Car Running bad under 3k rpms

[bradcurtis15]

My Daily Driver is a 92 FWD Talon TSI, 3 days ago it started acting up. best way I can try to describe it is it feels some what of a misfire or some kind of bogging... If i don't put in the clutch while its acting up the check engine light will appear. As soon as I engage the clutch the light will turn off.. I went ahead and change my plugs and wires, I'm about to snag my MAF off my eclipse and test that. Anyone else got any suggestions? My best guess would be MAF, Coil, Injectors, Fuel filter, Boost leak? Thanks.

 

[undefined0000]

O2 sensor maybe and sounds like boost leak. I have the same symptoms, but my car is automatic. It sounds like a boost leak because it might be running lean until you get in the higher RPMs when the mixture fixes itsself. (Taking a guess and trying to help out).

 

[bradcurtis15]

I changed the maf out.... same problem i unplugged the TPS and it feels a little better still having the issue but way less severe...
I think I'm going to swap the TPS out and see where that takes me...

 

[Diamond Star Werks]

check your timing. It may have jumped. I remember getting my evo cams off by one tooth each side and it would run bad till I raised the rpms above 3k or so

 

[bradcurtis15]

check your timing. It may have jumped. I remember getting my evo cams off by one tooth each side and it would run bad till I raised the rpms above 3k or so

Yeah jumping a tooth would make sense but I don't really push this car hard at all... I'll check the timing but I haven't heard very many story's of this happening. this car is 100% stock not one thing aftermarket. So I'm hoping its something simple. I was just reading on VFAQ and found this

Q: So what is an ISC and what is it good for?
A: The ECU attempts to control the idle speed by opening or closing the ISC. The valve on the ISC allows extra air to bypass the throttle plate. Since a stepper motor does not provide any feedback on its actual position, the computer simply counts steps and assumes that the valve lands in the correct place
During normal operations, the ECU uses the ISC for some very interesting things besides simply adjusting the idle speed. The ISC is completely shut when you kill the engine to make sure it stops quickly. The ISC is opened completely at startup to provide plenty of air. It is also opened during normal driving to prevent the car from bucking when you take your foot off the throttle to shift. If you run the air conditioner or turn the steering wheel, the ECU compensates immediately by opening the ISC a little to keep the revs up. This also happens during cruising to mask the effect of the increased load on the speed of the car. So I suppose this could also but a place to look.

 

[Diamond Star Werks]

I wouldnt focus too much on the isc. If it was not working correctly you would have an idle at a, certain rpm that wouldn't change. In an auto car if the isc didn't work it would stumble or die when put in gear. Manual can't really check like that.

Other symptoms would be, your car idling and you turn a/c on and rpms drop and do not raise up as there is no compensation for it.,,or if your siting still and turn your wheels and there is no rpm compensations for it.

 

[bradcurtis15]

My ac makes my car idle very low and will not rise.

 

[undefined0000]

Could be ISC then. It should open the throttle more to compensate for the extra load, I could be wrong though .

 

[Diamond Star Werks]

My ac makes my car idle very low and will not rise.

Then I would say it isn't work correctly then. Hence low rpms is,no compensation. I have rarely seen it cause problems/stumbling that high in rpms but it is possible. Check into the isc.

 

[acorn3583]

have you checked the EGR? similar issues with a friends spyder, turned out the block off plate was loose

 

[bradcurtis15]

I changed the isc and it seems to be driving okay I will know for sure after I make my commute to work so I will be getting back to you guys.

 

[Diamond Star Werks]

Sweet keep us posted bro.

 

[2GSXR]

I would definitely check for boost leaks. Especially if you've already done plugs, wires and MAF. Also check for injector operation by listening with a stethoscope (or the end of a screw driver if you don't have one) on each injector while the engine is idling. You should hear a clicking noise consistent with engine RPM. To check for coil operation you can unplug one at a time the wire from the spark plug and connect to ground and check for spark.

 

[bradcurtis15]

Just an update, my car is no longer bucking and running all crappy. One thing its still doing is idle surging while its warming up so I'm assuming its a boost leak or something simple. I cant complain though bought the car for 1000$ and only put 200 into it in maintenance in the last year so its treated be fairly good.

 

[Diamond Star Werks]

If its surging with the new isc I'm assuming you didn't do any biss adjustment. Try readjusting your biss screw and see if that helps it.

Try this http://www.vfaq.com/mods/BISS-1G.html

 

[bradcurtis15]

If its surging with the new isc I'm assuming you didn't do any biss adjustment. Try readjusting your biss screw and see if that helps it.

Try this 1G BISS Adjustment

thanks ill check that out this weekend when I have some free time. Ill keep you updated.

 

[Diamond Star Werks]

Update?