91 Integra LS - 152k - B18A

My car is stuttering between 3400 and 3600 rpm's. As I accelerate, when I hit this point, there is a momentary loss of power ("stutter"). This happens in all gears. It is most noticable when I'm accelerating slowly. Almost like a "dead spot" where the fuel, or air, or spark is cutting out, just for a second. First a list of what I've done to try to fix the problem, then a list of mods.

I have checked everything visually (vac hoses). I sprayed all hoses and the throttle body with carb cleaner, no change in RPM (i.e., no noticable vac leak)
Replaced spark plugs (NGK), spark wires (MSD).
Injectors are less than 1 yr old and I cleaned them (sprayed both ends with carb cleaner) and inspected them.
Set fuel pressure to factory setttings.
Replaced factory cap and rotor with MSD cap and new OEM rotor.
Took off electronic air control valve (EACV) also known as Intake ACV and cleaned it.
New battery, new terminals, new grounds wires.
Fuel filter less than 1 yr old.
Timing belt has about 30k on it, replaced at dealer.
Distributor has about 30k on it, replaced at dealer.
Check engine light is not on.

MODS:
Blox Intake Mani
62mm Throttle Body
MSD cap, wires, external coil
Clutchmaster lightened flywheel
B&M fuel press. regulator and fuel press. gauge

The following graph is a rudimentary visual aid for my symptom. The line represents power, the numbers nothing. As I accelerate, there is a dip in power at a specific point in my RPM range, this is what the graph shows. Disregard numbers on both axis.


My thoughts:
- Probably not related to the drivetrain as symptom is more pronounced under light loads and at specific spot (i.e., not clutch slippage).
- Probably not related to spark as parts are new (batt, grounds, terminals, plugs, wires, coil, cap, rotor) and again, problem is at specific spot, whereas most electrical problems would generate either random or very repetitive symptoms across power band (i.e., loss of spark, bad timing, bad ground, etc.)
- Prob not a vacuum leak, idle is steady, all hoses connected, rudimentary leak test negative.
- Prob not a fuel delivery problem as injectors are newish and cleaned, fuel pressure is fine, no fuel leaks, newish fuel filter, and fuel pump problem would likely show up under a higher load, i.e., higher speeds and not at a specific spot under light load.
- So, my guess is a sensor problem, MAP, TPS, EACV or other sensor that provides input to ECU regarding fuel/air delivery/mixture. The idle is perfect and the EACV was just cleaned so small chance of that being problem. TPS was set to factory voltage (.45) when installed with new TB and IM but could be malfunctioning? MAP sensor malfunction? Other sensor malfunction? What about O2 sensor? Throw me your theorums and I'll test them out, I'm stumped!


Modified by themilman at 1:19 AM 5/1/2006


Modified by themilman at 11:21 AM 5/1/2006

 

what kind of engine do you have? if its a VTEC engine, you ahve a problem when your VTEC engages... maybe your oil is low, maybe the soliniod is frozen... the car will realize this and then just not engage it, but what kind of engine is it?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by themilman &raquo;</TD></TR><TR><TD CLASS="quote">I sprayed all hoses and the throttle body with carb cleaner </TD></TR></TABLE>
Also I dont understand why you did this, you dont have a carb...
If this helps clean them anyway, i had no idea so disregard

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SlamminS85 &raquo;</TD></TR><TR><TD CLASS="quote">what kind of engine do you have? if its a VTEC engine, you ahve a problem when your VTEC engages... maybe your oil is low, maybe the soliniod is frozen... the car will realize this and then just not engage it, but what kind of engine is it?</TD></TR></TABLE>

VTEC does not engage at the 3400-3600 rpms

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SlamminS85 &raquo;</TD></TR><TR><TD CLASS="quote">Also I dont understand why you did this, you dont have a carb...
If this helps clean them anyway, i had no idea so disregard</TD></TR></TABLE>

IF there is a hole in a hose, there will be a change in the RPM because air is replaced by another substance, such as carb cleaner. Or you can also use Water. Its not to clean it...


Anyway, its sounds like the Map. Does it do it through out all gears? If so I am pretty sure it is the Map sensor.

 

I was under the impression that it engaged at 3500 and then on a GSR the secondaries open up at about 5500 which is when you hear the motor get louder... but i could be wrong, today im just stupid, finals week

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Schrader &raquo;</TD></TR><TR><TD CLASS="quote">VTEC does not engage at the 3400-3600 rpms</TD></TR></TABLE>
wrong!
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SlamminS85 &raquo;</TD></TR><TR><TD CLASS="quote">I was under the impression that it engaged at 3500 and then on a GSR the secondaries open up at about 5500 which is when you hear the motor get louder... but i could be wrong, today im just stupid, finals week</TD></TR></TABLE>
your under the right impression...im not sure about the exact rpm's but you've got the right idea.

i had this problem and it was because of the tune. do you have a chipped ecu? if so i would take it in and check the part throttle tune...

id need to know more about what setup and platform that your running before i could suggest anything else...

 

Dude try changing the o2 sensor.

 

What engine?
What ECU?
Is the ECU modified?

 

its a good thing this guy is helping us out

 

YOU GOT ALOT OF DIAG DONE, VERY HELPFULL.....THE NEXT STEP THAT I WOULD TAKE IS TO PULL OFF THE TPS CONNECTOR (ON THROTTLE BODY) AND TEST THE
THROTTLE POSITION SENSOR OHMICALLY. I BELIEVE ITS THE 1ST AND 3RD
WIRES. WITH METER HOOKED UP MOVE THE THROTTLE SLOWLY AND TEST
FOR AN OPEN (O.L.) IN THE POTENTIOMETER. G.L.

 

91 Integra LS - 152k - B18A
Stock ECU
Non-vtec

 

wow, that is a strange problem, i was hoping it was VTEC because that would make the diag easier

have you tried resetting your ecu?

completely disconnect the battery, then with it disconnected step once on the gas and once on the brake to discharge any stored electricity in an capicitors... then wait about 10 minutes, reconnect battery, and start car without touching any pedals... let it idle for about 10 to 15 minutes untill you notice your idle is just hanging at one rpm and is pretty solid, then take it out on the highway and drive not agressively but shoft a little higher than a grandma would, just make sure you go past 4500 in each gear basically, that should have it all set correctly

that might help, but who knows

 

When did the problem first start? Do you think that it could be a resonance in the intake shaking something?

 

Souds like a dead spot in your TPS, it's hard to test with a regular ohm meter, might be able to see it with a analog ohmmeter, but when I had a problem like this the only way I could see the dead spot is with an O-Scope. Works awesome to test sensors. You could try swapping your tps with a known good one, possibly a friend's tps. Give it a shot

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mstolars &raquo;</TD></TR><TR><TD CLASS="quote">Souds like a dead spot in your TPS, it's hard to test with a regular ohm meter, might be able to see it with a analog ohmmeter, but when I had a problem like this the only way I could see the dead spot is with an O-Scope. Works awesome to test sensors. You could try swapping your tps with a known good one, possibly a friend's tps. Give it a shot </TD></TR></TABLE>




hook up a graphing meter, and watch the voltgage change as you move the throttle.. graph it out..you should have a linear line from closed to open throttle with around .45 v closed throttle, up to 5v wot..

 

How would a TPS always cause a stutter at the same RPM? The OP said that the problem happens at all levels of acceleration, but is most pronounced at slow acceleration. Different acceleration should yield different throttle positions.

Here is another question for the OP, are there any CELs?

 

I don't think its the TPS, since it happens at various levels of acceleration, but thanks for the ideas. What is an O-scope? I will try resetting the ECU.

 

b sure to let me know when you find out what the problem is...

 

sounds like something electrical to me. try swapping a different DA LS ecu into it and see if that fixes it

 

I'm going to reset the ECU, I also have a reprogrammed ECU (Ericks racing) that I can put in it as well to test, although that's not a stock/stock swap so it may not help me determine problem.

 

im not a mechanic, i asked a friend that drag races hondas and he said its very common to have a *flat spot*. He said its because when honda made the motor they sacraficed hp for driveability and confort level. Good set of cams would def help.

 

i got a 91 ls too, wit about 155 thousand miles 5 speed special edition, i have the same stuttering problem.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mylsspecteg &raquo;</TD></TR><TR><TD CLASS="quote">im not a mechanic, i asked a friend that drag races hondas and he said its very common to have a *flat spot*. He said its because when honda made the motor they sacraficed hp for driveability and confort level. Good set of cams would def help.</TD></TR></TABLE>
the flat spot that typically happens like that is when VTEC engages on older models, where the power curve startes to taper right before the vtec power curve starts