hambob

I have a 98 4runner, 5spd, 180000 miles. I have been chasing this problem for about a year, at first it was minor but has been getting worse. It has a vibration at 900rpm through1200rpm(shakes the hell out of the cup holder). At 650-700rpm its smoother(barable). Its very similar to a slight missfire but no codes. When I start off in first gear it feels almost like clutch chatter but more like a hesitation. Which is why the first thing I did was replace the clutch. It didnt fix it so I did the clutch again(new flywheel). It seemed better but it was not. My mechanic cofirmed the clutch was fine. So I got an ultra guage and started watching the fuel trims. The vibration seems to be mixture related. When cold the the vibration is at its worst, short term fuel trim at around -15, LTFT around 3. As it warms up STFT goes to around -3, LTFT 3 and the vibration is less but you can still feel the miss when engaging the clutch. The STFT and LTFT do dance a lot. Sometimes -10 to +5 in one jump, i dont know if thats normal. I also looked at MAF readings, O2 voltage, timing(not entirely sure about this one, timing map unkonown), engine load all within spec. I have drivin 10000 miles with new plugs and they are whitish, looks like I'm running lean. Since I have been chasing this problem I have replaced:

Motor mounts and tranny mount

Spark plugs(OEM) and wires(OEM)

Cleaned MAF, IAC, Throttle body

PVC valve

Valve cover gaskets

TPS(got a CEL for it)

Harmonic balancer(it was cracked, I thought I found the problem but nope)
All fuel injectors, runs better but still vibrates/misses

Checked timing belt(twice), all good, marks line up. did sound a little rough when running with the cover off, tensioner maybe?

Fuel pressure is good (a little high, around 47psi) but fluctuates when vibrating, I cant tell if its the engine vibrating the guage or the fuel pressure fluctuating.

Switched the coils around, no change

checked crank and cam sensor, both giving ac voltage, i was told that they either work or dont.

My mechanic is stumped as well. Toyota wants 250 just to do a diagnosis(no thanks). I have been over the engine many times and cant find anything out of order. I get 23 mpg highway and 16 mpg in the city. It runs awesome otherwise. I dont really care if it vibrates but the missing makes driving really frustrating. I am always fethering the cluth so it wont shudder/hesitate. Its just not right. I had a 95 pickup before and it was awesome, I fell in love with yota trucks. My wife got pregnant so I had to sell the pickup(so sad). I was excited to get a third gen 4runnner but so far its been trouble. I have checked everything I can think of. I dont know what else to check. I want to do a sotoshi mod and other fun stuff but I cant justify doing them until it runs right. I'm stuck, please help.
Thanks for reading,
Hamish

crazypaint

Ever check out the rearend or driveshaft u joints.

hambob

It happens at a dead stop right from startup so I ruled out driveline stuff.