wastedracing

i have a 90 toyota 4runner v6 3vze engine and auto transmission i just purchased this car recently there are 180k miles

right now the car while driving more when cold but still does it when hot. the 4runner is pretty sluggish around the 2k-3k range and when your going at a constant speed around 40mph the car sometimes will shake like you are tapping the gas pedal as soon as i either apply more gas or take foot off pedal it will stop and will only continue if i get it at a certain rpm. the car runs pretty well on the top. also it will be sluggish while holding the pedal down at constant pressure and will surge a bit.

any ideas?

GVOLCRunner

Where to start, where to start. It could be a bunch of things. Give a little more info.

At idle, runs smooth or trys to stall out? Whats your idle RPM?
Im tired and cant think of more questions, but any more info?

List of possibles, in no particular order of relevance:
Slight Compression leak?
Not enough airflow, bad or clogged filter?
Clogged, or CLOGGING fuel filter or weak pump?
Dirty injectors or Spark, although if it doesnt idle rough and runs smooth, probably not.
Screwy TPS? Throttle position sensor and by extention, computer messup on your fuel/air mixture?

Ahh im gonna stop guessing. Without more info it could literally be 1 thing or a combo of like 20 things.


One thing you said, is it much more often when COLD?

Shaking or SURGING? Two different things, you description seems to indicate it is "surging" foward or not, exactly like if you just tap the gas. So, is it a front/back movement or a side to side?
Side to side is a little more problematic, as it indicates an out of balance engine, a.k.a misfire or dead cylinder or any of the other long list.

wastedracing

well the think i meant by the surging is it will be like going at a constant speed and then just rev up and start going faster like it cleared out all of a sudden. and no its not just the transmission down shifting. tranny is good shifts smooth.
doesnt stall at idle and isnt real rough its a little rough at idle enough to feel but definately not that rough i have seen rough no stalling out. idle when first started cold is high around 2500 then drops to around 8-900

just installed new airfilter.

the car is alot more sluggish when cold but still sluggish when warm.

when its at the constant speed with the pedal barely pressed just cruising it will jump forward and back like your tapping on the gas

GVOLCRunner

8-900 is if Im remembering correctly, right on the money in terms of spec.

Ok, so its like the engine just WAKES up. Ok, well thats better than side to side SHAKE.. thats usually BAD.

So, the surging.. without you changing throttle pressure.. easy way to look at it is this. Your throttle dictates how much fuel the engine gets, more pressue, more fuel.. GO FASTER. SO, if you are not changing the pressure on your throttle, but its shoots up all of a sudden.. that means theres a varible in there other then your foot in terms of fuel delivery.

That leads to a simplistic thinking - how does fuel get to engine. Fuel pump, fuel line, fuel filter, fuel rail, throttle assembly, injector and then engine. SO some where theres an issue. It could also be a computer issue, as primitive by todays standards ours are, as its fuel injected, there is a simple computer that helps figure out the air to fuel mixture, there could be an issue there.

So, it bogs down.

Ok, so probably not a fuel line or filter issue as those tend to be constant. A clogged filter is always clogged and your engine would always be starving, if it even started.

Fuel pump, probably not; but I have heard of weak ones acting up since the energy output of your truck is dependant on engine speed, but probably not.

So, we are up to the throttle and injectors. Maybe your throttle or TPS(throttle position sensor) is screwy. Or, good old fashioned gunky injectors.

It could still be a lot of things.. anyone on here experienced this? I have dealt with an engine bogging down, and it was a couple dirty spark plugs. To much fuel, and not good enough spark.


So, without obviously knowing with any high degree.. it sounds to me like a fuel mangement issue.

My theories, in order of strength
1.YOur ECM(computer) or part related like o2 sensor is fritzing out. The mixture is off or something.
2.Fuel filter plugged
3. Weak or fritzy fuel pump
4. SLight compression leak?
5. Plugged exhaust, messing up some sensors and pissing your comp off.
6.Tranny clutch weak. going.



Hope this is a little to think about.

wastedracing

this is an automatic so no clutch so were good there im almost 100% positive the tranny is in working order.

so i had a mechanic look at it for like 5 minutes and take it for a spin he told me that it could be the timing does this sound like a possibility? he wants to charge like 300 tho just to check it so that is a bit much for a bad hunch.

the person i bought it from told me that there mechanic said it needed a new catalytic converter.

i had the same mechanic that mentioned the timing problem tell me the cat sounded good however he didnt test anything or pull it to look at it he just listened to it for raddle or an air sound for the air trying to squeeze through.

iamsuperbleeder

Kinda sounds like the same thing that I noticed when the ERG valve went out on my 2000 Mustang. Between 1500 and 2000 RPMs, it would shake and stutter, but if you got into a different RPM range, you didn't even notice. Is it throwing the CEL?

wastedracing

ya i was reading other posts about the egr valve going bad isnt that as simple as unhooking it and plugging the vaccum line to check to see if thats bad?

GVOLCRunner

Every tranny has a clutch.. even auto's just work a little differently. How do you think it changes gears without dropping out of your truck.
just to let you know.

nah, the computer on this era isnt nearly as helpful as newer cars. Ive had all kinda stuff happen and my computer never threw a code.

Well, rough idle could mean timing but I dont see how that translates into a SUDDEN SURGE..obviously, timing could be an issue, I just dont think its the only issue.

So, I guess what you want to know is.. have someone look at it or deal with it? Well, to be honest probably be a great learning experience for you. Go buy a vehicle specific service manual, like a haynes or chiltons or the toyota service manual. It will probably take you a while to nail it down, it could be 1 or 10 things.

Or, take it to someone.. its easier and costs more. WHen I was first learning, and broke.. when something needed to be fixed on my truck, it usually spent a good couple days on blocks as I tinkered and tested. If you cant afford to go that long without it..


If the guy gives you a bad feeling, take it somewhere else.

wastedracing

does this at all sound like a clogged cat ?

GVOLCRunner

yea, it can happen. A clogged convertor will require more engine pressure to push the gases through, this will result in back pressure which can create surging. simple check for that, unhook your cat, and see if that fixes it. I would have thought your o2 sensor would have thrown a code, as if it were clogged you would have all kinds of backpressure.. but maybe not.

wastedracing

so you unhook the cat and take it for a test drive? wont it be incredibly loud?

GVOLCRunner

yea. muffler is behind your cat.. so try not to do this at 1 am.

wastedracing

lol nice well i might give that a shot and a few other things tomorrow start with cheap and easy and work my way up

thezrutherford

im having the same problem but notice when I unhook the throttle position sensor it no longer lurches. It was happening around 1700 rpms