I bought this car back in November and reworking the engine has been the project for the last few months. I finished 2 weeks ago but I didn't pass smog. I had high HC, but that passed. I didn't pass the CO test at 25 mph, but passed at 15 mph. NOX was good at both 15 mph and 25 mph. I've run some basic diagnostics from Chilton's/Haynes and I figured out that my o2 sensor is good. My map sensor also appeared to be good.

This is when the problem started.

Checking the map sensor involved disconnecting the vacuum hose running to it and applying vacuum with a hand pump. I applied 40 mmHg of vacuum then performed the test according to my service manuals. After that, I didn't reconnect the map sensor right away. I was sitting in the driver's seat, so I decided to rev the engine a few times. I heard some pops in the muffler (which is a fat ricer can...installed by a previous owner). I don't know why I didn't stop, but I continued to tap the accelerator. Then I heard some pops in the engine bay, of the same variety that I heard in the muffler. This freaked me out so I turned the key off. I think that I could've run super lean by opening up the throttle too much while sending a constant MAP signal to the ECU.

Now I also tried to spray some carb cleaner in the throttle body while the engine was running. My memory of the night is out of order, so I can't remember if I did this before or after the popping. In any event, I later remembered that I applied some rtv between the throttle body gasket and the t/b + butterfly valves. I'm thinking that maybe the carb cleaner could've dissolved some of that rtv, which the engine would've sucked into the intake manifold and possibly into the engine. I don't think this is likely, but I'm presenting the two things I did which I think could've caused the problem. (I admit that revving the engine with constant vacuum on the MAP sensor and using rtv...and also carb cleaner in the throttle body were bad decisions on my part, lets not focus on that =P)


Now...the problem: I start the car. If it catches, then it idles at around 300 rpm. Opening the throttle a little bit or all the way to WOT has little to no effect. The idle may climb as high as 1000 rpm.

Things I have tested/eliminated:

-Fuel pump, pressure regulator, injectors: I used a fuel pressure tester and the pressure I get at the service bolt is 40 PSI dead-head (key at "on", didn't crank), and 39-41 PSI when "idling". The pressure regulator could be bad, but from what I've read, the pressure should rise slowly or have too many PSI. Neither was the case. I recently replaced the injectors with remanufactured ones. It's possible that one or more are the wrong type. Tomorrow, I'm going to test if any individual one is bad by running it and disconnecting/reconnecting each injector electric connector, checking to see if the idle drops.

-Spark plugs: pulled, look good, albeit a little dark and a little wet (with gas). One suspiciously had a centimeter-thick ball of lint on the electrode. Very strange, but it could've been a dirty intake.

-Spark plug wires, distributor: used a spark plug tester to check all wires for spark. They all looked good. The distributor is new/remanufactured.

-o2, catalyst: the catalytic converter might be poisoned, but it isn't melted and blocking the exhaust. How do I know? I took the exhaust manifold off and the car still idles at 300 rpm. (I think it was actually 500 rpm before I took the exhaust off: placebo effect or backpressure).

-gas: I added half a gallon to the tank. There wasn't much in for most of my tests, so I just wanted enough to be sure that the pump wasn't sucking in air sometimes.

-compression: this is questionable, but I can't do a "proper" compression test. With such a low idle, I can only test the engine cold. The pressures were 90-90-80-80 psi. At first, I thought that these numbers could be just about right because the piston rings won't seal well when cold. They could still be way too low even with that in mind, though.

So, that's all I've done so far (that I can think of), thanks for reading all the way through to here. If you have an suggestions or ideas on what the problem might be, or even a relevant keyword I could search for (I tried searching for "hesitation" and "staggering"), please do share!

The engine is (as far as I know) the stock EW4, which is practically the same as the d15a3.