Car (not mine) is a 94 Formula, RK Sport headers, ORP, Magnaflow Cat-Back, K&N CAI, MSD Blaster coil, Taylor Plug Wires, Autolite plugs. I helped my buddy put in a new opti and water pump yesterday as he was having a miss EVERYWHERE and we finally traced it down (process of elemination) to the opti.

Install went fine, start the car up, and seemed fine. But after about 30 seconds it started to surge at idle only, from a programmed (had TTS Datamaster on the car at the time) 800 idle it would dip to about 600, then recover up to about 1000-1200 and return to 800, and repeat. Sometimes the surge would dip so low that the car would almost die, and twice it actually did.

Went through everything we could think of today and it still does it. Plug wires are fine and there's NO crossed wires. Plugs are fairly new. Swapped coils with no change. Swapped elbow's as the old one had a small tear and no change. Fuel pressure is fine, no injectors leaking. No electrical plugs missed, I saw NOTHING on datamaster that would indicate a reason for the surging.

The ONLY think I saw in datamaster was that the right bank was running a little more lean than the left bank.

Looking for ideas. Thanks.

 

My car did the exact same thing right after I changed my opti and water pump. Fortunately for me the problem was my intake elbow wasn't seated right on the bottom. Double check that, it stumped everyone for about 2 months.

 

Good idea and that's what I thought initially, but sadly it's not that simple. I dun' checked that there.

More info: Driveability below about 2100-2200 RPM is C-R-A-P he says. Above that, it cleans up and runs almost flawlessly, but doesn't feel like it's all there at the same time. I'm going to fart around with his EGR tomorrow (pull, clean, block if necessary) but other than that, I haven't a clue. We've got through all the primary stuff that seem to cause this issue.