SR bogging horribly!! Searched to no avail!!

[Speedracer5767]

Going to attempt to make this short and sweet. I've searched for hours and days on end. So on with the issue.
95 240, Stock S13 Blacktop, Walbro, FMIC, Z32 Fuel filter.

On cold start ups it runs great. After the engine has hit operating temperature it bogs horribly under boost. Coil packs all tested. 9 ohms resistance. TPS voltages are .5 closed and 4.45 WOT. New knock sensor and CTS. Timing is dead set on 15°. Idle is 850 at NOT. New NGK COPPER 7'S gapped at .28. Zero boost leaks. O2 seems to be fluctuating properly. Noticed in Consult The timing is being retarded to around -9° when this issue is happening. Wideband also reads high 10s - low 11s when engine temp is cold under boost. High 13s-14s when engine is hot and under boost. I'm truly at a loss for ideas. Need help severely! Thanks for any help in advance!

[Speedracer5767]

Bump for anything at this point. I also ohmed my injectors and all are 11.6 -11.7. Im leaning towards computer or maf.

[s14girl]

i found that with mine, but it was parked up with months, i took off the vacuum hose... well actually two of the air leads.. not to sure which was the vacum hose so i took both of them off, there very small on the left side under the bonnet.. leave them off for about 2 days and it should improve, it could backfire a lot changing between gears with it off but dont worry. you will notice a change in your petrol for the 2 days and not in a good way but best of luck with it

[Speedracer5767]

I dont think i quite understand what it is u did. U un hooked two vacuum hoses? Please elaborate a little more. And thanks for responding btw!

[s14girl]

http://www.keywordpicture.com/keyword/s ... m%20lines/ thats the best picture i can find.... il have my car back wednesday.. (kit gettin sprayed at the moment) but il have a look at exactly where they are so you can find the easier... pic aint the best so il write up Wednesday and let ya know... also what is the car boosting at...? what type of spark plugs are in the car, do you have a front mount intercooler? and last Q. what sort of fuel pump do you have in it?

[Speedracer5767]

Im running a walbro 255, fmic, and ngk bkr7es-11 at .30 gap. Stock boost 8psi.

[s14girl]

ah you know ur stuff too.. im waiting for my front mount and the same fuel pump.. il have car back tomorrow so il let ya know tomorrow evening about the vaccum hoses, my boost is at .4psi find it picks up a lot faster at that

[Speedracer5767]

Yeah it's aggravating that it only does it when the car warms up. I'm actually leaning towards an oxygen sensor causing my problem. Seeing as how when it's full throttle and it gets past its little hiccup it boosts/pulls fine. From what I anderstand at full throttle the oxygen sensor goes into open loop and it's at this point that it wouldnt make a difference because it only does it under partial throttle and half throttle when the O2 is actually sending feedback to the ecu. Regardless I'm putting a new O2 in anyway just for safe measures.

[surfpac]

Check the fuel pressure. Could be bad FPR. High 13's to 14's under boost doesn't sound too safe.

[s14girl]

sorry about the delay, car def 100 % back tomorrow and il check then, it could be ur 02 sensor but when you diconnect the vaccum hose it fools the ecu to think there is nothing wrong with the 02 sensor and by passes it...

[timmysvert]

i had the same problem with mine. are you running the stock fpr ? if you are whats happening is the fuel pump is over powering it and causing the spring to stick. i switched over to an aftermarket fpr and havent had a problem.

[Hoffman5982]

adjust your tps. Should be .45, not .5. Although it isn't as far off as mine was, but when mine was off it would stumble pretty bad if I gave it more than 1/4 throttle. See where that gets you

[Cgeigert]

What about coolant temp sensor? I'm having similar issues but it does it all the time now, not just when hot.

[PyR0NiAk]

What about coolant temp sensor? I'm having similar issues but it does it all the time now, not just when hot.

Whoa. Guess I've been afk. My bust guys.

Cgeigert is on the right path. Start with the coolant temp sensor.

adjust your tps. Should be .45, not .5. Although it isn't as far off as mine was, but when mine was off it would stumble pretty bad if I gave it more than 1/4 throttle. See where that gets you

This is also correct, but I don't think it's the reason for your idle changing.

Also, stop boosting when your motor is cold.

[Speedracer5767]

Small update:
I re-adjusted the tps and the car got a little better but i didnt like the range on the meter readings so i bought a new one. ( for those interested a 5-speed 93 sentra se-r 3 pin tps is the one to get. Exact fit. I put it on and adjusted it to. 45 at closed throttle. At wot the voltage only goes up to 4.1. Im hoping thats ok? The car ran better but now I have a good solid miss that I did not have before. It lightly sputters at idle now also. It didnt do that as bad before. so I'm thinking the tps was bad and was masking the main problem of the misfire. My idle also went up a couple 100 rpm's as well. As of now I'm going to replace spark plugs again and double check for a bad coil or a vacuum/boost leak again. The coolant temp sensor is brand new. I put that in when I did the swap. I think I'm getting close to fixing the problem. Also forgot to mention that it does run better now cold than it did before. Leading me to believe that the tps was indeed not working properly seeing as how the car does run better with the new one. Now to find a misfire......

[Speedracer5767]

I was also wondering if anyone has noticed the very close similarities between a 2000 to 2006 2.5 sentra or altima coil pack with the sr's. The connectors are the same and its a 1 bolt hold down just like ours except the hold down bolt is not offset to one side it's in the center of the coil on the front. I ohmed it out and it comes to 1.3. Could it be possible that is a feasible option to use that one? I'm not sure what the primary and secondary coil windings are as far as relation to the sr's. It just seemed to me like it would work since it's the same length as the maxima coils and the same connector. Google this part number and you will see what I'm talking about. AIC-4001G. Maybe I stumbled upon a good replacement?

[Speedracer5767]

Just an FYI....... i had a 2001 maxima come into my shop today. I decided to check the coil pack design and it seems that these are the ones all the forums are referring to except they say 1995+. However it all depends on what harness your engine has. I compared the 2001 and 1995 and they are different in design. The 2001 has a 1 bolt hold down like my sr has. The 95 has a 2 bolt hold down, and also the bolts are smaller. But i still have one question. When i look at the sr coils there are "E(-)__+__I" on the maxima coil they are "+__-(E)__I". I dont want to go back feeding circuits and fry anything, so when these coils are supposed to be direct replacements, no one ever talks about any re-wiring or re-pinning.

[Speedracer5767]

Does anybody have any insight on this???

[PyR0NiAk]

SR Coil packs are abundant on most websites, so people don't typically bother with that replacement.

[Speedracer5767]

So i rechecked for boost leaks and found 2 VERY tiny ones. One was the vacuum port on the bottom of the TB. My little cap was not sealing well enough. The other was on the wastegate to IC piping. I put clamps on both just to be safe. Still didnt fix it. Then i noticed something odd......I was using a semi-soapy water to look for leaks and something told me to spray around the oil dipstick tube. So i did and noticed that there was some air coming out of there. Not a crazy amount but enough to make little bubbles. Keep in mind I was pressurizing the system to like 25-30psi. i know that the motor will never see this much boost but I am still a little concerned. I am going to put a new PCV valve on tomorrow as a precaution. And my catch can setup is as follows:
Hose from crankcase to stock catch can--->hose from top of stock c/c to T-fitting on valve cover--->hose from front of T-fitting to aftermarket c/c---> last hose from aftermarket c/c to intake b/w MAF and turbo like stock . PCV valve is still routed like stock(from valve cover to intake line assembly). I also recently put in a new set of plugs and noticed something different than the last four sets. They were a dark brown. Seems to be burning oil? Im running Full Synthetic Mobil 1 10W-30 btw. All the while the car is running slightly better. But the main issue still persists...Any ideas????

[Cgeigert]

Unfortunately you're just going to have to run down the whole chain of things to check. I just had to do the same thing and it happened to be a bad battery. Luckily I have two sr so swapping parts was alot easier. What exactly is it doing now. Not boosting at all? Bucking? Can you tell if it's air, fuel or spark related? And if you haven't already done so, check for codes.

[Speedracer5767]

Final update!!!!!--->

After trial and error of swapping parts and buying new ones, I have fixed the problem. I recently purchased an intercooler setup for an S14 SR, had to fab a bit but it looks way better than my old one. Problem still persisted after the new kit, so that narrowed out any sort of a boost leak( new couplers and T-bolt clamps too). I started to look into fuel issues and all the injectors checked out great. No leaks or malfunctions, walbro worked fine with last setup and F/F is a new 300ZX, however......I went back to my previous suspicion of the FPR. I found a guy that had an Aeromotive Adj. FPR already setup for an SR. He was kind enough to let me borrow it to test with. So I bolted it on and went for some test drives. At first my a** dyno couldnt tell a difference, still felt somewhat "held-back". But the stumbling was not as noticeable....After about 9-10 good pulls up and down the highway and slowly upping the pressure at each stop, I apparently reached the magic number. Ending fuel pressures:

With Vacuum Connected: 39psi
Without Vacuum Connected:49psi

I feel pretty safe with these numbers. A/F stayed around 11 +/-2 at WOT. Mostly on the richer side of 11.
Slightly more stalls due to BOV venting to Atmosphere and it is much richer than with the stock FPR. It was maxing fuel pressure with vacuum at 32psi. Definitely hid itself on the UEGO. Consult was no help either due to slow OTC Scanner . Unfortunately my ECU had no LED so codes were unattainable also. Keep in mind this engine is in stock form, with32K miles, FMIC, WALBRO, Z32 F/F and BKRE7's gapped at .28.

This may have seemed a little drawn out but I didn't want to be that guy who never posted his fix. I'm sure there is someone having a similar set of symptoms as mine and could be going crazy like me . Its forums like NICO that help us. Hope this helps also.
-end rant-