I've narrowed the problem to the TPS.

I unplug the wiring harness, and the car idles high (2k) but it no longer fluctuates. When I plug in the TPS harness, it surges from 1k-2k nonstop.

The TPS was PERFECT before the JRSC was installed. Now it's started to fluctuate wildly unless I disconnect the harness.

What do you guys think the problem is??

 

vacuum leak

 

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

If you think its your TPS, then test it: &lt;.48v @ idle

Did you rebleed your coolant?

Use new gaskets where applicable?

Running a stock ECU with JR's fuel enrichment stuff?

 

Hi Mikey,
I havent tried pulling my tps yet,
I drove the car today and bled the coolant for a while, but didnt get to pulling the tps.
i'll do it next time!

Does yours do it non-stop?
Mine will do it for a while, but if you let it sit without hitting the gas, it will settle down and idle normally. Also it holds a proper 1500rpm idle until warm.

Someone else mentioned that the fast idle valve causes this too. And an ez way to check is to just take off your intake arm, to expose the throttle body, then plug up this hole with your finger, if that fixes the idle then the fast idle valve is most likely the culprit
heres a pic

 

tad , you charged yet?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by OnePointSicks &raquo;</TD></TR><TR><TD CLASS="quote">tad , you charged yet?</TD></TR></TABLE>

hehe, I suppose you could say that I officially am!

but i'm still waiting on the last piece of my fuel management(JR map controller)
so I haven't given it WOT for more than a second yet!

SooN though! soon as spoon!!

 

Hey Tad,

That's exactly what happens with mine. It sounds perfect on warm up, then once it warms up the idle surges. If i'm at a light, it will maintain a steady idle (after a bit of surging) at about 1400rpm.

 

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

That's exactly what happens with mine. It sounds perfect on warm up, then once it warms up the idle surges. If i'm at a light, it will maintain a steady idle (after a bit of surging) at about 1400rpm.</TD></TR></TABLE>

ah ok i see,
well its CLOSE to mine,
mine will maintain idle at a normal 750(or so) rpm once it settles.

but yeah very similar..
have you hunted for vacuum leaks yet? That really is the most likely culprit afterall...
intake mani gasket, SC/IM gasket, TB gasket.. check!

 

If it was a vacuum leak it wouldn't stop surging after I unplug the TPS harness.

 

not neccessarily,
pulling the tps harness could just be jumping(edit: i meant jumbling) your ecu enough so that the idle surge dissapears..

but can you drive it with the tps unplugged?!
check the tps voltage with the throttle shut,
as previously mentioned it should be .4something
if its set properly(which it most likely is unless you messed with it during the jrsc install) then you could try swapping in another one..

personally I wouldnt bet on that though..
i'm curious whether mine stops surging with the tps unplugged tho..
we'll see tomoro!


Modified by Tad at 9:10 AM 11/3/2004

 

It measures .47 with the accessory turned on..

 

You have a vacuum leak...

#1. When you start your car in the morning, or whenever the ECT shows a cold engine, the ECU knows to up the idle rpm (which disregard the strategy described below). Air bubbles in the coolant contribute to a cold/hot swing of the ECT signal and so if the engine was really hot, but ECT showed cold, ECU is going to want to idle up. So the fact that your car idles, when cold, at 1500rpm without surging, should come as no surprise.

#2. The surging is caused by the ECU's fuel-cut-on-decel strategy. Basically, with the engine warm (ECT indicates this), and the TPS showing &lt;.49v, and engine speed &gt;1100rpm, the ECU will cut off the injectors. I make no mention of speed, as this strategy is speed-independent - the ECU doesn't care how fast your going.

Now since a vacuum leak only serves to raise engine speed on Speed-Density FI systems, we can see that when your engine is warm, TPS says throttle is closed, your vacuum leak only serves to raise the engine rpm over 1100 at which point the ECU cuts off the injectors, engine speed falls below 1100, injectors cut back on + additional air from vacuum leak = increase engine speed - rinse, lather, repeat.

Now since you can make the surging stop by unplugging the TPS - well guess what the ECU is thinking about the position of the TPS?? Obviously it doesn't think its fully closed anymore. But since your TPS is now unplugged, how performance? The ECU uses the TPS for 3 things: to tell when its closed, to tell when it wide open, and the rate of change (how fast) which is used for an accelerator pump type of function (similar to a carb).

As Tas has asked: What happens to the idle when you cover the hole leading to the IACV?

 

Replace your ECT sensor. Sometimes they are bad but still test out ok.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EE_Chris &raquo;</TD></TR><TR><TD CLASS="quote">You have a vacuum leak...

#1. When you start your car in the morning, or whenever the ECT shows a cold engine, the ECU knows to up the idle rpm (which disregard the strategy described below). Air bubbles in the coolant contribute to a cold/hot swing of the ECT signal and so if the engine was really hot, but ECT showed cold, ECU is going to want to idle up. So the fact that your car idles, when cold, at 1500rpm without surging, should come as no surprise.

#2. The surging is caused by the ECU's fuel-cut-on-decel strategy. Basically, with the engine warm (ECT indicates this), and the TPS showing &lt;.49v, and engine speed &gt;1100rpm, the ECU will cut off the injectors. I make no mention of speed, as this strategy is speed-independent - the ECU doesn't care how fast your going.

Now since a vacuum leak only serves to raise engine speed on Speed-Density FI systems, we can see that when your engine is warm, TPS says throttle is closed, your vacuum leak only serves to raise the engine rpm over 1100 at which point the ECU cuts off the injectors, engine speed falls below 1100, injectors cut back on + additional air from vacuum leak = increase engine speed - rinse, lather, repeat.

Now since you can make the surging stop by unplugging the TPS - well guess what the ECU is thinking about the position of the TPS?? Obviously it doesn't think its fully closed anymore. But since your TPS is now unplugged, how performance? The ECU uses the TPS for 3 things: to tell when its closed, to tell when it wide open, and the rate of change (how fast) which is used for an accelerator pump type of function (similar to a carb).

As Tas has asked: What happens to the idle when you cover the hole leading to the IACV?</TD></TR></TABLE>

ooh someone knows his honda ecu's!!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Tad &raquo;</TD></TR><TR><TD CLASS="quote">ooh someone knows his honda ecu's!!</TD></TR></TABLE>

TO ALL: I have some .pdf's that detail how Honda's fuel-injection system works, which also includes some stuff on OBD2 too.

If you would like this info, please shoot me an IM with your e-mail address that can hold a single 10M file (Yahoo works great for this).

Sample chapter on how Honda's 5-wire (wideband) O2 sensor works + troubleshooting information for it. The first page is the table of contents - that should give you an idea of all the info that is available.

 

[QUOTE=EE_Chris]


Now since a vacuum leak only serves to raise engine speed on Speed-Density FI systems, we can see that when your engine is warm, TPS says throttle is closed, your vacuum leak only serves to raise the engine rpm over 1100 at which point the ECU cuts off the injectors, engine speed falls below 1100, injectors cut back on + additional air from vacuum leak = increase engine speed - rinse, lather, repeat.
QUOTE]

this makes sense,
so the vacuum leak is like an extra throttle that just open very slightly,
letting in air so the engine revs up.
But you're not in gear, so once you get up above 1100 it'll cut the injectors and the revs will drop down.

So if that injector cut feature wasnt in play the engine would just keep on revving up huh?

 

Exactly - any vacuum leak acts like you opening the throttle.

It would continue to rev up for sure - how high depends how big the vacuum leak.

 

One odd thing though, is that my idle surge stops if I let it chill,
it'll only surge maybe 4times at the most, then it'll settle and idle normally,
till I tap the gas then it'll start surgin again.

mikeys does that too ,but I think he said it holds a 1500 idle once it settles.

 

Thanks for the updates guys! This will give me some work to do in the next day or two haha.

Mine also settles sometimes when i'm at a stoplight and settles at 1500 rpms...any explanation for that? If I had a vacuum leak, wouldn't it be safe to say that the settling down wouldn't occur?

 

not necessarily. I installed a jr supercharger onto my car last summer and had the exact same problem as you did. It would surge from 1-2 rpm..and actually when I didnt have it parked it would steady to 1300 or so rpms. I checked everything, I at first assumed it was the TPS sensor and when I unplugged it it steadied out, then I looked into the iacv but it wasnt that either. When it came down to it it was just a vacuum leak inbetween the gooseneck and the throttle body. I would check your gaskets and retighten any bolts that were loosened or taken off during the install.

 

Would a propane test find out where the vacuum leak is? I've sprayed the whole region with soapy water / WD40, no bubbling at all.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MickeyA &raquo;</TD></TR><TR><TD CLASS="quote">Would a propane test find out where the vacuum leak is? I've sprayed the whole region with soapy water / WD40, no bubbling at all.</TD></TR></TABLE>

sorry but you kinda wasted ur time,
remember its under VACUUM, so its sucking in whatever watever you spray on it,
the only way to see bubbles would be for you get it into boost

I havent tried this, but the recommended trick is to spray with carb cleaner,
cuz i guess when the engine ingests carb cleaner it makes it rev up,

so when you find a spot that spraying makes it rev up, you've found your leak!

 

do brake cleaner , the car will run like **** if theres a leak.

 

I used silicon spray, and it found it very fast. It was kinda funny, I had open DP at the time, and after I sprayed it in, there was wet **** on the ground underneath the DP (silicon spray)

 

i had the same problem, replaced the gasket between the blower and manifold and the s-pipe.