Fuel delivery issue??

[s13sucksalot]

Okay, the car's been running goofy for awhile. what will happen is at higher RPM, the car will start engine braking all on it's own, regardless of throttle positiong. After pulling to the side of the road, and letting it sit for a while (and after a number of unsucsessful startups) the car will run again, appearing to have no problems. When it's doing this, before i pull over, it will occaisionally act like it's getting gas and pull real hard. i've heard ideas like the fuel pump, fuel pressure regulator, and mass air-flow sensor are going bad. i don't know what to think any more. i went out and drove the car like i hated it yesterday and it wouldn't act up and today, when i was passing a semi, it decided to go south. The only thing that really bothers me is how irregular this problem is. Any ideas or help would be greatly appreciated.

[s13sr20chris]

http://www.nicoclub.com/zerothread?id=81587

check that out and see if you can narrow it down to rich, lean, spark, etc. type of prob.

[s13sucksalot]

thanks for the input, but i think it's something more than this... we recently replaced the head gasket (that was a blast) and had the whole thing apart. everything seemed to check out okay.

[s13sr20chris]

your problem sounds like a maf that intermittantly messes up the a/f ratio. try watching maf signal voltage while you drive around.

[s13sucksalot]

what do you mean? should i hook up a voltmeter on the positive side of the MAF plug and make the car act up (this involves taking the car up to around 80-90)?

[s13sr20chris]

yeah, thats it. i will start with one wire and drive around till the car messes up. if the meter does not show anything then i move on. when you find the wire that moves with the engine you are geting somewhere. if its the signal wire then you prob have a bad maf.

[s13sucksalot]

thanks for the advise. the car messed up again today so when i pulled over to check thins out, i thought i would give everything a tug/wiggle test. when i went to tug/wiggle on the MAF plug, i realized it had dislodged itslef. plugged it back in, and it seems to be running okay. i got it home and made a bail out of a paper clip to keep it plugged in. i guess i'll see what happens.

[s13sr20chris]

cool, hope it works out.

[s13sucksalot]

nope, didn't work. car still screws up, but, it continues to take less and less time for it to get running again.... man i'm sick of this

[s13sr20chris]

hmmm, it really sounds like its in the maf circuit just by the way you fixed it the other time. if there is any way to watch the maf(preferably at the ecm) that would be very helpful.

[s13sucksalot]

do you mean hook up one of the ECM monitors or something?

[s13sr20chris]

no.i know this is not really feasable for a lot of guys but its really helpful to do it. you have to run probes from a multimeter to the maf signal line and the batt negative terminal. watch the meter display while driving to see if you get anything wierd.

[s13sucksalot]

okay, i'll try to get a bunch of wire and run something in through my window or something. BTW, the car hasn't acted up in quite some time now... Maybe it just had a bad bowel movement or something... i don't know....

[s13sr20chris]

dont you hate that! happens to me a lot. its a good time(when the car is not acting up) to get a good baseline reading on many sensors. watch what the maf and other sensors do so you can understand them more when the car is messing up.

[s13sucksalot]

i've recently put a new exhaust on it (high flow cat, 2 1/2" piping, new muffler). do you think the change in backpressure could have fixed or at least affected the problem?

[s13sr20chris]

only if the old was restricted.

[s13sucksalot]

it wasn't really restricted. it still had the factory cat and factory piping afterwards. there really wasn't much to the muffler. just a resonator...

[s13sr20chris]

by restricted i mean clogged up with trash or converter chunks.

[s13sucksalot]

oh, i don't think that it had any of that going on.... thanks for your help with all this s13sr20chris, i drove it for about 10 hours straight a few days ago, didn't act up once. i'll be going to dallas this wednesday, i guess that'll be the ultimate test. anyhow, i think i'm done with this forum and i'm going to start another or just read up on my heater... peace out!!

[adidasks7]

Coincidentally, it sounds like you have the exact same problem Im having. Please let me know if you figure it out. 4 me, once I go over about 4k rpm my car will bog, feels like im losing fuel, meaning i cant pass others very confidentlly and struggle up hills. Tho i drice a 99 maxima SE. Ive considered all the problems mentioned here. It seems to be getting progressively worse, the last time I, my check engine light came on and off while it was happening. I rented an OBDII scanner, and the only thing that came up was knock sensor malfunction. Which i suppose would make sense. I will let you know if I discover that this is the problem, I would appreciate any insight anyone else may have as well. Thanks !

[s13sucksalot]

Man, i don't know what to tell you. Honestly, i think my car worked the problem out of it's system or something. I just went to Dallas this previous weekend (4 hour drive) and it didn't act up once. Even after doing quite a bit of highway racing and a little drifing. go figure. If you do manage to figure out anything, please let me know in case this problem does present itself again.