Engine hesitates when accelerating?

Hello,

This could be a problem with your fuel filter. I have included down below that will take to a guide that will help you troubleshoot your vehicles problem. Go through it and get back to us with what you find out.

https://www.2carpros.com/articles/engine-hesitates

Thanks,
Alex
2CarPros

I have a problem when I get to 40-50 mph my truck rumbles as if I have a bad tire you can feel it in the cab get over 50 iut smooths back out, it does not seem to be as bad in very cold weather, my check engine light came on the other day it was showing vaccum leaks i replaced the gas cap, it seemed to help for a while but now its back, any help would be greatly appreciated.

what was the code? you need to post that info for us.the code won't say vacum leak.and with the symptoms you are describing,it could be anything.we are only as good as thr info we are given.i want to help you but i need more to go on.

i cut the catalytic converters off my exhaust and run true dual sraits on my 02 chevy 5.3. as soon a i cut them off and ran my truck the engine light came on and never goes off now. When i nail it to pass someone it drops to passing gear and takes off great, then it has a 1 second lug to it then it goes back to the power it normally has. i cut the convertors out when it had @ 2000 miles on it. it now has 138,000 on it. is there any way i can override the engine light from the converters being cut off to stop the lug?

You will not be able to override the check light, the engine and engine management system is designed to run with the cat converter, the system must run with converters in place.

CEL/SES On

What you need to do here is have the computer scanned for OBD2 codes, there's a problem within the engine management system that caused the light to turn On, this is your starting point of diagnosis

2001 Chevy Silverado 6 cyl Two Wheel Drive Automatic 97k miles

No error codes..On 1st morning startup attempt there is a delay b/4 it starts...I changed fule filter, distributor cap, rotor, plugs, plug wires and problem still continues.

Have you checked fuel pump pressure and drop off rate?

Starts fine but runs rough until it seems to run about twenty minutes. It never shuts off and when you give gas it takes off, but initially stumbles when you first give the gas. After it runs for a while the problems goes away. Replaced fuel pump and filter about five years ago and recently changed coil, rotor, distributor cap and module under rotor. Also, new spark plug wires.

Hi and thanks for using 2CarPros.com. Has the check engine light come on? If so, have you scanned to determine if there are trouble codes stored?

Here is a video related to using a scanner:
https://youtu.be/YV3TRZwer8k

If no trouble codes exist, I would then recommend checking the coolant temperature sensor. Here is a description from alldata of what it does. If the sensor isn't working properly and provides false information to the computer, the air fuel mixture will be wrong and can cause what you are experiencing.

The Engine Coolant Temperature (ECT) sensor is a thermistor, a resistor which changes value based on temperature, mounted in the left cylinder head. Low coolant temperature produces a high resistance, 100,000 ohms at -38°C (-39°F) , while high temperature causes low resistance 70 ohms at 130°C (266°F) .

The Powertrain Control Module (PCM) supplies a 5.0 volt signal to the ECT sensor through a resistor in the PCM and measures the voltage. The voltage is high when the engine is cold. The voltage is low when the engine is hot. The PCM calculates the engine coolant temperature by measuring the voltage. The engine coolant temperature affects most systems the PCM controls.

The scan tool displays engine coolant temperature in degrees. When the engine starts, the engine coolant temperature should rise steadily to about 90°C (194°F) then stabilize when the thermostat opens.

The engine coolant temperature and intake air temperature should be close to each other if the engine ha8 not been run for several hours, overnight. The following DTCs set when the PCM detects a malfunction in the ECT sensor circuit:
DTC P0117 ECT Sensor Circuit Low Voltage
DTC P0118 ECT Sensor Circuit High Voltage
DTC P0125 Excessive Time to Closed Loop
DTC P1114 ECT Sensor CKT Intermittent Low Voltage
DTC P1115 ECT Sensor CKT Intermittent High Voltage



If you find the sensor to be faulty, here are directions for removal and replacement. Additionally, there are pictures to follow for part and location identification.

REMOVAL PROCEDURE
Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
Drain the engine coolant. Refer to Draining and fitting Cooling System in Engine Cooling.
Lower the vehicle.
Disconnect the electrical connector from the Engine Coolant Temperature (ECT) sensor.
NOTE: Refer to Handling Coolant Sensor Notice in Cautions and Notices.
Remove the ECT sensor.
INSTALLATION PROCEDURE
NOTE: Refer to Handling Coolant Sensor Notice in Cautions and Notices.
Coat the ECT sensor threads with sealer GM P/N 12346004 or the equivalent.
NOTE: Refer to fastener Notice in Cautions and Notices.
Install the ECT sensor.
Tighten
Tighten the ECT sensor to 20 N.m (15 lb ft) .
Connect the ECT sensor electrical connector.
Refill the engine coolant. Refer to Draining and fitting Cooling System in Engine Cooling.
Start the engine and check for leaks.
Reinspect the engine coolant level. Refer to Draining and Filling Cooling System in Engine Cooling.

I hope this helps. Let me know if you have other questions or need additional help.

Take care,
Joe

This happens mostly in the AM starting. Truck will turn over nice, but in idle. Will run then HESITATE. When it does the HESITATE, the lights will dim,then sort of rev up then back to normal. Like run ,HESITATE, run,HESITATE. Let it set and warm up for about 10 mins. Then it has s slow acceleration. Once is going for about 5 mins, runs fine and doesn't do it again. Till the morning again. Must also mention this happens on warm and cold mornings.(plugs changed, oil changed,sir filter changed.) Thanks for the help!!

The first thing I would do is monitor the fuel pressure through this entire period to document what the pressure does. This engine is extremely pressure sensitive and must have over 55PSI at all times.

My 00 silverado will stumble for several seconds, or will die when first started. At times, it will take awhile to crank over. At one point, it died when backing out from the driveway. No DTC's in PCM found. Other than that, Truck drives fine with no change in milege. The fuel pump was replaced at 55K (Warranty repair). Truck has aftermarket air intake and throttle body (Installed at 40K miles). Had no problem until it approx until 80k miles. My thought was a bad fuel pump, or maybe something with the exhaust. I would appreciate your input. Thanks.

Do you hear the fuel pump for a few secs when you turn key to run? If so do a fuel pressure test if not check ECM B fuse and fuel pump relay then report back

I have a half tank of gas. I leave work and make a few stops at the stores. shuting the truck off each time, starts up just fine. i go to the last (3rd) stop and when i get in and starts just fine, but with a hesitation when i give it gas, won't go a couple feet ,..kills, start up fine,..hesitation,..kill,...now i push it to the side and try starting it,..won't.
I look thing over, when to auto parts store get computer, it reads no codr, no error., i get a ride home and after approx. 2-hours i go back starts up finebut no go, it kills.i'm trying to think of everything:
I'm in southern MN.,...-5 deg.'s with a windchill -30,..i'haven't had this happen yet this winter or evr with this truck, last year the shop did work on two faughlty fuel inject jets. and its been alot colder. I looked at the vacum hoses, tomorrow i was going to try the air filter, put some isoprothyl in the gas before i start it,..because it runs for a while, maybe clear the line? and was running just fine today before that. now sitting in the groc. store parking lot, I need to get it out before they plow!! I would appreciate any help or suggestions.
Thank You.

Sounds like a bad fuel pump. You need to hook up a pressure gauge to the fuel pressure service port and measure the pump's output pressure. It should be around 55 to 60 PSI.

[quote:5adc8a30ca="dennyp"]Sounds like a bad fuel pump. You need to hook up a pressure gauge to the fuel pressure service port and measure the pump's output pressure. It should be around 55 to 60 PSI.[/quote:5adc8a30ca]

my oil pressure went down half as well when this started happening,...>if the press. is below that,..i need new one ,...right?...and is the pump in the gas tank,..?...and they can just quit like that,..all of a sudden??...

pump is in the tank. If the pressure is low, replace the pump and the fuel filter.

when i first start my truck my throttle is very hesitant, and my truck feels like it has no power at all. if i let it idle after trying to run it, it feels like its gonna die. it almost sounds like it is cammed. I have changed my PCV valve cleaned my air intake and throttle body. i either think it is my o2 sensors or my coil pack. please share your info with me.

Use a gage and check for proper fuel pressure fuel pressure. Can you check for applicable trouble codes? Some of the national brand autostores will check codes for free.

I forgot to ask litre size of engine?

It's a 5.3 v8, I took to autozone and they said it was the MAF, I changed it and it is still doing that. The check engine light flashes when I press on the gas.

What was the actual code number? The code doesn't tell you what to replace, just that the system thinks there is a problem on that circuit, somewhere.

Recently replace lower and upper intake manifold gaskets. Replaced fuel injector spider, distributor, distributor cap and rotor, new spark plugs and wires, and crankshaft position sensor. Cleaned Throttle body. Fuel pressure is 65 PSI. New fuel filter. No codes being sent. Any ideas? It starts quickly and idles well but when trying to take off, it stumbles, hesitates and sometimes backfires. Checked timing and it's good.

Hello, I'm Danny.

It sounds like you may possibly have plugged catalytic converter or converters. Most exhaust or muffler shops can check for you. Not having check engine light on or codes stored makes it hard to diagnose but with that high of a mileage that it what I think. Here are a few tutorials to view about Catalytic converters:

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

After having this performed keep us updated and we'll go from there. Hope this helps and thanks for using 2CarPros.

Hi,

Prior to replacing the gaskets, did the vehicle act the same way? Also, you indicated fuel pressure at 65 psi. Is that with the engine off? I ask because max (according to the manual with engine off) is 62. (see pic 1)

Is there any black smoke from the exhaust? Have you checked for vacuum leaks?

If you haven't checked for vacuum leaks, start there. Make sure everything on the air intake tube is back together properly and tight. Also, it's easy to leave a vacuum hose off. Here is a link that explains how to check:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let me know if his helps, what you find, or if you have other questions.

Joe