Mac2118

iTrader: (1)

I've been having a rough idle/bogging issue that I've been battling for quite some time. Yes, I've searched on here and numerous forums trying to find similar issues, causes, and solutions.

94 Civic DX with b18c on Hondata s300v3

When the car is cold, it idles fine (~1500rpm), when it warms up the idle drops to 850-900rpm. As it idles, the idle will get lower and lower, roughly to 700-750. The car will start shaking like I'm having a misfire and then the IACV takes over and the rpm's jump up to 1000-1100. This will happen over and over until I turn the car off. No CEL's are present.

Back story:

Drove down the road one day and felt a hesitation coming from the engine. Turned around and went home. I had a similar issue before with a blown ICM, so I swapped the dist. for a spare one that I have. No change.

Disconnected the O2 sensor while it had a poor idle and the idle went back to normal. I left it unplugged and it idled normally for 10 minutes (with a cel for the O2). I assumed that I had a bad O2, replaced with a new NGK O2 sensor - no change.

Since someone is going to say: "Clean your IACV!" Its been cleaned. carb cleaner + brush + compressed air. I know its working because its what brings the idle up when its about to stall.

Because of the issue happening, I did a compression test and had 120, 210, 210, 210. I ended up finding that I had a leaky exhaust valve in cyl 1 after a leakdown test. I tore everything apart and rebuilt it. I now have 220, 220, 225, 225. (not bad for my first engine rebuild )

Timing? Pretty much right on. I've had the head milled, so when I put everything right on at TDC and manually turn the crank 6 revolutions my cams are off approx 1/4 tooth. I'm curious if this is the cause.

Valve Lash? Intake set at .007" and Exhaust set at .008".

Vacuum leaks? None.

I have attached a datalog of when this happening.

Does anyone have any ideas before more of my hair turn gray?

Former User

Post the CEL codes.

Did you bleed the cooling system?

Does the engine have an FITV?

The ECT reading (152) seems low.

Mac2118

iTrader: (1)

No CEL codes.

I bled the cooling system twice to make sure.

No FITV. I'm running an AP1 TB.

I don't think the car was fully warmed up when I ran the datalog. The coolant needle was a bit below half.

I took some pics of the timing so it'll make more sense than what I explained. I'll get them uploaded shortly

Former User

Was the problem occurring when you did the data logging? If not, that's what you need to do.

This^ is the fully warmed up needle position for my Civic.

Mac2118

iTrader: (1)

yes, the problem was occurring during the datalogging. I can watch my wideband move lean as this bogging takes place (into the red and max out)

I have watched my Fuel Pressure while this is happening and it is steady at 42psi.

Mac2118

iTrader: (1)

Attached is the picture of my crank pulley when my cams gears are lined up perfectly. When my crank is at TDC the cams are 1/4 tooth off (I thought I had a pic of that, but I don't). The head had to be resurfaced and I was curious if that much timing being off could be the cause of this issue?

Former User

Focus on the lean condition. Measure the fuel pressure and test the FPR.

You might also want to replace the thermostat (low ECT reading).

Mac2118

iTrader: (1)

Fuel setup:

Wahlbro 255
AEM Fuel Rail
AEM FPR
B&M fuel pressure gauge

Well, it does the bogging even before it warms up.

Fuel pressure:

Off: 5psi
Running: 39-40psi
Running/pinched: 48psi
Running/bog: 39-40psi
Running/bog/pinched: 48psi

Injectors - all ticking while engine running. Checked with screwdriver to ear.

Measured resistance of injectors: all 11.8ohm

Video of said issue. When turning the key to prime I do hear a slight squealing noise. Its not the best video, but every bit helps. Ignore the random vibration in the background, my turn signal corner is slightly loose where it connects to the drivers side fender. One of the few things I'm taking care of.



Fuel Filter, thermostat, and plug wires were replaced 3/15 with less than 200 miles on them currently. Plugs are new out of the box and gaps double checked (NGK v-power).

This issue started after I got the head back from being milled. Sorry, I'm trying to think of anything that would help diagnose this.

Former User

ECU needs new tune?

JarvisW

Slight squeal? I had an Aftermarket IACV do that a few years ago. Tapped it with a screwdriver handle and it stopped. But it went out later, so maybe listen in that area next time it happens.

Mac2118

iTrader: (1)

The "squeal" noise comes when I turn the key to the on position and the fuel pump primes.

As for the tune, I originally thought that. I have tried the stock USDM B18c1 and JDM b18c stock maps and have been met with the same results.

On other forums I've seen that people experiencing a similar issue have had exhaust leaks. I went over my pretty much new exhaust and saw that I have condensation dripping from where the intermediate pipe and axle back meet up. I'm going to get another gasket and replace it. Will it make a difference? maybe?

I still have a feeling that this is a mechanical timing issue since its off a slight bit. I may pick up a set of adjustable cam gears and fine tune my timing. As one member here on H-T said "my timing was off a half tooth and the car ran like ****". My cams look like the ones in this thread: Is my mechanical timing off? - ClubIntegra.com - Acura Integra Forum but of course there are no replies.
When I went to install the timing belt, starting on the Ex side, I noticed that the belt and grooves on the cam gear were off a quarter to half a tooth. Hell, I've tried just about everything else. If I have to get a new tune, its a 2-3 hour drive with the car on a trailer and $350/hr on the dyno, vs attempting to reset the mechanical timing that the tuner might have me do before I can even get in.

JarvisW

Yeah, if it happens every time, or when you can hear it with the key on, check the IACV. I chased that noise and couldn't find it till I unplugged it and the noise stopped.

It was almost like a pieazo buzzer ,but higher pitched.

And it caused my car to bog and idle like crap later too..

Oh, ALSO causing mine to bog at certain RPMs was a likely mis-adjusted timing belt. Not the marks. I've seen them run fine 1/4 tooth off. I mean the tensioner wasn't tightened right, and once I did that correctly, it stopped the odd midrange bog..

So, going over your belt setting first may be better than buying gears, unless you just really have to spend money lol.

Mac2118

iTrader: (1)

I wanted to update this with my solution in case anyone comes across this in a search. Bad ignition coil.

I started treating this as a crank no start condition. I first tested for spark, it was orange. I then took the cap and rotor off and measured the resistance of the IC: 1.1ohm (spec is .6-.8). Secondary was 16.x. I reassembled and tested my ignitor which passed, I also had a weak spark from the IC itself. I removed the IC and found little "oil" spots where it was grounding itself out. Replaced with a new coil and its been running fine since. Long story short, I discovered that I had 2 distributors with 2 bad coils.