Regular "miss" in idle after UIM/LIM job - Page 4 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 08-22-2007, 10:43 AM   #31
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Ok...read through again with more detail. Each time I put on an upper manifold I put the gasket on the upper and put it down on the lower. It is my belief that you did that part perfectly fine.
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Old 08-22-2007, 05:36 PM   #32
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Your EGR tube should have had a flat flange (or hat) on the LIM side. That is what the outer clamp is designed to clamp against the LIM, to seal it off. Perhaps it broke off at some point, and you did not even notice. Heck, it could have fallen out even before you disassembled everything. The clamp piece (with the single bolt) is actually steel, since the EGR gasses are so hot.

I noted the same "gasket/runners do not fit perfect" issue with my manifold. But I really thought it would clamp down just fine and seal. If anythen didn't seal perfectly, I figured it would be the internal runners, not the perimeter of the manifold. I need to check that carefully.

My freind indicated that the 950 to 1000 RPm idle I am at now was what he had all along, so I am guessing that I got everything to at least the performance he had - but without the coolant leaks!

Ken
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Old 08-22-2007, 10:12 PM   #33
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Quote:
Originally Posted by BillBoost37
Stop tearing it down!!!

All you need to do is use a 13mm wrench to get the tube from the egr to lim off. Nuts on both ...wiggle pipe out and you'll see a crack in it near the lim. New tube time or holler if the dealer thinks you should take out a mortgage for one. I've got a few used in good condition spares here.
I stopped. I hadn't gotten far (alternator off, some harness connectors undone, and the TB cable bracket off). A "crack", you say! Hahahaha...Two-thirds of the cricumference of the pipe was slit on the inside of the bend where it was hidden from sight. An amazing remote diagnosis, BillBoost! I'm hoping that that is the source of my problem. And I'm happy to not have had to tear into the work I'd just done. I did have to remove the airbox and the TB support bracket in order to get to the EGR pipe at the LIM; but that'* a lot easier than what I was contemplating doing. Thank-you very much. People like you make these forums fantastically useful.
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Old 08-22-2007, 10:19 PM   #34
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Quote:
Originally Posted by BillBoost37
Ok...read through again with more detail. Each time I put on an upper manifold I put the gasket on the upper and put it down on the lower. It is my belief that you did that part perfectly fine.
Thanks for mentioning that, BillBoost. It puts my mind at ease in that regard.

What do you think about my IAC? I'd never had one in my hands before, and, while the plunger did move back and forth easier after I'd sprayed it with TB cleaner, it was still pretty hard to move. And then, in the process, I pulled it out entirely. I got it back in, and it seemed to move in and out the same way as before I pulled it out. But I wonder if maybe I ruined it. I'm thinking it might be stuck in its halfway position and so is not much of a problem in our current warm weather; but maybe I'll have idle issues come winter?
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Old 08-22-2007, 10:30 PM   #35
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Quote:
Originally Posted by rockken_cosworth
Your EGR tube should have had a flat flange (or hat) on the LIM side. That is what the outer clamp is designed to clamp against the LIM, to seal it off. Perhaps it broke off at some point, and you did not even notice. Heck, it could have fallen out even before you disassembled everything. The clamp piece (with the single bolt) is actually steel, since the EGR gasses are so hot.

I noted the same "gasket/runners do not fit perfect" issue with my manifold. But I really thought it would clamp down just fine and seal. If anythen didn't seal perfectly, I figured it would be the internal runners, not the perimeter of the manifold. I need to check that carefully.

My freind indicated that the 950 to 1000 RPm idle I am at now was what he had all along, so I am guessing that I got everything to at least the performance he had - but without the coolant leaks!

Ken
Ya, I noticed that about the EGR tube when I looked more carefully at it an hour ago (see my recent post to BillBoost). I'm surprised that that egg-shaped black thing is steel, it'* so light. Thanks for the explanation, Ken. Maybe all I have left at my age is my life-long habit of observation, without the quality of accuracy of was used to before my eyesight punked out on me. Well, as long as I can bounce stuff off you guys in these forum I shouldn't go too far wrong.

So, did you put the UIM gasket down first then lower the UIM on to it, or did you assemble the gasket to the UIM and lower the assembly to the LIM?
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Old 08-23-2007, 03:33 PM   #36
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I put the gasket on the UIM, clipped it into place, go the best fit of the runners, and installed it, thinking any clamping force would set everything into place. Glad to hear you found the EGR tube crack. Let me know what your idle is after everything is running again.

Ken
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Old 08-23-2007, 07:57 PM   #37
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Quote:
Originally Posted by rockken_cosworth
I put the gasket on the UIM, clipped it into place, go the best fit of the runners, and installed it, thinking any clamping force would set everything into place. Glad to hear you found the EGR tube crack. Let me know what your idle is after everything is running again.

Ken
Yes, I have great expectations. I ordered the EGR tube (and a new surge tank and cap and hose) from a dealership, but it won't come in until Saturday, so I'm in a holding pattern until then. I'll let you know how it turns out, Ken. Thanks.
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Old 08-25-2007, 11:01 PM   #38
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Good news! I got the EGR tube ($22 at the dealership) and installed it and the "missing" is gone. The vacuum tester gage showed improved vacuum, but when the engine warmed up a bit it still fluttered. I'm going to assume that'* normal, at least for where the tester was installed

The EGR tube was difficult to install. It was a lot beefier than the old one and would not bend easily. The exhaust was right there by the LIM. I ended up taking out the two bolts holding the EGR valve mounting bracket so I could move the EGR valve back far enough to get the tube in after connecting the LIM end of it. It was still tricky getting those two bolts back in--again, very little clearance for hands and wrenches.

The engine fired right up, 1100 rpm, until warm, then about 900 rpm. I put it in gear, and tach dropped to about 700 rpm. When I put it pack in park, the idle settled at about 800 rpm. I took it for a test drive and it performed very nicely, very responsive.

One thing that bothers me is the sound I heard when listened at the exhaust pipe. It sounded like a gentle rattling, or intermittant grinding. I don't hear it around the front of the car, though. Is this bearing noise? At 187000 miles, maybe it'* to be expected. I should get a stethescope and listen around.

But there'* no more hissing, no "missing", no spitting at the tailpipe, and it'* running smoothly and powerfully. I'd like to thank everyone who'* weighed in on this thread. It'* been a very educational experience for me. And the wife is happy: priceless!
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Old 08-25-2007, 11:16 PM   #39
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Glad to see you have it fixed. Believe it or not, the EGR tube cracking is kinda common. The one on my '94 SSEi was cracked and boy it was annoying. I got one from Pat (1993 SLE) and fixed it right up.
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