Cold start idle drop, code 9 thrown, AFR's may give clues

[af_1132]

Evening ladies and gents,

I'm getting ready for another strip trip, and I want to get to the bottom of an idle drop on cold starts.

Right away, it will start up near 2k, and always has after the tune, which is fine for me. Recently, it will fall dramatically to below 500rpm pretty quickly, and if I don't lightly press on the throttle to keep things up, it will throw a code 9 for the CYP. As the car warms up to above 60deg. C, I can take my foot off the throttle. The idle struggles at around 800 or 850rpms and rises as things warm up to operating temp. The operating temp idle is 1050 rpms and was set by the tuner at Blacktrax. Having a code 9 has not affected at temp operations whatsoever, which makes me think the CYP circuit was shorted by the erratic idle. I also found cylinder 3's spark plug wire not fully fastened down, so I gave it a push in until I felt and heard that satisfying pop. I haven't driven it since then, so that could potentially make a difference at the next start up.

What is the Innovate MTX-L saying about AFR's throughout all of this?

1. As soon as the display begins reading, there is a subtle bump in the amount of fuel being supplied per ECU instructions, which makes sense. I take my foot off, at this point, and as the idle drops, the AFR's rise to around 20 to 22.4.

2. The coolant is just above 60deg. C now, and the AFR's will read in the high 17's and low 18's when my foot is off and the idle has risen to the stuggling ~825rpms.

3. The coolant is between 90 and 92deg. C, and the idle is at ~1050rpms, and the AFR's read in the 15's, and then at 14.7 after a little driving. Since the Bisi Level 2 cam went in, this thing will not idle smoothly below 1000rpms.

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- After reading through threads, I took off my IACV and FITV and will be cleaning them thoroughly with carb or TB cleaner. I will put them back in and let you all know the differences. If the problem persists, I will unplug the IACV once up to operating temps, and check for a falling idle. If there is no change, then I will know it's time for a new IACV. If the idle falls as it should, then I'm guessing the problem lies with the distributor or my stock O2 sensor. I am running the stock 4 wire sensor and the Bosch wideband for the gauge, which Blacktrax then decided to pin to the ECU once they got ahold of my car. I've gotten no codes for O2 sensors, but I could unplug the stock O2 from the harness and see if things change and a code is thrown.

Can anyone bring their similar experiences or knowledge to the table in order to lead me in the right direction? I would appreciate that very much. Thank you.

[93redcb7]

if you had it tuned on a stock cam and put a stage 2 bisi in after, you likely need a new tune

[af_1132]

Sorry, I wasn't clear. I've had only one tune and it was after the Bisi level 2 cam was installed, along with H23 IM and other things.

[af_1132]

I cleaned and put the FIT and IAC valves back on. I did not adjust the FITV. The O-rings look okay, so I reused them. I started her up and I have good news and bad news:

1. The idle is at a strong 2k and does not fall! In fact, it stays at 2k for a while...hmm...

2. I nudge the throttle ever so slightly, and now we have a prolonged idle surge from 900 to 2k. Yuck.

There could be too much air in the cooling lines, so I need to burp it.

I could have a vacuum leak due to old o-rings, ugh.

[af_1132]

OFF TOPIC: Just read through the erratic idle fix DIY. I will be deleting the air boost valve ASAP.

[dj_ender]

Yep, you have to cap it/delete with most "stage" 2 cams.

[af_1132]

I bled the cooling system and not much air came out. The surge persists at a faster rate, but the same range. Since the FITV sits higher than the thermostat housing, due to my double stacked plates, there could still be air in there. I wonder if I should bleed again with the FITV unbolted and lowered below the level of the bleeder valve.

I just ordered a 3x block off plate special for $55.00. I just have to get the specialty O-rings now, ugh.

[af_1132]

I've decided to just put the FITV and ABV plates on when they and the O-rings/gaskets arrive. I presume the air boost valve was causing the original bad cold idle below 1050 rpms anyway. I will post up my results.

[wagon-r]

Recently, it will fall dramatically to below 500rpm pretty quickly, and if I don't lightly press on the throttle to keep things up, it will throw a code 9 for the CYP.

I want to thank you for this. I have had a code 9 for the CYP on my car for months and I've been going nuts trying to find out why. I replaced the distributor - twice - and it is still there. I replaced my ECU with a known good ECU and it also immediately threw a code 9. After reading your post I got to thinking. The code 9 always comes back immediately after I clear the OBD codes - but I always do this while the vehicle is idling.

So, today when I started the car, I made an effort to keep my foot on the throttle and not let the engine rpm drop below 1500. It didn't throw a code 9.

It wasn't a long trip, so I need to try this again when I'm able to drive for miles. I'll also try clearing the OBD codes while at higher engine rpm and see if it comes back immediately. In any case, you have given me some hope.

[af_1132]

No problem, my good sir. I had a feeling the whole time that my CYP was just fine, and that it was being tripped by the crazy low idle on this agressive cam. I just got the block off plates in the mail, so I will be posting my results once the ABV plate is in place.

Bisi really needed to make it clear that this was a necessary delete on the cam card or something.

[af_1132]

Dah!

I have the FITV and ABV blocked off now with nice billet aluminum plates, and I fired it up again.

Car idled at 1.5k, then fell to it's death, no CYP code 9. I started it up again, feathered the throttle, and I didn't need to do it for more than 10 seconds before it was able to remain at 1.5k on it's own (AFR's are at 16.5 to 17.5). Then, about 5 minutes in, the idle jumped to 2k as the AFR's reached ~14.8. Dah, it was going so well! Then the slow surge came back.

At the low point, AFR's are at 22.4 as the ECU tells the injectors to back off fuel, and a code 9 is thrown.
At the high point (2k), the AFR's reach 14.7.

I turned her off and tightened the block off plate Alan screws. I thought at first that there was air in the coolant lines, since I hadn't bled since the coolant bypass. I bled the lines again. I checked my PCV valve and there was a film of oil in the tube past the valve. The grommet was also brittle and came out it pieces. So, now I am waiting for a new grommet and I have a new PCV. I'll start her up in the morning with the grommet in place.

If all that doesn't work, I guess I will have to try the carb cleaner idle raise trick from the erratic idle fix DIY. I really hope that works.

Ugh, I can't go to the track like this, it is so embarrassing...

[af_1132]

Wow, this is the most frustrating thing ever! Of course, none of those things made a difference. I sprayed chemtool B-12 Carb/TB cleaner around and it was getting decidedly sucked in at the IACV.

I switched out all my plentum plug nipples, since some were tearing, and cut down any torn edges on vacuum lines.

I wanted to rule out the FITV block off plate, so I removed the TB and got a new gasket. I checked the seal, checked the gaskets, and shined a light through the mating surface at the block off plate and nothing gets through to my eyes on the other side. I just don't think the FITV plate has a leak.

I also saw a small stream of oil coming down from the IM side of the PCV tube, so I switched that out and got real clamps, not those banjo crappers. That doesn't leak anymore, but of course the idle problem is still there.

I switched out IACVs for the one that was on my F22A1 manifold, and unplugging causes the expected drop in idle.

I just wish I had not removed the IACV and FITV to clean them, why why why??!!? The idle was relatively fine beforehand, compared to the erratic nature now. The ONLY thing I can think of as causing a problem now is reusing the IACV and FITV gaskets. They are old, and so I am getting new ones in the mail from Majestic on Thursday. Do you guys use any special sealant for those interfaces?

Here's to hoping that I don't have to buy a new IACV.

[af_1132]

I got a new Denso IACV in, and it idles just fine.

So, I will never recommend that these be cleaned out and reused. I cleaned two identical IACVs with Chemtool TB and Carb cleaner, and both caused vacuum leak, whether I used new double ring gaskets or not.

So, if your IACV is clogged and dirty, fork out the cash to get a new one!