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Rough Idle... so many things have been done.


nequamminor

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My '95 Z34 has been irritating the hell out of me lately. The 3.4 DOHC has 199700 miles on it, but that's besides the point. I've replaced the O2 sensor and an injector. It has new LIM, UIM, and plenum gaskets. The IAC is in pretty good condition, and the plugs and wires have less then 5000 miles on them, granted the wires are duralast, the best automotive brand known to man, however they are in good shape. The idle is steady at times, however other times it has a lope to it. Probably not more then 100 rpm, but very annoying, and lately the idle will sometimes lope about 50 rpm rather quickly back and forth. Around 900 rpm is where it normally idles. Its just that it lopes and is very annoying. The coils and ICM may be factory original, but I don't know for sure. Any suggestions? TIA

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If I start the car, and start driving almost immediately after I start it, it acts weird. If I try to be nice w/ the car its slow, but then i get on it, and it just kinda snaps to higher throttle position. Its kinda hard to explain. Imagine a R/C car with 2 or 3 settings for the speed. Its either slow, or probably 1/2 throttle. From then on up it acts relatively normal. After the first or second minute its running it acts almost completely normal. When its warm, it acts pretty good. No hesitation otherwise while its warm.

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Start by checking the electrical connection at the EGR valve. Check for water in the plug. Unbolt the EGR valve from its mounting plate and spray the pintle with carb cleaner. There may be a lot of carbon build up.

 

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I have 2 egr valves. One is rebuilt, the other I found online for 50 bucks. I'll try the 50 dollar one today. Although they are both relatively new and fairly carbon free.

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My 3.4 used to do the same thing,h asent done it in a while. id start the car in the morning and youd think i had a cammed 350 in it. idled at about 300 and then would idle normal after a bit. but if i tried to drive while it was idling rough if i went to accelerate it hesitated and then would kick in quite abruptly and drive normally. not sure "EXACTLY"...what it was but it should be an easy fix, im going to try some injector cleaner after i replace my tank this weekend.

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I've had a couple of 3.4's and one had a screwy mass air flow. The other ended up being a PCM. Both had that wierd idling problem although they both were worse than what you say yours is doing.

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