The problem is hard to describe. When driving around at part throttle the car has a tendency to surge, stutter, misfire, whatever you want to call it. It it highly noticeable to the driver, and you can hear it too, but it doesn't register on the wideband, which shows a constant 14.7:1.

As soon as you put your foot on it, the hesitation/stutter goes away and it runs strong as hell!

Car: 1988 CRX
Engine: Turbo 1g B16, DIY OBDI conversion, running Uberdata 1.70 with closed loop disabled, wideband and street tuned. It has the Endyn breather mod with extra vents on the valvecover, so no PCV system, and all the emissions crap has been removed. It is running 450cc DSM injectors.

Things I've already tried:

Electrical:
Checked all the OBDI conversion wiring at the distrib and at the ECU, reverted to old BINs, added and subtracted timing (problem seems to lessen with more timing until it begins to ping), cleaned and sanded all engine grounding points, checked all engine bay wiring (de-loomed and re-loomed).

Spark:
New distributor, new plug wires, new plugs, timing is set at 16 degrees in Uberdata and at the crank.

Fuel:
New fuel filter, tried stock 240cc injectors with old bins before all this crap started happening, all wideband tuned, with closed loop enabled and disabled (happens either way). Fuel pressure is steady at the rail, but I would see a fuel anomoly in the wideband readout anyway.

Mechanical:
Cam timing is bang on (stock cam gears) and I put on a new timing belt. I even blew my old engine and swapped in a new shortblock - same problem, so it's not in the bottom end (obviously). Tried running with and without the turbo, no difference. Swapped MAP sensors with known-good ones, swapped throttlebody with a known-good throttlebody. Valve adjustment was done recently, 0.006" intake, 0.007" exhaust.

At this point I'm out of ideas. Help!!

 

how's your throttle cable does it got any slack or not tight?

 

The cable has some slack, yes I also adjusted the throttle stop so it's not sticky.

 

have you checked your dizzy wiring?

 

Yup! I actually cut all the joints and reflowed the solder just to make sure...

 

Do you have two O2 sensors? Reverse them, take the plug out of O2 #1 and plug it into #2 and vice versa.

 

Nope! The ECU is running closed-loop disable, with no O2 correction at all. I have a TechEdge 2.0 wideband that I keep in the car for making sure nothing goes wrong and the O2 sensor is completely unplugged and sitting in a box at home.

 

FIRST OFF what did u set ur plugs at, 2 steps colder? (this is a start) then gap around .30

then i would add more fuel/less timing, maybe its lean/timing issues

my car did that when i switchd to 3 bar w/a bad vacuum source, switchd vacuum source and it workd fine

after that, i would say stick with what u know works and slowly work up
CHECK fuel pressure across the board, and the wideband i have takes a good minute before it registers correctly
check for vacuum leaks

good luck

 

I'm having the same problem (although I cant say I have a wideband.) and it pisses me off. I've checked my plugs, wires, injectors, and i still have a misfire code. I have bee ntold it is because im running really rich (I'm still running a FMU ) But this doesn't seem to be your case.

Cap and Rotor? I'm doing mine today probably.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 90crvtec &raquo;</TD></TR><TR><TD CLASS="quote">Do you have two O2 sensors?</TD></TR></TABLE>

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by raene &raquo;</TD></TR><TR><TD CLASS="quote">OBDI conversion</TD></TR></TABLE>

My guess is no.

 

how's your timing map at that load?
It could be a timing issue

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by japearl &raquo;</TD></TR><TR><TD CLASS="quote">
Cap and Rotor? I'm doing mine today probably. </TD></TR></TABLE>

Literally a brand new distributor, same problem

I thought maybe the timing belt had stretched so I threw another one on there... same problem. I'm really stumped!

 

well bump for your problem. napa was closes so no cap and rotor going to try and change around injectors hopefully. keep us updated

 

i have that problem all the time

even tho ur wide band says 14.7-1
richen it up

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rev-speed &raquo;</TD></TR><TR><TD CLASS="quote">i have that problem all the time

even tho ur wide band says 14.7-1
richen it up</TD></TR></TABLE>

I did this on Friday... put it to 13.0:1 at over 10"/Hg, same thing

Thing is, if you step on it, it clears up, which makes me think it's throttle-related or MAP-related, except I've already tried a known-good TPS and MAP

 

when it stutters, is this around a certain vacuum value? or is it reguardless of the vaccum? could your timing in uberdata been fucked with? did u try a map in crome? (i had problems with uberdata, not saying its bad i just have better luck in crome)

 

Ya, it could very well be a timing issue! I think my timing's OK but I don't really have that much to compare with.

Here's my Uberdata 1.70 map that I'm currently running on, with fuel added on the low cam to read 13.0:1 or thereabouts.

Map

It also seems to take a lot of throttle to get moving. When it was good I would cruise at 16"-18"... with this misfiring problem I have to gas it to 8"-10" in order to drive the same speed.

I haven't touched the distributor or timing from before this started happening except when I replaced the distrib. I never really touch my timing maps, haven't for a long time.

The problem always happens at &gt; 8"/Hg, never happens if I floor it, and smooths right out when I give it more throttle than 8".

 

what did you use for a base map, gsr? and import a b16a, im looking at my crome base and it has more timing than yours in low cam, plus idk if my uberdata 1.7 is mess up because the fuel charts are fucked up but, in 24" and 750 rpms your timing is -2, that might **** some **** up around idle

 

i made a new lower ignition timing for your bin, try it out it seems to have a little more timing in vaccum

 

CRAP just realized I left the laptop + burner at my parents' place... I won't be able to try it until tomorrow night!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by raene &raquo;</TD></TR><TR><TD CLASS="quote">

I did this on Friday... put it to 13.0:1 at over 10"/Hg, same thing

Thing is, if you step on it, it clears up, which makes me think it's throttle-related or MAP-related, except I've already tried a known-good TPS and MAP </TD></TR></TABLE>

richen it up more
it should fix it

by the way if ur using a lm-a don t trust it
its always off

 

I'm running the TE 2.0 (2a0 to be specific).

Do you think it's an injector problem? I shouldn't have to run richer than stoich to prevent misfire unless one of the injectors is faulty... but I've already tried a different set of injectors

I'll give it a shot tomorrow night along with Boosted Chemist's map Thanks guys!

 

no problem with injectors

i think its timing and a/f together
some cars that i tuned had to run in the low 12s to prevent this hic-up

 

Bump for a fellow misfire member...

I hope that I don't have any more issues once I have my new shortblock.

 

I think I might try retuning it on Crome starting off a P30 map this time, see if that helps!