Hello all, I have a problem with my 86 crx si. It doesn't happen all the time, it is worse when the car is cold though. Basically, it runs fine, but occasionally it hesitates between about 2750 and 3200 RPM. I mean, it just won't go. I usually have to down shift to get the RPMs up in order for it to go. Other times it is fine, and pulls hard through the whole RPM band. This problem has not been getting any worse over the past 6 months. However, I notice that the car is backfiring now, in fact it blew a 3" hole in my muffler the other day. Since the backfiring started, the car idles bad, it tends to sputter and miss. My mileage has dropped about 5 MPG as well.
I replaced the head gasket, timing belt, waterpump and radiator in Novemeber. The problem i describe started before I did any of that work, so I don't think I caused it. The spark plugs, dizzy cap and rotor, and plug wires are less than 6K miles old, replaced before the head gasket job. I have tested for vaccuum leaks by spraying starting fluid on the hoses and I didn't notice any difference in the way it idles. I tested vaccuum advance when I set the timing, and it seemed to behave the way it should according to the FSM, but I am not really sure. Could it be the Vaccuum advance in the dist? How would I test for that?
Thanks in advance for any help, I guess I am off to get a new muffler now.

 

one more thing I just remembered, the PGM-FI light came on once, right before the sputtering and backfiring started. I can't find any info on how to pull codes on this old thing, only see stuff for 88 and up. Anyone know how to pull the codes for it?

 

Do you have an Egr valve position sensor? if so, have you try that?

 

those codes are in Haynes