Long story, but I'll try to break it up into its basic elements...

- Bought non-cranking car for $500. Diagnosed as ECU, considering previous owner had checked for compression, replaced plugs & fuel pump.

- Before exchanging ECUs, I cleaned the throttle body and Idle Air Control valve. The spring popped out of the IAC vavle, and I'm not 100% sure I put it back in the right way, but it starts working later, so I'm guessing I did??

- Eventually got replacement ECU, and car crunk right up. She was just purring in my yard!!

- Only problem was that there was white smoke coming out of the tail pipe and the oil filler tube.

- Eventually got some Bars Leaks "Head Gasket Fix" #1111, because I've heard great things about this stuff. Initially, I only put a couple table spoons straight into the radiator. But it appeared full, so I put the rest of the 24 oz. bottle into the reservoir. Smoke had stopped almost instantly. Drove around for at least an hour with heat on high. Then I realized that the reservoir was clogged or something, because the fluids hadn't moved in there. I checked the radiator, and it wasn't full!! So, I took the reservoir out, poured it into the original bottle it came in, then poured just less than half into the radiator for good measure! The radiator was still not topped off, so I put some 50/50 in there until it was, then topped off the reservoir. Drove it around for another hour or so with heat on high.

- Everything was great until the next day. I decided I'd give it one more run from one end of town to the other end, which I needed to do anyway. Even replaced a 15amp "Blower Motor" fuse that was missing in the fuse box, and got the second fan to work by jiggling the switch around. Had the heat on high again. Didn't really dog it out like I did the day before. But TODAY, as I get two blocks away from my house, exactly as I'm thinking about how I didn't do the Idle Relearn Procedure, the cars idle starts to drop. And then after 5 - 10 seconds, the idle got to 500 then just died. Crunk right back up, then died. Crunk up one more time for the green light, then I made it to the stop sign. Died there. Crunk up the last time and I pulled into my yard, where it died.

- Pulled out the OBD2 scanner. No logged/historic faults (even tho, the Service Light has been on during all these drives??), but there were two pending faults --> P0134, P0154. I believe these are the pre-cat O2 sensors, "no activity detected". s***. I've never had an O2 sensor REALLY cause a problem before, so I figure the problem must be elsewhere.

- I cleaned out the PCV valve and the whole line. No help. Same instant stall at idle.

- It started to rain as I was putting my stuff up, so I figured I'd go try to drive it around with my foot on the gas everytime I braked. Plus, I already had the idle relearn procedure written out from when I replaced the ECU. Drove it around until normal operating temps, took it to a parking lot near me, then proceeded with the instructions. I tried it at least 10 times, and I could *never* get the MIL to blink. I think my problem might have been that I didn't release the pedal ALL the way, but I think it still should have blinked??

Anyway... I'm at a loss now. Also, I did check the spark plugs... and all four looked a tad dry if you ask me. So I'm guessing the engine is running lean for some reason or other.

I really don't think the IAC is my problem since I already cleaned it and it was running just fine. Ditto for the relearn procedure... I don't think that would make it stall at idle after it was running just fine for 60 or 70 miles.

Car runs great, so long as I keep my foot on the gas when braking... but the spark plugs show that the fuel/air mix might be a little lean. So, perhaps this is an EGR problem. Never cleaned EGR before, so looking for a writeup on this or any other advice. Don't know what else to do anymore, really.

This is a (1.8L) QG18DE motor, by the way...

My profile was showing '94 Hardbody from a truck that I also just purchased last month. But it appears that there's no Hardbody sub-forum here... which is kinda strange. But whatevz...

Well... I think I might have found the problem.

Took off the throttle body in order to look for the EGR valve, which I have yet to find. But I think that the EGR is not the issue.

As I was taking off the throttle body, I realized that there was a coolant passage running thru the IAC valve (probly didn't notice that before, because it was low on coolant before I had gotten it running and decided to clean it out the first time)!!

Soo... it appears that the gasket is not doing it's job. I'll be going to order a new gasket.

But there's something else that's worrying me. The plug on the wiring harness attaches to the IAC looks to be a little damaged from the coolant eating away at it. I'm wondering if there's an easy way to diagnose this while the car isn't able to run. I've got a multimeter if anybody has suggestions for what pins to test.

Thanks!!

I guess there might not have been a blown head gasket, and the coolant was getting in thru the IAC valve!! Very silly design if you ask me. Just ridiculous.

Well... I took the IAC valve apart, and I'm starting to notice this corrosion (white, gritty/powdery corrosion) that is ALL over it and the throttle body, that was definitely not there just 80 miles ago, before the Bars Leaks bull crap.

It's also all over the EGR valve, too, and the thing right below with coolant lines running all thru it... thermostat?? I've done a little mechanic work before, but mostly just follow the book. No book for this car. And I have never done anything with the coolant system before, excluding a heater core on a Volvo 850.

But anyway, this corrosion stuff, at least on the throttle body and IAC is definitely BRAND NEW!! Not good. I can't remember what the IAV gasket looked like before, but I don't remember it being all "beat up" and gritty like it is now. I can only assume that this Head Gasket Fix actually caused it, too??

Dunno... but I ordered a new gasket. Hoping that the IAC motor and harness plug haven't been completely destroyed from this mess. In order for the coolant to get to the wiring harness, it had to go THRU the motor.

The way this Bars Leaks Head Gasket Fix works is very strange business if you ask me.



I'm just not so sure that the coolant was getting thru the Idle Control Valve gasket BEFORE I put this stop leak in it. Otherwise, the motor, its plug, and its wiring harness would have been wet BEFORE.

(I also see that there is a Hardbody sub-forum here, but I didn't see it 'cause I was only looking at the "Nissan Forums" category. Duh-hur!! )

I've been awake a really long time man, I will re-read this tomorrow and get back with you.

Welcome to NICO

Cool... And thanks for the welcome.

Brevity is not my strong suit, but I can give you a TLDR now that I've figured out what the problem is and tell you what I'm really looking for now...

- Poured nasty head gasket fix into radiator, causing corrosion at the ends of most all hoses. I assume it's eating at the metal and then causing gaps for the "nasty coolant" to seep past the ends of each hose. NOT GOOD!

- Biggest offender that has been causing the no start issue is that it seeped past the Idle Air Control (IAC) valve gasket!! This put it in the intake, but I likely wouldn't have noticed it had it not gone THRU the motor and out the plug to reach the female plug on the wiring harness.

Sooo... long story short is that I ordered a new IAC valve gasket for just $4 that should be here Thursday morning.

Until then, I'd like to figure out:

(1) if the IAC valve motor still works, and
(2) if the female plug on the wiring harness is still good.

Would be of great help so that I don't have to put this together more than once.

1: If the IAC is dead, it should throw a code.
2: What's the physical condition of the plug?

Well, I managed to find the FSM.

It took me a good while to find the section on testing the IAC motor. It told me to check resistance between 4 sets of pins, basically. Three were within spec, but one was out of spec at just 7 ohms!!

So I already ordered the gasket from the dealership for $4, and I doubt they'll let me return that even tho they still haven't called me to come pick it up yet. But I was able to use a coupon to Advance Auto and get a new IAC valve for like $78, and it will be here in 2 days.

Only problem is that I am unable to test the wiring harness for the IAC valve. It doesn't look fried or anything, but I have had to clean coolant off that harness plug for 3 days. First day, I used napkins and a hair dryer. second day, I was able to use napkins again. Third day, I realized that I should have been shaking the hell out of that plug to fling the remaining coolant/water.

I can only hope that it's completely dry by now. I'm going to go check it and then drain the coolant out of the system, since that B.S. head gasket fix is obviously destroying everything it touches. Should have done that days ago, but I've had all kinds of other problems to deal with.

Anyway.... some way to test the wiring harness plug would really help me out a lot in preparation of the new IAC valve / motor..... but it didn't appear that this info was available in the FSM. That section was rather large, tho, so it's possible I could have missed it, but I don't think so. In order to test the wiring harness, you hook the motor up and turn the key between on and off.... but that doesn't help me if the motor doesn't work!!

Hmm... still haven't gotten a chance to drain the coolant yet.

But my friend came over and solved the issue of coolant still in the wiring harness plug!!! I was patting it out onto a napkin and still had little droplets falling out. Told him how I've done this for days and even used a hair dryer. He said... perhaps some compressed air would get it out?? DURR!!! I've got an air compressor!!!

Surprisingly, I never think to use it for blowing air all that much. But it seems to all be out for sure now. Guess there's no point in testing it anymore. Just hope it didn't fry my computer!!!! Sheesh.

Soo.... I finally got the IAC valve installed today. Drained the old coolant. Flushed it at least 4 or 5 times with tap water from a hose. Drained that. Then filled it up with distilled water and crunk her up.

It was idling fine, but then started smokin within a minute. I hopped in and hit the gas... NOTHING!! I check the throttle body, and I forgot to connect the throttle cables!!

I connected them, and then hit the gas. Can't really remember what happened exactly, but the important thing to take away is that very shortly the car was dying at idle. I was desperate, so I threw in a little bit of that head gasket fix just so we can take this car to a dealership and get some trade-in value for it or something!! We're DESPERATE!! Finally, the white smoke stopped. Somewhat good. But still stalls at idle.

Soo... I don't think to check the OBD2 scanner, because I'm just sure that everything should be working. I figure, maybe I can do the Idle Relearn, unlike the first 10+ times I tried it. Sure enough, I'm unsuccessful with 7 tries or so. The MIL just will *not* blink. So, I then wonder if somehow the head gasket fix has already corroded the IAC valve and gotten past the new gasket.... take the plug out and it looked wet. I rushed home to get my tools, since I was at a nearby parking lot.... I pull the IAC valve motor out, but it's still dry. I guess the flashlight just made the plug look wet, and that's all. Whew... half-way relieved.

I finally decide to check the OBD scanner up, and I got a couple new codes...

P0120 - Throttle Position Sensor/Switch (TPS) A Circuit Malfunction
P1705 - excessively high or low voltage input from TPS sensor

In addition to the two old codes I got, which I think are just "ghost" codes, however, I did spill quite a bit of antifreeze on these O2 sensors in the dark parking lot....

P0134
P0154

Soo... I've ordered a TPS also from Advance with another $40 off coupon, equalling like $76 with tax and all. Will be able to pick it up first thing in the morning.

Is replacing TPS as simple as taking the old one out and dropping the new one in. I assume that I won't need the dealer to do the ECM/PCM reset, so long as I'm able to do the idle relearn, which I've been unable to do.

I hope to God that I don't have another ECM problem, because I already replaced that bastard once. This is just a bunch of ... If this doesn't work, I'll be selling this thing for scrap metal.

Anybody?

Is it possible to replace just the TPS switch without replacing the whole throttle body?

Most people say you need to replace the whole thing. Would like to know for sure before I buy this non-returnable electrical part.

I'm pretty sure it's not available separately.

Hey man, I am having similar issues with our 2001 Nissan Sentra GXE. Idle is high and fluctuating. While installing the new Idle control Valve I noticed coolant in the tube connecting the intake to the air box. Does the ICV leak coolant or would I have a leak somewhere else? There is no coolant mixing with the motor oil as far as I can tell. The oil appears clean.