so coming home from the track my car starts acting up.



at part throttle, like keeping pace at highway speed, it just stumbles a lot, all jerky and bleh.

so i get home, adjust the tps, it was .6 at idle instead of 1.

okay that should fix it, right? wrong. still stumbles, if anything worse.



stumbling goes away when im engine braking or giving it more then part throttle.



what could be causing this?

j9 thought it could be the afm, so i replaced it.

nope still there.



gonna buy a fuel filter tomorrow and see if that fixes it. its kinda acting like my other na did when it was clogged.

How's the idle? Does the car have an O2 sensor? EGR?

idles randomly.

bounces 1200-1700ish randomly, if i drive it enough it sometimes levels out at either 1000 or 1500. it does its own thing.



02 sensor and egr are there, and should be working. all emissions are there.

It could be a bad TPS. Try to pullssome codes out when is acting badly.

it does it when im driving at part throttle, no other time...



i replaced the tps like 2 days ago. cause the one on it was all rusty and ****.

Hmmm. I'd try the TPS.



Was it acting up before you changed it?



Do you still have the rusty one? Put it back!

Vacuum leak?

starting to think that, it idles wherever it wants to.



althought seems to steady out after drivin it for a looong time. but then itll act up again.



****.



i hate vacuum leaks.



i still hvae the walbro in from when it was boosted.

although after i put it back to na, i never heard the pump whine until the end of practice before the stumbling started. and when it was turbo it always was loud...

maybe its just too rich. it seemed to be missing a little up top randomly.

swapped out the walbro for a stock na pump and changed the plugs.



**** got worse, part throttle was basically just cutting out completely.



changed the fuel filter, thought is was fixed. after a few minutes driving it came back though.

it seems like it only does it after its warmed up for a few minutes...

although the fuel filter was leaking a little bit which may be causing it but **** that ill get a real clamp on there tomorrow.



maybe the tps has a dead spot? i had my multimeter on it and moved the throttle and didnt see one, but maybe its hiding in the baaaarely open position.

doesnt matter what i set the tps to it does it



doesnt do it right after starting it, starts happening 1-2 minutes into driving it.

if i redline through some gears it takes a few seconds of holding it at part throttle for it to start bucking.

fuel leaks fixed

still stumbling.



its fine engine breaking or WOT, but like part throttle keeping any sort of speed just cruising it stumbles and bucks and bleh.

it just makes it a pain in the ass to drive anywhere.



and im basically out of ideas.

guess ill pull the uim and get a look at the injectors, maybe ones halfway clogged i dont know.

Try trading out your coil packs, I had the same stumble with my RX7 and it was the ignition.





Also, is everything grounded correctly? Engine Fuse box and ECU? By engine I mean do you have more than that skinny ass wire to the fire wall, a thick battery cable size wire should be run from the bell housing to the frame as well.

have some 6 gauge wire ran everywhere.

from the battery ground int he back (relocated battery), to one of the ecu nuts, through the firewall to the shock tower, motor, and other shock tower, and stock battery ground wire.



it got worse today. went to crank it, started then immidietly died, flooded, eventually got it started. idle is worse, below 1k bouncing feels like its dying, stumbles much harder now, basically like cutting out.

cut out flooring it at high rpms a few times too...





JIMS! i didnt realize that was you. havent seen you round these parts in a while.

replaced the coils and wires with known good ones.



still there

stumbled a couple times redlining through the gears too.



im stumped.

gonna go see if i can find the rusty tps and see if that fixes it.

maybe pull the uim and get a look at the injectors.



good thing i have spares of everything cause i seem to be damn near replacing everything trying to track this down.

one of the uim nuts was loose and one of the primary injectors has a cracked pintle cap. looks like i forgot the spacer that goes between the primary rail and the block.



ill put it back together tomorrow and hopefully itll work.

replaced the injector with the cracked cap, stumble is gone.



yaaaaay.



im still talking to myself.

Excellent!!!



http://www.xsltblog.com/archives/The...urns-Excel.jpg

**** my car does that alot it stumbles at crse speed too ...maybe mine are getting clogged too

they werent clogged, just one of the pintle caps on the primary injecotrs was cracked.



i get to tear the uim off yet again, cause the thing smells BAD like gas so im assuming is leaking.

i know one of the secondaries is but im gonna check the primaries just in case.

fire bad.

I know the injector o-rings are prone to damage if you don't lube them before you stick them in the fuel rail.

two were torn when i pulled em out but i replaced them.



it looks like one the secondaries is leaking around the bottom bushing/oring thing.

cars been sitting since last night, pulled the seconday rail and wtf, theres no fuel in it? theres some in the feed line from the primary but none in the return lines at all.



is this normal?



one of the secondaries was leaking, but that was only while it was running and wouldnt explain why the whole rail was dry.

if it leaks it cant hold pressure.



no pressure = fuel leaks back to the tank.



aka you are gonna have a long cranking start until you fix all the leaks.



kevin.

fixed the secondary leak, cranking time seems normal. though it was long when i first started it after putting it back together.



i also shut it off with a cutoff switch, any difference there?

so with no leaks you still have no fuel in the rail after turning off the car?



and cranking time seems normal?



thats odd.



kevin.

err, it was empty when i pulled the rail to fix the leak.



after fixing the leak, cranking time is normal.

oh well, whatever dont worry about it, it seems to be fine, secondaries arent used for cranking anywho.



kevin.

yup.



the other secondary randomly started leaking the other day. i got pulled over for no front plate, and was thinking, why the **** is my idle at 2500. the cop even cracked a joke about it.



got home and the other secondary was covered in gas. wtf.