Confused and need help...

[SinGarage]

Please bare with me as I'm trying to be as specific as possible.

A little background. I have a completely bone stock 1990 SOHC Auto with almost 400k miles on it. It's having some idle surge issues and the engine light is on.

Last weekend I changed the clutch fan since it froze on me. I took out the stock airbox, loosen the alternator for slack, took stock plastic intake pipe off, and changed the clutch fan. After putting back together I started getting an idle surge. The engine light turned on but drove ok.

It was slight at the beginning then gradually got worse. I would be in a stop light and the car would surge and feels like it would lurch forward if I didn't have my foot on the brake pedal. Then suddenly the engine light turned off.

After running errands (constant stops), at one point, the car did not want to start. It just kept turning over but wouldn't start. Eventually it did turn on after like a minute or 2. I then proceeded to drive back home hopefully making it. I dreaded every stoplight as it wanted to die every time I was coming to a stop. I had to put it in neutral to keep the idle high.

So I checked out the codes when I got home and to my surprise, I had several.

12-MAF
23-Idle Switch
34-Knock Sensor
45-Injector Leak
51-Injector Circuit

I just can't believe all of them would just suddenly appear. Possible but not likely all at the same time. There is probably one circuit is affected and triggering the rest to turn on.

What I've done is cleaned the IAV and MAF. Checked for any vacuum leaks but didn't find any (sprayed carb cleaner). Changed cap and rotor since it was time to changed them anyway. I checked the injectors and found #1 to change idle while moving it. I'm assuming it probably needs a new O-ring. I will buy a new ring kit for all injectors. I have also changed the temperature sensor and fuel filter like 6 months ago.

At first I thought my fuel pump is going out because I was starting to lose power gradually. But when I changed the clutch fan, it ran better. I'm assuming this could have been the culprit since I was losing power and getting bad gas mileage (drag on the engine).

Now I am just stumped at what it could be. I would like to get Zilvia's input as I don't want to start changing parts blindly.

Any help or suggestions would be greatly appreciated.

[SinGarage]

Been driving fine since I posted last. Engine light turned off today and died twice driving to work. I will be checking the TPS today. Anyone have anything else they can think of?

[holemilk00]

400k? have you changed the MAF?

[SinGarage]

I have changed the MAF last year. It is a used part and might have failed already. I will check with another good MAF and also the TPS today and will post results.

[SinGarage]

Changed to another good MAF and still the same. I cleaned both and no change. Unplugged both while running and at both times it died.

I checked the resistance for the TPS and it was good. Just in case, I also changed to another known good TPS and no change.

Now I unplugged the IAV while running and nothing changed. Could my IAV be bad?

[SinGarage]

Ok, I've changed the fuel pump (used), injector o-rings (new), and IAV (used). Did this on a Friday night and car ran great and all the CEL's went off. Drove the whole day Saturday and same thing, the car ran great. It felt more responsive with more power. Drove it on Sunday, the CEL turned on and a very slight idle surge but the car did not die. Now it's Monday, drove it to work with no problems and the CEL's are off. This is starting to get really frustrating.

[SinGarage]

Ok. I have been driving the car daily and has not had a problem lately. Only problem now is it's running so rich that I can smell gas and my mileage went to shit. What I haven't mention is if that little black plastic box on the driver side connected to the air box has a big hole in it. Would this affect it to being rich?

[SinGarage]

Ok so just letting everyone know. After checking all the MAF, IAV, and TPS, they all were running the correct voltage and resistance. What I didn't check was all the wiring. After noticing all the contacts were crusty, I cleaned them with contact cleaner and applied dielectric grease, car ran perfect. Car has been running perfect for the last week like nothing happened. I'm assuming all the readings were incorrect from one or all of the sensors due to the resistance.