Rough engine between 2300-3000 rpm under acceleration. Why? Need help

[slapdappy]

sagging tranny, vibration 2300-3000 rpm

Colchin Auto here in Denver (Arvada actually) checked my 4R because my mileage was 15mpg even though I was driving more gently and smoothly than I ever have before and ever will again. Besides finding 2 substantial vacuum leaks and a dirt MAF, they determined the u-joints in the driveline each needed a full pump of grease and the transmission mount was worn out. Saggy transmission = misaligned driveshaft = vibration @ 2300-3000 rpm.
What's interesting is the noticeable reduction in this vibration since the appointment. I assume the driveshaft is running straighter. I assume the fully greased u joints and the full-of-grease slip yokes have much less play/wiggle room and thus the shafts are actually spinning straighter and truer. I plan to replace the tranny mount (rear engine mount according to Toyota) soon and will post the results.
Nice young man who makes the appointments and is very knowledgeable happens to own a '98 ('97?) 4R. He said go ahead and fill joints, including slip yoke, with grease until it squeezes out other side. I deliberately did not do this because of warnings here and on other sites about overfilling them, especially the slip joints, and blowing them out after hitting a big bump. This guy said 'nope, go ahead and fill them'. I'm following his advice. If I blow a seal I'll let you know.

 

[highmile]

Same here

I am having a similar problem with my 2002 SR5. It has 366k. Two days ago it had a very rough acceleration after a cold start and the CEL came on for a few seconds then went out. I turned off the engine, turned back on, and it was still a little rough but not too bad. The next day it was much better but still rough/missing(?)/chugs when pressing the gas hard. Once it gets up to speed it runs perfectly smooth. There is no CEL and no codes to be found by the code reader. Here's what I've tried so far with no noticeable improvement:
-Sea foamed gas tank, oil, manifold
-changed oil (after 150miles of sea foam)
-replaced air filter
-cleaned MAF sensor
-cleaned throttle body
-checked all vacuum tubes
-put fuel injector cleaner in gas tank

Based on some of the forum advice, I'm considering replacing the fuel filter. It was last replaced 130k miles ago. I am also considering replacing the MAF (although I think it's good, but can't be sure). Finally, I saw some advice saying the cam position sensor could be the culprit. I've seen some advice to replace coils and plugs but if one of those things were bad then I think I would get a CEL and code. The plugs were replaced 130k ago and the coils are original.

Please provide this new forum member any advice on this problem. Thanks!

 

[highmile]

Fixed!

I did replace the fuel filter but that did nothing noticeable. Next I replaced the wires and plugs and that fixed it. Seems like it may have been the #4 wire as that one looked pretty bad but there's no way for me to know for sure as I don't have test equipment and there was no CEL with code to indicate #4 was misfiring.

I am having a similar problem with my 2002 SR5. It has 366k. Two days ago it had a very rough acceleration after a cold start and the CEL came on for a few seconds then went out. I turned off the engine, turned back on, and it was still a little rough but not too bad. The next day it was much better but still rough/missing(?)/chugs when pressing the gas hard. Once it gets up to speed it runs perfectly smooth. There is no CEL and no codes to be found by the code reader. Here's what I've tried so far with no noticeable improvement:
-Sea foamed gas tank, oil, manifold
-changed oil (after 150miles of sea foam)
-replaced air filter
-cleaned MAF sensor
-cleaned throttle body
-checked all vacuum tubes
-put fuel injector cleaner in gas tank

Based on some of the forum advice, I'm considering replacing the fuel filter. It was last replaced 130k miles ago. I am also considering replacing the MAF (although I think it's good, but can't be sure). Finally, I saw some advice saying the cam position sensor could be the culprit. I've seen some advice to replace coils and plugs but if one of those things were bad then I think I would get a CEL and code. The plugs were replaced 130k ago and the coils are original.

Please provide this new forum member any advice on this problem. Thanks!

 

[DK327]

[MENTION=78997]Drcoffee[/MENTION] did you ever figure out what's causing this and/or fixed the issue? I've been experiencing the same thing and on my recent 2K mile trip, decided to drive within that range (2300-3000RPM @ 70-80mph) for a few hours and watched the Scangauge close for any anomalies and did not notice anything out of the ordinary. I'm now beginning to think it's gotta be some sort of resonance at that RPM range and nothing to worry about...

 

[Pioww]

I had this same issue with losing power in that rpm range 2750-3300rpm. It was more noticeable when there was an increase in humidity, like when it would rain. The moisture issue made me think it was an electric issue. TPS or MAF. My problem was the TPS throttle position sensor. Gas mileage improved. Gas mileage was slowly getting worse. If you notice mpg dropping it would be worth just swapping out the sensor. I don't remember how much it was, I did this about a year ago, but it was close to the cost of a tank of gas. The best part is getting up to speed at highway entrances is better due to better acceleration.

Also that rear driveshaft zero. Ends to be greased every other oil change. That is wheee the clunk is In the drive line. Like the big clunk when you shift from drive to reverse. That is when the tolerance is loosest, greasing the lower driveshaft before the u-joint had the biggest effect for me. I play around with the driveline trying to track down every little jiggle and click.

For people complaining about the exhaust. Check the last section of exhaust. The design is poor. I had a leak just after the last joint. You cannot see it unless you take it off. This was leaking for forever and I did not know it. I found out when my cooler was stuck melted to the rug in the back. The heat from the exhaust from a long drive fused them together. The leak is suttle, but is bad your health. Carbon monoxide, make you feel lethargic, not good. Longing idling could probably be lethal, depending on how it is. The last joint the way it is designed, when it rots the exhaust goes straight up. There is a lip for the joint where moisture collects, figure heating and cooling cycles. All the exhaust bolts broke in removal and were a pain in the ass to come apart, which is why most exhaust shops just cut for removal.

My 2 cents.

 

[manualdr5]

I have a similar experience with a resonating vibration starting at around 2900 RPM regardless of speed. Before I bought the truck I had Toyota check it out and one of the various service issues they mentioned was a warped flywheel. Not sure exactly how they determined that and I never asked. I just finished doing a clutch job and in the process I changed the flywheel but I still experience the same vibration after 2900. Yesterday i changed the fuel filter and noticed a slight difference. The vibration was reduced which at least isolates the issue to the engine running rougher at higher RPM's. My next step will be to change the plugs and wires. If that doesn't do it I'll begin checking the electrical stuff related to the alternator as mentioned in this post. If anyone else has any more troubleshooting ideas please let me know.

 

[PatrickStapler]

I had this exact issue after I got my truck last year. I didn’t know the age of the plugs and wires so I started there. In my case, I had one plug wire just laying in the coil connection...not snapped in. So it ran fine st low RPM, but as soon as I hit 2000-2200 RPM it would miss.

 

[VernySanders]

Just out of observation, I stumbled onto this thread because of RPM issues I'm having only under load. (Think it's a clogged cat, going to delete them because I have no emissions in my state.) I'm glad to know that with a quarter million miles on my rig all I need to worry about is sensor related issues with my engine. Living in Michigan all my buddies have American vehicles and swear by them. They also swear AT them when they break constantly lol. Cheers guys.