Reaches normal temperature then loses acceleration power?

Tiny
BRANDI VOLENEC
  • MEMBER
  • 1994 DODGE RAM
  • 5.9L
  • V8
  • 2WD
  • AUTOMATIC
  • 174,787 MILES
There is no check engine light at all, works fine in the morning, and in the afternoon (live in AZ) and it is over 100° outside, the truck will lose acceleration power after we go over the lip of a bridge. My husband has to tap the gas repeatedly, to get it to catch again. We have changed catalytic converter, throttle position sensor, and spark plug wires (found one that was melted). We are stumped and so is my mechanic.
Tuesday, July 11th, 2023 AT 5:57 PM

12 Replies

Tiny
BRANDI VOLENEC
  • MEMBER
  • 8 POSTS
It also hisses and feels starved for air, around the air filter. I apologize for not reporting that in the initial post. First time poster here.
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Tuesday, July 11th, 2023 AT 6:04 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Hi,

A hissing is usually the result of an engine vacuum leak. Have you checked for that as a possibility? Here is a link that explains how it's done:

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

Let me know where you hear the hissing sound also. If it is loud enough, record it and upload it for me to hear. Note, pay attention to the hissing. If it seems to quiet the hiss when the engine is under a load, that is most likely the cause.

Next, even if the check engine light isn't on, there are still likely codes stored. This truck has an OBD1 system that doesn't require a scanner to retrieve codes. Follow this link and let me know if you find anything:

https://www.2carpros.com/articles/retrieve-trouble-codes-for-chrysler-dodge-plymouth-odb1-1995-and-earlier-car-mini-van-and-light-trucks

Let me know.

Take care,

joe
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Tuesday, July 11th, 2023 AT 8:49 PM
Tiny
BRANDI VOLENEC
  • MEMBER
  • 8 POSTS
Hissing sound is around the air filter. Like a sucking hissing noise. We have also changed the distributor cap but could not remove the rotor. I have become sort of a master with the check engine light Morse code reading. It flashes 55 end of codes. We did have a code prior that was for 2 O2 sensors as well as the purge valve solenoid. We replaced the solenoid and check engine light went away. I have done the check engine Morse code several times since.
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Tuesday, July 11th, 2023 AT 8:55 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Hi,

We need to determine where the hissing sound is coming from. It is likely a vacuum leak. It has been a while, but I know this truck doesn't have a mass air flow sensor. However, in its place is a MAP sensor (manifold absolute pressure sensor). That can be throwing things off if unmetered air is getting into the engine. It's mounted on the throttle body. See pic below. Also, check the PCV valve and hose. It runs from the valve cover to the intake. That can create a large leak. See pic 2 below.

Try the procedure I attached above and let me know if you find anything.

Let me know.

Joe

See pic below.
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Tuesday, July 11th, 2023 AT 9:23 PM
Tiny
BRANDI VOLENEC
  • MEMBER
  • 8 POSTS
You are correct on no MAF sensor. Will check for a leak tomorrow after he gets home from work. It's 9:50 pm and a storm is brewing outside. Will check back. My mechanic did say gasket leak, and we bought all the gaskets, but when we took it to a shop for a compression test, it came back as catalytic converter pinging at 10. We already replaced the PCV valve and hose. As far as fuel their test came back normal for the pump. So, we will run the vacuum leak test tomorrow. Thank you. I will let you know.
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Tuesday, July 11th, 2023 AT 9:57 PM
Tiny
BRANDI VOLENEC
  • MEMBER
  • 8 POSTS
I apologize for the delay. Update, have now replaced spark plugs as well as the ignition coil. Still does it. Reading up and someone suggested resetting by disconnecting the battery and holding them together, then let it idle in each thing for a minute each. Also, for that person it ended up being a short in the engine wire harness. Should we reset?
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Tuesday, July 18th, 2023 AT 12:41 PM
Tiny
BRANDI VOLENEC
  • MEMBER
  • 8 POSTS
It stalls out. After we let it rest for 30 minutes we can drive a bit further.
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Tuesday, July 18th, 2023 AT 12:44 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Hi,

I didn't realize it stalled and you had to wait for 30 minutes. I thought it lost power. Now that I know that, to me it sounds like you have a faulty crankshaft position sensor. When they begin to fail, often heat adversely affects them causing a loss of spark to the plugs. Once they cool, they can work again.

Interestingly, this can happen and not set a code. Do me a favor. Take a look at this link and let me know if it mirrors what you experience:

https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor

When the engine stalls and won't restart, I need you to check for spark at the plugs.

Here is a link that explains how to check:

https://www.2carpros.com/articles/how-to-check-for-ignition-spark

Let me know.

Joe
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Tuesday, July 18th, 2023 AT 8:31 PM
Tiny
BRANDI VOLENEC
  • MEMBER
  • 8 POSTS
Definitely sounds like the CSS. Which really sucks because my mechanic did mention that a while back. My husband doesn't know what I just read and thought it was for something else. So, he disregarded it. But the mechanic didn't explain it properly to me as well. Misinformed. Grrr
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Tuesday, July 18th, 2023 AT 9:47 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Hi,

As far as the sensor, if it is the cause, there will be no spark to the plugs. Also, if you have a tachometer in the vehicle, it won't move at all when cranking. If you have a live data scan tool, which your mechanic should have, there won't be an RPM signal when it won't start.

Let me know what I can do to help. Note: This sensor is located on the transmission bell housing. I don't know if you want them, but I attached the directions below for replacing the sensor.

Let me know if this helps.

Take care,

joe

See pics below.
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Tuesday, July 18th, 2023 AT 10:19 PM
Tiny
BRANDI VOLENEC
  • MEMBER
  • 8 POSTS
Final update: it was the fuel pump. The first shop tested the fuel pressure but didn't leave it on long enough for the problem to arise. We took it to a second shop, and they ran the fuel pressure test longer. Got it back mid-September but had to play catch-up on all our clients. Sorry for the late response.
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Monday, October 2nd, 2023 AT 10:10 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Hi,

Thanks for the update. I'm glad to know you were able to find the issue and resolve it. Also, no problem whatsoever for the delay. I'm just glad to know it's fixed.

Take care of yourself and feel free to come back anytime in the future.

Joe
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Monday, October 2nd, 2023 AT 7:28 PM

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