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Old 06-28-2010, 07:25 PM   #1 (permalink)
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Default Rough running, rough idle.

96' Tracker with 5sp manual. Starts good cold and runs smooth until warm-up. Then at an idle, surges from nearly dying to 1000rpm, and back to dying for about 15 seconds, smooth's out for 15 seconds then goes back to surging. Keeps doing that while at idle. Part throttle, normal acceleration, and just going down the road you can feel and hear it missing. WOT has good power and seems smooth. Gas milage is at 22mpg or so on a good day. No check engine light, and no codes. Has new plugs, plug wires, rotor and cap. Timing set correctly. Little tube from the EGR to Manifold cleaned and clear. Any ideas?
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Old 06-29-2010, 08:09 AM   #2 (permalink)
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Quote:
Originally Posted by weidnerl@wwt.net View Post
96' Tracker with 5sp manual. Starts good cold and runs smooth until warm-up. Then at an idle, surges from nearly dying to 1000rpm, and back to dying for about 15 seconds, smooth's out for 15 seconds then goes back to surging. Keeps doing that while at idle. Part throttle, normal acceleration, and just going down the road you can feel and hear it missing. WOT has good power and seems smooth. Gas milage is at 22mpg or so on a good day. No check engine light, and no codes. Has new plugs, plug wires, rotor and cap. Timing set correctly. Little tube from the EGR to Manifold cleaned and clear. Any ideas?
go to The KickFix Repair Pages, for Sidekicks and Trackers and read, be prepared for the flood of info. I'd start with vacuum leak testing and compresson testing. 22 mpg way too low. my 97 gets 29.5mpg driving around town, no lie. leaning toward vacuum leaks with idle fluctuations like that and good WOT.
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Old 06-29-2010, 09:53 AM   #3 (permalink)
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the flood of info is because , nature hates a vacuum and there are some many places for a leak to happen. And many many many failure modes of engine and EFI parts.!@!!

the EFI and motor are both very complex.
motor must pump air, and induction cant leak.
the EFI must have good fuel pressure and the injectors not leaking or clogged.
it must not have leaking EGR. or stuck iSC , or IAC.
CEL is useless, unless ON.
off the CEL means that car is not smog polluting, and NOT THAT motor is running right!
Forget the CEL. (scan tools are the clues to knowing what is going on , not a light)
change the logo onlight to "gross polluter" and now you know.

your motor is surging (hunting)
this is caused (symtom to actual problem) by 1 of 2 things.
1: ISC is hunting for proper RPM ( 800 hot or 1000 rpm a/c on)
2: AFR is gross lean.

full power says CAT is not melted and plugged.
full power says fuel pressrue may be ok.

so why the surge.
the ISC is trying ( ECU slave) to lower RPM or RAISE it.
on some years.
ECU will surge. keep resetting the ISC and then trying to idle motor to spec.
my 96 gets 29.5mpg all the time. (with crap 10% ethonal)

first and formost, complete the tune up with filters.

the surge can be a symotom of many a thing.
if the IAC sticks open and motor gets hot, the ECU will NOT understand that.
it does not know the IAC got stuck so keeps trying to pound the ISC to death to correct the malfing IAC. It only knows, gee, why is rpm way over 1000 rpm hot,why. and is helpless to know.
so it cycles the iSC in the hope (wrong) that it is stuck.

now imagine any other sources of illegal air.?
same story ,the ecu only knows the RPM is way high.

Keep in mind to that the MAF on this car operates at idle ,(unlike some cars)

so if its bad, all is lost.
clean it, too. CRC maf cleaner, GM says tap it at idle gently and RPM must not change.


motor can lean surge.
AFR is lean ( hot motor) and the EFI can enter closed loop (clue 1)
and the ISC cant control idle because motor is gutless(lean) so hunts.
this is not your fail path. I think.

EGR must not leak, if the ECU cant control idle due to EGR leaks then , bingo.
do not assume the EGR is good just because 0400 is clear.
this is bad thinking. EGR tests take high speed running. so if the EGR monitor is pending then that means it has never passed. ( actually it has not completed)

there is no redundancy to the system.
so you become the sole solution to the problem and discovery with tools and measurements.

your post is good because it shows motor makes power, few ever tell what motor does good and bad. key that is.

cheers.

PS: there are lots of thing to do and check to get a clear diagnostic profile.

many people think wrongly.
that :
i have this.
so just replace that.

this is not going to happen.
unless you have the most wonderful guardian angel.

Hit list:
1: no EGR leaks.
2: TPS idle switch closed at idle every time.
3: ISC not stuck.
4: IAC not stuck.
5: no vacuum leaks.

these are the common 5.
all assume motor is good.

Global:
motor good (means no vacuum leaks too)
fuel pressure good (in spec range )
all actuators good.
all sensors good. Good O2?
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Old 06-29-2010, 10:45 AM   #4 (permalink)
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Quote:
Originally Posted by kick-fix View Post
the flood of info is because , nature hates a vacuum and there are some many places for a leak to happen. And many many many failure modes of engine and EFI parts.!@!!
Kick-fix
Thanks for the detailed response. Before I can wade into the details, this 64yr old pea brain needs to understand the acronyms. I know EFI,IAC,AFR,ECU,TPS,and EGR. But do not know what ISC, CEL, and MAF are. Any chance you could quickly define these for me. I will spend some time today looking at your kick-fix site, then tackle your response.
Thanks again!!
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Old 06-29-2010, 02:49 PM   #5 (permalink)
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Old 06-30-2010, 02:41 PM   #6 (permalink)
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mAf measures the AIR flow to induction.
CEL is check engine lamp.

ISC is idle speed contoller but suzuki keeps changing

IAC <> ISC ( enen though they have both, swaps names) funny
but to me the ISC is electric.
and IAC is 100% thermo.
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Old 06-30-2010, 02:51 PM   #7 (permalink)
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keep in mind at all times, all motors, bad idle can be
1; bad idle controls
2: Bad (all the other stuff)
see, no motor will ever run and idle correctly unless all else is good .

the idle setting pages lists (partially) the things that are unconditional for idle setting.

Truly, IDLE is THE LAST item on a engine repair list.

just mess u, by adding an induction air leak.
or mess up cam or valve timing !
or a misfire on one cyl. will wreck idle.
or too lean ,like a bad 02 (biased falsely rich) can make idle fall.(or hunt,surge)
depends on mode your motors is in, cold or hot?

Really, it's a huge list.
that is why service techs make such good money ,using instruments to find out what is REALLY going on.

in a real shop, they stiff the tail pipe.
with 5 Gas analyzer.

bingo , in 1 instant they KNOW what is going on. no fiddly farting around.

all other ways are slow, error prone and laborious.

sorry , if obvious. but lots of posters think there is magic here.
no not at all.
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Old 06-30-2010, 03:05 PM   #8 (permalink)
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Slightly off topic, but to poster: You should NEVER post your email address or use it as a forum name, bad security, and opens you to all sorts of spam and internet garbage (and sometimes even worse.....)
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