Hesitation? Misfire? Vibration under light load
Champion
Joined: Jun 2004
Posts: 2,811
Likes: 2
From: Ft Campbell, KY/TN
I had a missfire problem with my 1996 with acceleration that was not a consistent misfire, but made the truck run like garbage. I DID get codes. I brought it to a mechanic shop. They were really busy and could not take the truck in but he took 15 mins to take a look at it (even hooked up a scanner).
Here is what he noticed:
1. The wire from the coil to the dist "should be in the valley between the head and the intake." That is true and it was laying pretty close to the other wires.
2. THE MOST IMPORTANT: The small wire clips on the fuel injector connectors (EV1) were missing from the injectors corresponding to the miss cylinders. He said that those small, insignifigant looking wire clips are important to ensure a tight seal on the connectors. He advised me that there would be a miss "every time" without them. So, I got new pigtails and the problem was solved.
I made a thread about it.
Here is what he noticed:
1. The wire from the coil to the dist "should be in the valley between the head and the intake." That is true and it was laying pretty close to the other wires.
2. THE MOST IMPORTANT: The small wire clips on the fuel injector connectors (EV1) were missing from the injectors corresponding to the miss cylinders. He said that those small, insignifigant looking wire clips are important to ensure a tight seal on the connectors. He advised me that there would be a miss "every time" without them. So, I got new pigtails and the problem was solved.
I made a thread about it.
Thread Starter
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Registered User
Joined: May 2011
Posts: 13
Likes: 0
So, my last post stated that the colder autolites fixed the light load misfire problem. I was correct in that it was running great immediately after changing the spark plugs (as I believe it has in the past when I've changed the plugs) but a few days after changing them it started doing the same thing and running rough under light load. Why would brand new spark plugs cause it to run well for a 100 miles or so and then start running rough again? The spark plugs look normal. Could all this be because I have a weak spark due a failing coil and the brand new spark plugs work well enough to utilize whatever juice the coil is putting out and then after they get used a little bit, they aren't able to use the weak coils energy efficiently enough? OR... Could it be running well after I change the spark plugs etc. because I disconnect the negative battery terminal (which resets the ecu?) and then after the computer "learns", it isn't using the info correctly?
And wouldn't surprise me at all. How's your plenum, and how old are your O2 sensors?
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Joined: May 2008
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Registered User
Joined: Jul 2004
Posts: 10
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"97 Ram Truck", Spot ON Re "Hesitation Backfire"
My 1999 Ram Van Wagon 5.2 Started hesitating, back firing and loosing power whenever it went to closed loop. No Check Engine Light. Tried many details re intake and ignition but sure enough it was a bad upstream O2 sensor. New OEM type at AutoZone $53!
Thank You for the wisdom,
Tom LaMers
New one-piece intake manifold.
Thank You for the wisdom,
Tom LaMers
New one-piece intake manifold.
Registered User
Joined: Oct 2016
Posts: 15
Likes: 0
From: santa rosa California
same problem vibration at 45
I have a 1997 Ram 1500 w/ 5.9l V8. Things have improved after replacing my plenum pan gasket but there is a slight shudder/vibration/hesitation/misfire(?) under load and light throttle while going up slight to moderate inclines, if I give it more gas and it shifts everything seems to be smooth. Also, I have had an issue a few times where the engine will die right after starting it up. It has also died once or twice while driving at a slow speed (2 mph). Also... There is a slight shudder while coming to a complete stop while in gear, I tried stopping while in neutral yesterday and didn't notice the same vibration. I adjusted the throttle valve cable bracket the other day thinking that it might improve if it was a torque converter slippage issue but the symptoms have not improved. My next step was going to be checking and cleaning the TPS and also doing a compression check. I am definitely doing this this weekend and would appreciate some advice on whether or not you think I am heading in the right direction. I guess I should check my 02 sensors while I'm at it and am not sure how but I'll search around and see if I can find a how-to. When i replaced the plenum gasket i also replaced the intake manifold gaskets, cap, rotor, spark plug wires and rerouted them, spark plugs, cleaned the throttle body and plenum and installed a 180 deg thermostat which is getting replaced with a 195 before next winter. Thanks for the help, I'll post in the newbie section this weekend.