Came by an 85 Civic wagon with a d16a1 from as far as what I've found online probably came out of an 89 Integra.

Had surging idle- replaced IACV and the valve it is attached to that sits on the throttle body behind the throttle plate. (Replaced with used parts).

Didn't fix it so unhooked IACV and adjusted throttle up (mechanically, not via TPS) so it would idle at around 1,000rpm.

Idle is steady now but not coming all the way back down in rpm after letting off gas. Kicking the gas pedal really quick will bring it down to normal idle. (Nothing is sticking though as far as I can tell.)

Was going to just run it like that but first tank got 17 mpg.

Internet says this is an obd0 system, but when I turn the key on the LED just blips once and doesn't repeat. I have 2 ecu's for it; they both behave the same.

Would like to attempt to get a code since there are so many things it could be and I'm lost and confused at this point since it seems like it could be more than a single problem.

If it is an obd1, I can't find the test point. (Looked everywhere, where it would be on an Integra.)

Any ideas?

 

Huge variances in fuel mileage can stem from a lot of things. Poor compression and timing would be my first "guesses" A lot of things will need to be checked, such as the condition of the brakes and wheel bearings, alignment angles and so forth.

Does the engine produce decent power? Condition of the engine oil (fuel logged = compression)

 

Has good power. Rolls fine in nuetral. Drives straight. No noise from running gear. Oil is clean. Plugs are black. Thinking it's just really rich but can't figure out why.

Haven't checked timing though. Seems to run too well to be that far off but good advice anyway. Will check.

 

Forgot to say compression is good.

 

Define "good".

 

Blackened plugs indicate rich combustion. There is too much fuel, or not enough air getting into the engine. Since you judge output to be acceptable, fuel should be the culprit, if any in this situation. Oxygen sensor?, exhaust leak?

Ignition timing and cam timing should be checked as well.

Is this carb'ed?

 

I'd definitely give that o2 sensor a check & most likely replace it, fuel economy will take a nose dive if that goes out.

 

Possibly dirty fuel injectors or bad fuel pressure regulator or even dirty air filter.