Woo! Car is running! But idling like crap!

[CRyan]

Well guys, finally got the car running, sort of.... Here's the symptoms-

At idle, it is running pig rich.The car will rev above 2500 rpm, relieving that the problem could be a faulty mass air flow.Above 2000, the car seems to be relatively smooth.The oxygen sensor is from a 91 tt 300zx. I ordered one through Nissan yesterday (87 300zx single turbo).The plugs are covered black, they all are- ruling out a hung injector.I know cam to crank timing is right on the money, and I played with the CAS to see if anything would happen...nothing...it is right now advanced all the way.Car has open downpipe.There is a little popping in the intake mani...This scared me enough to check compression again, with the best compression tester. I have got, starting with #1 cylinder, 160,158,159,160.

Wait- I didn't tell you all how I got it this far. Long story short, cam timing was WAY off, as if they were just thrown in, and there was air in fuel line. Got that fixed, now it's perfect.

Anyone have any suggestions?

Reason I checked compression again was to make sure I didn't bend a valve anywhere.

Plausable assumptions as of now-----Maybe CAS is off a tooth or two?oxygen sensor?IACV?AAC valve?

Please, remove any of these causes if you have decent argument as to why it wouldn't be any of these.Also, what is "timing" mode and why would I need to set it for anything?

I can't see why it would be any vacuum leaks because I thought vacuum would lean it out, not flood it out and idle like crap...

Thanks guys!

Modified by CRyan at 1:43 PM 9/30/2009
Modified by CRyan at 2:00 PM 9/30/2009

[CRyan]

Sorry forgot to mention, it is a s14(a) sr20det with open recirculation valve 300zx, lightened flywheel, and stock SMIC, with stock piping

[CRyan]

Anyone?

[boro drift]

sr20det with open recirculation valve 300zx, lightened flywheel, and stock SMIC, with stock piping

Sounds like a boost leak. I would suspect your bov, and the side mount intercooler.

[JesterX18]

well heres my take... A vacuum leak can cause a car to run rich due to the fact the o2 sensor is going to pick up the excess unmetered air and determine that there isn't enough fuel in the engine to make an ideal air fuel ratio of 14.7. Its going to dump more fuel in to correct issue and its still gonna see the unmetered air and add more fuel never actually fixing the problem, just causing the car to run rich especially at idle. As for the o2 sensor i dont know if a 300zx 02 sensor is compatible with an SR ecu, but seeing as how you bought it and installed it im going to assume it is. As for your idle air control valve IAC that can cause an engine to not stay running by choking it of air due to not opening. The spring often gets plugged with carbon, and wont open all the way. I dont think it would cause the engine to run excessively rich but im not completely sure. As for the AAC i may be wrong but i didn't think SR's came equipped with an AAC valve. The AAc valve is used on ka engines to increase air velocity using a butterly valve in each intake runner while idling and low rpm for better fuel dispersion in the air fuel charge and torque. I dont really know much about the boost leaks but i have heard that open air BOV can cause SR's to act like this one. But just to be sure i would check your couplers and piping. Let me know what you think...

[CRyan]

Fantastic answer sir! That is what I needed to know- I will be sure to acknowledge this to my fellow mechanic, who seems to know how to come up with something from a little bit.

Thanks!

[JesterX18]

No prob man, hope you figure it out.

[CRyan]

Well got news and bad news. Good news is the car is running somewhat more stable. I fixed by finding a bad connection to plug on oxygen sensor...noticing that it still ran like crap, but sid not smell like it was burning nearly as much fuel, I swapped in some new spark plugs and baam- sounds a little better. Now the problem proceeds to this---

firstly, at idle, it seems to surge between 300 and 800 rpm. Vacuum is reading -20 on a snap on gauge, so I know it's right.

Secondly, unless the engine is seeing over 1600 rpm, the oil pressure light is on. Is this because of it's odd idle?

Any help will be greatly appreciated

thanks!

[boro drift]

firstly, at idle, it seems to surge between 300 and 800 rpm. Vacuum is reading -20 on a snap on gauge, so I know it's right.

You have a vacuum/boost leak.

Secondly, unless the engine is seeing over 1600 rpm, the oil pressure light is on. Is this because of it's odd idle?

It's not because of the idle. It could be a few things like, bad sending unit,or a loose connection between the gauge and the sending unit. And, check the oil pan for dents,(they get smashed on the boat ride over here sometimes).

The foolproof way to tell if something is wrong with your oil pressure, is to install a manual gauge.

[CRyan]

Just to inform everyone keeping an eye on this thread, turns out the rough idle was from the (as boro drift said) was from me thinking that a recirculation valve could be ran open. I pulled the vacuum line off of it and plugged it and she idles like a champ now. Sort of.

Still idles super high (1000) rpm, but I am sure after being an idiot and adjusting the screw on TB instead of IACV valve, that could have caused something.

Still no oil pressure, but it occurred to me that when removing the timing cover I didn't break the bolts loose on the oil pick up, until after we pried (slightly, of course). So I am sure it is just acting like a straw with a slit in it, ya know?

Hopefully that is the problem, I should have it checked and re checked by the end of the week. Got to hear what compressor surge (I assume) sounded like the other day also.

Sounds pretty damn terrible if you ask me.

Anyway - Thanks for the help - Hopefully have an update and a little movie of first roll out of the car next time I am on.