Serious Tech Question, b16A2 Trouble

[pspence77]

Ok, Here is the deal and I appreciate any help before I spend $600 on the parts I think I might need.

I have a B16A2 swap that ran like a champ for the last year since I did the swap. Lately though its been running like crap. It only has 50k miles on it. It lopes and misses at Idle really bad. Here is what I have done.

Relpaced Cap, Rotor, Spark plugs and wires...
Checked all fuses (good)
Checked Fuel injectors and pump, functioning properly
Compression check done, everything OK
Timing checked and rechecked, top dead center and good

I cant get the fault codes because the ECU that came with the engine was from a 1997 Civic Del Sol (European Spec). See I had the swap done while I was in Germany. My whole car was striped to bare metal, and when the swap was put in, the Del Sol's wiring harness/ECU/Guage Cluster were used. Anyways....So by process of troubleshooting with manual and much work here is my theory. I believe it is the TPS (throttle position sensor). After following the steps in the manual which shows how to adjust idle, the idle failed to move above 500 RPM. The case on the TPS is cracked and turning the screw all the way in and out to adjust the throttle had no effect. I'm assuming that this tells the PCM (Program Control Module) about how much air is coming through the intake and in turn the amount of fuel is sent out through the injectors to achieve the correct mixuture.

SO if this is malfunctioning, I might get the bad idle, and the car is running like super rich. The TPS must be replaced in conjunction with the Throttle Body, so thats what I'm assuming I need to replace. Everything else is good and running fine. The thing is before I spend $400 to $600, I'd like any second opinions to confirm or shoot down my suspisions. If I do have to buy a new Throttle Body, I might as well go for and aftermarket one, but do they come with a TPS or what?

Thanks so much in advance
(If you read this post and have no clue but no someone that might, I'd appreciate you forwarding it to him/her)

[05 tC]

Does the engine run bad all the time or just at idle? Do you have the Helms service manual? The Helms manual has a troubleshooting section for all the engine sensors. If the TPS was bad the engine would studder while you were driving. Could also be a problem with your HO2 sensor. I think the screw you were turning to try and adjust the idle is part of the Idle Air Control (IAC) valve.

You shouldn't have to replace the entire throttle body if the TPS is bad. A TPS from almost any Honda should work as a replacement, they are all the same.

[pspence77]

Yea, the engine studders and shakes real bad while at idle. And it only idles at about 500 rpm too. However, when I rev it up above 3k or so, it sounds fine. I was also considering the o2 sensor. The engine was running really rich for a while so do you think that this couldve affected the sensor? I looked in the maual and I guess you gotta troubleshoot the sensor with a multimeter. I've trouble shot all the other sensors and they have come out OK. To be honest, I'm just puzzled beyond belief.

[05 tC]

If the engine was running too rich for a while it could have damaged the HO2 sensor.

Here are the possible causes for a low/high idle:
-IAC valve mechanical malfunction
-Throttle body clogged port, improper adjustment
-Intake manifold gasket leakage
-Intake air hose loose leakage
-Vacuum leak
-ECT sensor incorrect output
-TPS incorrect output ('96 models only)

Is the engine still running rich? When the engine is under no or little load (like at idle or when driving at a constant speed) the ECU runs in Closed Loop mode. In closed loop mode the ECU uses the HO2 sensor to calculate air/fuel ratio and uses that data to control the amount of injected fuel. If the HO2 sensor is bad that could cause the ECU to think the engine is running too rich or lean and the ECU would then try to correct the air/fuel mixture. I'm not positive if the idle would be affected that much if the air/fuel ratio was too rich. Unless there was so much fuel in the clyinder that the engine was almost flooding out.

Here are the possible causes for the engine to run too rich.
-Fuel pressure regulator clogged, stuck closed
-Fuel return pipe clogged
-Fuel injector leaking
-Gasoline doesn't meet Owner's Manual spec.
-Primary HO2S (heated oxygen sensor #1) deteriorated
-EVAP purge control solenoid valve leaking, stuck open
-Valve clearance