DOHCRagtopguy Posted July 21, 2003 Report Share Posted July 21, 2003 Well, the ragtop seems to be developing a stalling problem. The RPMs drop way down at idle and she just dies. This just cropped up today after it's been running like a champ. Of course, I'm not getting any SES light or anything. Stalled out on me like 4 times this morning on the way in. I suspect the TPS may be going on it, but the fact that I'm not getting any code thrown is puzzling. Any opinions, ideas? Quote Link to comment Share on other sites More sharing options...
Slade901 Posted July 21, 2003 Report Share Posted July 21, 2003 do an idle re-learn first. Quote Link to comment Share on other sites More sharing options...
DOHCRagtopguy Posted July 21, 2003 Author Report Share Posted July 21, 2003 I'll try that and see what happens. Good idea. Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted July 21, 2003 Report Share Posted July 21, 2003 Yeah, idle re-learn first. I dont think you will get a code for TPS, I didnt get one. I replaced mine and it idles SO smooth. I think the only way you will get a code is if the sensor is completely dead and sending a signal. If its old, it'll send a bad/weak signal. Robby Quote Link to comment Share on other sites More sharing options...
DOHCRagtopguy Posted July 21, 2003 Author Report Share Posted July 21, 2003 OK, I tried the idle re-learn procedure. Disconnected for 5 mins, hooked back up, ran for 15 mins in drive, fan came on. Shut it down, set for 1 minute, fired it back up, back in D for 5 mins, fan came on. Drove it around the block a couple of times, stalled out again when I left off the gas. Doesn't show any improvement. Also, when the A/C is engaged, the idle doesn't change at all. Would that be a symptom of bad IAC valve? Damn I wish I had a scan tool. Now I am unsure if it's the TPS or the IAC. I'll have to figure it out quick, this left foot braking is a bitch. I'm willing to get a new TPS, that's only about 20 bucks, the IAC is much more. I took it out and cleaned it up, looked pretty good, not much carbon at all. Still no SES light. Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted July 21, 2003 Report Share Posted July 21, 2003 Does it just die, or struggle to stay idling, then die? Robby Quote Link to comment Share on other sites More sharing options...
DOHCRagtopguy Posted July 21, 2003 Author Report Share Posted July 21, 2003 It just dies. Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted July 21, 2003 Report Share Posted July 21, 2003 Try the TPS. Mine would sometimes die when I had to brake hard coming to a stop light or something Robby Quote Link to comment Share on other sites More sharing options...
DOHCRagtopguy Posted July 21, 2003 Author Report Share Posted July 21, 2003 I think that's what I'll do. I had a 92 Z 24 (3.1L) that showed similar symptoms, but it threw a code. Changed that TPS, it was fine. Thanks for your help Robby. I'll let you know. I hate just throwing money at the damn thing, gets expensive. Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted July 21, 2003 Report Share Posted July 21, 2003 Yeah, sure thing man. I hope it works out for ya. And yeah, stuff adds up fast when your trying to fix something, before you know it, sometimes, your out a lot of money, and you cant think where it went Robby Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted July 21, 2003 Report Share Posted July 21, 2003 I mean personally, I would NOT change anything until you know FOR SURE what it is...I just don't want you to waste any money that is not necessary. Especially since everything you are referring to replacing is monitered by the ECM. You're right, if you're NOT getting an SES Code, than you shouldn't just guess as to what is happening. The TPS voltage is monitored by the ECM, from about 0.5-5.0 volts. Anything out of range, throws a code. Also, don't be under the assumption that somehow the TPS controls fuel delivery!! The TPS has ONLY 2 purposes, to tell the ECM when you are at idle, and when you are above 70% throttle, that's it!! The IAC is a possibility because it doesn't have a direct INPUT connection into the ECM. In other words it can't tell the ECM what is has actually done, it can only TAKE commands from the ECM. The ECM relies on OTHER sensors, specifically RPMs, to tell whether or not the commands to the IAC have been successful. Just my 3 cents:) Quote Link to comment Share on other sites More sharing options...
DOHCRagtopguy Posted July 21, 2003 Author Report Share Posted July 21, 2003 I hear you gmrulz4u. However, since I don't have a scan tool or know anybody that does, I'm kind of reduced to this. The TPS is relatively cheap, and easy to do, so I don't mind. The alternative is to take it in to the damn dealer and get raped! Sometimes I have a feel for this shit, so I'll give it a shot. Oh, but for the old days when I could fix a smallblock 327 with a screwdriver and a matchpack! Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted July 21, 2003 Report Share Posted July 21, 2003 In fact, after reading some more, I would almost definately say it IS your IAC Valve. I read a few places online, and that is one of the most common symptoms of a bad IAC, when you let your foot off the gas, it dies. Remember, the IAC goes bad internally, and electronically, it's not humanly possible to tell just by looking at it!! The reason it's extremely rare to get an SES light for a bad IAC is because, like I said before, the ECM is programmed to ONLY set an IAC code if the "closed throttle engine speed is 200 RPM above or below the desired (commanded) idle speed for 50 seconds"!!! See, what the hell happens in the case of the IAC closing completely off throttle, stalling the car?? Well, no SES light... That's just one of the MANY things I HATE about OBD I engines... Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted July 21, 2003 Report Share Posted July 21, 2003 All you have to buy is a MULTI-METER!! I HAVE a Scan Tool and it's handy, and cool/neat to watch, but it's not the savior to all diagnosis. I would scan your car in a second, but I live in Ontario, and you're in PA. You can verify a bad TPS by just using a $10 Multi-Meter... Also, going back to the IAC, scan tools only tell you what the ECM thinks and wants the IAC to do, it doesn't tell you what it's ACTUALLY doing...which again, is frustrating... For example, my Scan Tool will display IAC = 8 counts. This just means the ECM is telling the IAC to move to the 8 count position, even though the IAC could do whatever the hell it wants, and stick at 30 counts etc... Quote Link to comment Share on other sites More sharing options...
DOHCRagtopguy Posted July 22, 2003 Author Report Share Posted July 22, 2003 I have a digital multimeter, how can I check them out? I'm challenged when it comes to electronics and such. Quote Link to comment Share on other sites More sharing options...
DOHCRagtopguy Posted July 22, 2003 Author Report Share Posted July 22, 2003 After driving it in to work today, now I am leaning toward the IAC valve. It the TPS was bad, I think I'd be getting surges due to fuel being intermittently injected when the ECM would thing the accelerator is moving. Plus an erratic idle and surging. I get none of that. It just dies when leaving off the gas at 20 MPH and under. Plus no idle kick-up with the A/C on. Think I'll take the one out of my wife's 3.4 and see if there's any difference. I guess there's no way to check the IAC with a multimeter? Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted July 22, 2003 Report Share Posted July 22, 2003 Yeah, there's really no way of testing an IAC with a Digital MultiMeter. There's a special tool that GM has called an "Idle Air Motor Tester", but of course it's almost impossible for anyone to get their hands on it. And yes, it almost HAS to be your IAC! I can't think of anything besides an IAC or a bad ECM that would cause your idle to NOT increase when loads such as A/C are applied. The ECM commands various idle/RPM speeds as loads are applied and removed, if it's not doing this, it could be the ECM, but the chances of that are almost nil. So the only other component that matters in this situation is the IAC, it has to respond to the ECM's command, if it doesn't, it's bad. Quote Link to comment Share on other sites More sharing options...
DOHCRagtopguy Posted July 23, 2003 Author Report Share Posted July 23, 2003 OK, I'm picking up a new IAC valve today and am gonna put it in here at work before I drive home. I'll let you all know what's up. Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted July 23, 2003 Report Share Posted July 23, 2003 I'll be waiting to hear what happens... MAKE SURE that you disconnect the battery for a few minutes, and do the proper IDLE RE-LEARN procedure...otherwise it will be a useless exchange... Quote Link to comment Share on other sites More sharing options...
DOHCRagtopguy Posted July 23, 2003 Author Report Share Posted July 23, 2003 I'm happy to report that the problem is solved! She's idling nice and smooth again right around 700 RPM in D. No hint of stalling. Thanks to everyone for your help. Saved me some bucks for sure. The people on this board sure know their 3.4 motors. Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted July 23, 2003 Report Share Posted July 23, 2003 I hate to say "I told ya so":) Just kidding Glad to hear it's running smoooooth... I don't even have a 3.4L, it just applies to all engines... Quote Link to comment Share on other sites More sharing options...
DOHCRagtopguy Posted July 23, 2003 Author Report Share Posted July 23, 2003 Wise ass Canuck! If you ever get around these parts, look me up, I'll buy you a cold one! Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted July 23, 2003 Report Share Posted July 23, 2003 Perfect! I may be a Canuck, but I'm actually a fan of MILLER BEER! Good 'ol Milwaukee beer For me, it's gotta be MGD(Miller Genuine Draft)!! Quote Link to comment Share on other sites More sharing options...
rglguy Posted July 24, 2003 Report Share Posted July 24, 2003 bud is king of american beers, miller tastes like water and liquid shit!! haah j/k Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted July 24, 2003 Report Share Posted July 24, 2003 Now, now boys...lets not get into a fight over BEER! Let's all just drink it instead! Quote Link to comment Share on other sites More sharing options...
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