backfiring under boost, only at WOT

[burntricer]

As the topic says whenever i punch it i cant boost to the stock 7 psi, it coughs, sputters and back fires, with a big black cloud of smoke. I first thought boost leak. but there is ABSOLUTLEY no way there is a boost leak, ive checked, and checked again with a boost leak tester.

heres my set up

S13 RedtopStock setupKA24E mafsFord Probe BOVstock everything else...

i cant figure out why i cant boost properly

[nwmrkt]

does that BOV recirculate?

[burntricer]

yep and it is

[dcmxsa]

how are your spark plugs? and are they gapped right?

[IanS]

could be a TPS problem

[mistyblue240sx]

hey i had the same problem a while back.....it took me like three weeks of testing......after taking almost everything apart.....i pretty much gave up cause everything seemed to be functioning properly.....so a friend suggested that i regapp my sparkplugs.....and i was like no way that cant be the problem....so i regapped it to like .28 took it for a drive....and i was like whoa ....that was it....CHECK YOUR PLUGS....it only takes like 2 minutes

[92SR20S13]

+1..probly your plugs..i just went through the same problem!

[burntricer]

plugs were good, gapped per spec, just black from running rich.

[adrianfromthecastle]

Mine does the same... more on the end of 1st and 2nd gear... I'd like to know too, I'm thinking plugs too tho, cuz its been awhile and I think its time to change my plugs out anyways

[burntricer]

plugs are solid, now, my car also doesnt wanna start in the morning or after it sits for a couple hours, i have to hold the key to keep it going till it picks up... any thoughts on that aswell?

[burntricer]

one more thing, this only happens to me when i mash the gas, but if i roll into the throttle it flys. and boosts 5 psi no prob

[IanS]

it sounds like your flooding out when you WOT, have you checked your TPS voltage. What octane fuel are you running?

[mochee_garage]

if you checked the plugs.. probably your TPS..

[burntricer]

it sounds like your flooding out when you WOT, have you checked your TPS voltage. What octane fuel are you running?

i run premium which is 91 here... i had checked the tps voltage before. ill do it again tho, what is optimal?

[T-rev]

check your coil packs, or have them tested. I dont know how to test them or if a shop can or whatever, but I think your boost is blowing out the spark.

I had the EXACT same problem, to the letter. Car ran great until I WOT'ed it and then it felt like I lost 1 cylinder. I drove like that for months, until one of my coil packs bit the dust completely and it ran on 3 cylinders. I tested the ohms on the (dead) coil pack as well as a good one, they both came up ~1 ohm. I replaced the buggered coil pack and hang-freaking-on! we are firing on all 4 cyl again.

I was told a coil was either good or bad, no in between, but I guess they can be on their way out

[Nismotouched]

check the coil pack resitence, mine went back and I had a major misfire over 3000rpm...so annoying.

[chicos240]

You have no vacuum leaks?You have no boost leaks?Whats your timing set at?I have never seen anyone running a KA maf on an SR.Cough and sputter sounds like a not enough fuel or air issue.How is your Fuel Pressure?Have you upgraded your fuel pump yet?Before you go crazy, try the plug idea, it is the cheapest.If you know anyone with an SR maf, see if you can borrow it.keep us posted

[Tx-Sx-FS]

id say MAF issue is nothing else, when i was settin up my car i had 2 connectors backwards and it sputtered real bad...check wiring

[IanS]

You have no vacuum leaks?You have no boost leaks?Whats your timing set at?I have never seen anyone running a KA maf on an SR.Cough and sputter sounds like a not enough fuel or air issue.How is your Fuel Pressure?Have you upgraded your fuel pump yet?Before you go crazy, try the plug idea, it is the cheapest.If you know anyone with an SR maf, see if you can borrow it.keep us posted

there are lots of people on here running KA24E MAFS, including myself, its the KA24DE MAFS that is not compatable, It deffinatly sounds like spark is being blown out due either to a bad coilpack or improper plug gap, what kind of spark plugs are your running, what heat range and brand.

[chicos240]

Thanks for the clarification, i came from a ka24de to an s14 sr20det. i know not of these jedi tricks

[burntricer]

there are lots of people on here running KA24E MAFS, including myself, its the KA24DE MAFS that is not compatable, It deffinatly sounds like spark is being blown out due either to a bad coilpack or improper plug gap, what kind of spark plugs are your running, what heat range and brand.

could be because 3 of my plugs bolt holes are broken, ill secure them down tighter and see what happenes

[chicos240]

What plug holes are broken. Are you saying your spark plug holes are stripped?

[T-rev]

its probably just the small 10mm bolt that grounds the coil pack to the valve cover thats stripped, since it just threads into aluminum.

A common misconception is that this bolt is to hold the coil pack down, it does that, but more importantly it is the coil packs ground. No solid ground means you have intermittent coil packs not firing.

Crank them suckas down, even if you have to re-tap or use a larger/longer screw

[chicos240]

O RLY?I was putting my engine back in, and noticed that the coilpack had a black wire with a bare end on it. So I further investigated and peeled the electrical tape off and soon found that this wire was connected to all the other grounds from the coilpacks themselves. I left it dangling. When I was ready to start the engne, I turned the key and there was no love. There was crank and movement but no fire. I took that little dangling cable that was joined to the other grounds and I connected it to the head via a screw...and voila! It all started beautifully. So my question is, if those little screws are for grounding? Why didnt it start up?Or why would the coilpacks be grounded to another wire?

[IDriveFords]

The screws may help with grounding but they are not a ground. First off those screws go into the valve cover, which has a rubber gasket between itself and the engine block which means it isn't grounded. The main ground wire is in the actual engine harness and ties into all the other grounds. I know this b/c I have unloomed and reworked almost the whole freaking harness and the coil packs are definetly grounded within the harness. Although I do believe the coil packs are grounded to the valve cover to some extent but that is by no means a proper ground and probably wouldn't be enough. BTW if you are running the KADE maf with an sr I dunno how you got it to work because the ECU mapping is completely different; however I've heard the KAE maf does work. BTW the coilpacks are really easy to check even if you don't have an ohm meter: get a friend and pull them one at a time and put a well insulted flathead screwdriver in them and position it somewhere on bare metal to get it to ark (try the nissan engraving on the valve cover). disconnect the fuel pump and have a friend watch while you crank the car. Crank it until you see it ark twice and then stop. Do this with all 4 cylinders. BTW you don't have to hold the screwdriver if you/your friend wanna avoid being shocked; you can usually prop it up somewhere and get it to stay. Now if you don't particularly like said "friend" tell them ot shove their finger inside where the coil pack goes over the plug and say "ouch" when it hurts. *Disclaimer: I am not at all responsible for any serious injury, death, or loss of bladder control that may result*
Modified by IDriveFords at 4:57 PM 8/29/2007

[T-rev]

ok my mistake. I had another look at the coil here and saw it has 3 wires, + - E, I guess that would be pos, neg and signal. When I had the coil packs out I noticed the bolt that holds them down goes through a metal insert, I just assumed it was grounding to the head via the VC, again my bad.

However, if he doesnt have those tightened down, the spring inside the coil pack could lose contact with the spark plug, and result in the same issue.

[IanS]

FYI I broke one of the coilpack bolts, I figured it would be ok, and it was, until I went WOT, it would miss very annoyingly, I thought it had popped up, so I pulled the cover to find it right where is should be, i stuffed a chunk of radiator hose between the cover and coilpack to hold it down tight, car still missed hardcore, I then used an extractor to pull the old bolt and I put a new one in, the miss was gone. It may not be the only ground, but I garuntee you need it. Ive actually seen a grounding panel that connects all the coil pack bolts together, I think enjuku sells it, but I cant seem to get onto their site right now.

[hungryjoseph]

replace your coilpacks

[chicos240]

Like this one...that phase2 sells.

I dont see why you cant make your own

[burntricer]

plugs are brand new NGK BRK6ES11

im going back out to tap out the holes for the bolts

now its doing something weirder, popping and sounding like a miss at 5psi...