Engine Hesitation?

Hi and thanks for using 2CarPros.com.

This could be several things. If the check engine light is on, have the computer scanned to determine trouble codes and possible solutions to this problem.

If there is no check engine light, I would start by checking fuel pump pressure. If the pressure is low at first, it can cause the symptoms you described.

Here are general directions for checking fuel pump pressure:

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

and

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

The pressure specifications are:
Engine NOT running 60 - 66 psi at 0 rpm
Note: Check pressure with the key "on" and the engine not running.

Do this and let me know what you find.

Take care,
Joe

I am trying to figure out why my truck is hesitating. When I first start off the RPM's will climb until it shifts from first gear to second gear and then it does it again from second to third but just not as bad. I have replaced the fuel filter but it did not solve the problem. What do you think is causing this?

Have you checked for vacuum leaks? Has the check engine light come on? Have you tested fuel pump pressure?

Let me know.

Joe

I havent checked for vaccuum leaks or the pump pressure yet

yeah the check engine light has been on for a little while now

IF the check engine light is on at times, there will be a trouble code stored in the computer. Take the vehicle to a nationally recognized parts store and have them scan the computer. Most will do it for free, so there is no money out of pocket for you. After they identify the code, you should know what the problem is. Let me know what you find so I can help you with further questions.

Joe

My 98 chevy pickup started to have a awful mean hesitation upon acceleration and a surge upon decelleration first thing i thought of was ignition so here is what ive worked on, i was taught never to throw parts at the car however ive done as much diag time as I can the problem was before/remains after the following has been done
1.new ignition wires cap rotor and plugs
2.fuel filter replacement
3.checked maf sensor with voltage meter
4.SES light does not illuminate
5.the engine does not temporarly shut of just loses power when driving.
replaced tps sensor and IAC valve performed sweep test no breaks
it continues to bang harder then originally had the problem and now also it stalls when shifted from drive to park. Any help would be highly appreicated.

Thanks, NIck

Thanks for the donation

The following could cause your problem:

Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires

I was wondering if any one could help out with a 7.4 liter that stumbles at 1/2 throttle or so? Plugs and wires didn't help, nor did a tps. no check engine light . but it does idle a little rough. please help

Did you use AC Delco plugs and wires? If not, change to AC Delco. Any other brand will not work and/or help. If there are no vaccume leaks and the PCV valve is not sticking, then it sounds like the the timing is off a little and the distributer gear may be worn. This is a commonly overlooked problem. You can take the distributer out to check or have the timing checked. Remember, the timing on your engine must be checked at operating temperature and with a scan tool -- a timing light will not work.

This guide can help.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please run down this guide and report back.

hi I have a 1997 chevy c1500 with a 350 and automatic transmission 2wd I have issues with hesitation while accerlation when engine is cold when the engine is driven for a few miles the hesitation is gone and drives normal it only happens when the truck is first started and driven there is no check engine light on I replace spark plugs and wires on it and air filter if you know whats going on please help it driving me crazy about the hesitation while accerlating when engine is cold?

The place to start is by having the diagnostic fault codes read and recorded. The people at many auto parts stores will do that for you for free. The problem is though, a sensor reading has to go outside of a specific voltage range for a code to set. That sensor can sometimes report the wrong value but one that is acceptable to the Engine Computer. In that case your mechanic will have to look at live data on a scanner to see what doesn't look right.

Another thing to consider is a vacuum leak or a leak in the fresh air tube between the air filter box and the throttle body. Every manufacturer other than Chrysler uses a mass air flow sensor to measure the weight of the incoming air. A leak anywhere that lets air sneak in without being measured will result in no gas to go with it. That will cause a lean condition and typically a hesitation. Once the coolant temperature reaches a certain point, the system goes into "closed loop", meaning the computer adds the oxygen sensor readings to its list of things it uses to calculate fuel metering. That can result in the computer requesting extra fuel to get the lean mixture back to where it should be, and the hesitation will be gone.

Engine Performance problem
1997 Chevy Silverado V8 Two Wheel Drive Automatic 135 000 miles

I have a 1997 Silverado with a 5.7L Vortec. Recently my engine has started to stumble and hesitate during acceleration. I have recently changed the spark plugs and fuel filter, cleaned the air filter and replaced my cap and rotor. Any suggestions?

I had that problem...then it was too late ( stuck in the middle of now where!) It was my fuel pump....had it replaced and it runs like a dream. Hope that helps.

my 96 chevy truck has a issuse when hot it stumbles when u accelarate,also hard start when cold.replaced fuel pump and filter,ignition coil and module,replace map sensor,replaced cap,rotor,and plugs,replaced air filter,replced the spi unit under throttle body. truck carries 60lbs of fuel pressure. possible cat converter problem? please if u can be helpful let me know.Thanks!

Hi
Check engine light on? Could be two problems one stumble maybe MAF try cleaning. Cold start temp sender ECT near thermostat housing.
Let me know
Thanks for donate

no codes present on truck.was told by another mech possible cat converter plugged.ck engine light has been taken out by some one else.tech said their where no codes.

Cloged CAT is not likely with your symptoms. What about MAF and temp sender?

My 1500 Chevy Pickup started hesitating last week (as if it were running out of gas) and now has completely broke down. When I left it in Idle and then floored it- the truck made a groggling sound and it felt as if the fuel filter was clogged. I changed out the fuel filter, checked a couple of sparkplugs (they were loose, but still in good condition), and made sure the air filter wasn't damaged or clogged- no improvement. I haven't checked wires or anything of that nature, because Im kind of fed up. Do you guys have any insight on what the problem might be?

spray starter fluid into intake and if it starts then the fuel pump probably died.

https://www.2carpros.com/car_repair_video/test_fuel_injection_pressure.htm
Go here and checkout our video.
I agree with Tim...turn key to on, can you hear the pump for 2-3 seconds? Listen at the tank, remove the cap if you have to.

Once in a while when im on the highway and try to accelerate my truck slows down and i have to floor it for it even to pick up the speed again, and after a couple of seconds i let go of the gas and press the gas and its good again. For some reason it also wont go past 70 something mph. I know its not the transmission, or fuel pump. What do you think is wrong with it?

Hi,

I have to be honest, what you described sounds like a typical low fuel pressure issue, but if you already check it and it's fine, then my next suspect would be related to a bad catalytic converter. Often times the insides of the converter will come loose and block air flow. The result is a loss of power.

Here is a link to test for a bad converter:

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

Next, I need to know if you have checked for diagnostic trouble codes. The vehicle has an OBD 1 system. You don't need a scanner to check for codes. All that is needed is a short jumper wire or even a paper clip. If you haven't try this. Here is a link that explains how it is done:

https://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method

Let me know what you find and if there are any diagnostic codes, let me know what they are.

Take care,
Joe

I will try it in the morning, but i don't think its had to do with the catalytic converter or fluid pressure. i am going to try it and let you know what happens.

I will watch for your reply. I am just trying to think of something that is related to vehicle speed rather than just RPM.

Also, make sure you check for trouble codes. That could answer our questions.

Take care. If I don't hear from you, have a great Christmas.

Joe

hi i recently bought a 1993 silverado 4wd from a friend i noticed that sometimes driving at normal speeds anywhere from 25 to 55 that sometimes when i floor it to pass someone the truck starts to go but doesn't have very much power like its hesitating then a few seconds later still having it floored it will jerk and take off and have PLENTY of power. the transmission doesn't slip or anything but it does bang going into second gear.it also hesitates sometimes when taking off from a stop but only if i give it alot of gas it will do the same thing . it will hesitate for a few seconds and then take off with plenty of power. the last thing is when im going very slow 5-15mph and barley have my foot on the gas it will kinda of jump up and down like its gonna die but if i give it more gas it will go back to normal.any help would be great thanks!

Check throttle position-/MAF/MAP sensor and fuel pressure then report back.

I have same truck and it does that too. However not so extreme when idling. But it wont shift into overdrive and when accelerating from a stop it is sluggish and wont downshift or hit passing gear when flooring it.

1993 Silverado K1500 5.7L.
Engine runs fine at all RPM's in park. While driving though it stumbles and sputters bad when I put my foot in it. It will shift fine in D4 or manually shifting lever, as long as I don't push the accelerator too hard. Check engine light is on, but it's been on for 6 years or more. I can get up to normal speed, just takes longer. Doesn't seem to be clutch slipping. Gas mileage dropped also when this started.

Scan the computer for code/s if any present comeback with it-also check the fuel pressure

Code was 32. Didnt' check fuel pressure, but one clue might be in Park I can rev the engine up all the way without running bad.

Clean out the EGR valve/Ports and see what heppens

cleaned out the EGR valve. Replaced cap and rotor. Engine light went out. Runs great in park. In gear it still cuts out when applying more than light/slow pressure to the pedal. When I get up to speed finally (45), on a warm day, I punched it and XMSN slipped but RPM went higher and smooth instead of cutting out. So it seems the XMSN is slipping. But the cutting out off idle in gear seems more like ignition/fuel/sensor. It's TBI and doesn't have vacuum line on fuel Press Reg or valve port on fuel line, so don't know how to check regulator or fuel pressure.

My truck keeps stumbling. I have had the gas tank change it was rusted and a new fuel pump and filter. I also changed the throttle body. I am leaning towards the new throttle body. When I start moving it starts stumbling and at low speeds it does it. When I put it in park and rev the engine the rpm's go up and then falls low and acts like it is going to die. When I park it and turn the wheel it dies. Any suggestions? I also ran sea foam and that did not work. The motor is brand new and I had the timing check it was right on. Thanks.

check for a vacuum leak at bottom of tbi unit. they like to blow gaskets there you can use choke cleaner to check if rpm changes you found it. Or put smoke through brake booster hose if you have power brakes any leaks will show up there. also check hoses leading to map sensor if soft replace them as they suck together and do not let the map work correctly.

Ok I did all that rpms did not go up I can't ad smoke since I don't have a machine I notice that I have a leak in the hose going to the fuel tank. It's the line that goes from the back of the fuel filter into the tank. It is leaking in that rubber fuel line part. It only leaks when the pump is turned on. It is a small leak.

Here is a guide to help you

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

So a while ago I asked a question about my truck (K1500). It was stumbling when I hit the gas and was acting weird had fuel pump and fuel tank replaced also the throttle body replaced almost at the same time. So I was not happy with the throttle body everybody I kept taking it to kept saying it was a fuel issue so I had put a can of pb blaster out my dad thought it was carburetor cleaner and sprayed it with the truck on. It runs so much better no stumbling or anything. Could this be a throttle body problem? After he sprayed it I got an EGR code I just changed it. After he sprayed it the code set. The only problem I have is if I am sitting it acts like it wants to shut off but does not. Thanks

check the base of TBI unit for a vacuum leak then cross a and b at aldl and see if any codes then get back to us. it could be the EGR is partially clogged and doing same to pintle on valve or a vacuum leak. check all hoses for soft if soft replace them as it may be the hose leading to map sensor on firewall sucking together as that happens as well.

my truck hesitates on acceleration,but gets a little better when it gets to 160*.when first started the idle fluctuates up and down.items i've replaced,map sensor,idle air control valve,throttle position sensor,egr valve,fuel filter,fuel injectors and connectors,distributor,ignition control modual,timing chain,tempeture sensor,ecm,plugs,wires,cap and rotor.i have no codes to be read.and after 100's of dollars i still have the same problem as when i started..