Engine Bucking Issue

[The1TrueOutlaw]

I bought a 92 Stealth Base (SOHC) about a month ago and on the drive back to my house the CEL came on. It also had an intermittent bucking issue and trouble holding an idle. It would have almost no power then it suddenly catches and takes off. I checked the codes and came up with these three:

Ignition Coils
O2 Sensor
Vehicle Speed sensor

So I changed out the coils and that turned off the CEL completely and reduced the idling issue but I still have the bucking problem. Then I started search the forums and facebook group and found that these seem to be the most common causes:

Plugs
Coils
Wires
Leaking caps on the ECU
MAF Sensor
EVAP leak
TPS
Rare occasion the O2 Sensor or fuel pump.

The dealer I bought it from put in new plugs.

I have my doubts that it could be the fuel delivery as I can hear back firing on downshifting going down a hill.

As for the O2 sensor I assumed the code was being thrown by the coils not producing enough power to burn all the fuel and some was getting to the sensor. And the O2 sensor seems to be the least mentioned source of this kind of problem.

I have been trying to hold off on just replacing things part by part and I'd rather test every thing and verify that they faulty before throwing my money at a mystery. I started with cleaning the MAF sensor which helped some. Then I fogged the EVAP system and I couldn't find any leaks. Since the ECU is pretty easy to get out I pulled it and I found this:

WP_20150723_002.jpg

It looks to me as though the board itself may be damaged. I've seen where ninja performance can repair the ECU but I have no experience with getting ECU's worked on or whether or not this actually repairable.

The only other issue I have is a rusted out hole in my downpipe. But I haven't found anywhere that mentions exhaust leaks leading to this kind of issue. Unless maybe this could be throwing off the 02 sensor?

Any comments and knowledge you guys can provide would be much appreciated.

[j2k4]

You're definitely barking up the right tree - most 1G cars share the affliction of leaky caps, and you seem to have a typical example.

What to do and who can do it is another question - I've had mine re-done; I used Seth Peck, but I don't know what's going on with him these days.

I'm sure someone will chime in with a viable option, though, so stay tuned.

[Street_Chally73]

I'd send that ECU off to Chris & if it hasn't already been done yet, replace the fuel filter as well.

My car was terrible when I first got it throttle response-wise & traced the majority of my issue back to a dirty, reversed fuel filter...Not sure how a PO managed reversing the flow, but they did.

GL with getting your bucking issue resolved!

[sohcstealth]

A hole in your downpipe will mess with your O2 sensor.

You need to make sure you have no exhaust leaks before the O2 sensor, even on a SOHC.

[The1TrueOutlaw]

Thank, guys I appreciate the feedback.

I'd bet the fuel filter is still the original, I don't think the previous owner did much in the way of maintenance. I'll have to pick one up.

I'm gonna send the ECU off to Ninja this week, hopefully the turn around time is pretty quick. I had a feeling the exhaust leek may be affecting the O2 readings since I had that code when I got it and it needs to be changed out anyway. I'll replace it while I wait for the ECU, hopefully I can find one off a part out or something.