So i've got a '98 c70, about 125,000 miles. I just had a 60,000 mile tune up at the end of December, beginning of January. I had the CEL come on with a MAS fail shortly after, i've replaced the MAS and had the CEL reset. Since then the car idles rough when started and if i don't let it warm up or rev the idle up to about 3000 RPM's for a min or so it sputters, shudders and comes close to dying if not actually dying. If you just try to power though and step on the gas it sputters, shudders and has no power, but once the RPM's kick up it takes off fine. Then once they drop again i'm right back to the shuddering. Now this only happens the first time i start the car up for the day. Once it's been started once the issue disappears until the next morning when i start it again. It's happened through both cold and warm mornings so i don't think the ambient temp effects it.

The other thing she does is if you romp on it on the free way and let the RPM's get up there, it will shudder and misfire. Doing this on the freeway got my CEL back on, i took to my mech. The CEL came on from a couple of the cylinders misfiring. My mech thought that maybe since the MAF was bad the new sparkplugs, replaced in my tune up, could've gotten corroded due to the improper fuel/air mixture. So i went about cleaning them, they were not corroded at all, they looked as new as they were.

So i've had the CEL come on once more since then, but it cycled and reset it's self. I've googled around and am thinking it might be the air pump that sucks air through the filter and into the engine, sorry the exact name of the part is eluding me now. I keep reading about the fuel filter and this type of problem, but that should've been replaced in the tune up.

Sorry for the rambling, i'm at work and trying to bust out a quick but through breakdown. I don't want to leave any info i can think of out, as it may help.

Thanks guys.

 

Was the cap rotor and wires replaced at the tune up?

 

They were. That's half the reason I'm confused by this, most of what could be the problem should've been replaced in my tune up.

 

Next I would do a compression test to make sure you do not have a burnt valve.

 

there was a recall on the throttle assembly that describes the problem you are having almost exactly.

 

98 models do not fall under the recall/service campaign.