Engine seems to run Lean (rough idle)

[Richard Craneum]

I did some maintenance on my son's Tracker.

Is a 94, 8v, Manual with TBI.

No ( CEL ) Check Engine Light/Engine Service Light is ON .

We replaced the Air filter, was full of leaves and dirt, pretty clogged up. Replaced the Spark Plug wires with Duralast (Auto Zone brand) that are made in USA (no Chinese crap). Replaced the Spark Plugs, the plug that was installed were Autolite and replaced them with Bosch Platinum (used them on a Geo Metro before and worked fine).

When I start the engine, it runs rough in idle. If you feather the throttle, it backfire by the intake. Once it picks up speed (RPMs) seems to run smooth. The exhaust starts to smell in the same way burnt powder does. I think is Sulfure on this case and you can hear from the tail pipe like is missing.

Ran the engine until reached normal Temp.
BTW, is that about 1/2 way on the gauge?

I removed the Dome fuse, thinking the engine was breathing better since the filter was new vs the old one and making it run richer and the engine adjusted to it. So by resetting the computer I was hoping to go to a nominal settings. Seems not to help.

I am wondering what went wrong? It could be the plugs? I doubt it but will not be surprised if is. I kept the old ones and might try them tomorrow to see if that is the problem.

My thinking is the engine is running leaner and have not adjusted to the new amount of air. But should it learned by now?

Anyway, any other thoughts on this?

Pics of my Tracker are here
1994 Geo Tracker

In case that I miss some.

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Since the thread got lengthy, let me narrow down what I have so far....

Brand new...
Fuel Filter, Air Filter, Oil Filter w/ Oil (Mobil 1), Spark Plugs (Bosch Platinum and tried AC Delco OEM plugs), all Vacuum Hoses, Timing Belt, Rotor/Cap/Wires.

Test done...
MAP Sensor, Ignition Timing (holds at 8 deg), Visual inspection of Key Way for Crank Timing Belt Cog, Fuel Pressure Regulator with hand held pump, Fuel Pressure holds at 39 PSIG, ECU for blown Capacitors, EGR.

Each time I fixed some, the engine seems to run a bit better.

The next new thing is the O Sensor which is on order.

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IS FIXED !!!!


SPARK PLUG WIRES WERE BAD !!!!!







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As stated before. The engine ran like an old car. Kind of shaky and smooths out after a good warm up. Just need it some TLC. I changed the Plugs, Wires and Air Filter. Just after that, the engine start to run like crap. Shaking and popping when it ran under load. I was thinking, the new Air Filter was giving too much clean air since the old was was really plugged up, so it had the symptoms of a Lean Running engine.

I asked for help here and had tons of helps, great forum !

Check Jerry's Site The KickFix Repair Pages, for Sidekicks and Trackers a lot of excellent info.

According to the website, I did a lot of checks. From Fuel Pressure (I found I had a bad Fuel Pressure Regulator), EGR Checks, MAP Sensor, Vacuum Test, Timing Belt and Ignition Timing. All seems to checked out. Even I cut the Catalytic Converter to see if it was not plugged.

But I remember that I bought a Spark Plug Wire Set from Auto Zone (by the way, not all they sell is crap) seems to be the root of the problems. I got the OEM type AC/Delco and now runs great.

I forgot about a symptom that occurs when a vehicle is under load and is a Bum Ignition Coil. I had a Honda that did it. But with the modern cars, I have never encountered and forgot all about it.

The Tracker is a mix of Old and New. So if your car, hesitates, runs somewhat rough, no power at all it could be bad Spark Plug Wires (I think on my case was Coil to Rotor cable), Worn Rotor, Worn Cap.

The wires cost about $29.99 for the OEM at Advance Auto Part
Cap and Rotor was like $8.00 a piece at Auto Zone.

If your Tracker Experience that and you have not replaced any of them, do so, is part of the Maintenance according to the Owner's Manual and is pretty cheap to do.

By the way, Bosch Platinum Plugs seems to run just fine and was only a $1.00 more than the OEM and last way much longer.

[jtgh]

no on filter,
this motor will run find either way,
the Map sensor detects the flow of air thru motor and all injection is based on this and tempatures, load, and rpm.
the EFI has no problem handling a good air filter , not in the least.
a dirty filter reduces power, not Air to fuel ratio. (despide Air flter ads to the contrary)

are you saying car ran pefect , the after tune up it didnt.

yes, then did you replace spark plug wires 1 at a time? not all at once.?

did you gap the plugs to spec ( no matter what the box said to do)

do you need spec, (nice plugs btw, real nice)
i think your duralast parts are ok. (not bottom by all means)

8v dizzy goes CW.
16v dizzy goes CCW.

all are 1,3,4,2.

correct wires and gaps, then its ok.

[Richard Craneum]

It ran fine,seems to be. A tad rough at idle (signs of an old engine) but smooths out when warmed up.

Now shakes pretty good at idle. I have to ease on the throttle to rev it up. But if I tap it, tends to stall or backfire.

We replaced the wires one at the time with the plugs too.

When you hit over 1000 RPMs runs smooth. I have not test drove it yet, we just coated with Herculiner the inside.

According to the Tach on the dashboard, seems to run about 600 RPMs is that the correct number?

Seems to act like perhaps, out of time or too lean.

We did not messed with the distributor so the Timing issues I think is not it.
The air filter was pretty clogged and like I said before, less air and the engine adjust for a lower volume of air, like been in high altitude. So, when the new filter came in, the air volume increased, therefore, the engine was running on less fuel before and now is lean.

That is what I was thinking.

But if some else, I am all ears though.

[jtgh]

nah,
EFI is instant. (electronic fuel injection)
as soon as more air enters motor , the ECU detects it in 1000th of second and responds.
it that were not true, the throttle would be sluggish on all cars. its not,

i think you should look for a dead cylinder. (or stuck open egr)

800 rpm is normal , hot, and is regulated by the ISC idle speed control valve.
the ECU lets in more air, the map detects it and mixture stays perfect instantly. (the Speed Density System its called)

the O2 sensor , just adds and subtracts 2% to fine tune it to perfection.

i think you have a dead cylinder.
youd find that out fast driving it, it will be a dog.


neighbor has sentra with a hole'd piston, runs smooth after 1000 rpm.
lacks power. idles like a loping mule.
Daughter couldn't even tell it was bad.shrug.

[Richard Craneum]

A dead cylinder, I am going to check on that one. That could be very true. I checked all the cables and they seem plugged right, but I am going to check with the old cables. I am going to replug them and see if there is any changes.

Is just a hunch, anyway, I will re-gap the plugs too.

I hope is that simple

[Richard Craneum]

Well, it was simple. The roughness is fixed. Just the plug wires they were not completely seated at the distributor.

Fires now on all 4s.

I think the problem is now an accel issue. If you tap the throttle, backfire some by the intake. You have to go easy on the throttle.

Any suggestion on where to start looking?

I am thinking on low fuel pressure, clogged filter or worn out fuel pressure regulator.

I will start with a bottle of Techron, replaced the filter, needs to be replaced anyway.

Anyway, where do you place the pressure gauge and what is the correct pressure?

[jtgh]

1; crossed over wires on dizzy
2: lean mixtures. check fuel pressure at test port on fuel filter (new filters save pumps from destruction)
3: slipped timing belt.
4: or some one pulled dizzy and did not reset timing.


94 8v

1,3,4,2 CW (not ccw)

[Richard Craneum]

I replaced the filter and threw a bottle of Techron.

The old filter seems to be the original. The fuel that came from the filter was like Coca-Cola (rusty color) with some particles, seems like rust to me.

Is there another filter that needs to be changed? Strainer perhaps?

Anyway, ran the engine for a bit, seems to run fine. I do not know about the distributor been out of whack, but worth a try. My next project is the timing belt. I think is the original, so as maintenance, needs replacement and is a good time to check all up.

Now when I feather the throttle, it pops by the intake. Ease on it, it climbs really well. Not test drive yet, so I do not know if will bogs down or not.

The Idle seem to rose to about 800 RPMs, but seems to go back down to about 600 RPMs.
What is the correct idle RPMs ?

[jtgh]

thats a bad sign.

tank may be rusted in side.

rust has no limit on size can be chunks down to micron in size
and the small stuff flies true the filter and lands on the 10 micron screen , wrapped around the injector.

it then clogs, instant lean.

[Richard Craneum]

Good, so all I need is remove the injector and give a good cleaning?

Any words of caution on that?

The injector can be cleaned, right?

Anyway, for year and type of fuel tank. I am not surprised that is rusted as heck !