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RX jerks when driving at constant speed


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It's nocticeable in 1st through 3rd, when going a constant speed. Its sort of a jerking, surging motion. Any ideas to what this could be? A friend said there should be a valve stem to release air from the fuel lines, that might fix the problem, but I don't seem to have one of these. The car also likes to idle low and die if I don't keep on the gas a little. I thought about adjusting the idle speed, but you are supposed to disconnect the purge line, and I'm not sure which one that is.

 

Also I adjusted my ignition timing, and I got it lined up right on the dot, but the distributor is clocked all the way to one direction, so any further adjustments are impossible. What's the deal with this?

 

Thanks for any ideas,

--Todd

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If it's a turbo then I'd check, vac lines, the movement of the vac advance in the disty and clean if nec., and the fuel pump. From reading similar threads and my own experiance it'll be a tired fuel pump. They do that when they are on there last legs this prob has been discussed in countless threads. Oh yeah make sure your TPS is set properly too.

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The thing is I don't remember the car doing this before I changed the engine. Its a pretty voilent jerking motion, that I don't want to just "live with." Its got a jdm engine now, and I've put about 70 miles on it, new seals, hoses, gaskets. I replaced the spark plugs, spark plug wires, disributor cap and rotor, water pump, oil pump, air filter. I put in an optima red top battery, switched the idle air control valve and gasket, cleaned the coolant temp sensor, and a bunch of other crap I'm forgetting :) I have not however done anything with the fuel pump. I can't think right now about what TPS is.

 

--Todd

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The thing is I don't remember the car doing this before I changed the engine. Its a pretty voilent jerking motion, that I don't want to just "live with." Its got a jdm engine now, and I've put about 70 miles on it, new seals, hoses, gaskets. I replaced the spark plugs, spark plug wires, disributor cap and rotor, water pump, oil pump, air filter. I put in an optima red top battery, switched the idle air control valve and gasket, cleaned the coolant temp sensor, and a bunch of other crap I'm forgetting :) I have not however done anything with the fuel pump. I can't think right now about what TPS is.

 

--Todd

TPS is the throttle position sensor and it's on the throttl body , little black box 2 ph illips screws adjust as per manual.

Vac advance unit on the disty goes but some times the actuator in the disty itself gets gummed up, a little cleaning[ i used brake cleaner] and oil works wonders. Can you here any leaks hissing at all when the motors running?

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If your disty is at the end of the adjustment, then it is probably off a tooth. Being an 88, yours should not have a vacuum advance. I think a knock sensor/tps sensor is likely. Check for error codes; if either sensor is REALLY out of whack, it will come up.

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Ok, haven't been able to check in often due to a fried hard drive:banghead:. But I figured out the problem. I messed with the distributor. Turns out I had done the ignition timing very wrong. I'm an idiot, and also 2 of the connections int the wires were receded into the boots. But now the ignition is all set to stats, and the RX is running very pretty. It still has a very slight jerking, but not very noticeable. I rechecked the codes, and got abnormal o2 sensor, and something about the wastegate I think, 32 and 44.

 

anyways, thanks guys

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  • 5 weeks later...

the 88 rx has an optical disty, so the vac advance only applies to 85-86 models

 

there are 2 screws that hold the throttle body in place, the holes are slotted and you can clock the mechanism one way or the other

 

whats inside is an idle switch and a WOT switch, take off the sensor and shake it, if it rattles toss it and get another one

 

check the idle and WOT switch per instructions in the haynes manual, chapter 6 engine emissions and controls, throttle pos sensor

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If it's a turbo then I'd check, vac lines, the movement of the vac advance in the disty and clean if nec., and the fuel pump. From reading similar threads and my own experiance it'll be a tired fuel pump. They do that when they are on there last legs this prob has been discussed in countless threads. Oh yeah make sure your TPS is set properly too.

 

I've replaced 2 fuel pumps on my t wagons now and have replaced a friends too, I think maybe it has to so with there location, all the shaking?

At least they aren't in the tank:) .

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