ducktape

I've searched RX7club trying to find some help with this trouble. Nothing seems to work.

Background-
This is an 87 TII with the following minor mods:
-Walbro 255lb/hr pump
-"Free-flowing" exhaust (near-stock)
-Ricer Air-filter
-Pulsation Dampener replaced with banjo bolt
-Huge grounding cables (battery-to-chassis-to-motor)

The car has the following known problems-
-No speedo cable (broke off)
-BAC disconnected due to a broken electrical clip

About a month ago, during one of the first warm days my car developed pretty serious engine stumble/hesitation. It started with the infamous 3800 hesitation, and steadily got worse. Soon it was blowing the 15A "Engine" fuse (in-cabin fusebox). The problem has gotten so bad now that the car is almost undrivable.

Start the car cold and everything is fine. The car will run and drive okay until it's warm. Once warm, the car will buck like crazy in every gear. It almost feels like it's running on one rotor, like the ignition had been cut. The problem is most apparent in first and second gear, when the car will barely move at all. Get it up into 3rd gear or so, above 4k rpms and the car acts almost normal. Run it in high gear for a few minutes, and the stumbling gets even worse. The car will instantly die when returning to idle (like coming to a stoplight), and almost no amount of throttle short of WOT will bring it back to life. Fuel is still present, as I'm getting multiple backfires during this extended take-off process in first gear. I tried removing the plugs to clean them and noticed that the front-leading plug feels cooler to the touch than the others. Yesterday, while driving it home it began to buck and sputter. I opened the hood and disconnected one of the leading plug wires, the car ran identical. i plugged the first one back up, and disconnected the second leading plug wire... The symptoms remained the same. It feels almost like fuel cut, but with backfiring.

I've done a lot to try to solve the problem. Replaced the leading coil/ignitier/plugs, cleaned the plugs (they foul after a few minutes driving like this), replaced the alternator, and moved the grounds around trying to get a good one. I re-crimped the Walbros power and ground, and even installed a crane HI-6 capacitive discharge system to try to increase the power of the spark. Nothing has worked, and I'm at my wits end.

Does anyone have any suggestions?

Thanks,
duck

HAILERS

So....when are you going to go out and buy a LEAD coil assy from the junk yard to fix your problem???

ducktape

SureShot

Since you are not getting huge backfires, you’re getting fuel cuts, not ignition breakups.
There is a good chance your TPS has gone non-linear.
Pull the IC,
unplug the TPS,
clip on an ohmmeter,
and hold the throttle open.

As you work the TPS plunger in & out the meter should swing smoothly from 0 to ~5K ohms.

If it jerks the needle up & down , or goes high, the ECU will interpret closed throttle and give a fuel cut.