update: it's recurring now. see last post.

Car was running fine today. Yet for the past few weeks it had some smoothness issues under 2k rpm when it was cold out (<40F). Maf has been replaced recently too.

Few minutes ago i start it up and notice an odd shaking, not really vibration but a steady "dum dum dum dum dum" type sensation. Look at my rpm and they are stable.. Drop it in gear and it gets bad. The car is lutching forward and stopping with each spam. rpm are stable still (according to the tach). i drop it back in park and rev it to about 3k.. it smoothens out but as soon as i let it go to about 1500 it begins all over again. I let it warm up and take it out for a test drive...

Bad. Whenever i stop it begins to shake and lurch. Voltage dropped about 1.2v at under 13. tach still showed somewhat stable operation, no CEL. I drive some more and i can feel the engine stutter as i drive. It is not random, but very repetative and steady. give it some gas and power delivery is smooth although i can feel the trembling (and somewhat hear it) still.

Park it and i go out.. touch the hood, listen, nothing out of the ordinary (usual timing chain noises, valves etc. been doing it for 2 years). get back in and it is somewhat smooth. slight unusual stutter through the wheel but almost normal.

drop it in gear again.. lurch, stutter, cough. heat/ac have no effect either way. it's engine related. right now i've parked it wondering what it may be..

again, maf is changed about 3 months ago to the new design. car was fine 3 hours ago.

coils?

related notes: for the past few weeks i've noticed a power vacuum that feels like a dead mad about 2k. usually happens during a turn when the car shifts between 2nd and third gears, possibly overdrive ~30mph. it feels like a plateu but enough to make me look and wonder if i am pressing the gas.

shifts fine except since the last maf change (i assume, not sure since when) it seems to shift ~6k vs 6.2k as before. odd.

but right now my problem is an apparent engine system malfunction. help guys, i need this thing running.

 

do the headlights coming on/off change anything?

how does the car sound and feelat ~5000 rpm?

check the codes anyway

 

Went out to start it again. Lights off, climate etc. all off. Started fine and idled fine. Voltage was ok too. Then again, the engine was hot from earlier.

Behaved normal in gear too.. i just put some 93 in it (it had 89 in but that can't be because i ran 89 when the gas was 3$+ and it wasn't an issue) and revved it to 6k in first. Smooth and flawless. Reached 4 in 2nd but had to cut it because cops tend to be around that 35mph area. All was good.

parked it back in and i played with the lights. In gear with the headlights on (btw i have the hid so they should consume less + no front parking lights) i get a 1V drop but it didn't affect anything. In P/N volts go back to their usual 14.2. Brake lights alone cost .6V but in gear with the mains on they only give me a .3 decrease. Let it idle for a few minutes in and out of gear and it seemed fine.

In a very simplistic language here are the events so far: 6 hours ago car runs fine. 3 hours later, car breaks. Car continues to remain broken regardless of what i do. Car is parked. 1 hour after car works fine. No CEL. Car is fueled up and engine/systems restarted. Car runs fine. Car is parked.

I dread starting it up tomorrow. What happened earlier isn't normal. It was systematic engine vibration and stutter that was very consistent.

I'll try to get the codes tomorrow and i'll post what happens when i start it again in a few hours.

 

just a tip but...check your main ground bolt... i had similar problems like your stating above in my 97 max. to check it follow the negative battery cable from the battery to where it connects to on the "block plate" its a 10mm bolt make sure thats tight!!

 

last time fuel filter was changed? I thought ALT.. but, now sounds like something else.

 

very well could be a vaccum leak.. see how cold start treats you

 

never. car was fed 93 from QT, Chevron, shell, race trak. maybe 30 gallons from all the rest combined.

few tanks of 89. never 87.

honestly the car has gone to crap ever since i moved to the city. my suspension is creaking left and right too but it does not affect anything yet.

i'll check the ground tomorrow.

i am due for an oil change in both the tranny and engine as well so that will give me some time to look around it. plugs have 5k on them too...

will have to be some sudden hose breakage.. i'll update once i crank it in like 8 hours.

 

So what the **** are the codes? The Park/Neutral-Reverse switch won't throw a code but will make the car act funky. I'm not familiar with how it affects autotragics but I had unstable running when cold and racing sporadically racing RPMs when warm until I changed mine.

I'd hit the cheapo basics if they're near time for replacement anyway. Plugs, filters, PCV, check ground wires, etc. Pull the codes yourself or stop off at an AutoZone (or equivalent and have them do it for you). They'll usually give you a nice printout on most likely components for each code if any come up. Just as easy to remove the kickplate and turn the screw yourself though.

 

Dumb question - but could it be transmission related? It sounds 'similar' to when my bearings were going, in terms of the lurching/jerkiness.

Otherwise, sounds pretty nasty.

Good luck dude. I'm not mechanically inclined so I'll leave my input at that.

 

No codes. At least nothing the OBD could pull.

Car ran fine today but it always does when it's 55 out, aka warm. I'll definitely crank it up when its about freezing (should be tonight) with a cold engine and see what happens.

Meanwhile i looked over the engine. Fliuds are there, no broken hoses, ground bolt is in place, batt terminals check, i dont see any signs of wear or electrical burn etc.

Sigh whatever it was it happened on its own and went away on the next restart. I am thinking either something got clogged, there was condensation in a bad place or it has developed a cold weather illness i'll have to verify later tonight. Components wise, coils are still my only logical explanation but i don't get any other symptoms of coil failure.

 

It's back. This afternoon, 47F outside. Crank it, it shakes and all just not as bad as last time. When i hit the gas it roughens a bit at first then smoothens out (but not completely) at 3500+rpm. That's in park.

I shut it down a few times with no effect. I just drove it to where i had to go and parked it. During the trip though i restarted it a few times and it changed nothing. Cold or warm. Nada.. same crappy vibration. I did notice however that the engine started hard, with a rumble. Pretty much instantly from when i turned the key. In any case i started harder and faster than under normal conditions.

I did my errands and cranked it again. Problem is gone. Like last time, time between shut down and restart was 30 minutes give or take.

This is insane.. my car is sick with something. help

 

How is your coolant level? Possibly a IM gasket leak, and after the car sits coolant leaks into the engine and as you know you cannot compress water, so it runs rough untill it gets it out. I had an 83 RX7 with similar symptoms. Only it was a warped rotor housing. You would also see water in your oil at change if it was leaking. Something to look at. Also exhaust may be whitish I believe for a bit.

 

doubtfull. changed the oil a few days back and noticed nothing odd. i'll go play with the EGR valve, could be sticking (and i am out of ideas)

 

Cylinder misfire, But no code....... It's happened to me only a handfull of times...... I reved the engine and drove it hard untill the cylinder firing was in sync again. no problems since it's all good.

 

Could it be a weak alternator? What about the voltage regulator? Might also be a clogged or partially clogged fuel injector (dump a bottle of octane boost in to clean it out). Just a couple of thoughts.