spiderw31 Posted November 1, 2009 Report Share Posted November 1, 2009 So I've been chasing this stumble / misfire that only occurs at light throttle in 4th gear on and off for some time now. Some might remember I had asked about it way back before my t-belt blew up. Anyways, I think I may have found the issue. I got to thinking, what happens only in high gear at light engine loads? Answer: EGR. I tried disconnecting the EGR valve, and sure enough, the stumble is gone! So , I think I'll try giving the EGR and passages a good cleaning, and replace the valve if that doesn't work. That does lead my to the other half of the issue though. Accompanying the stumble, there was a very noticeable hesitation to quick throttle inputs. Now with the stumble gone, the hesitation remains. Basically, if I'm running in 4th with the TCC engaged at light throttle, if I stab the throttle very quickly (but not hard enough to unlock the TCC) there is a bit of a hesitation before the engine responds (maybe 1/4 to 1/2 second or so). Now this might not seem like much, but it is enough that in the scenario I just described, the engine will bang real hard on the mounts. It feels strong enough to break one, and as if something just hit the front end of the car. Now I've also noticed a slight lag like that if I open the throttle quick enough at idle sometimes. So my question is this: is this possibly just a limitation of how fast the speed density / MAP OBD1 system responds (as in normal), or should I keep hunting for the culprit? I should note that many parts have been changed or checked (to many to list all now), and I'm kinda at a loss for where to go. Help is certainly appreciated! Quote Link to comment Share on other sites More sharing options...
spiderw31 Posted November 2, 2009 Author Report Share Posted November 2, 2009 Bump for any ideas... Quote Link to comment Share on other sites More sharing options...
Galaxie500XL Posted November 2, 2009 Report Share Posted November 2, 2009 I'd be suspicious of the throttle position sensor. It's supposed to allow the computer to compensate for sudden changes, since the airflow and mixture will lag the throttle, the TPS allows the computer to make changes as soon as the peadal moves. This is a simplistic explanation...but close enough. Usually a bad TPS gives a 'rubber band' feel to throttle response. Quote Link to comment Share on other sites More sharing options...
spiderw31 Posted November 2, 2009 Author Report Share Posted November 2, 2009 Thats what I suspected as well, so I changed the TPS out. It made no change. I also tried swapping out the MAP with one that I knew was good (it was just laying around, so why not?) with no change as well. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted November 2, 2009 Report Share Posted November 2, 2009 P4 OBD 1 ECMs read the TPS(and a LOT of other sensors as well) once every 6.25 or 125 mSec, i can't remember which. so it reads it at either 80 or 160 times a second. so trust me, what you're dealing with isn't normal. Quote Link to comment Share on other sites More sharing options...
spiderw31 Posted November 2, 2009 Author Report Share Posted November 2, 2009 P4 OBD 1 ECMs read the TPS(and a LOT of other sensors as well) once every 6.25 or 125 mSec, i can't remember which. so it reads it at either 80 or 160 times a second. so trust me, what you're dealing with isn't normal. OK that's good to know; thanks. Any ideas for what to look for? New CKP, ICM, O2, tested replacing the MAP and the TPS, full tuneup, all new gaskets from the block up, vac lines check out OK. Car runs absolutely great with this one exception. Oh, and I can't ever seem to get better than 17MPG average no matter what I try. Quote Link to comment Share on other sites More sharing options...
Galaxie500XL Posted November 3, 2009 Report Share Posted November 3, 2009 Bad fuel pressure regulator? Quote Link to comment Share on other sites More sharing options...
spiderw31 Posted November 3, 2009 Author Report Share Posted November 3, 2009 I've tested the fuel pressure previously, and I know it was good at idle. I think I checked it with the throttle open as well, but I suppose to recheck couldn't hurt. If memory serves my though, it was about 40-45 psi stable. Quote Link to comment Share on other sites More sharing options...
SigEpCutlass Posted November 3, 2009 Report Share Posted November 3, 2009 Have you checked to ensure the resistance of fuel injectors are at spec? Quote Link to comment Share on other sites More sharing options...
spiderw31 Posted November 3, 2009 Author Report Share Posted November 3, 2009 Have you checked to ensure the resistance of fuel injectors are at spec? No, but at the same time, the car runs beautifully 99.5 % of the time. I'd expect if I had an injector issue, it would manifest itself more often that this. If it wasn't for the fact that the issue is relatively easy to recreate inadvertently, I wouldn't be concerned with it at all. Quote Link to comment Share on other sites More sharing options...
spiderw31 Posted December 2, 2009 Author Report Share Posted December 2, 2009 Well, now the hesitation can be felt with quick throttle inputs in any gear, and I'm inclined to think it is the TPS. I'll order a replacement and hopefully that will resolve the issue. Also, I think that although the rubber in the dog bone looks visually ok that it probably needs replacing since it is original. That right there would make the issue much more noticeable. Anybody know if there is a poly option available for the dog bone? Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted December 2, 2009 Report Share Posted December 2, 2009 you can make them yourself... i actually have a guide saved to my laptop for it. Quote Link to comment Share on other sites More sharing options...
spiderw31 Posted December 3, 2009 Author Report Share Posted December 3, 2009 you can make them yourself... i actually have a guide saved to my laptop for it. Really? Could you get it to me? Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted December 3, 2009 Report Share Posted December 3, 2009 http://elantragtclub.tripod.com/elantra/id557.html yeah, its meant for a hyundai, but it works the same for a W... Quote Link to comment Share on other sites More sharing options...
spiderw31 Posted December 3, 2009 Author Report Share Posted December 3, 2009 Thats pretty slick... I might just give that a shot! Quote Link to comment Share on other sites More sharing options...
mfewtrail Posted December 3, 2009 Report Share Posted December 3, 2009 Here's another option. http://www.kazmotorsports.com/tpsgarage/TGP/Engine/motor_mount.htm Quote Link to comment Share on other sites More sharing options...
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