backfire between shifts, severe bogging sometimes, recirculated BOV

[KingTurd]

Greetings all.

I have a relatively annoying problem with my sr20det (s13). After boosting slightly (or moderately), releasing the gas and then pressing the gas again, I usually get a backfire. It really only happens when boost of any kind is made. It will only backfire once I touch the gas. For example, if I make slight boost, release the gas and coast, nothing happens. However, if I make slight boost, release the gas, coast for about 2 - 3 seconds and touch the gas it will backfire, but only the instance I press on the gas.

My blow off valve is not vented to the atmosphere, its recirculated. Its a TurboXS RFL. I am not sure if I have it too tight or too lose. It does open after very slight boost (as well as when im making no boost at all), and opens very well upon higher psi. Im afraid to make it too tight as I might risk surge, yet I sometimes think its too loose. Anyone got any tips on how to tell its just right? The car idles at around 15-16vac and coasts around 20-21. The spring seems to be decently stiff, but I am not an accurate gauge of that As of right now it has one washer installed and the cap is tightened all the way down.

Also, in the same token, the car "seems" to pull timing like crazy. The timing is set to 15* w/ no TPS as per the manual. For example, sometimes the car will feel very sluggish/slow/retarded when boost is being made, and other times it pulls hard. I might have found a source, however. The manual says that the TPS sensor should be adjusted between .35 and .60 volts. Those arent exact numbers (I cant remember what they are at the moment) but I know that its between those two. However, when I was adjusting it, I could only get it as low as .30 and as high as around .47--meaning turned all the way one way and the other. Granted the voltage is within specs, but it just seems odd that the highest voltage I can obtain is .47 volts and not at least .60 volts. Maybe this is the culprit? I had it turned all the way to one side, reaching the .4x volts and drove around like that. It would lag severely after a while of driving it. I havent checked the resistance on the TPS, only voltage under operation. As of right now the tps is basically set in the middle, and it still does the hesitation, but not nearly as frequent.

Maybe the TPS is causing the backfire? It does smell slightly rich. Also, when I bought spark plugs I got them for a '91 ka24de as I had read somewhere that these would work (gapped correctly, of course). The sluggish operation seems to happen with time, almost like after things start to get heated up. Then again, it pulls file other times. Lets face it, intermittent problems blow.

Any ideas? This message seems rather unstructured but I was trying to type the problems as I thought of them.

Thanks in advance!

[FSUDrifter]

my car is having a similar problem. seems to bog sometimes under boost. have you checked for boost leaks?

[KingTurd]

I checked for boost leaks a few times after I put everything together, and it was solid. I dont think it would be a boost leak because the hesitation would happen all the time (or most of the time). This only happens rarely-intermittently. It still feels like timing is being pulled. When the car is operating correctly, it pulls pretty hard. When the timing gets retarded, it feels worse than a geo metro (relatively speaking).

Anyways, I checked the resistance of the TPS today. It was pretty low. So, I adjusted the TPS until the resistance read 0.7kohms as per the manual, gas pedal fully released. The resistance seems to move smoothly as the gas is being pressed. However, according to the manual, when the gas is fully pressed, the resistance should read "about 5 kohms". Mine reads 8.4 - 8.5kohms at WOT? All of this was with the engine at operating temperature as well, not while it was cold. If I remember correctly, resistance lowers as heat rises. I could be wrong though Also, when the resistance of the TPS was adjusted to 0.7kohms, the output voltage of the TPS while the car was running was way off. I believe that the voltage at idle/resiting position was around 0.26 volts, where it should be at least 0.35volts. Im getting all my information from the s14 FSM, so I am wondering if all the values im getting are correct for my s13 but would be incorrect with an s14?

A friend of mine that is a nissan tech said that for some reason the car is dumping fuel into the car while I am on deceleration, causing the backfiring when I press on the gas pedal again. I guess Ill research some sort of closed position switch, if the s13 redtop sr20 even has one.

Any ideas?

[KingTurd]

Actually I dont know if the TPS is the problem here or not.

I have several FSM's for different cars: the s14 sr20, an older s13 ca18det (aka 200sx) and a b13 (for the sentra ser in particular).

Now, according to the s14 FSM (I have an s13 redtop RWD), the details about the TPS are the following:

Resistance (in kohms):Completely released - 0.7Partially released - 0.7 - 5Completely depressed - Approximately 5

Voltage at rest: 0.35 - 0.65 volts.--------------------------------------------According to the b13 FSM, the supposed TPS replacement if I were to get one, lists the following:

Resistance (in kohms):Completely released - approximately 2 Partially released - 2 - 11 Completely depressed - Approximately 11

Voltage at rest: 0.35 - 0.65 volts.-------------------------------------------

After some adjustments and a little modification, here is what I was about to get:

At rest: 0.50 volts/ 1.34 kOhmsWOT: 4.13 volts / 8.95 kOhms

The voltages seem to be right but the resistance is not within specs. I think Ill just start looking elsewhere. Not sure where to start though. From what I remember, backfiring usually results from rich conditions. Also, Ive read from here that backfiring is common among sr20's. And yes, I do have a test pipe.

Perhaps leaky injector? I bought spark plugs from a DOHC ka24de, gapped within specs. Wonder if that has anything to do with it.

[KingTurd]

Checked the injectors, no leaks and o-rings are fine. Guh. There was a tiny leak at the BOV. Fixed that, still backfires. Other than that, no boost leaks at all.

Maybe sr20's are meant to backfire. I dont have a catalytic converter, exhaust is straight through. It just gets annoying after a while!

[AE86Gio15]

check the coolant temp sensor

[1wayIsSideways]

im having a similar problem with my black top. i have a stupid hesitation from around 3300rpm until 4400 rpms and when i hit full boost (6psi) it pops and sputters and often backfires. My car also seems to be running rich. im new to sr's and everyone tells me something different. think it could be the same thing?

[KingTurd]

im having a similar problem with my black top. i have a stupid hesitation from around 3300rpm until 4400 rpms and when i hit full boost (6psi) it pops and sputters and often backfires. My car also seems to be running rich. im new to sr's and everyone tells me something different. think it could be the same thing?

Well, mine does not backfire while accelerating normally. Mine backfires after a decel after accelerating. For example, if I am driving normally and slightly boosting, Ill let off the gas to shift. If I press on the gas within 3 seconds or so after the BOV releases air, it will backfire usually 90% of the time. It ONLY backfires the instant I press on the gas. If I let it coast for like 7 seconds and then press on the gas, no backfire. Now, if my BOV was vented it would be an easy fix. However, it is recirculated and there are no leaks. This is why I am rather confused on my part. For some reason it keeps dumping fuel in after I let off the gas, of the BOV is causing it to mess up. The BOV I have is a TurboXS RFL which originally was made for venting, since it originally came with the horn. However, I took it off and replaced it with a tube so that I could recirculate it.

Your situation seems like an easier thing to spot, e.g. boost leak. However, checking all the normal sensors (tps, mafs, coolant temp sensor) might be a good thing to check for you.

[1wayIsSideways]

i took my 240 for a drive earlier and realized mine backfires EXACTLY like yours. my BOV is a greddy. but it is open. maybe i should recirculate it. i will go try that now.

[TchouikoS13]

Check you sub-harness. Mine was all ****ed up and i had simlar problems as yourself.

If i gave it a wiggle it could mean the difference between running on 4 cylinders and 2.

[KingTurd]

i took my 240 for a drive earlier and realized mine backfires EXACTLY like yours. my BOV is a greddy. but it is open. maybe i should recirculate it. i will go try that now.

Well if you have the option to recirculate it, then it would be nice to have another test in parallel with mine. I would like to see the results of your BOV being recirculated versus being vented. I started to get into cars when I bought a DSM--probably one of the biggest mistakes in my life, but I learned so much from it because I was fixing it every week. Anyways, I remember the stock BOV was vented when I bought it. I had no idea what a blow off valve (or a recirculation valve) was at that point in time. however, it would backfire almost exactly the same. I recirculated it and it ran just fine with no pops.

Then again, all of the intake and exhaust was custom made myself. I really dont know if that is the issue, as there are no leaks and its 2.5" piping.

Check you sub-harness. Mine was all ****ed up and i had simlar problems as yourself.

If i gave it a wiggle it could mean the difference between running on 4 cylinders and 2.

Thanks, Ill give that a shot. A loose wire could explain the randomness of my hesitation/timing retardedness (is that a word?) Luckily my swap was a complete harness, uncut wires and everything. I might have scraped some shielding off the wires as I was pulling them through the firewall. The only thing I really havent checked yet are the voltages at the ecu. It appears that the voltages coming from the sensors I have checked are all where they are supposed to be. I am just hoping to possibly get the backfiring cleared up first as it might ruin the turbo or the engine if its running rich all the damn time.

Thanks for all of your suggestions and keep me updated!

[aaron m]

Hmmm, i have a similar problem too.

[1wayIsSideways]

recirculated it and back fire is gone. but the hesitation is still there. i think it is my fuel pump since its still the stock ka one. and it probably doesnt help that i have a bad o2 sensor.

[KingTurd]

recirculated it and back fire is gone. but the hesitation is still there. i think it is my fuel pump since its still the stock ka one. and it probably doesnt help that i have a bad o2 sensor.

Glad to hear your backfire is gone. I am also using the stock ka fuel pump and I havent had a problem with it yet. Hell the fact alone that my car runs rather rich leads me to believe its suitable for my setup as is, but im usually wrong. *puts on flame suit*. So far no melted valves yet! Also, how do you know you have a bad 02 sensor? Did you put the ecu in diag. mode 3 or whatever it is?

[1wayIsSideways]

the only evidence i have to explain a bad o2 sensor is the fact that the previous owner said it was bad and also when i first crank it and drive it drives horrible for a min or two.

[KingTurd]

the only evidence i have to explain a bad o2 sensor is the fact that the previous owner said it was bad and also when i first crank it and drive it drives horrible for a min or two.

Well you could always do a resistance check and ecm diagnostic check just to be sure. No sense in spending $70 if you dont have to.

[1wayIsSideways]

i already ordered an o2 sensor and walbro fuel pump. hopefully these fix my problem. got them both with a hks turbo timer harness for $215 shipped