Losing power

Tiny
BRAD04
  • MEMBER
  • 1994 CHEVROLET S-10
  • 4 CYL
  • 2WD
  • MANUAL
  • 208,000 MILES
My S10 cranks and idles fine. However, once it warms up, it loses power on the slightest incline. This has been getting progressively worse. Check engine light comes on and goes off randomly.

I have replaced plugs & wires, fuel filter, blown head, coil packs. No vacuum leak. The truck does not have a cat. Converter as it was taken off years ago. Thinking maybe it the fuel pump or MAF sensor. Just not sure.
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Wednesday, July 28th, 2010 AT 2:31 PM

53 Replies

Tiny
HMAC300
  • EXPERT
Check your fuel pressure, if it's TBI it should 9-11 p.s.i. if it's port fuel then 48 p.s.i. You could have a bad MAF sensor as well I would start with these here are guides to help you.

https://www.2carpros.com/articles/how-to-replace-a-mass-air-flow-sensor-maf

and

https://www.2carpros.com/articles/engine-has-low-power-output

Please run down these guides and report back

Cheers
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Thursday, July 29th, 2010 AT 8:38 PM
Tiny
BOOPERIII
  • MEMBER
I had the replace the MAF in my truck got one for $78.00 all fixed!
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Saturday, August 18th, 2018 AT 9:21 PM
Tiny
S-10 COLLECTOR
  • MEMBER
  • 1994 CHEVROLET S-10
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 170,000 MILES
My S-10 used to accelerate quite quickly, but for the last few months, it's been struggling to reach 60 in less than 15 seconds. It sat all winter, but all the fluids have been changed. I also changed the fuel filter, PCV valve, air filter is clean, and it just had a tune-up about 5,000 miles ago. There is the correct amount of air in the tires. I took it to the shop and they hooked it up to the diagnostic and found nothing wrong. Besides the acceleration problem, there seems to be nothing else wrong. Except for horrible gas mileage. I used to get 26, now I'm down to 17. Yikes! Please help. Throw out any suggestions you think would work! Thanks!
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Saturday, August 18th, 2018 AT 9:21 PM (Merged)
Tiny
SWILLIAMS
  • MEMBER
Have the exhaust flow tested. Sounds like the converter or the muffler is partly plugged. Also check ALL the wiring to the sensors and engine, Sitting that long may have allowed a mouse or two to snack on the wiring.
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Saturday, August 18th, 2018 AT 9:21 PM (Merged)
Tiny
CHRISTIAN SHAY
  • MEMBER
  • 1994 CHEVROLET S-10
  • 4.3L
  • V6
  • 4WD
  • AUTOMATIC
  • 175,000 MILES
I have a single cam with a 4.3 Vortec that is half Jasper and half Vortec. I am trying to figure out where to start. My truck starts and runs fine at idle though it is a little rough coming out of the exhaust. But when I am driving down the road it loses power when the engine warms up. But when I floor it it seems fine then goes right back to being starved of fuel it seems like it it is getting too much. I am not sure but I can put it in neutral and it is fine and if I shift it manually down it runs fine.
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Saturday, August 18th, 2018 AT 9:21 PM (Merged)
Tiny
HMAC300
  • EXPERT
Scan for codes and check fuel pressure with a gauge auto parts rent it. Do that first. See link.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
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Saturday, August 18th, 2018 AT 9:21 PM (Merged)
Tiny
PORRAS7
  • MEMBER
  • 1994 CHEVROLET S-10
  • 4 CYL
  • 2WD
  • MANUAL
  • 94,000 MILES
This is a 2 part? My truck has been sitting for about 6 years in the garage. I've had the plugs changed, oil and filters changed, fuel filter and pump changed, the gas tank drained and radiator flushed. The last few times driving the truck after about 20 miles or so it seems to lose power when going through 1st and 2nd gear and once while driving 45mph in 4th gear. What would cause this. It feels like it runs out of gas. Would an engine cleaner or fuel pump cleaner possibly clear this up? What are your thoughts? Also after 20-30 miles of driving, it seems the clutch goes away after it heats up. If I stop at a stop light I have to pump the clutch several times for it to catch a gear and go. All of your input is greatly appreciated.
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Saturday, August 18th, 2018 AT 9:22 PM (Merged)
Tiny
RASMATAZ
  • MEMBER
Sounds like the clutch is slipping if not could be one of the following below

Oxygen sensor
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
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Saturday, August 18th, 2018 AT 9:22 PM (Merged)
Tiny
DISTLER_AARON@YAHOO.COM
  • MEMBER
  • 1994 CHEVROLET S-10
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 173,000 MILES
I have a 94 s10 v6 and about half the time I drive it, it runs fine, the other half any time I come to a stop or almost a stop it accelerates very very slow. Once it picks up speed it runs a little better but still loses almost all acceleration after I stop, I have replaced fuel filter, spark plugs, wires, cap, button, and just today the knock sensors, the fuel pump and transmission tested fine and with this being my work truck im completely out of ideas
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Saturday, August 18th, 2018 AT 9:22 PM (Merged)
Tiny
INTERNETMECHANIC
  • MEMBER
What was the fuel pressure spec? Any applicable trouble codes? If you have the spider fuel system, the fuel poppets may need cleaning. Any testing needs to be done when the problem occurs. Yeah, intermittent issues can be tough.
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Saturday, August 18th, 2018 AT 9:22 PM (Merged)
Tiny
DISTLER_AARON@YAHOO.COM
  • MEMBER
After I changed the knock sensors and the catilic converter the change engine light when off and hasnt been back on and no codes are comming up but the problem is still occuring I forgot the fuel pressure spec but the diagnopstics read that it was fine. I thought it was the pump at first because in the morning to get it to idle right you have to give it some gas someone told me that it might be a torque converter. It feels like with a manual trans. When you are trying to go with the clutch not fully engadged. It wil still go but I could get out and walk faster than it picks up. Thank you for any info you could give me
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Saturday, August 18th, 2018 AT 9:22 PM (Merged)
Tiny
INTERNETMECHANIC
  • MEMBER
If the engine races while going slowly, I would have to suspect a transmission issue, of some kind.
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Saturday, August 18th, 2018 AT 9:22 PM (Merged)
Tiny
STAN57
  • MEMBER
  • 1994 CHEVROLET S-10
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 186,000 MILES
Engine boggs down at about 2000 Rpm let off and idle down come back up to 2000RPM same thing Starts fine Idles fine
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Saturday, August 18th, 2018 AT 9:22 PM (Merged)
Tiny
JMALECKI
  • MEMBER
Hello
How many miles since the fuel filter was changed, if it has been a while start by replacing that and see if the problem goes away. It sounds like the filter may be plugged, if that doesn't help check the fuel pressure you may have a bad fuel pump.
John
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Saturday, August 18th, 2018 AT 9:22 PM (Merged)
Tiny
JURRJEN5
  • MEMBER
  • 1994 CHEVROLET S-10
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 176,000 MILES
Well one day I pushed my gas pedal and I got no power. So all the way home I held it to the floor. It made this wierd putting sound kind of like a gocart would make so I changed the fuel filter, fuel pump, spark plugs, and idle control valve. Ive gotten a lot of power back to my acceleration but not like it should be I honestly do not know what else to do to fix this problem on my 1994 chevy s-10 4.3 vortec 4x4 so if you have any ideass let me know thankyou
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Saturday, August 18th, 2018 AT 9:22 PM (Merged)
Tiny
RASMATAZ
  • MEMBER
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
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Saturday, August 18th, 2018 AT 9:22 PM (Merged)
Tiny
SAM77
  • MEMBER
  • 1994 CHEVROLET S-10
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 166,000 MILES
The past couple of days I've read through everything here I could find and it gave me quite a bit of help but my blazer stills has a problem.

About 5 months ago I bought a 1994 S-10 Blazer with a 4.3L Vortec engine code W. It wouldn't start and after checking fuel pressure found out the fuel pump wasn't working. I went ahead and bought a new AC/Delco pump, pulsator, strainer, electrical connector w/pigtail, sending unit, dist. Cap, rotor, plugs and wires, 2 fuel filters, changed engine oil and filter replaced the exhaust from the cat convertor back (old muffler and exhaust was rusted badly). Dropped the fuel tank and cleaned it out and installed the pump and sending unit. Put the tank back in the vehicle, installed one of the new fuel filters in the fuel line and put all the ignition stuff I bought in it. Put a fuel pressure gauge on it and made sure everything was working. I had fuel to the pressure gauge at the schrader valve so it seemed I was ready to fire it up. I tried that and it wouldn't start. I had hot blue spark but no fuel was getting to the plugs. I read in my manual that any problems found with the CMFI unit the entire assembly should be replaced. Well I was short on cash so I pulled the upper plenum and took the unit out, sprayed carb cleaner in the poppet valves and rusty nasty smelling fuel came out. Used some air (low) and blew everything dry and reinstalled it. Put on a new plenum gasket and bolted everything back together. After everything was bolted down and electrical connectors were back together I got in turned the key and within a few cranks of the engine it fired up. I let it warm up while I cleaned up the shop and took it for a drive. Everything was working fine. Drove it everyday to work for just over 4,000 miles then one day on the way home on the highway going up a hill I noticed I was losing power. Never did die but I had to step lightly on the peddle. Anymore than that and the engine rpm's fell. I made it home and when the weekend came I took it back out to the shop and decided to do some testing. Didn't know about this forum but I had the repair manual. Heck I can fix this myself. Yeah right. I read in the manual that if the fuel pressure didn't approach 61lbs. On acceleration that the pressure regulator on the CMFI unit was bad and it should be replaced and this past weekend I replaced it. Well after reading through a ton of threads here I found out that its a good idea to replace the fuel line assembly (nut kit). I didn't do that and I really didn't look over the plenum to see if there was any wash. Well it's still doing the same thing it was doing. I put a fuel pressure gauge on the schrader valve and here is what I found out. With the key on/engine off and the fuel pump running I have 60lbs. As soon as the pump shuts off the pressure drops to 58lbs but within a couple seconds climbs back up to 60lbs. I turned the key off and let everything set for 10 minutes and the fuel pressure then was 58lbs. I started the engine and the pressure was between 51lbs. And 58lbs. (Needle was fluttering back and forth). I increased the throttle to 2,000 rpm's and the pressure gauge needle flutters between 49 and 60lbs. Around 2500 rpm's and the engine starts to cut out, bog down or whatever. It won't throttle up anymore than that. It starts good and idles good and I can drive it in town but I can't take it out on the highway. I put a vacumn gauge on it and at idle it has 19 lbs/inches? And if I increase the throttle it increases to around 21 or 22 lbs/inches. I didn't pinch the return fuel line to see what would happen to the fuel pressure but I think I performed everything else. I'm really leaning towards replacing the fuel line assembly (nut kit) like I should have done when I replaced the CMFI unit. All the fuel pressure readings stay the same with the engine cold or when it's at operating temp. What do you guys think? Where should I go from here? Sure would appreciate any help you can give me. Sorry for the long winded post but I wanted you to know what all I've done.
Also wondering what would make the fuel pressure gauge needle flutter? Don't believe it's supposed to do that.
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Saturday, August 18th, 2018 AT 9:22 PM (Merged)
Tiny
DE772601
  • MEMBER
Hi
Well the gauge is going to move a little bit but did you check to see if you may have a bad trottle position sensor. Try this first and hopefuly this will help.
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Saturday, August 18th, 2018 AT 9:22 PM (Merged)
Tiny
JIM14086
  • MEMBER
  • 1994 CHEVROLET S-10
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 167,000 MILES
Hello. My 94 s10 pickup with 4.3 w engine starts and idles fine. But acceleration when cold (open loop) is very bad and the more I try to accelerate the worse it gets. It feels like it is starving for gas. There are no engine codes and I installed fuel pump tester which reads 55 to 60 psi all the time. Even while the problem is happening. If I just wait for the temperature to increase to 195 degrees or closed loop everything operates fine. I am stumped. Any idea's?
Thank you.
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Saturday, August 18th, 2018 AT 9:22 PM (Merged)
Tiny
RASMATAZ
  • MEMBER
Check and test the coolant temperature, throttle position and the manifold absolute pressure sensors
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Saturday, August 18th, 2018 AT 9:22 PM (Merged)

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