Engine surge/Rpm gauge jumping

[JamesG]

Hi, I the last few months I bought a 1990 eagle talon tsi awd. Its had the head replaced, new head studs, new water pump, new timing belt, new alternator, new air intake, new battery, new spark plugs and wires. After all these had been replaced I turned down the 16g turbo all the way and it still seems to jump to 12lbs of boost. It still has the stock injectors and fuel pump. It has a three inch megan racing catbact, test pipe and down pipe. After replacing the exhaust it seemed to cut out when the turbo passed 10lbs. This is an issue but its not the issue I have ended up with. Driving the car and keeping it under 10lbs seems to run fine. But within the last few days especially today, the rpm gauge seem to jump around Example, When I first started the car and drove it a few blocks away it drove fine. After leaving this place I clearly could tell and feel the engine surging, the rpms would try to drop near to nothing and the engine light would come on. After revving the engine the rpms would jump to normal activity until I released the gas. It would then drop below five hundred rpms nearly killing the car. When trying to drive the car home I would push the gas, it would run normal for literally a second with an imediate surge following. It acts like its either not getting gas or possibly a bad distributor. Someone please help me with this issue, It would be greatly appreciated!! Thanks to anyone with any help, as I desperately need it

By the way, when revving the engine and giving it more gas the check engine light goes off every time, if that helps any..

 

[turboglenn]

YOu should check the codes but usually in my experience when the CEL goes off if you give it gas that's usually a sign the TPS is bad

 

[JamesG]

Dont mean to ask, but whats the tps? Do you also think thats why it surges and the rpm gauge jumps around.. This is the first time it has done it like this. It did it before, but most days it runs really good, so I dont know whats wrong..

 

[jpmxrider489]

Tps= throttle position sensor

 

[Talondvr]

Terry's Talon Troubleshooting Tips #3 - Fast Idle (aka. Idle Surge)

This is a good guide for checking and adjusting idle.
Basically you want to check for boost leaks the check your timing, Throttle cable adjustment, TPS (throttle position sensor) and ISC (idle speed controller). Technically you wont want to mess with adjusting the BISS (Idle screw) unless you have a way of logging the ISC position. A miss adjusted or bad ISC can cause problems with the ECU.

 

[mnelsen]

throttle position senesor, or boost leak. but more than likely tps since ## cel comes on. i had the same problem with mine.

 

[dalesocks]

Check the tps voltage with an ociloscope if you can get one and make sure voltage is smooth with no glitches.

Or a data logger with graph.

 

[JamesG]

Thanks for all of the info, im sure it will help me out. especially that link, it seems to show all the issues I have been experiencing

 

[TSIGuy510]

Thanks for all of the info, im sure it will help me out. especially that link, it seems to show all the issues I have been experiencing

that article was awesome, that guy had the same symptoms that my car is having now and its been getting worse. i know the egr and vac line are good. so it sounds like its the isc. oh and btw nice car jamesG it looks oddly similar

 

[dsmlover07]

Yes i use terrys guide helps a lot, so much info there, regarding idle, and surge, run down the list and eliminate things as you go.

 

[TSIGuy510]

eh i just ran some test and everything came back good on them. The TPS was 5.27kohm and the ISC was 30.6 30.4 30.6 30.8 sound ok?

 

[Diamond Star Werks]

tps may be okay and I can't remember for a 1g but 2gs have adjustment on the tps. It may very well be all fine and dandy but be adjust wrong causing inaccurate readings thus causing the surge problem. It may need to be adjusted if it can be adjusted.

Loosen the tension of the accelerator cable.
3. Connect a digital voltmeter....to the signal wire of tps and a good ground...the neg batt terminal.
4. Turn ON the ignition switch (without starting the engine) and check the output voltage from the TPS.

Standard Value: 0.48 - 0.52 volts

5. If it is not within specifications, proceed with adjustment procedure.
TPS Adjustment
6. Loosen the TPS mounting screws and turn the TPS body, until the specified output voltage is reached.
7. After adjustment, hold the TPS in position while tightening the mounting screws.
8. Turn the ignition switch to the OFF position.
9. Adjust the accelerator cable freeplay.
10. Disconnect and remove the voltmeter.
11. Disconnect the negative battery cable for at least 15 seconds. This will erase any stored trouble codes from the Control Units memory

 

[TSIGuy510]

awesome, thanks for the help. but which wire is the signal wire? is there a way i could check it with my safc? it has a sensor check feature and i know the throttle % works on it but not sure if its spot on accurate.

i checked on my safc and its between 0.475v and 0.480v do i need to adjust it?

 

[Talondvr]

The Green w/white stripe. That's from the service manual because its too cold and dark out to check mine.

If the isc ohm's are good, and the throttle cable is adjusted properly, and you have no boost leaks, I would guess your base idle needs adjusting. I would think the safc would be accurate if hooked up properly but I really

 

[Diamond Star Werks]

awesome, thanks for the help. but which wire is the signal wire? is there a way i could check it with my safc? it has a sensor check feature and i know the throttle % works on it but not sure if its spot on accurate.

i checked on my safc and its between 0.475v and 0.480v do i need to adjust it?

Well that is pretty close but yea I would try adjusting it just a tad to about .5v. If and when you adjust it you can see it change % adjust it up and then back to slowly till right when it just hits zero%.

 

[TSIGuy510]

yah all the numbers came back good. but the guide said that even tho the isc has the correct numbers showing it could still be not working the way it should. and idk if autozones alternator tester would pick up regulator problems or not but i got that tested and they said the alt was working and the batt was good.

Well that is pretty close but yea I would try adjusting it just a tad to about .5v. If and when you adjust it you can see it change % adjust it up and then back to slowly till right when it just hits zero%.

will do thanks for the help

 

[Diamond Star Werks]

Oh yea one more thing to consider before I go to bed. Idle motors go bad just as well as get stuck. I've had one apart testing it on a maxima and it would try to move(accept voltage) But it was simply stuck. So volt and ohm tests my not find a stuck IAC. Good luck man

 

[TSIGuy510]

whats the diff from a IAC and ISC?

 

[JamesG]

This thread has turned out to have lots of info. The tps is exactly what my car needed, I also replaced all hoses just to confirm no leaks. By the way tsiguy510, thanks! They are very similar , id have to say the best color choice. Many people stare at the old schooler when I cruise it Im buying classic plates for it

 

[4g63dreams]

But wouldn't turning down the turbo to 10psi and not adjusting fuel ratios cause it to surge like so?

If I'm not mistaken, decreasing air intake and keeling fuel at the higher setting means rich? Unless the ecu detects and adjusts automatically. Im just learning here...

 

[Diamond Star Werks]

IAC/ISC same thing just different name. I've just always known them as IAC but there is no difference really. Both are names for the component that regulates the amount of air allowed past the throttle body in order to stabilize idle. No turning down the turbo boost would not cause it to surge. You do not run any boost at idle neither with light throttle. And limiting your boost simply limits your power. You can route the vacuum lines from the turbo to limit it to 5 psi and it will not affect driveability. It will simply give a vtec the thought that it might just be close to being as fast. The computer automatically adjusts AFR accordingly with the MAF reading, MAP sensor, and 02s. Limiting boost neither cause rich nor lean conditions.

 

[TSIGuy510]

This thread has turned out to have lots of info. The tps is exactly what my car needed, I also replaced all hoses just to confirm no leaks. By the way tsiguy510, thanks! They are very similar , id have to say the best color choice. Many people stare at the old schooler when I cruise it Im buying classic plates for it

yah i agree about the color, it catches alot of eyes.

MJcanada i figured they were the same thing but i just wanted to be sure...it just sucks that i have to pull all my hard piping off to test it stuffs annoying to get on and off .

 

[4g63dreams]

IAC/ISC same thing just different name. I've just always known them as IAC but there is no difference really. Both are names for the component that regulates the amount of air allowed past the throttle body in order to stabilize idle. No turning down the turbo boost would not cause it to surge. You do not run any boost at idle neither with light throttle. And limiting your boost simply limits your power. You can route the vacuum lines from the turbo to limit it to 5 psi and it will not affect driveability. It will simply give a vtec the thought that it might just be close to being as fast. The computer automatically adjusts AFR accordingly with the MAF reading, MAP sensor, and 02s. Limiting boost neither cause rich nor lean conditions.

Ahh I see. Thank you very much.

 

[JamesG]

IAC/ISC same thing just different name. I've just always known them as IAC but there is no difference really. Both are names for the component that regulates the amount of air allowed past the throttle body in order to stabilize idle. No turning down the turbo boost would not cause it to surge. You do not run any boost at idle neither with light throttle. And limiting your boost simply limits your power. You can route the vacuum lines from the turbo to limit it to 5 psi and it will not affect driveability. It will simply give a vtec the thought that it might just be close to being as fast. The computer automatically adjusts AFR accordingly with the MAF reading, MAP sensor, and 02s. Limiting boost neither cause rich nor lean conditions.

Well said! @4G63Dreams, The only reason I turned down my boost to 10lbs was to keep the car from cutting out @full throttle @higher rpms. The 16g turbo has too much boost to run any higher without a new fuel pump, and fuel regulator. I actually have the boost controller all the way down and it still seems to creep over 10lbs. at maximum boost. The previous owner crushed the stock blow off valve, it also is not recirculating anymore. So im thinkin ill have to replace it with a recirculating valve until I can get it dyno tuned(I had the same issues with my 06' sti when i changed it to atmospheric). If that doesnt work ill need to buy a new boost controller.

 

[TSIGuy510]

im trying to pull out my IAC right now but am trying to figure out a way to do it without removing the coolant lines, there is no way around it is there?