Hi!  My first time posting-- thought I would throw a question out there and test your collective knowledge.  I have a 93 sidekick (4dr 16v, manual), and it has an annoying stutter.  It happens in second gear before shifting into third, and in 3rd gear at around 2000rpm, and right after shifting into fourth.  I don't notice it in 5th unless I really make it pull hard (1500rpm or so) and then it is only slight.  I also don't need to be accelerating to notice it; if I just cruise at the right rpm in 3rd gear especially, this will happen.  Warm or cold, doesn't matter. 

The engine doesn't seem to be missing when this happens.  But just in case, I replaced the ignition wires with good ones (NGK), plugs, cap, rotor.  Timing is advanced (12*) but I retarded it to factory specs and still happens.  Checked the timing belt, and the marks still line up on the cam and crankshaft.  Crank keyway is fine (just replaced the crank b/c that keyway was all wallowed out, actually).  Again, it doesn't sound like the engine is missing. 

Compression is fairy even across the cylinders (cold: 150, 135, 130, 140).  New air filter.  Sprayed some cleaner in the throttle body.  Idles smooth and sounds good, although sometimes it has a hard time picking a speed.  It never races, however. 

I did replace the exhaust manifold recently with the manifold with the longer down tube (this same engine had a couple different versions of the manifold, from what I understand, one thicker and longer).  So I had to splice in several extra inches of wire to the o2 sensor to reach on the new manifold.  Could this extra resistance be the problem?  I can't remember exactly how it drove before that fix.  I just bought it recently, and it had all kinds of problems, which I've been fixing slowly one by one.  But I can't recall if this is a problem that developed after that fix or not.   

Thanks for your time; I would welcome any suggestions...

What RPM are you doing the shifts ...

I've found that with larger tires on my 4dr manual, I need to rev to around 3500-4000 before shifting or it might bog down when accelerating hard.

In second gear it happens at the top end of the power band, and in third gear it happens in the middle.  Fourth gear it stutters at the bottom.  So I don't think that is it, but thanks.

Are you sure it is not your rear trans mount? or a u joint? check your spark plug wires(pull one off and look inside the boot) and see if they are the type that have the wire wraped around the center conductor? if so you have to run a non resister plug(racing plug)or pull them off and go back to a cheap wire set.

Spark plug wires match plugs.  I believe the trans mount is snug, but will check when I get home.     Though the problem really seems to originate from the motor. 

There is another, possibly related problem that is much more intermittent,  that on occasion when I am accelerating, it will bog down a bit and then as I increase the throttle,  suddenly the lost power will return in a moment and will accelerate normally. 

I'm guessing a sensor or computer problem...

I am thinking fuel filter or pump, put
a pressure guage on the fuel line and
see if you get a drop in pressure when
this is happening

Wild

Spark plug wires match plugs.  I believe the trans mount is snug, but will check when I get home.     Though the problem really seems to originate from the motor. 

There is another, possibly related problem that is much more intermittent,  that on occasion when I am accelerating, it will bog down a bit and then as I increase the throttle,  suddenly the lost power will return in a moment and will accelerate normally. 

I'm guessing a sensor or computer problem...

I had a 16v that done a simalar thing, it shudder then died but as soon as you moved the throtle pedal it sparked back into life and ran fine again. Never did get to the end of the problem as the ex walked away with the trucklet but I was thinking along the lines of Wilds idea or a  TPS problem ?

Pull a boot on a spark plug wire and see if it is the mono mag type for me, Thank's

Could it be clutch shudder? Worn pressure plate or bad throw out bearing?

From your description it appears to be a load based problem....

Typically that means ignition or electronics, seeing as you have changed the plugs and wires
with my favorites it rules them out. You said the timing is set to factory spec.

As it's not at the same throttle setting that tends to rule out TPS, but not always. The second problem you mentioned steers back to TPS.

Basic stuff
- Fuel filter and pressure as "Wild" said?
- Vaccum lines all good no leaks?
- Rotor and Cap good?
- The Mass Air Sensor is clean, no code? (Air Flow Meter)
- Does it happen more hot or cold?

If everything else checks and it happens more hot than cold I would be suspecting an Ignition module or long shot, coil.

I would be switching the TPS just to see if I could get rid of the second problem and it might clear up your first one as well.

Zag

Thanks all...  Replaced the fuel filter last night.  No diffference.  I'll have to take it in somewhere to get the fuel pressure checked, as I have no gauge.  I double-checked the wires last night, and they match the plugs as they should.   It has a new cap and rotor.  The timing is at 12* according to the timing cover, but that is because it doesn't run as well at 8*.  I can't hit 10* because the distributor is pushed all the way to the firwall (as retarded as it gets) at 12*, and then if I pull the distributor out and put it back in one spine over, it is now at 8* when it is positioned as far towards the motor as possible.  Definitely runs better at 12* although the same stuttering problem is present at both settings.  Makes me think that my RPM gauge is off, so that when I think I'm timing at 800 RPM I'm really not.  So that 12* is really not that advanced.  I hear nothing indicating that the timing is too advanced. 

One interesting thing that I haven't repeated enough to be sure of, is that the bogging down and then suddenly surging behavior doesn't seem to happen when cold.  And if it doesn't happend once I start driving the vehicle, it won't happen at all.  In other words, it most consistently when I've driving the thing for a few minutes (stuttering but no surging at this point), turned the key off, and then started it again.  Now if it surges, it will surge until I turn the key off.  This makes me suspect the computer... what do you guys think? 

I haven't looked at the MAS, but there is no code. 

The clutch is new, as is the throughout bearing.  But I put it in myself and could have screwed it up.  If it was the clutch, shouldn't it happen after I disengage it?  In third I can accelerate from say 1500-1900 rpm no problem.  It's always smooth.  1900-2400 is almost always choppy. 

Any way of checking the ignition module or coil?

So what does" they match" mean? I guess ya just can't help some people  mine runs great     

  Makes me think that my RPM gauge is off, so that when I think I'm timing at 800 RPM I'm really not.  So that 12* is really not that advanced.  I hear nothing indicating that the timing is too advanced. 

Do you need to use a jumper on the diagnostic plug when setting the timing?

Someone else pointed this out to me by email, so I that makes two now.  I didn't know this was necessary, but I guess it keeps the computer from trying to correct the timing while setting it, right?  I'll have to look in my book to see for sure, and if so I'll re-time it tonight with the jumper.  You guys rock.