Engine just started shaking violently below 2,000 RPM

[jeffreykuhn]

My 97 4runner (4wd 6cyl) is currently idiling very roughly and the engine continues to shake up to 2,000 rpm where things settle down a bit (idiling or driving). This poblem just started and the truck was previously running great.

Attempted remedies
1) Fuel treatment (dewater)
2) Psyfon off fuel (assuming it was bad), replaced fuel filter (assuming it was clogged up), and refilled fuel tank
3) Cleaned the MAF unit
4) Cleaned the throttle body

The spark plugs, spark plug wires, and air filter were all replaced within the last 10,000 miles. The 4runner still accelerates great, doesn't hesitate to shift, and doesn't seem to be misfiring.

Any sugguestions?

The long of it...
My 4runner was doing great until... A friend was watching the car for me this break and a few minutes after getting a new tank of gas and the engine began to shake and the check engine light came on.

When I returned, we takle about the problem a bit and decided that it must have been a bad tank of gas. We added some dewatering treatment to the tank and drove around a bit.... no difference. We then siphoned off the rest of the tank of gas, replaced the fuel filter, and filled up the tank with gas again putting in fuel treatment. Still.... no difference.

Following this we were suspicious that it must have been a pre-existing problem that had just reached a critical level. I'd read on this form about the MAF unit and oiled filters. My buddy helped me use electrical cleaner to clean the MAF sensor as described in the form..... still no difference... the car was shaking badly during idle.

Accordingly, we cleaned out the throttle body... but nothing. I'd appreciate any help or sugguestions that can be offered. Thanks.

 

[mole177]

perhaps there may be a vaccum hose lose or broken ?

on solaras there was something called the IAC- Idle air control valve.

I don;t know where they are located on the 4runner though.

basing on the symptoms you described, it sounds like the IAC.

 

[trd_style]

was it jerking or rattling? if it's more like a jerk, it could be your spark plugs. even though it might be new but get that checked.

checked your oil to see if it's filled up correct?

hope these helps. good luck!

 

[Xandarin]

My guess would be a broken motor mount. It would throw your whole engine off balance and make it rumble like that in low rpm's. If you give it some gas while someone else is looking at the engine, does it torque a lot and twist?

 

[jeffreykuhn]

Problem resolved

So... it allways tends to be the simplest thing. I was tired of troubleshooting the 4runner so I took it into a local mechanic. Turns out one of the spark plug wires that I installed in the last 10k miles had burnt up. I'd used denso spark plugs but non-toyota wires. After talking to the mechanic I learned that some boots do not fit the denso spark plugs well. Now the 4runner has genuine toyota wires to go with the denso plugs and its running great. Thank you to all who replied to this thread.

P.S.
My brake light has also been flashing lately. The mechanic informed me that a flashing parking brake light was often the symptom of wearing brake pads... as the pads wear the brake fluid begins to drain faster... or so I'm told. Anyways... maybe that last bit will help someone in a search.

 

[trd_style]

Re: Problem resolved

So... it allways tends to be the simplest thing. I was tired of troubleshooting the 4runner so I took it into a local mechanic. Turns out one of the spark plug wires that I installed in the last 10k miles had burnt up. I'd used denso spark plugs but non-toyota wires. After talking to the mechanic I learned that some boots do not fit the denso spark plugs well. Now the 4runner has genuine toyota wires to go with the denso plugs and its running great. Thank you to all who replied to this thread.

P.S.
My brake light has also been flashing lately. The mechanic informed me that a flashing parking brake light was often the symptom of wearing brake pads... as the pads wear the brake fluid begins to drain faster... or so I'm told. Anyways... maybe that last bit will help someone in a search.

so it WAS the spark plug wires, not the spark plugs. ehh. at least you got it fixed.