: Idle speed adjustment...

03-18-05, 06:01 PM
:banghead: O.K. How does one go about adjusting the idle speed on a '98 Catera???

I'm assuming there is a procedure where one must stand on one leg on a three legged stool while patting your head and rubbing your stomach...

I see the set screw, and attempted to adjust it, but it either ignores my efforts or bumps the idle up to 800-1000 rpm :want: ; neither of which is what I want. I am idling BELOW 500 rpm & after checking out a couple of others, they all seem to be around 500-600 rpm, I believe mine is a bit low.

Sooooo...How do I do this?

Thanks in advance for any help you can provide!

I REALLY need to find the factory manual for this thing...

03-18-05, 06:20 PM
:welcome: Welcome to the world of Catera Ownership. You're are indeed right about one thing --- you REALLY DO need to get the service manual ;) Go on eBay. Make sure that you get the "second edition" of the 98 manuals (you can see the words "SECOND EDITION" in red on the covers). You will find them for anywhere from $20 to $80 a set. They are a "must have" for any Catera owner.

Now to your original question. There is no idle adjustment in the classic sense. Idle speed is electronically controlled by the Engine Control Module (ECM). I have no idea what screw you might have turned. If you can describe it to me in detail, I will try to figure out what you have done. (I suspect it involves some sort of adjustment to take up slack in the cruise control or something like that.) Not to worry, though -- it is unlikely that you caused yourself too much grief :D

Welcome again. You have come to the right place. There are a lot of very helpful people in this forum.

03-18-05, 06:45 PM
By the way, Steve, would that second edition 98 Service manual for the Catera be good also for the 97 or should I be looking for a specific manual for the 97? thanks, i know this may sound stupid but what i am thinking is that they might have made some mistakes with the 97 manual that they are corrected with the second edition. Knowing how they made bigtime mistakes with the 97, it's easy to repeat the same thing with let's say a manual.

03-18-05, 08:07 PM
Hey, Steve, thanks for the speedy reply!! O.K. The screw is on the throttle linkage on the top, right front of the upper intake plenum. It is opposite the TPS & will control the throttle angle/opening. As I am very adept at the Ford product, I am familiar with PCM/ECM/whatever name you want to give it operation. But...Although the PCM controls idle and adjusts it for varying loads, there is a procedure for setting base idle on the Ford product, so I assume (yea, I know!) that the same applies to GM, et al. I can tell you that like em or not, the Ford PCM is WAY better at monitoring steady, stable idle than this GM is!!! On my Lincoln, if you tweak the steering wheel, you won't even see the load as the PCM gets the input and bumps idle up to compensate. On this thing, the idle lopes every time you turn the wheel! I do a lot of stop/go driving & if I toss it into neutral, it sometimes drops to 200-300 and recovers and then cycles up/down.

In any case, I'm running what appears to be too low a base idle speed (around 400 rpm). It seems to me there has to be a way to make this thing idle properly. I'm thinking about pulling the tubing off the front to examine how dirty the throttle bore is and possibly cleaning it, but I'm not sure that will correct this. SO, how do I command the brain to maintain proper idle speed??

03-18-05, 10:22 PM
Theoretically the 98 manuals should be accurate for 99.999% of the 97 stuff plus they would have the advantage of updated procedures for things like wheel alignments, etc. The little diagnostic stuff that techs discovered during the 97 model year get incorporated in the next year's manuals. However, there are some subtle changes from 97 to 98. I guess if I owned a 97 and a 98, I'd pop the extra $50 or so and own both sets, if for no other reason than to keep the evil spirits of tricky car repair at bay :) Seriously, though, for most use, the 98 manuals would be fine for the 97s. In the 98 manuals, when they refer to "first design" you could generally assume that applied to 97s (since it implies early 98s. Hope this helps.

03-18-05, 11:18 PM
Regarding the idle problem, attached is a PDF from the service diagnostics described as "The engine runs unevenly at idle. If the condition is severe, the engine or vehicle may shake. The engine idle speed may vary in RPM. Either condition may be severe enough to stall the engine."

Hope this helps.