Ok. So I need your help again.

Background:
89 C4 with 49,000 miles. Just pulled the engine and replaced the clutch, spark plugs, valve adjustment, dist rotors, replaced all belts, lots of rubber hoses, and rear main seal.

Problem:
Car idles perfectly and runs smoothly until about 4,000 rpm and then she hesitates and backfires pretty badly. If I mash the gas she is good until about 4k as well then the same symptoms as above. It appears as though the car isn't reving as fast as it should, as if something is holding it back. I had the battery load tested and it failed. Bought a new battery and haven't had time to install it. Wanted to see if it sounded like it could be a battery or something electrical.

 

Wow -- that's a new one on me.
Higher rpm-limited... hmmm...

OK -- these rather naively perceived items might, maybe, could 'soft' fail that way: (I think)

• Battery and/or Coils (not 'juicing' up at increased discharging rates?)
• Fuel filter (This I KNOW can exhibit just such signs as described. My 'low fruit' [and low cost!] pick as culprit.)
• Air filter
• Bad gas (??? oh, never mind. That one's just plain goofy.)

Edit-
Doh!! -- Like I said, it's NOT those evil filters! Ewww -- E-lectricity was my worst subject in school. So... Hey, Rube!!

 

Oops forgot to mention the fuel filter and air filter are both new. Probably not bad gas. I'm thinking battery. But the weird thing is that it seriously runs perfectly fine when just driving around town. Not until you get on it does it start to act weird.

 

Bad alternator can cause you problems, but when it happened to me the ABS alarmed first, once the battery got too low.

Distributor belt?

Plugs wires correctly attached?

 

I had a similar problem with a different brand of German car - problem was the alternator was putting out too much voltage, and the over-voltage was killing the engine controls. I limped along scratching my head when a caught a wiff of sulphur, and found the battery was getting hot. New alternator, and everything was fine. Watch out if that is the problem - you will have a sudden rash of burned out light bulbs as well.

Regardless of engine speed, the voltage at the battery terminals should be between 12.5 and 14.5 volts. 13.8 volts is just right.

 

is changing the alternator a DIY job?

 

Sure is ...I've replaced mine. i'm sure there is a thread on here which explains how. I'll have a look unless someone beats me to it in the mean time. Point to note, before you start make sure you disconnect the battery!

 

thanks for the battery tip. sounds so much like a duh statement but I've definitely messed up simple things like that before.

 

This video should help on the alternator replacment DIY.
https://rennlist.com/forums/964-forum/406255-fan-bearing-replaced-with-rs-hub-diy-video.html

 

woohoo...thanks man. that thread looks very informative.

 

What's the DC voltage output of your alternator? Are you seeing any AC voltage?

 

I would also re-check your ignition timing, maybe the belt between the two rotors is out a tooth or the dist. itself is not phased correctly at TDC.

 

did you definately plug the air meter back in???

 

just talked to the service advisor and he says the stator diode is bad.

 

just out of curiosity, why would the air meter be unplugged? And where is it?