93 Cruiser Rough Idle, Hesitation And Enging Shakes Violently At 40 Mph

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My 93 landcruiser just hit 200K Miles. Lately the tachometer has been bouncing between 900 and 300 rpm's while idling in drive at stop lights, etc. Off the line there is hesitation. I will give it gas and it will move slowly. Once rolling it will pick up with a normal acceleration curve. Additionaly, at about 40 mph and about 1200 rpm's when I am coasting and gently give the engine gas, the engine will start to shake violently. I have been to two dealerships and they are unable to find a problem. I have replaced plugs, wires, cap and rotor. The computer is not spitting out any code. Check Engine Light is off. Any suggestions on what to do? Anything will help. Thanks, Adam
 

semlin

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ok, first offis your coolant level down at all? the missing could be a head gasket.

after that cracked intake bellows, vacuum hose leak, vacuum hoses crossed, filthy throttle body, bad TPS,
 
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Coolant level if full and not going down. I guess Ill slowly start trouble shooting.
 

IdahoDoug

 
 
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A little (or a lot) of history is in order here. Have you owned it since new and this just started? Did it sit in a garage while you were on a 3 month trip and you just got back and it started? Has it done this since you bought it only last week in this condition? Etc, etc. You get the idea.

Welcome to the forum, BTW.

DougM
 
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Reply

I Have Owned This Landcruiser For Over 90000 Miles. I Just Moved To Il From New Mexico And The Problem Started After I Arrived Here. At Frist I Thought It Was Bad Gas But Now I Am Going On A Month Here And Having Filled Up Many Times At A Number Of Different Stations, I Can Exclude Bad Gas, Plugs, Wires, Cap Or Rotor. The Car Performed Flawlessly On The Road Trip.
 

IdahoDoug

 
 
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Then I'd loosen the clamps at both ends of the pleated rubber tube that connects the air cleaner lid to the throttle body and find the cracks in the pleats at the bottom. A few tight wraps with duct tape and you'll be back in business until a new one arrives. Around $90 I think.

DougM
 

semlin

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just a couple more thoughts

did you do all that maintenance before or after your long drive?

when the idle fluctuates is it stumbling and stalling or is it simply fluctuating?

is the idle problem maybe only when the AC is on? AC problems could cause the idle fluctuation.

also, next time it happens look at your temp gauge and see if it is moving. i am thinking a bad t-stat, an airlock in your cooling system or a bad temp sensor. the ecu temp sensor could cause this problem if the temps are fluctuating or it is bad.

you have eliminated bad gas, but not a fuel line propblem. you can check your injectors somewhat by putting a long screwedirver against them and putting your ear to the screwdriver. they should all sound the same. at your mileage preventative maintenance on the fuel pressure regulator and filet is overdue if not done recently.
 

NorCalDoug

problems solved daily...
 
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Suggestion would've been to check the plug wires. I had almost the exact same symptoms after I hosed down my engine compartment. Turned out I had gotten some water under the plug ends of my plug wires. It didn't help that they were old anyhow. Running on 4 out of 6 cylinders will produce very similar results to what you described.

Given that you've replaced the plugs and wires...I guess it rules that out.
 
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Another simple thing I would try is just to run a can of BG44K through it and see if that cleans it out and cures your problem. Unless this is not your brand of choice, and then there are several other alternatives out there that give similar results.

Oh yaa welcome :flipoff2:
 
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While parked and in a shakey idle state, give a tug/push on the wire harness at the back of the engine between firewall and valve cover. See if the problem goes away momentarily. You may need to cut through the protective plastic and mend a broken wire. I believe thase are fuel injector control wires, and there is an area in the wiring loom that is subject to melting and chaffing. Good luck, JOE
 
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Sounds like it may be a vacuum leak. Check your EGR valve. Recently had same symptoms and found a small hole rusted through mine, creating the vacuum leak. If that's it, replace the adjacent modulator at the same time.

I don't think a damaged/leaking bellows from your air cleaning housing would cause your symptoms.

Good luck.
 
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