Intermittent idle problems, smooth then misses....

phils89sc

Registered User
This has been going on for quite awhile now on my 89 SC 5 speed. I just did the EGR delete since my EGR tube to the manifold broke. I have checked all of the vacuum lines in the vicinity I was working, and replaced the PCV line with new hose, as well as put on a new throttle body gasket. I have replaced the vacuum line on top of the inlet plenum that gets really soft after awhile with a new line w/ clamps.

What it does may not sound bad, but to me, it is irritating. I will start the car in the morning, starts right up just fine. Idles nice and smooth for awhile (I watch the shifter to gauge smoothness), then when it finally reaches operating temp, and the idle is at about 800 rpms's, you can hear a slight sputter every5-7 seconds or so in the exhaust (flowmaster cat-back). I probably didn't notice this when I had stock exhaust because it is so quiet. So, it sort of acts like a vacuum leak, but I can find none! I am going to reseal the intercooler tubes, again, replace the Oxygen sensors, and check the TPS voltage.

I also replaced the supercharger at the same time as the EGR, and used the Orange Permatex on the inlet which doesn't appear to be leaking. I have put on a vacuum gauge, and it sits right at 18.5-19" at idle. At full throttle my boost max's out at about 11 psi and I have zero detonation.

Between the sputters, and I will say again, they are very slight, it runs very smooth. Is this normal?

Oh yeah, another thing it will do is if I rev the engine while parked, when I let off the gas, the idle will drop for a second or two down to about 550-600 rpm, like there was a load on it, then it will come back up to 800 and stay there.

I have new Autolite DP plugs gapped @ .054, new Bosch Wires, and new DIS module.

Any ideas what can cause this? Or is this me just being very picky about an engine that has 230K+ miles on the clock?

Thanks for all your help,

Phil
 
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Please help!!! I am trying to make 4 wire O2 sensors work, but can't figure out what the pin-out is!!

Thanks

Phil
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I can't offer any help on this one (except to bump this back to the top), but I am experiencing the same kind of intermittent "blip" in the idle. It hasn't been bad enough for me to really go after it, but it is annoying all the same. Everything you described is what my '92 is doing.... Relatively speaking, how many cars are there that run as strong as our's do after 10+yrs and 180K+ miles? But then, if you are on this BBS, you are probably as obsessive about peak performance as the rest of us..............
(misery loves company) :D
 
When my DIS was on the way out, before it threw a coil related code, it would do that. Idle... and and occasional kick where it felt like it shut off for 1/10th of a second then back to normal. Check also that your plug wires are seated completely on the plugs.
 
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