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1989 sidekick misfire when cold or when under electrical load
03-07-2018, 01:22 PM
Post: #1
1989 sidekick misfire when cold or when under electrical load
I have a 1989 Suzuki sidekick that I recently purchased. I brought it home and noticed it wasn't running right so I started researching and following much of what I found on kickfix.com

At this point I have repaired a damaged crank key and replaced the water pump, timing belt, cap, plugs, wires, o2 sensor, water temp sensor, thermostat with a 180 degree, new radiator and replaced the auto trams fluid and oil. Timed with light to 8 degrees at 800 rpm

Test I have performed are:
Compression 160 each cylinder
Fuel 40 psi and stayed at 40 for 5 min when car turned off
Checked for vacuum leaks and couldn't find any
Ecm gives me code 12
Cleaned egr and pcv
Checked isc and it appears to function properly
No crack in exhaust manifold

Car runs pretty good, but it misses when it is cold. Rises to 2000 rpm then drops to 1500 and slowly to 800. The missing stops when fully warmed. It will miss again if I turn on lights or any other electrical circuit that makes Ecm think motor is under load. Mpg is around 20 which makes me think it is running rich.

Your ideas of where to look next will be appreciated. Ecm, isc, tb air leak, cat?
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03-07-2018, 11:21 PM (This post was last modified: 03-07-2018 11:40 PM by fixkick.)
Post: #2
RE: 1989 sidekick misfire when cold or when under electrical load
welcome. !!!! gee you did everything, nice work. nice tuneup job!
plug gap at 0.028" and not .045 out of the box is always wrong.?
stuck rich, it is at 20mpg, that is bad, 28 is possible.
code 12 , means it not in limphome ,

the wires connected to the fuel injector pair are not, hacked? monkeyed with?
its not and air leak this car only races idle speed with that, and at perfect Air fuel ratios, with that.
if it has full power the cat is not melted inside.
its not the ISC its only for idle controls.

o2 wiring? is one suspect ( the 1 wire sensors are not very good, the ground can fail easy, find a way to ground the manifold with say 12-15gauge wire to the battery to body ground lug, making this o2 senors ground far better.... and check all grounds in the engine bay,there all with lugs, to body etc.

the issues is, why is the ECU over injecting.
is it ECU inputs or the injector leaking (its not) or wires to it messed up.
input are o2, and MAP


make sure the MAP sensor hose and nipples are all clear and no cracks.
see this complex loop thing at map, that loop is only so when water freezes inside one side can work, cute now? under special freezing conditions.
the manifold port there on the map can clog, check it very carefully even clean and blow test it.
Gasses from EGR+PCV can clog things here.
we can test the map at key on , then idle and gunning throttle easy want to? ,ask.


[Image: 89-vacl-map1.jpg]

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03-07-2018, 11:30 PM (This post was last modified: 03-07-2018 11:32 PM by fixkick.)
Post: #3
RE: 1989 sidekick misfire when cold or when under electrical load
map, pin 2 gray-green , meter volts DMM
key on 3.9v
idle hot 800rpm = 1.2v
gun engine watch meter rise to maybe 3.5v , just make sure it shoots and tries to get 3.5 and not over rev engine. volts.

to do this one must back probe (pin 2, with needle probe) you can use battery minus lug for meter ground black lead.
cheers !

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03-07-2018, 11:32 PM (This post was last modified: 03-07-2018 11:33 PM by fixkick.)
Post: #4
RE: 1989 sidekick misfire when cold or when under electrical load
warning, some of these cars, the 2 wire injector, signals failed, on the ECU, 2 wires, so the owner , (or shorted and blew up the ECU driver to it) and then he hot wires the j
at near the injector and or the ECU same 2 wires, at ECU, just look carefully both ends (visual inspected)

red and yellow pair

[Image: 89-90schem1.jpg]

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03-08-2018, 12:18 AM (This post was last modified: 03-08-2018 12:21 AM by Jamestb.)
Post: #5
RE: 1989 sidekick misfire when cold or when under electrical load
Thanks for the tips. I will check the injector wires and test the map. I did previously check the map vacuum line and cleaned the filter. Everything looked good. Plugs are at .28. I feel like I have full power. Doesn't seem to bog, but I have never owned a sidekick before so don't have a comparison.

I'll also ground the manifold and double check ground wires.

One thing I didn't mentioning previous is that the idle used to race a little because the vsv for the dashpot would take 3 to 5 min to come online. So I just put the dashpot vacuum line direct onto the intake. I had the missing problem before moving the vacuum line.
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03-08-2018, 02:28 AM (This post was last modified: 03-08-2018 02:29 AM by fixkick.)
Post: #6
RE: 1989 sidekick misfire when cold or when under electrical load
the dashpot is active even key off, see it hold open throttle, key off
going to hard vacuum makes it dead. (just after started, and vacuum hits)
and with dead, DAsh pot the ECU goes nuts.
after all it (ECU) knows it must work and adds fuel based on DP working you killing the DP dead, is why the car runs rich cold. You fooled that poor ECU little brain.

so forget all my first posts.
DP dead.
it stays open for 3 to 30 seconds, 3 in Florida keys, 30 in Alaska. SECOND not minutes.
the ECU controls that DP 100% and used the VSV to do that. never seen one that did not work right, unless ,
1: vsv bad.
2: wrong vsv
3: vsv connect up wrong.
4: wire to vsv shorted.

hopeful not ECU transistor shorted,.to VSV DP.

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03-19-2018, 12:23 AM
Post: #7
RE: 1989 sidekick misfire when cold or when under electrical load
I found a very small leak in the vacuum hose that went to the vsv for the dashpot. That is fixed and working properly. I also replaced the iac, grounded the O2 and tested the map sensor. I am still getting a missfire when the ISC is operating. Any ideas on what to check next? What do you think about unplugging the block that sends the signal for the lights and fan?
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03-19-2018, 03:22 AM
Post: #8
RE: 1989 sidekick misfire when cold or when under electrical load
that block is only the fast idle input to the ECU (CALLED A WIRED 'OR' LOGIC " DEVICE, If any input goes true, the output to the ECU goes true for fast idle.
air leaks on this engine do not caused misfire, ever, (its speed density system).
in order, called basics in the business (ASE)

only bad compression on any or all cylinders.
bad spark, replace the VR sensors or known to like to fail, and the thing there attached, inside the distrib. igniter. fails.
This ISC operates at all times, its just idle controller that thing (plus one other thing , deceleration dash pot actions)
The ISC never ever cases misfire, unless RPM falls below 750 RPM and if falls to 400 (like EGR does stuck open) the engine shakes a hard, and is gross misfire, (illegal rpm caused only)
same with all vacuum leaks of ANY kind, causes fast or worst fast idle and with full power and never causes misfire, did you know your right foot is a human IAC/ISC> its a fact.
and works totally opposite of any 16v (air density system is hard right different)

here if the engine is perfect and no melted cat here is the misfire causes.
just 3
1: spark bad. (even the distributer bad and is common on 89/90 , never on 91, up, most cases.
2: fueling way rich, like if the vacuum hose to the MAP is bad in any way or clogged on both nipples and the hose. or the filter device seen on that line is cogged.
3: egr stuck open RPM below 800, even 400.

when you get misfire, please tell
hot engine 180f+
cold engine, below 150F is cold. 150f is the magic temp.!
idling what is rpm
not idling or driving
even terrain... hills ,flat or
what is right foot doing, (3 things off pedal or cruise or wot)
what is the speed.
what gears misfire.
if it misfires, parked in any way shape or form hot or cold say so, as that is 10x more easy to fix than driving.

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03-19-2018, 03:33 AM (This post was last modified: 03-19-2018 03:37 AM by fixkick.)
Post: #9
RE: 1989 sidekick misfire when cold or when under electrical load
above is generic
cold only misfire.
it's too rich, a tuned up car, spark good , is too rich
the fact turning on the fan for faster idle tells me and i bet if you raised rpm to 1000 using your right foot it would do the same thing , at 1000 RPM , and will after all 1000 fast RPM only
The ISC can never cause misfire, in and of it self, ever. if it did, that means (only added air caused misfire, as would your right foot the same way)
It tells me the ECU is adding to much fuel, to that added new AIR, its ONLY job is that, and the MAP reads say, low vacuum too low it will cause the ECU to over inject, every time. (the map sensor on this car is what we call the KEY STONE device, (the heart of the system EFI)
The O2 sensor can trim it, but not if the map was super wrong. (02 is for only fine trimming the AFR, air fuel ratio, in fact the 02 corrects the normal map errors only at ilde and cruise and not wot.

(fast idle mode) opens the ISC and adds air to the induction for 1000rpm and then regulates RPM there, in closed tight loop (firmware loop for ISC servo actions)
so what causes rich? (defeat the EGR temporary, to get it out of the problem loop here)pull its vac hose and golf Tee, the end of hose.
02 stuck at 0v, for any reasons. (3 in the list, its bad, wires bad or exhaust cracks near by making it read 0v all time time)
map reads wrong, my map covers this 100% and how to test it and test the vacuum lines for trouble (clogs or splites)
injector leaks
fuel pressure at 55psi (not yours)
injector wiring hacks.
Bad ecu,
id be all over the map output voltages, key on, idle and gunned. per my map page.

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03-19-2018, 12:58 PM
Post: #10
RE: 1989 sidekick misfire when cold or when under electrical load
I previously tested the map according to your test page and it tested good. I checked vacuum lines and have no leaks. I dont believe I have a leaking injector because I did the fuel pressure test and it held 40 psi for 5 min. I have also plugged the egr and retested with no change. I do not get a missfire when I hold throttle at 1k with my foot. I only get a missfire when I turn on lights, a/c or fan. It will happen regardless of whether the engine is cold or hot.

I am thinking of changing the caps in the ECU or maybe have the injector cleaned and tested.
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