
34- MAP sensor signal voltage low
42- EST electronic spark timing.

To begin.. did you unplug the tan/blk wire to set the base ignition timing? It is either on the p/s, under the dash taped to the wiring harness or under the plastic cover on the firewall, p/s.

The other codes all refer to bad grounds as a possible cause. Double check all ECM grounds on back of cyl head and be sure the engine is grounded good. If all ok,get a meter and get back to me for further tests

During cold season or weather 40 degree or below my 94 chevy 350 pick-up, it has all new tune-up which it did improve the problem some what but not all the way. i pulled no engine code. Now when i start to drive it, it does the same thing acts like it is missing or hesitating to take off but it does accelerate never has stalled. If i give get on it pretty hard it runs and takes off great. now after maybe 5 mins or so pretty much once i notice the temp gauge has moved up some it runs great. and yes it has 400000 miles on original engine doesnt smoke and runs great any other time and trans and rear end with just minor repairs. Also just a simple question beside i figure the trans is just old but the transmission shift hard into second gear only shifts better after warm up. i have always serviced the transmission at least every 60,000 miles has clean fluid i maybe do perform a flush on it when i get the chance i know it needs a new filter.

I may be of little help

I'm still stuck in the carburetor age

Are you using fluids recommended for those extreme conditions?

I don't live at the northpole as it sounds like you do, but it get's cold down here in s.c. too..........anything under 6o degrees is cold to me!.....but really, at 20s and 30s, just about any machine needs to warm up to operating temperature before you can expect tip top performance.

I mean like---artificial warmth or just let it idle for 5-10 minutes before you take off! Even way back, your horse didn't operate well till he had a warm up!

I really am trying to help....this is how i approach the old vehicle way---as i still drive....if you still think you have a mechanical issue and no one else jumps in with another answer....i will find you another expert, let me know if that's what you want.

I'm sure you are probably familiar with this or something similar.....ex-girlfriends '82 mustang 2oo 6 cylinder was very cold natured.......i fell into this at a yard sale for $5 still boxed up. It installs on the lower radiator hose as close to the radiator as possible.......warm water rises!

I had it plugged into a timer and drove a post in where she parked.

She was a bit on the "lazy, inattentive" mode at times, so i kinda put a small hose clamp around the plug portion and a piece of 550 cord (parachute cord) and tied that to her car and tied the extension cord to the post

Presto!!!---if she backed up, it unplugged itself! (and the wires didn't get snatched out!)

I know they make "dipstick heaters" too---i know little about how good they work

But i can tell you this

The timer was set to come on 3 hours before she drove it

The window stayed defrosted because i guess that was "default" on the heater box, and the heater core got warm

And there was "warmth" coming out of the vents when you 1st cranked up

The engine and radiator were pretty warm

It ran a lot better, until it fully warmed up

This thing came from napa originally, and after seeing this one, one of my friends got one, i think it was under $40, but don't hold me to that ---i still have it.......it was used it about 8 years ago

Just some thoughts---thought it could help

The medic

The truck runs and drives perfect without the lights on. But as soon as i switch the lights on, it acts like its not getting gas, if im driving and keep the throttle in the same position, it will just quit like theres no gas untill i move the throttle. For a while, i was only driving at night so i didnt realise that it only happened with the lights on, so i replaced the alternator, and fuel filter, which didn't help at all. So i have no idea of where to start troubleshooting.

check battery for condition including load test most places do for free.. then replace belt and tensioner which is recommended every 60,000 mi.

New battery and belt too, forgot to mention

check fusible link for generator it may not get proper voltage with lights on maybe a strand holding it together. what is voltage at battery with lights on and off

94 chevy 4.3 v6 starts fine,runs good till warms up,then like toilet,wont idle when give fuel no skips but will flutter then run then flutter. Have changed fuel filter, put 2 cans dry gas in,not fouling plugs.Any ideas??

Is the check engine light coming on at all?

only came on once when i floored it,light stayed on for 2hours and it idled w/out fluttering once,when i started it next day back to fluttering when warmed up

You need to have the codes read first to give you a starting point.

when engine running rough there is no check engine light on , although code should be under history of codes correct?

Engine idles fine in driveway. When it is being driven, i can go about two block before it starts to spit and sputter as if its not getting gas.

The light doesn't have to be on. It has a memory as long as you don't disconnect the battery. You may need a professional scan tool for that one though. that is a transition year.

good morning my name is Roy and I will assist.

the first thing I would do is to check the fuel pressure. sounds like a failing fuel pump. you can rent a tester at a parts store.

Roy

New on computers having trouble here...figured it out. Thanks for the help!

Hi Jack,

Here is a link to an article from this site that features written instructions and pictures showing and explaining the process of checking the fuel pressure yourself. If you decide you would like do this yourself you can purchase a fuel pressure gauge online from sites like Amazon.com.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Thank you for visiting 2CarPros.

Kindest regards,

Renee
Admin

Fuel pressure is 58psi. Spec is 55. I have no engine check light or codes at all.

I am just putting in my two cents to see if you have installed spark plug recently? Here is a guide that can help you:

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

Please let us know what you find.

Best, Ken

I have not replaced my plugs lately, no.

Always starts ok. When I drive away immediately after starting, it will barely move and runs Very rough and Service engine light flashes; but if I let it idle for 10-15 minutes before driving, it runs fine...Fuel Injection 'spider' and fuel pressure regulator were just replaced

You need to count the flashes to read the code. should be quick flashes at first to tell you the first digit and then a pause, then more quick flashes for the second digit.

Hey Jack,

Thats where I would start here is a guide to help you.

https://www.2carpros.com/articles/how-to-change-spark-plugs

Please let us know happens so it will help others.

Best, Ken

I am tellin' you, if your Vortec has more than 100,000 miles eliminate the distributor by replacing it, only $35 on eBay it is billet aluminum and comes w/ cap and sensors, these plastic distributors all go bad and produce a wide range of faults and loss of power.

Good to know Bob. Let us know if we can help again.

https://www.2carpros.com/questions/new

Cheers, Ken