I have a 99' Z24. just put in a turbo system about a month ago. did a t3/t4 with external wastegate. This is my problem. for some reason the car is now hesitating under low rpms. once you give it some gas it kicks ya in the butt and your good to go. had it to the shop cause the check engine light was on and a few codes came up. IAT sensor. i actually popped it like a cork from the charge pipe. couldn;t find one out of a Z24 at the wreckers but i did find one from a 2.2 (pre-ecotec) and used that. figured it was the same. MAP sensor. not to sure about that one. i was playing with it on the weekend. And yes i do have a check valve on it. the one thing i was wondering was though. on a stock engine the vaccum line runs from the manifold to the MAP sensor. so its a sealed connection. At idle it is sucking air in threw the check valve in bursts. when i put my finger over the vavle the engine idled like @!#$. and yes i do have it on the right way. i actually just checked it thinking i did screw it up. try to suck air in, won't let you, but blow air out and its no problem. third code was an O2 sensor down stream (cat). Now i know i screwed up on this one. when i wired in my a/f gauge to the pink/white wire i cut it, then wired it in. but it never affected my engine before. i also read that a vaccum leak can screw with the O2 sensor. my boost gauge reads about 15 vac. but Uchi says his is at 20. vaccum leak????

first of all you need a 2 bar map sensor, not sure if you have it or not...stock is 1bar only reads vaccum... just like your stock pcm!!!

lol, i dont even know where to start! lol....

first step is turn your car off. second step is getting hptuners, an fmu, ms, anything to add fuel based on boost...third step is getting a 2bar map sensor... and... what do you have a check vavle on? the map sensor? thats another big no no, map sensor needs to see vaccum and boost

i really hope you are kidding about cutting the wiring to your down stream o2 sensor and wiring in your wideband, cause that would mean you did not read anything on this site before starting your project... no offense, that could possible cause a few electrical problems in your pcm....uuhhh, are you on stock exhuast? if so, stop it... get an exhuast

my guess is a lot more then a vaccum leak based on the info you provided...

oh yea, get a new iat sensor.... gm screw in one, do a search... its a camaro part, you'll need a weld on bong...

im by no means an expert, but if you have any questions pm me, i'll try to help! Good Luck



|Forged 8.9:1 Wiseco Pistons|Forged Eagle Rods|HPTuners|60trim|Tial Wastegate|
|Precision Intercooler|2.5" Exhaust|2.5" Charge Pipes|630CC Mototron Injectors|
|Stock: Fuel Pump, Transmission, Manifold, TB, Head, Head Gasket, Ignition, Suspension...|

im running a 1 bar map sensor with no check valve.....then i bought a check valve and put that in.......then the car gave me some hesitation problems ...so i remove it and never had a problem again......but i have to fake the 2 bar with my HPT...hope that helps any...

Yeah get rid of the check valve...these MAP sensors don't seem to like them very much. Just run without one and you'll be fine. That should take care of your low RPM hesitation. At cold idle, my boosted 2.4 is at 16-17 vacuum, and after it warms up it's about 21 vacuum. You may have a vacuum leak and yes that does mess with the O2 sensors. Check all your connections and anywhere else there could be a leak from.


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450WHP Turbo Ecotec swap in the works...

Yes its the stock map. the check valve should have taken care of the boost. the reason for the valve is to vent the air under boost and still read pressure under vac.

exhaust is 2 1/4 from the downpipe.

a/f gauge and wideband are two different things. i hooked up an a/f gauge. its not hooked up anymore though.

remove the check vavle and put the stock z24 map sensor back in.

OK. but will that be affected by boost. cause i have heard that non-stop. Put on a check valve!!!

Need to remember. this problem only occures at rpms between 1000-2000 and only when the engine is cold. after about 10 minutes, the car is fine. that why i still wonder if its the pink/white wire that a cut on the O2 sensor. cause i did extend it with another wire. so what i'm thinking is that the wire i used isn;t the same gauge, so the heater isn;t getting enough power under low load and that is why it is stuttering. cause once it heats up there is no need for the heater and it runs good

if it is the o2 behind the cat it has nothing to do with driveablility. the second o2 sensor only senses catalyst effieciency (if your cat is working properly)

OK agreed. O2 is out of the question now i think. since its the heater wire i tapped. should matter. leaning towards the MAP sensor. at idle air is coming ut of the valve in bursts (i checked to make sure it was in right. blow and it goes threw, breath in and no air). but when i put my finger over the valve to seal the vac car idles real rough. Since stock is just a vac line from the manifold to the MAP. putting my finger over the valve would be the same thing.

I also have a MAP sensor off of a 04' ecotec engine. kinda just sitting in my garage. Ill that work? can;t remember if its a 2 bar or 1 bar. also would the exhaust manifold O2 sensor off of the ecotec work as well. cause i think its a 2 wire.

Take off the check valve. Boost will not affect your stock MAP sensor. This will fix your problem.


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450WHP Turbo Ecotec swap in the works...

removing the chekc valve does nothing. read my post then suggest something. A 1bar MAP sensor can't handle boost. All a check valve does is vent the boosted pressure into the atmosphere. The problem only occures at LOW rpms and when the engine is cold. I put in a MAP sensor from an 04 ecotec engine i have and it didn;t solve the problem either. But the sensor does work.

You can't use a 2bar MAP with an Ecm set for a 1bar MAP. Also, there's no such thing as a 1bar no handling boost. It will peak at 5v at 0Hg/psi but won't go higher if you have boost. So yeah it will handle it but won't tell the Ecm.



Gilles
2.3 Ho

Others have blown their diaphram inside the MAP sensor because of boost. that is the reason for the check valve. When you start to look into the subject, everyone says to use a check valve. The MAP sensor from the 04 ecotec isn;t a 2bar. its a 1bar. but i thought i might be having issues with mine, cause it threw a code before