So seemed to be that open loop was fine and closed loop was not. Sometimes it would hesitate or stall at idle (different than what you described), sometimes feathering the gas, sometimes at cruise, never at WOT. Symptoms were very similar to what you mentioned above, the only exception being that idle was not exempt from issues. Allowed a mechanic to throw parts at it for a little while before saying screw it, I'm going to diagnose properly and fix it myself. I have spent months working on a very similar issue in my 95 RMW w/ 165k. If your diaphragm reverts to its original position (closed). Then put your finger on the vacuum opening releasing the diaphragm.

Though the openings, stick your thumbs in and push the diaphragm back. A super simple test that ever body can do, in a matter of minutes. Making the problem get worse and worse.Ĭonclusion: This problem is one that could throw the best mechanic for a loop, and can get quite expensive and frustrating to fix. So, as soon as the EGR kicks in, it creates a top end vacuum leak (lean fuel mixture) and throwers the CPU out of wack, as it's trying to compensate by dumping more fuel until the leak gets so bad that the CPU can no longer compensate. That is why it passed the vacuum test as it was done on idle. The problem is that the EGR is only solicited in a closed loop environment, and under partial throttle. It I due to a defective EGR valve at the diaphragm. But oddly enough, It passes.Īnswer: It is a vacuum problem. Bad compression? Does not smoke, idles fine and still beats the pants off of a civic. Bad fuel pump?! Idles fine and still runs like a demon at wot. If you can start your car no problem on super damp mornings, then no. Many people will go for the bad opti and wiring. Troubleshooting: Ok, so not many leads to go on. When hot (closed loop) it will start to stutter/hesitate when feathering the throttle at light acceleration and on highway (cruise).

Datamaster obd1 software