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Unread 05-14-2009   #1 (permalink)
jd5
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Default Rough Idle, hesitation, no engine codes

I had some trouble codes, engine running rich and the car had bad hesitation (undrivable), which led me to replace the MAF, and the O2 sensors. I have done the PVC valve/gromit, gapped the plugs, Dist cap and rotor. Fuel filter is new too. Checked for vac leaks best I could. No more codes, and the exhaust smells better. Rough idle is still there, and the hesitation while accelerating is still there but VERY subtle/intermittant. Now the RPM gauge is bouncing around a little. Just wondering if my computer might be going bad. When I do a KOEO test with a scanner, I can't do another one right after it, unless I shut the ingition off/back on. I don't remember having to do that before.
...or is it a vacuum leak that I cant find?

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Unread 05-14-2009   #2 (permalink)
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recheck #4 and #8 cylinder wires. They are right next to each other and easily switched
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Unread 05-14-2009   #3 (permalink)
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Default Good there

The wires are correct. The idle is not THAT rough. Just seems like a vac leak. Also, the hesitation is so subtle, that sometimes it is hard to discern from small bumps on the road.
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Unread 05-15-2009   #4 (permalink)
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Default

Possibly a Pick-up coil on the way out. usually erradic Tach needle is a sign of this. Testing the Pick-up coil requires removing the TFI module though. If all the ECM grounds and Main grounds are in place and are good. And the wires, cap, rotor, and plugs are good, its more than likely a TFI or Pick-up coil and/or its wiring.
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Unread 06-07-2009   #5 (permalink)
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Default Still have problem with idle

I have determined that it is not just a rough idle, but the car also hesitates a bit under 1000 rpm. When above 1000rpm everything is fine. I don't think it is a vacuum leak any more because the exhaust smell is rich. I have now replaced the TFI/ICM to no avail. The only other symptom is the wonky RPM gauge which settles down a bit after the car is warmed up.
I'm just wondering if it is a bad coil, because of the RPM gauge problem. The PIP is only other thing to replace, but that's a pain to replace and I hear they don't go bad very often.
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Unread 06-07-2009   #6 (permalink)
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Quote:
Originally Posted by jd5 View Post
I have determined that it is not just a rough idle, but the car also hesitates a bit under 1000 rpm. When above 1000rpm everything is fine. I don't think it is a vacuum leak any more because the exhaust smell is rich. I have now replaced the TFI/ICM to no avail. The only other symptom is the wonky RPM gauge which settles down a bit after the car is warmed up.
I'm just wondering if it is a bad coil, because of the RPM gauge problem. The PIP is only other thing to replace, but that's a pain to replace and I hear they don't go bad very often.
On the Contrary, they Fail very often.
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Unread 06-07-2009   #7 (permalink)
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Check the ECM grounds first and then, if they are in good condition with good connections, it sounds like your EGR valve may be sticking open. Is there a lot of carbon buildup in it?
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Unread 06-07-2009   #8 (permalink)
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Default PIP diagnosis/replacement

If the PIP is bad, it's intermittently bad, therefore testing a problem with the PIP might be tough. So I suppose the best course of action would be to just yank the distributor off and replace the PIP?

Oh, and the EGR is clean and articulates with vacuum.
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Unread 06-07-2009   #9 (permalink)
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Usually PIPs act up when warm. Too much resistance in the internals. And if its intermittent, yes its hard to diagnose. But eventually it will Fail and leave you stranded. YCYDYP
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Unread 06-25-2009   #10 (permalink)
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Default Update

I tried replacing plugs and wires last weekend. I found a glitch on Amazon.com where they were selling a full set of Splitfire plug wires for $5 and capitalized on it (price has since been corrected to $70, sorry guys). I ordered 8 Autolites at the same time. After I intalled them, any latent hesitation problems disappeared!

I fixed the wonky RPM guage while I was under the hood, it was the "input" connector on the coil. Apllied some dielectric grease and reseated it, and "BAM" - good to go.

I still could not fix the rough idle, so I broke down and took it in to the local shop. They were suprisingly patient with my semi-ameteur tinkering as I told them everything I did. Guess what? The MAF that I bought from NAPA was bad!

The mechanic there warned me about buying generic parts, and also cautioned me to put Motocraft plugs in later. I can't tell you how many times I have heard that from mechanics, but I thought maybe because the MAF was a Borg-Warner, it would be ok. But the part came in a cheap box, and if it got dropped by a NAPA employee...

On the other hand, I'm not one to blindly believe the mechanics, I wont be changing the plugs soon. The guy gave me an analogy of buying a bulb for a Toyota at Kragen Auto Parts, and said it wont fit. That was particularly hilarious, because I JUST replaced the headlight bulb on an '07 Toyota Tacoma with a Sylvania I bought at Kragen. And I never go to Kragen!
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