I've been chasing a problem with engine performance for a few weeks now. I'll be upfront about cleaning the engine just prior to having this problem, I also filled the tank just prior and wonder if (on auto-pilot)I used regular gas instead. I tried to be careful when I was cleaning the engine, but perhaps I doomed it anyway.

Some of the facts:
-1995 105K
-changed the fuel pump (following the manual because of low pressure), fuel filter and pressure regulator
-no codes until after the regulator was changed, now throwing an H42, not sure what to do about that.
-pressure seems to be low at around 38/40 when the pump is primed, holds steady and about the same after it is started.
-I do not see any pinches, etc. in the fuel line.

The engine seems to idle a bit rough with a few very slight mis-fires if I rev to 2500-3k rpms or so. If I try to drive it, acceleration is terrible and sometimes I have to put the clutch in to keep it from stalling. I have been afraid to get it above 20-30 MPH, so I don't know if it does any better at higher speed. I only take it through the neighborhood after I replace a part. The mis-fire/backfire is much more pronounced when I try to accelerate. It bucks an awful lot too.

I can change oil and brakes and do basic maintenance, so I am about out of ideas. My only other thoughts are to change the gas, the opti or perhaps an injector(s) is bad. Would the car behave this way if I got the opti wet while washing it? Any other idea or thoughts are appreciated.

I am betting your drowned something...

Check the plug wires and plugs at that end... and then comes the fun part, the opti end... I suspect that is where your problem is.

Remember, it takes three parts to make an engine run - fuel, spark and air. You have dealt with fuel, air is usually abundant enough to get the job done, and next up is spark.

Considering the bath, I am betting spark... Check the coil wire, too.

Code 42... I think that's spark control. knock sensor. could be more effect than cause.

DTC 42 - Ignition Control (IC) Circuit (Shorted or Grounded Circuit) - See more at: http://tech.corvettecentral.com/2011/ ... des/#sthash.6qBzG5z6.dpuf

Hope this helps.

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Thanks Bogus, it looks like I'll be replacing the opti then. That should make the H42 go away. I'll clear it after the replacement and address it if it returns.

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Thanks, I did find this post this weekend while trying to diagnose it. I just didn't know what to do to fix it.

I am not saying replace... I am saying diagnose... the problem is that diags are as annoying as replacing!

If it is the original Opti, then by all means, replace.

Waterpump, wires, plugs, too.

My recommended parts list:

MSD Opti
AC Delco pump
Taylor wires
NGK platinum plugs

Check the serp belt, idler and tensioner for condition. If OEM, replace.

Opti might not be the problem. Could be another culprit such as bad wires, etc. Run the car in the dark and see if you see arcing wires. That's just one idea. When is the last tune up?