With the cold weather coming back my Tracker is back to varying it's idle between 800 and 1700 rpm when in gear and the engine hasn't been running for at least 10 minutes.  In the past someone has recommended replacing vaccum lines.  Is this likely to be the culprit?  Also where are all of these lines?  Any other ideas why this only occurs in cool weather?  It ran great all summer.  Last winter I had the idle jacked up to 1300 rpm.  Like that it ran okay and didn't surge, but raced to 2200 rpm or higher when in neutral or park.  I'd like to figure out what the real problem is.

my 90 tracker does the same thing and always has since I bought it 3 years ago. Except it doesn't do it when driving or when I'm on the gas, just when idling until it's warmed up. When I start it cold, the idle goes high then as it starts to warm up, the idle bounces up and down in a pretty big step for a few minutes until it's fully warm, then it smooths out at a normal lower idle from then on. I'm not sure what causes it, but it would seem as if there are at least 2 different sensors that are arguing with each other as to if the engine is warm or not...

my 90 tracker does the same thing and always has since I bought it 3 years ago. Except it doesn't do it when driving or when I'm on the gas, just when idling until it's warmed up. When I start it cold, the idle goes high then as it starts to warm up, the idle bounces up and down in a pretty big step for a few minutes until it's fully warm, then it smooths out at a normal lower idle from then on. I'm not sure what causes it, but it would seem as if there are at least 2 different sensors that are arguing with each other as to if the engine is warm or not...

That sounds exactly like what my engine does.  How long does it take yours to warm up enough to the point that it doesn't do that?  

well, it depends on how cold it is. Usually it warms up enough to quit doing it in about 10-15 minutes...

It's the cold start air bypass,
it's located at the base of the
Throttle body and has hot water
running thru it to activate it, seems
to be a problematic part of the Mikuni
TBI system

Wild

Is there a fix or do we live with it?

I live with it, it's done it since
it was fairly new, I think if
you take the thing apart and
lube/clean it that it might behave
for a while.

Seems to me that there is a bi-metal
spring or somthing in there that gets
stuck or sticky, water doesn't go thru
the spring, it's just heated by it

Wild

I have a similar problem, not as bad I don't think.  I just live with it.  During the winter, I start and let my engine run for 10-15 minutes, depending on how cold it is and she usually runs like silk after that.

Is there a fix or do we live with it?

This is the fix.
It works very well.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=7926805799&rd=1&sspagename=STRK%3AMESE%3AIT

This is the fix.
It works very well.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=7926805799&rd=1&sspagename=STRK%3AMESE%3AIT

Can you give more details on what the fix includes?

This is actually a part that replaces one of the factory parts in the throttlebody----Very simple repair-----
The package includes the replacement part and detailed instructions.

It may be the same method I found in Zuwharrie bbs. last May. I had the surge idle, maybe 700 to 1600rpm.
Used his method and corrected the problem.. All I did afterward was increase the idle speed a little..The article is in Zuwharrie bbs., Topic 4772.0, reply #8, March 22, 2004, by Red Tin Top..If you can't locate it, let me know and I'll type it out on this bb. It is so simple, you can't believe it..

I couldn't find the post on the Z board.  I tried something last spring where I removed the cover with the 3 screws and blocked the air passage in it with a tube.  That did not correct the surging problem for me.  Is what the post was about rakkasan?

Yes it was. The tube and bolt fixed mine..Sorry..

I couldn't find the post on the Z board.  I tried something last spring where I removed the cover with the 3 screws and blocked the air passage in it with a tube.  That did not correct the surging problem for me.  Is what the post was about rakkasan?

Kieth,

This may be the info...

Your up and down idle is probably caused by a thermal wax pellet housed inside the throttle body.  Its purpose is to create a high idle by creating an intentional vacuum leak until the motor warms up.  When these pellets get old they sometimes cease to function, causing this loping idle.  It sounds like there's someone in the truck revving it up every few seconds.  Very annoying.

To find this pesky thing, look at the TB from the front and notice a small round plate held on to the left front of the TB with three screws.  The wax pellet thing is in there.  Get the screws out however you can (they are probably stuck) but be prepared to replace them if you trash them.

Back out the threaded thing inside and you will see the hole into the throttle body.  At this point get yourself some rubber hose the same diameter as the inside of the threaded opening and screw it in there real tight.  You can either run a bolt into the end of the hose and leave it hanging there or you can carefully cut the hose length so the cover blocks it off completely when you replace it.


Sorry to hear you're still having the problem.  It's very intermittent for mine, but it does still happen.  I haven't really investigated the "fix" above, but I'll probably give it a shot.