Hesitation before boost

[bias]

Just added my 3" exhaust and for some reason the car wants to hesitate at 2500-3000rpm it's not major but I know it's something going on. I checked for boost leaks and checked for codes but nothing. Changed the pcv and O2 sensor. Could it be the Tps? If so what replacement do I use? The car doesn't smoke but sometimes I get a small backfire? When I crank it up it want's to idle low until I give it some gas. When it's warmed up it stumbles a little. I adjusted the maf sensor and most of the stumble is gone but the hesitation is still there?

[syphrus]

How did you adjust the MAF? are you using stock ca maf? just curious cause mine acted about like that, and i found out, the car had a ka-e maf on it. Also check your ground, i had to run an extra ground for the MAF right to the body, otherwise mine will run like that.

[bias]

My maf is the stock CA. It has a adjustment screw made into it. I'm not sure about the exact settings I just turned it a little until it seemed to run smooth at idle.

[new200guy]

not sure what maf you have but that sounds like the wrong one came with your motor set. if you have a lambda sensor then you should have a non adjustable maf sensor. that may or may not be your problem. i would say get the manual and go through the tests to make sure your sensors are properly set up.

[RS12Turbo]

They are adjustable...........there is a black rubber cap on the maf body, pop that off, and you'll see a solid hole. You have to drill through that cover to expose the adjusting screw.I don't know if the s13 FSM shows how to do this, but the S12 fsm for the ca18et shows how step-by-step, and the maf's look identical between the two.

On a different note.......have you checked your timing? Mine would hesitate going from vac to pressure under light boost....come to find out, my timing was around 13-14 degrees. I adjusted it to just past the 15 degree mark, I'm guessing 16-17 degrees, and it took care of the problem

[bias]

Thanks! I checked the timing and it was off a little. Everything is good now. It still seams to stumble a little at idle but nothing major at all.

[bias]

Well I thought all was well until the car started hesitating on me again. I just changed the plugs and put the old oxygen sensor in. It's hot as hell and the car is still running way better. I'm taking the O2 sensor back. The one that's on my car is bosch but the part# is not available at my parts store? I thought by replacing it i would get a little better performance but "Oh Well"! More money for something else.

[Masterdebater]

are u running an afc by any chance

[RS12Turbo]

Problem could be your Bosch o2 sensor.....I've never had any luck with them on Nissans. Get a NTK sensor for a '84-'86 200sx with ca18ethttp://www.sparkplugs.com

[bias]

No afc .

[bias]

Thanks for the info I'll look into that asap. I had to take the old one back and store credit so I hope they will have one.

[Masterdebater]

hmm mine was doin this when i tried an fmu. check ur fuel system and make sure everything is flowing in sync.

[bias]

I think it's the fuel pump. I just changed my filter and when I pulled off the fuel line there was no pressure at all. Not too long ago I had a bad line on my tank. I got the pump with the engine I guess some things you can't take for granted and have to get new.

[Masterdebater]

get a walbro 255 lph pump for like 100 on ebay.i got mine for 60 off a friend lol but my buddies sr blew the stock 240 pump in like 2 weeks if that.im sure its a fuel problem

[bias]

Ok I'm a little pissed! I'm new to tuning and turbo so a lot is a mystery to me. I just got a Q45 fuel pump(same as 300zx right?) and spent all day getting it on. I took my car for a drive and the car felt slower than it did before? I still feel some hesitation when I get off throttle but it just feels slower? Boost kicks in on the gauge but I can't feel it until it gets to about .7bar? I have a modded ecu to up the boost it's high for the stock turbo .9 bar but I have been checking it often to make sure it's not blown. I felt power all the way up until now? I have yet to get a boost controller and I'm not sure what the stock wastegate is set at but if it was 7lbs wouldn't the wastegate open and it not read .9bar on the gauge? I'm thinking I need a SAFC to do some fine tuning and a wide band ratio gauge? I don't see any black smoke like it's rich? Please help!!! I need to now what to do next.

[mbmbmb23]

It's probably your timing...I doubt it's your fuel pump. Maybe take this opportunity to add a fuel pressure gauge to your setup to know for sure?

Check all your MAF connections and check that the shielded MAF wire is completely shielded.

Just for the heck of it I would try an OEM ECU and see if it still hesitates like that. Who knows what mystery timing map and fuel curve are on that tuned chip. Could that chip be tuned for a different "butterfly" setup than what you have? I think the butterflies are acutated by the ECU between 2500-3000 rpm so maybe the tune isnt meshing with what you have.

-m

[bias]

So how did changing the fuel pump make so much of a difference?

[rotorific]

Do you have an exhaust leak? Hesitation can be caused by that.

-Gabe

[Masterdebater]

if ur running a stock fuel pump at that much boost u are starving the air of fuel...