So I was pulling up to a stoplight and pushed in the clutch only to have my car stall. It has never shown any signs or hesitation before. It was pretty instant. Now the car will not idle well, if at all. It is either very rough, or just dies. Other than that the car drives just fine when in motion. There is no hesitation when accelerating at all.

The car is a 98 GS.

I thought it would be the MAP sensor. So I replaced it. It made no difference. Still wont idle well, if at all. But here is the funny part. If I have the MAP sensor unbolted, but just barely in the hole, the car runs like a champ.

I have checked the O2 sensor and the injectors. All seem to function just fine. The only CEL codes I have are for evap leaks, large and small. I have had those a while (just like everyone else) and they have not effected the way the car runs.

Any ideas what is ruining my idle? Are there anymore relays or sensors I can check on? I also did a vacuum leak test and found no problems.

It sounds like you iac on your tb isn't letting air past the butterfly valve. I would test the resistance across the pins on the iac solenoid. The pins are numbered 1-4 from left to right and the resistance acoss 1&4 should be 35-52 ohms and the resistance across pins 2&3 should be 28-52 ohms. Hope this helps.

So, if I get bad readings, Do you think I am looking at a new solenoid, or a new ECU? Thanks for the reply!

Your testing the iac not the ecu wiring. If you get bad readings replace the iac solenoid.

Well, the IAC selonoid turns out to be ok. It is doing what it is supposed too. I am so busy at work, that I didn't have time to fight with the car anymore, so I took it to a shop here I have had really great luck with. The mechanic seems to believe that the #4 Injector is causing the problem. He says the car is running rich, and when that injector is cut off the idle behaves more normal. He can't prove it for sure, because the injector passes other tests, without just changing it. But that is his belief.

What do you guys think, is that a possibility? They want to much for injectors at his shop IMO ($385 for one), and 2 hours to put it in. So this I can just do myself after I get a reasonable injector.

First off, that cost is way out of line (Hell, I'll sell you a whole used set for 1/2 that price :P ). Definitely do it yourself. Why? Because I have doubts that that is your problem. Though possible, it seems more likely to me that you're sucking air somewhere else.

Ya, Needless to say, I didn't take him up on his "offer". I picked up an injector online for 60 bucks. I guess when it gets here I will pop it in and see if that makes a difference.

I'm fairly sure it isn't a leak somewhere, although I also can't believe that, because that is exactly how it behaves. After fog test the only leak was small, with the EGR valve, (I have the large and the small evap leak codes).

Anymore suggestions are greatly appriciated! You guys are a big help! I have my doubts about the injector also, but all the sensors seem fine, and I'm out of ideas.

Did you check the TB on the inside? Is it all clean or full with carbon?

Check the TPS also (right-side on the Manifold)

Jeronimo

Well, an update, and a cry for help.

I replaced the injector today that was supposedly causing the problem. It made no difference (like we predicted). The car still runs rough. I did notice that it is not running smooth even at higher rpms. I guess it just has enough momentum at higher rpms to smooth it out a bit. It is really bad at about 1500. It shakes the whole car. When I start the car cold, it runs, slightly rough. After it warms up it runs much rougher. If I run the rpms up to 3-4000, and then let off the gas, it will drop back down to idle rapidly, and die, or sputter really bad and recover.

What I find most strange is it was working perfect, and then turned this way instantly. I would have thought it was a loose hose or a plug for a sensor somewhere.

Here is what I have done:

I did have a leaky spark plug gasket. I fixed that a few months ago. Could oil in the sparkplug well caused any of this? It's all cleaned out now, and the car ran fine for a month or so after I did this repair. I am pretty sure they are unrelated.

I did have a cylinder drop test done. 1,2,3 had very little drop. On 4 the Idle increased temporarily then dropped back down to the same rough Idle. I did find the O2 voltage high, fuel trims up to 50 at times. I guess its just running rich. That is what made the mechanic think the injector in #4 was bad.

I checked the timing. It is correct. I have had the map sensor, 02 sensors, and IAC circuit tests done with a lab scope. All where performing within perameters. I did try a new map sensor like I stated above. There was no difference in Idle. I also had the mechanic force the 02 sensors rich and lean, both reacted properly and seemed to track together @ higher RPM.

My fuel pump pressure is fine, and there was no significant presure drop when I tested the other injectors for leakage.

I am out of ideas. I do not want to take this car to satan or another shop, because I really dont know what else they could check.

Any Help? Thanks in advance!! If I didn't explain anything well enough, just ask and I will clarify. Thanks for all you guys do here!

Ok. So I did some searching on here. I have noticed that sometimes people have poorly running cars or rough running cars due to air in the coolant system. I have recently changed my thermostat, so I thought I would burp the system to see what would happen.

The car still doesn't run right, but it is better. What else can you guys tell me about this? I made sure the coolant level was full, and ran the car with the cap off until it was warmed up. It still would bubble a bit. It didn't really quit. Now the car runs smooth when you go to higher RPMs. It will Idle at 1000-900. But its just a little rough.

If I go up to 3000 rpms or so, and hold my foot steady on the gas, the rpms will drop off by about 500, then if I let my foot off the gas, it will drop the rpms down to 2-300, or kill the car.

Do you think I need to burp the system more? It's the only thing that has seemed to make a difference, and I'm pretty sure the rest of the car is working right.

Also, Air bubbles in the coolant can move around. That would explain the instant problem, instead of coming on gradually. However the car ran fine after initally fixing the thermostat.

Any Ideas?

Edit: I took the car for a spin. It runs better. However, when I press in the clutch while coasting, the car will drop down to idle, and keep running. Then I can stop and it will stay running.

But If I press in the clutch, step on the break and come to a stop quickly, like at a light or stop sign, and let the rpms drop freely, the car will drop to 100-200 rmps. (I do mean 100) or just die. I haven't checked the speed sensor. Where is it and what does it do? I was pretty sure it just controlled the speedo.

Is the TB all clean, even the EGR return port etc.? Also try taking out the IAC, just pull the pin slowely and careful out and put it back in the TB. Helped my problem together with new MAP in the past.

Also reset the ECU and let it run idle for a few minutes.

Just replace both the egr valve and the idle air valve they are both cheap...

This is a 7 year old thread. Check how you have the messages sorted so that you see the most recent threads first.

Corbin
'97 GSX dressed like a '95 ESi

Haaaa lol DOH!