SR20DET bogging/hesitation on and off

[Nissan87]

So here's the problem I've been having...

Symptoms when the problem is occurring:


loss of power under moderate load
odd thing is boost will keep rising normally but RPMs stay the same; usually happens when I'm trying to go from 10% throttle to a little more when going up a hill
OR when I'm going from maybe 20% throttle to 30/40% throttle on level elevation
exhaust sounds slightly quieter
sometimes, when starting engine, RPM doesn't go up to normal 800/900 RPM, and only struggles up to about 600 but holds steady and CEL comes on. If I blip the throttle, the RPM goes up to the usual 800/900 RPM and CEL turns off



Other times, the engine sounds and runs great and it sounds "punchier" when blipping the throttle. When those problem symptoms are occurring, the engine response feels like it lags a bit.



Current mods:


Stock blacktop S13 SR20DET (recently rebuilt with OEM parts)
HKS SSQV BOV (vented to atmosphere) (I know, I'm getting it recirc'd soon because I'm using a MAF, but not sure if this is the main cause of all these symptoms)
New Walbro 255lph pump
Stock 370cc injectors
Stock T25 turbo
Stock (and clean condition) MAF
Straight 3 inch exhaust with no resonator or cat
Reman ECU

I was going to wait until I get a fuel pressure gauge, and my wideband hooked up (soon), to further help diagnose this problem, but I wanted to post this to try to get some ideas to what it could be. I don't think it's a boost leak problem because the engine boosts normally without any sudden drops.

Cold starts in the morning or at the end of the work day don't show these symptoms (but noticed it's sometimes happening even at these times now). It used to only happen after a long drive and the engine sounds like it's being restricted a little.


I had my fuel pressure checked at a shop which checked out normal, but they only were able to check it while the car was only under light load or maybe when the symptoms weren't occurring.

I'm thinking it could maybe be a bent fuel line (was told by someone that the fuel pump gets more overworked when it gets hotter, so a bent fuel line could make these symptoms occur only when the fuel pump is hot).

I'm thinking it could also be a wiring or ECU problem. I don't know if this is normal, but ever since I got the car, there would be a tick sound every three seconds coming from somewhere near the front side of the driver side door or kicker panel fuse box. When it ticks, the RPM drops slightly during idle and the clock light on the gauge cluster fades slightly. When it ticks again, the RPM rises slightly and the clock light comes back a little brighter. This cycle would repeat, and it's always been occurring. Other than this and the once in a while "hesitant" engine starts, I don't have any idle issues.

I'm going to be checking the fuses and fuel lines soon, and setting up my Power FC (to rule out the Reman ECU as being the problem, though I'm not having any other problems with it) once I find a reputable tuner nearby. But the really odd thing is this only happens sometimes, and boost keeps rising when the problem happens but no power.

Any thoughts on this would be greatly appreciated.

[dorkidori_s13]

sounds like it might possibly be your fuel pump. you need to be able to monitor your fuel pressure from inside the vehicle while its driving. i had a VERY similar situation like yours occur last year when my Walbro took a dump. for the life of me i didnt think to really watch my fuel pressure gauge in my car as it was rising... turns out it i watched it on various degrees of throttle position accelerating and the pump was no longer supplying consistent and rising pressure (fuel pressure was jumping all over the place). swapped out the pump and car ran like a champ again.

not saying that the pump IS your problem, but walbros really only have a 3-4 year life span at most of daily driving them. ive had tons of issues with them in past and switched to a denso supra pump (which requires a bit of wiring to get a proper 12 volts to it seeing as the S13 wiring only allows for 9-10 volts at the most to hit the pump)

[dorkidori_s13]

also, venting an SSQV wont really cause the issues youre describing. the SSQV is one of the only atmosphere vented BOVs the SR can use that doesnt always cause the the rich bogging issue due to its design and the way it vents air.

i havent had mine recirculated in years and i RARELY get that annoying low end bog out on a stock ECU/MAF setup.

regarding your MAF and claiming its in "clean condition"... have you actually pulled the MAF sensor out of its housing and cleaned it before with MAF cleaner and a q-tip?

OH, while im thinking of it (and this will cause a TON of annoying problems as it did with me for about 6 months), unplug your MAF and look inside the plug... MAKE SURE ALL OF THE PINS ARE MAKING PROPER CONTACT AND THAT BOTH THE PLUG AND PINS ARE CLEAN (again, MAF cleaner works well with cleaning this). if the plug pins are bent out of shape and not making proper contact with the pins in the actually MAF itself, this will cause all SORTS of annoying and unsolvable issues including many like what youve described above! i found my pins were flattened out and not properly contacting my MAF, i wound up just wiring in a new plug and worked like a charm!

[Nissan87]

Wow thank you for your all your tips and feedback. I'll try checking the MAF pins. I've just sprayed the sensor with electric parts cleaner but haven't really checked out the pins and plug.

And I just recently replaced the walbro with another one, thinking that might solve the problem, but the symptoms are still there half/most the time