Stang70Fastback Posted January 7, 2014 Share Posted January 7, 2014 This has existed on this car for years, and I've just been too lazy to bother filming it until now. It is exaggerated in colder weather, so I figured now was a good time to take a video. In this video, I am basically just barely touching the pedal with my foot and just eeking it forward until what you see here. The delay between each "event" isn't me purposely leaving space - it's just how long it takes for be to slowly put pressure on the throttle. I say this because I want to emphasize that what I am doing here happens not only when I actually press the throttle, but even if I try to ease the engine up. Basically, the engine seems to completely cut out for a split second. Enough for the revs to drop a few hundred on the tachometer. Once it does that, I can rev up and down all I want without issue, but if I take m foot off the throttle completely, and then go back to the throttle, the same thing happens when I initially move the pedal. I don't know how this would be a MAF issue, and in m limited knowledge, I was thinking maybe the IAC Valve was over-reacting and closing too quickly as soon as I touched the throttle, but I don't think that would cause the engine to instantly cut out - it wouldn't lose air that quickly I don't think. It almost seems electrical in nature - as if spark completely stops for a split second. Again, this has been happening for at least a year or two, so it hasn't gotten any worse. Any suggestions? The only reason I care is because it makes it difficult, if not impossible, to gently accelerate smoothly in slow traffic or from a stop. Not a huge deal - and if I am accelerating normally it doesn't matter since it isn't really noticeable. But when I am trying to crawl slowly, it's more apparent. [ame=http://www.youtube.com/watch?v=bhPjrLFsnVw]98 Subaru Legacy 2.5L Odd Hesitation - YouTube[/ame] Link to comment Share on other sites More sharing options...
boattlebot Posted January 8, 2014 Share Posted January 8, 2014 has the check engine light ever been on? even if it hasent i would read the codes, the check engine light only comes on if it is emissions related, so thier might be some codes in thier that arnt setting the light Link to comment Share on other sites More sharing options...
Dangerzone3 Posted January 8, 2014 Share Posted January 8, 2014 Ericthecarguy (Youtube) had a similar problem with his 97 2.2. He went through a series of videos trying to fix the problem but did not get any results. After doing a lot of maintenance work on the engine it was still present and he kind of ruled out the engine and claimed it was a transmission problem. Is yours an automatic?? Here's a link to the video: [ame= ] [/ame] Link to comment Share on other sites More sharing options...
Stang70Fastback Posted January 8, 2014 Author Share Posted January 8, 2014 Mine is an auto. I suppose it is possible it is transmission related. That never even crossed my mind. There are no codes thrown by the ECU. Link to comment Share on other sites More sharing options...
spooln30 Posted January 8, 2014 Share Posted January 8, 2014 So that only happens at that rpm right? I'll try that on my 99 LGT and report back cuz I think mine does the same thing and is probably normal. Link to comment Share on other sites More sharing options...
Dangerzone3 Posted January 8, 2014 Share Posted January 8, 2014 Mine is an auto. I suppose it is possible it is transmission related. That never even crossed my mind. There are no codes thrown by the ECU. I think it could be something either in the transmission or the drivetrain that is slipping. However, in your video you're not driving but the symptoms still occur. So I'm guessing in your case it is an engine problem. I would definitely start by replacing the spark plugs. This is a very common symptom with a bad spark plug. Also, clean the MAF sensor. Even if it doesn't help the situation, your car will thank you. It could also be a leak in the intake between the MAF and the throttle body or could be a fuel pressure problem. Link to comment Share on other sites More sharing options...
spooln30 Posted January 8, 2014 Share Posted January 8, 2014 It's definitely not a trans or drivetrain parts. I know if I blip the throttle on mine it will kinda do the same thing. I also highly doubt it has anything to due with the spark plugs or wires. If these were faulty it would cause a misfire where his problems isn't but more of a hiccup. I would rule out the MAF and the intake hose because if the hose had a hole allowing more air in it would lean out and stumble throughout the entire rpm range same with the MAF. With low fuel pressure I am pretty sure it would've thrown a lean condition cel like the MAF/hose would. I am sorry I reread your first post and mine doesn't do the same thing as yours. Mine is when I apply full throttle for a second and it feels laggy. I believe your issue is TPS related, it makes total sense to me now that I've read it again. Seems like the TPS is glitching out for a split second. If you have a scan tool or access to one with data readouts look at the TPS % and its voltage. With the key on engine off (KOEO), press the throttle slowly and watch the voltage. It should rise slowly in conjunction with how your pressing the throttle. If you notice a flat spot, missing voltage reading or any glitches you found the problem. You should also have a voltage reading of 0.70 volts with KOEO without pressing on the throttle. They are adjustable so if it's not at 0.70 volts then adjust it until it is. GL. Link to comment Share on other sites More sharing options...
Stang70Fastback Posted January 8, 2014 Author Share Posted January 8, 2014 Yeah plugs and wires are relatively new. You know what, the throttle position sensor makes worlds of sense. Never thought to look at it. I will look at this via OBD and report back. Link to comment Share on other sites More sharing options...
Zues Marine Posted January 8, 2014 Share Posted January 8, 2014 do you have an ELM327? if not, you should invest the $12 for it Link to comment Share on other sites More sharing options...
spooln30 Posted January 8, 2014 Share Posted January 8, 2014 Yeah the Elm is pretty cool but beware of cheap knockoffs on Amazon and eBay. Link to comment Share on other sites More sharing options...
Stang70Fastback Posted January 8, 2014 Author Share Posted January 8, 2014 I have a Bluetooth OBD Key (ELM 327) and the Torque app on my phone Link to comment Share on other sites More sharing options...
spooln30 Posted January 9, 2014 Share Posted January 9, 2014 Cool. Do they give throttle % and voltage readings? If they are only $12 maybe I'll pick one up. Where is a good place to buy them from? I've heard that a lot of places sell knockoffs and won't link with the app. Link to comment Share on other sites More sharing options...
twisty Posted January 9, 2014 Share Posted January 9, 2014 i have one, and while i can see a lot of stuff, a lot is disabled/ not available for my 95 wagon. i assumed it just wasnt available in the ECU. mebbe i should buy the full version of torque and see if they are there afterwards. Link to comment Share on other sites More sharing options...
Stang70Fastback Posted January 9, 2014 Author Share Posted January 9, 2014 It's your ECU that doesn't offer those things. I've plugged the unit into more modern cars and get mountains more data. Speaking of data, I got a chance to look at mine. Looking at the Throttle Position Sensor data, I discovered that when I slowly depress the throttle, I can actually get the sensor up to 1% (a lot, I know) before I get that odd cut-out for a split second and the engine starts to rev up. And when the happens, there is no change in the throttle position, so that's working fine. I thought maybe it was related to INITIALLY touching the throttle, but I can hold the throttle at 1% with no change in engine RPMs. Go past that point and I get that odd dip and then RPMs will start to climb. Also looked at the MAF readings and those seemed normal (dipped when the engine cut out, but it all seemed to match what the engine was physically doing.) ALSO looked at the timing and that ALSO seemed fine. It basically matched what my pedal was doing, notthe engine (it would ssmoothly increase as I depressed the pedal.) So in other words, the only sign of anything wrong looking at the DATA from those three sensors is the MAF dipping, but that's not actually a problem itself, just a result of the RPMs dropping. Hmm... Link to comment Share on other sites More sharing options...
purebluedoor Posted January 9, 2014 Share Posted January 9, 2014 i have the same lag on my leggy. and then 1-2 she shifts like a bucking bull, then 2-3 is smooth. im auto too and have been doing everything to fix this prob too. figured cold air intake, exhaust, plugs, etc etc would help. doesnt. so my personal conclusion is the transmission or tcu. so i put the sport mode on the tcu and the lag is still there, idk about more or less present, because the cars revving up higher, but mostly no effect. ive had mechanics drive the car to check the trans and they say shes good -im going to swap all diff fluids, and do a tranny flush once its not snowing. then replace the right wheel berring. i vote.... 5sp thats my only conlusion Link to comment Share on other sites More sharing options...
Stang70Fastback Posted January 9, 2014 Author Share Posted January 9, 2014 It really doesn't seem like a transmission problem though. Why would the transmission cause the engine to basically cut out for a split second? This happens in Park and Neutral as well... Link to comment Share on other sites More sharing options...
Dangerzone3 Posted January 9, 2014 Share Posted January 9, 2014 It really doesn't seem like a transmission problem though. Why would the transmission cause the engine to basically cut out for a split second? This happens in Park and Neutral as well... That's my point... and as i said, start with the basics like spark plugs, MAF sensors and fuel system. Just because they've been recently replaced doesn't mean it can't go bad. Link to comment Share on other sites More sharing options...
Stang70Fastback Posted January 9, 2014 Author Share Posted January 9, 2014 I should point out that this issue also vanishes after just a few minutes of idling. Link to comment Share on other sites More sharing options...
camroncamera Posted January 9, 2014 Share Posted January 9, 2014 This has existed on this car for years, and I've just been too lazy to bother filming it until now. It is exaggerated in colder weather, so I figured now was a good time to take a video. In this video, I am basically just barely touching the pedal with my foot and just eeking it forward until what you see here. The delay between each "event" isn't me purposely leaving space - it's just how long it takes for be to slowly put pressure on the throttle. I say this because I want to emphasize that what I am doing here happens not only when I actually press the throttle, but even if I try to ease the engine up. Basically, the engine seems to completely cut out for a split second. Enough for the revs to drop a few hundred on the tachometer. Once it does that, I can rev up and down all I want without issue, but if I take m foot off the throttle completely, and then go back to the throttle, the same thing happens when I initially move the pedal. I don't know how this would be a MAF issue, and in m limited knowledge, I was thinking maybe the IAC Valve was over-reacting and closing too quickly as soon as I touched the throttle, but I don't think that would cause the engine to instantly cut out - it wouldn't lose air that quickly I don't think. It almost seems electrical in nature - as if spark completely stops for a split second. Again, this has been happening for at least a year or two, so it hasn't gotten any worse. Any suggestions? The only reason I care is because it makes it difficult, if not impossible, to gently accelerate smoothly in slow traffic or from a stop. Not a huge deal - and if I am accelerating normally it doesn't matter since it isn't really noticeable. But when I am trying to crawl slowly, it's more apparent. i have the same lag on my leggy. and then 1-2 she shifts like a bucking bull, then 2-3 is smooth. im auto too and have been doing everything to fix this prob too. figured cold air intake, exhaust, plugs, etc etc would help. doesnt. so my personal conclusion is the transmission or tcu. so i put the sport mode on the tcu and the lag is still there, idk about more or less present, because the cars revving up higher, but mostly no effect. ive had mechanics drive the car to check the trans and they say shes good -im going to swap all diff fluids, and do a tranny flush once its not snowing. then replace the right wheel berring. i vote.... 5sp thats my only conlusion Our '98 GT 4EAT Wagon does this exact thing. It has always bugged me. Happened even after brand new plugs, wires, air filter, O2 sensor, timing belt and associated tensioners, etc. after the headgaskets were replaced. Still behaves this way after Sport Mode mod, new knock sensor, ATF drain & fill... Link to comment Share on other sites More sharing options...
Dangerzone3 Posted January 10, 2014 Share Posted January 10, 2014 From all these symptoms, the only thing that I can pin point now is the fuel system. Maybe a clogged filter or a bad pump. Maybe when the car warms up a bit the fuel is able to flow more freely and readily. Other than that, I don't know what else it can be, but it seems like a common problem!! Link to comment Share on other sites More sharing options...
twisty Posted January 10, 2014 Share Posted January 10, 2014 have any of you guys taken a look inside the throttle body to see if there is a lip of carbon build up just behind the butterfly? just curious, this whole problem sounds mechanical to me, more than it does a sensor/ fuel fail. just a thought, im probably wrong tho. Link to comment Share on other sites More sharing options...
camroncamera Posted January 10, 2014 Share Posted January 10, 2014 have any of you guys taken a look inside the throttle body to see if there is a lip of carbon build up just behind the butterfly? just curious, this whole problem sounds mechanical to me, more than it does a sensor/ fuel fail. just a thought, im probably wrong tho. In my case, I'm pretty sure I Chemtooled the heck out of the throttle body area when I had the intake manifold off at the time of headgasket replacement. Link to comment Share on other sites More sharing options...
Tr00b Posted January 10, 2014 Share Posted January 10, 2014 http://legacygt.com/forums/showthread.php/strange-hesitation-202183.html?highlight=strange+hesitation I have something similar. Can't get rid of it either. Mine shows up as a chug-chug after a quick application of the throttle from a settled down low idle less than 1k rpm. I have 5 SPD. Link to comment Share on other sites More sharing options...
Zues Marine Posted January 10, 2014 Share Posted January 10, 2014 i have one, and while i can see a lot of stuff, a lot is disabled/ not available for my 95 wagon. i assumed it just wasnt available in the ECU. mebbe i should buy the full version of torque and see if they are there afterwards. the full version gives you a few more things but yeah, there is a few that the ecu cant report that would be handy... i use the coolant temp°, gps speed -my vss is dead...,voltage..and something else ...o2 maybe?? Link to comment Share on other sites More sharing options...
spooln30 Posted January 12, 2014 Share Posted January 12, 2014 I should point out that this issue also vanishes after just a few minutes of idling. Well you never stated this before. Have you cleaned the IAC? Link to comment Share on other sites More sharing options...
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