Soooooooo, to make a long story short, I had to replace my water pump. Ordered a new one, wait 4 days, put it in. BAMM all of a sudden my car WILL NOT IDLE. Bullshit, everything was fine before I replaced it. Pull up to a stop sign or red light and the engine will die unless I have my foot on the gas.

What the hell could cause this? Me wonders? Wait, I only changed the water pump, this is odd. Now I realize the engine is also surging at idle and whilst driving. In say 3rd or 4th gear while driving I can feel it going then backing off, then going and REALLY backing off, like it's going to stall. WTF????

I took off the throttle body(btw ALL emissions removed) and adjusted the idle speed thinking, it's cold so better bump up the idle. Same thing happens. Even idling at ~1500 it'll still pulse up to 1800 then stumble down to 800 or so. Even if I rev it to say 2500, the revs will creep up to 3000, then stumble back down to 1500. This is aggravating...

Checked for vac leaks, and I have none, at least so the can of carb cleaner sprayed all over says.. So I'm thinking it has to be something else, but what?

Now I'm used to having to keep my foot on the throttle until she warms up a bit when it's cold, but this is just not right. Even when she's warm it's still a surging idle.

TPS has been set multiple times, same issues. I have even unplugged the tps and nothing changes.

Any help gentlemen, would be greatly appreciated!

 

Your FD alternator... do you have the proper connector for it? I know it sounds weird, but I've seen idle issues from a non-charging alternator. I ask about the connector because I have a temporary fix for my FD alternator, which consists of 2 wires with spade connectors to adapt the S4 connector, so it's very easy to install them backwards.

 

In working on your car, did you remove any of the white/green plastic vacuum valves, and if so, did you accidentally reinstall one in the reverse direction?

 

FD alt has been in for years now and has never given me a problem, don't know why a problem would just start up now, and she's giving me 14.5 volts, but I'll take a look at it.

I don't have any of those check valve thingies on my engine, all that stuff has been removed.

I'm just gonna go ahead and start stripping her down, maybe I messed something up the last time I had the intake off, we'll see....

Thanks for the replies

 

Just 2 days ago my air flow meter plug was half way off. (looked connected but wasnt fully connected) Started to not hold an idle and i was confused as hell. Pushed it on all the way and problem was gone. Worth checking while your at it.

 

Okay, so I took off the intake to find nothing wrong at all. Unconnected then reconnected the afm and coolant temp sensor. Started her back up and the same thing. Engine surging at all rpm's, and she'll die at anything under 1200.

Aside from that she's running great. Although I'm about ready to take a shotgun to her....

Could any sensor that I still have on the car cause this? I disconnected the afm while the engine was running and it died, so that's working. Coolant temp sensor? I honestly have no idea, and I've had this car for a while now.

Again, any help or insight would be greatly appreciated.

 

Really the best thing you can do is grab the fsm, go to the ECU and do a pinout check of all the "input" voltages.

http://www.rotaryheads.com/PDF/2nd_g...systems_na.pdf

Page 4A-30

This is the best (and I still think it's also the easiest/fastest) way of telling if you have something disconnected, a cut wire, a short, etc. Look for the "smoking gun" if you will. A voltage of 0 or 5 is a sure indication something's amiss. If the voltage falls somewhere along the range, then the wiring and sensor are probably good.

I thought you would have had to remove the alternator to change the water pump. That's why I asked what kind of connector is on it. If the connector is on backwards, you can get some funky issues.

 

Yes! I will be doing this, because now it won't start. Although it was running the other day.

So far I haven't really tested anything other than the tps, which I know is good. I was starting to think that it might possibly be a bad afm. Seeing as I happen to have a spare one, I was just going to swap them out and see if it helps.

I did have to remove the alternator, but it's connected via the stock Fd connector. I just spliced wires into that. It only goes on one way.

 

Remember, start with all the inputs. (Left column of that page) It's more likely that it's one of those. A bad output means a bad ECU, so we'll start with something more likely Can't hurt to check all the +12v supplies and grounds as well.

 

Thanks, I will get around to that tomorrow, its cold and dark already here. The help is appreciated!

On a side note, I did swap out the afm. It was bad. It was stuck in the closed position when I pulled it and was very sluggish through the entire sweep. So, I popped in the other one I had and it almost started for about 2 seconds, then back to just cranking.

So after that I pulled the battery. One, to reset everything and two, because all that cranking took a toll on the battery. I got the battery on a charger right now.

So I guess we'll see what tomorrow brings.

 

There's a good possibility that the engine won't start because it's flooded. Try a deflood and see if it'll start now.

 

Tried deflooding, got nothing. Seems like she isn't getting any fuel at all.

Anywho, I pinned the ecu, here are the results..

All were done with the ignition on, but not running. As I could not get her started. The following results are all in volts.

water temp switch 1H 0.03v
Initial set coupler 1J 5.45v
crank angle sensor(g) 1N 0.745v
crank angle sensor(g) 1R 0.740
crank angle sensor(ne) 1Q 0.743
crank angle sensor(ne) 1T 0.736
Ground 2C 0.009
02 sensor 2D 0.029
AFM 2E 3.910
Variable resistor 2F 0.000
Throttle Sensor 2G 0.945
Atmospheric Pressure 2H 0.000\
Water Thermo 2I 4.95
AFM(IAT) 2J 0.22
IAT 2L 4.67
ground 2R 0.011
ground 3A 0.012
ground 3G 0.007
battery 3J 11.83

Still won't start. An d there's snow on the roads. I need to get her started. I wanna have some fun sliding around!

Just cause it may well be flooded, I'm going to swap out the spark plugs with some new ones.

 

Now that the car's not starting at all, you need to see if you're getting fuel and spark. It's hard to actually test to see if you have fuel pressure, but you can at least tell the fuel pump is on by opening the AFM flapper a little. There's a switch inside that will turn the fuel pump on. There's also a yellow connector near the intake snorkel with 2 prongs that you can jumper, and that turns it on as well. If you hear a gushing noise, then you've probably got fuel. Check for spark by holding a plug wire near a ground, then have someone crank the engine. See spark? Good. If you have both fuel and spark, then try deflooding it again. It may be flooded really really bad.

It's weird that the atmospheric pressure sensor and variable resistor are reading 0.00 volts. The variable resistor actually has a lot to do with the idle mixture, and I wouldn't be surprised if that was part of the problem. I've never actually located the atmospheric pressure sensor before, but that's something worth investigating as well. You also need to check pin 2B, even though the car's not turbocharged, the "boost sensor" is what most people in the real world call a MAP sensor, or the "manifold absolute pressure" sensor.

The variable resistor is right behind the passenger's side headlamp. Unplug it and read the resistance across it.

Apparently the atmospheric pressure sensor is close to the ECU, and it has a 4-prong connector. See page 4A-73 for more information. Check to make sure that's plugged in, and see if you can get a reading at pin D.

 

"Water Thermo 2I 4.95"

This is not proper. This reading is telling you that the wiring/connection plug to the sensor are in need of a look over. Should read 2 to 3 volts w/the engine cold and key to on.

This sensor is located at the top and behind the water pump so in your recent repair work you likely left the plug off or one of the wires in the plug are pulled back within and not making proper contact.

 

I know I have spark, never lost it before. Sounds weird but I've lost the leading coil before and had the car running on only the trailing plugs. Also lost the trailing coil before and had no tach. So, I've been down those roads before. It sounds like I don't have fuel. That's just my ear and 'feel' telling me that. If anything I'll just connect a timing light and find out.

I didn't know that about the boost sensor though, thought it was just a turbo thing. I will go back and check that.

I thought the atmospheric pressure sensor was in the cabin, pass side above the ecu somewhere, I'll check next time I'm out there.

I thought that water thermo sensor was a little funky. I KNOW it's plugged in, because I forgot to plug it in after I changed the water pump. Since then, everything's been downhill. Perhaphs I managed to mess up the connection somehow, maybe pushed on of the wires in the connector back. This will be the first thing I check.

Again, thanks for the help boys!

 

Tested the boost sensor.
pin 2B getting 3.450v which is within spec

Looked at the water thermo sensor and it's plugged in, no wires are loose/kicked out. Could this be the cause? A bad water thermo sensor?

Found the atmospheric pressure sensor, it is in the pass side kick panel. Not very hard to find if you know what you are looking for. It's plugged in though. looks like the wires have never been touched.

 

The sensor can affect driving quality in different ways. To say this is your problem, who knows, but it definitely should not read 5 volts w/key to on and this is a red flag.

 

5 volts at the water thermosensor means that there's an open somewhere. I had an issue once where I thought my thermosensor was plugged in, but since the connector had a little rubber boot a the back, you couldn't see that the wires were pulled just a little bit out of the back of the connector.

So you have a couple issues to sort out.

1) Unplug the variable resistor and check the resistance. It shouldn't be reading "OL". The resistance between the Green/Black and Black wires should be less than the value between the Brown/White and Black wires. I can't seem to find a specific resistance value in the FSM. Also, check that on the harness side that you're getting 5v with the key on, and the black wire is ground.
2) Do the same for the Atmospheric pressure sensor. Unplug it, key on, check the harness side voltages. B/W to ground = 12v (I'm pretty sure of this. Seems like it's coming from the main relay, so I think it's most likely going to be 12v there). B should be ground. Brown/White should be 5v. The green/yellow wire goes to the ECU, so that's an output from the sensor, so no need to check that.
3) Unplug the water thermosensor. Check that you have 5V at one wire, ground at the other. Make sure that you tug lightly on the connector and watch the terminals to see if they pull out easily.
4) Actually check to see if you're getting fuel. It's easy to push the AFM flapper in with the key on to hear the fuel pump kick on. If you hear that, then go try cranking the car and watch the tachometer. If it's bouncing, you probably have spark. If any of the above 3 checks turned out bad, fix whatever was wrong.

 

Wow, some really good info here. Thanks AGreen

I will check all that first thing tomorrow morning. In the exact order you have laid out.

I'm pretty sure I need a good variable resistor, the one on the car now is completely rusted, I can't even turn it. Trust me I've tried.

I'm suspecting the wiring for the water thermo sensor, or the sensor itself. Don't know if that's the root cause, as I clearly have multiple issues.

 

I'm really glad you're taking action on the advice. You'd be surprised to see the vast number of threads that I (Satch too, I know for sure) have taken the time to methodically lay out info like that, only to have the person go down some stupid rabbit hole that leads them nowhere. Most people don't really understand electricity too well, and I get that. That's why I lay it out plain and simple, but some people still refuse to grab a multimeter and follow instructions.

I still think the engine's flooded pretty bad, but take care of those issues first and see if it starts after getting everything in order.

 

Okay, was checking everything when low coolant buzzer started going off. filled her up, and it took a lot of fluid. Finished checking everything, and everything was within spec.

Kept trying to start her, would start then cough, then die. Changed the plugs.

Started again, and this time I got some smoke and a 2k idle, but it's smooth and stable.

I knew the idle was going to be sky high, I'll just adjust that tomorrow.

Turns out I had the same issue with my thermosensor that you did with yours, AGreen. Wires were a little pulled out of the boot in the back, and not making it all the way in to the terminals.

Anywho, it seems to be sorted out for now. Thanks again for the help!