91 DA Revived

Hello,

I just got the below engine tuned. We made 380hp on 11 pounds of boost a very mild tune. It has been running good for about a week now but last night it started to idle rough. It sat over night and I started it the next morning and same thing on start up. Basically it sounds like it has a giant cam in it just lops when at idle.

Here is the odd thingI was looking over everthing to see if something came loose or maybe a vacum line came off and moved the map sensor ( it is not on the throttle body it is mounted to wall of engine bay with a vacum line ran to it.) and notice and the line pinched it idled stronger.

so I proceeded to stick a tiny vice grip on there to see what happens. When I cut off some of the vacum on the line to the map sensor it idles super nice. as soon as I remove the clamp it idles rough again.

Any thoughts it seems like its pulling tons of vacum or enough to change the tune. Is that possible the motor has about 200 miles on it as of today.

Please Heeeeeeeeeeeeeeeeelp!!!!!! LOL

85mm B18b1, Darton Sleeves
Arias Pistons
Eagle Rods
Golden Eagle intake Manifold
GSR Cams
Top Mount SLS manifold
Precision 6262
Precision Intercooler
255 Walbro/rewire
Hondata S3000-Running open loop on o2
Omni Power 4 Bar Map sensor.
ID Injectors

Im sure there are others

96_coupe

I'm not sure if it could affect it but have you checked all the vacuum lines to see if any of them are leaking? Old lines like to get britle and can crack, also the lines swell if and oil gets on them and makes them likely to fall off. I would start with that.

Is it only when its cold? hot? both? Good luck and congrats on the numbers

Turbo-LS

iTrader: (4)

Is there any major difference in ambient temp since you had it tuned? Do you have a wideband in the car? Whats the a/f at idle clamped and unclamped? Do you have an aftermarket throttlebody on the car?

91 DA Revived

It happens when its cold or hot I only have like 3 vacum lines running off the manifold. so check all of them and nothing has fallen off.

Its odd that when I pinch the vacum line to the map sensor it starts to idle better. Obviously when that is done it changes the location in which the ECU is operating the engine at that time less vacum would place it somewhere else on the tunning map right?????

Im just wondering if the engine is now creating more vacum that it altered the tune it also bucks a tiny bit while holding the throttle steady at cruise almost seems like a IACV valve but it seems to try and correct the idle but it could be bad.

Any other thoughts... if it was the IACV would pinching the MAP Sensor Vacum line correct it, That is where im lost.

Thank you!

Turbo-LS

iTrader: (4)

You didnt answer any of my questions, I cant help you if you dont tell me what i asked.

91 DA Revived

Is there any major difference in ambient temp since you had it tuned? Do you have a wideband in the car? Whats the a/f at idle clamped and unclamped? Do you have an aftermarket throttlebody on the car?


Temp Is close to the same maybe a 5-10 degree difference.

Only running a stock o2 sensor ordered a AEM wideband last night for this reason. I know I should have had one already.

Throttle body is a BBK.

I tried to download SManager from Honda-tech but my computer will not run it. Im not sure why its a brand new computer and it is windows per Hondata is should work but I run the program after download and all i get is a error

kbouchard1092

You tried downloading Smanager from Honda-tech? Or did you mean hondata? YOu should be downloading the lastest version from Hondata.

http://hondata.com/smanager.html once you download it check for updates. although the lastest version you should be able to download from the hondata forum.

AS far as youre problem what map sensor are you running? Once you get the s300 software downloaded you can see what youre reading are at idle. That will help with diagnosing it. Maybe its just a bad map sensor. Or if you have a aftermarket sensor you need to make sure its entered correctly into the parameters in the software once you get that working.

Turbo-LS

iTrader: (4)

While the car is running unplug the IACV. if the car stalls you need to adjust the throttle stop set screw to get the car to idle correctly. this is a common thing with aftermarket TB the set screw can losen up some times. If car doesnt stall when you disconnect the IACV still be sure the idle is at 750-800rpm without the IACV and then plug it back in

91 DA Revived

Did that last night made no difference when I unplugged the IACV. But that would not explain why the car would also missfired when curising as well. like I said it just started out of nowhere kinda odd. It seems like a sensor issue or Tune. The engine sounds strong and I cant imagine it would be bad compression or something like that being that you can pinch the Map sensor hose and boom it idles like perfect.

mikesrex

what kind of dyno was it tuned on? has it ever been street tuned?

91 DA Revived

Dyno Jet, and no has not been street tuned at all just on the dyno and off. I would imagine that a nice street tune would hlp but the randon difference in idle from that day to the next is odd to me

carnot

Is the engine RPM changing during idle or does the motor just sound like it is running differently? You stated in your OP "Basically it sounds like it has a giant cam in it just lops when at idle." Does it sound like the motor is missing or is the idle surging? Do you have a manifold vacuum/boost gauge hooked up? If so, how much vacuum is the motor pulling at idle?

91 DA Revived

Good question. At idle it is pulling about 20 with the wierd Idle. When I do the wierd pinch in the line for the map sensor it idles better and the vacum on the gauge shows a bit more at 23 for vacum. I have tried to hold the engine at 2000 RPM when the vacum line if no pinch and it revs up and down on its own almost like there is an inactive IACV.

However when I pinch that hose to the Map Sensor it idles better and holds better at 2000rpm with no issue.

carnot

Before this issue was the motor idle RPM ~750-1000 and then all the sudden it started this behavior? Do you still have the FITV?

If the vacuum increases when you crimp the line between the IM and the MAP sensor this suggests there is a leak either in the line or MAP sensor.

91 DA Revived

Problem found and soon to be resolved. I took a stock map sensor and put a caving line on it and sucked to see if it was holding caving and or blow in it to see if.it would hold pressure as expected it did. Took my omnipower sensor and did the same but it would not hold vacume or pressure closely inspected and found a crack in the case. New one on the way.

Thanks everyone