Quick Maf sensor testing question

[93_jdm_fd]

That's what I was wondering since it's a twin turbo, twice as many pipes and hoses to block off. I will pick up some parts from the plumbing section to build a vacuum/boost leak tester. So which end of the intake system did you plug off, the piece right after the twin turbo cast pipe or the 3" rubber piping that you just removed from that twin turbo cast pipe?

[93_jdm_fd]

So after work today I drove home, parked and let the engine idle. I unplugged each coil one at a time and found #5 and #6 didn't really change compaired to 1-4 coils. I had this same problem before but never really thought anything of it because the engine still boosts fine and runs great other than the lumpy idle.

When I first got the engine back in and running it had this same problem and I played around with then and swapped coils around, injectors around and it still seemed that #5 and #6 cylinder had no real change when either the coil or injector to that cylinder was unplugged.

Again I did buy this car with no engine, found a blown engine with only a few sensor, bought from members on here good working parts to my knowledge but how would I know if they were good working parts when I didn't remove any parts with my engine because they weren't there to begin with. I bought used coils, mafs, CAS, igniter, injectors, mafs, and the only sensors that came with the blown engine were the tps, and whatever sensors are under the intake manifold.

I'm pretty much ready to pull the engine and buy another one just to put in. I love this car and can't stand the lumpy idle, it drives me nuts. "hey man nice car" oh wait is that how it runs!!

[Frankyy]

I pressurized the intercooler and piping wich leads to the whole intake side, what's your compression on all cylinder did you use regular non synthetic oil to break in your rings after rebuild?

it might not be related but I'm just throwing ideas out there to eliminate issues, I'm also having bad afr after a shot of gas been trying to solve this for a month now. I'm on the same boat as you are haha

[93_jdm_fd]

I used royal purple 10w40 for about 1000kms, then I switched to royal purple 10w30. I checked compression and I have an average of 160psi on all cylinders. I did the other day unplug my maf sensors one at I time and the engine stalled and died.

It's been shitty raining out for a few days now and I haven't really done anything with the car. Thursday night is shop night so I'll check for some vacuum leaks then.

[93_jdm_fd]

So last night I installed my vacuum tester and found the AAC valve idle adjust screw leaking. I removed the vavle and took the screw all the way out. It has a rubber gasket that was torn. I replaced it will an o-ring and reinstalled it. Retested and found no air leaking and the intake system was holding a steady 10psi of pressure.

I also replaced the coolant temp sensor which i guess is the exact same sensor as the intake air temp sensor. Anyway it still has the lumpy idle and only seems to run really rough when the engine is cold. What other sensors are temp related? I replaced both 02 sensors and the coolant temp sensor with the last few days and nothing seemed to help. It's really rough when cold.

[Skym]

It might be a combination of things that need to be adjusted.

Didn't know that engine was rebuilt, was cam timing done correctly???? When block, head have been skimmed (even with stock cams), it's recommended to degree your cams -

http://www.camshaftshop.co.nz/index.php/Camshaft-Information/sole-purpose-of-degreeing-your-cam.html

As said in above link, you can get retarded cam timing if don't degree cams properly. I found out that a stuffed CAS (failed bearings) can pull / retard ignition timing by 1-2 degrees which can make engine run rough and having cams retarded might throw out CAS settings, ignition timing on stock warm up ignition table, ignition maps, etc.

o2 sensor can cause missing if makes engine run too lean when above certain coolant temp. Unplugging them should smooth the idle out, as engine is not being forced to run leaner than it should at idle. But o2 sensors don't affect initial cold start, etc (ECU runs in open loop, which means it ignores o2 sensor input up until certain coolant temp is reached), that's ECU tune related, or cam timing related.

[93_jdm_fd]

The block was just bored out and the head was checked for and leaks, cracks, etc. Nothing was removed from the block or head surface. I replaced both o2 sensor last week also. I set the cam timing with the #1 coil and "modified" plug wire to 20 degrees. I did buy a used CAS which was probably for sale for a reason. I would love to buy a new one just to rule it out but I don't think you can get a "new" one anymore.

I'm moving back to Edmonton soon so I will probably get it sorted out there, way more parts available. Even just to go to my buddies place and swap over his CAS, ecu, and coil harness to see if anything helps. My car pulls really hard and drives really smooth just has a lumpy idle and a bit rough when cold. I may have different cams but when I had them out I didn't see any markings to identify them as being aftermarket.

[Skym]

Head should be checked for straightness, skimmed (aluminium head). Block being iron takes a higher temp to warp, so usually is ok.

If ECU tune is out, o2 sensors can make ECU run engine leaner hence the rough idle (even if new).

When CAS bearings fail, CAS creates a CAS error code on stock ECU and engine gets harder to start when hot, cold and starts to missfire. I think you can buy a new CAS, but last time I asked it was nearly 1K.

Can rebuild CAS, but have to buy new bearings x2 with different part numbers from NTN in Japan. The CAS electrical / donut part is supposedly not made anymore by Mitsubishi, but they make clones of it in Taiwan? and this place sells them -

http://www.tweakit.net/shop/product_info.php?cPath=57_289&products_id=2181

Rebuilding CAS seems fairly simple to do when thinking about it, but removing the locking pin on shaft for the part which engages exhaust cam (grind weld off locking pin, knock out locking pin via hole punch), removing bearings via 3 prong puller and refitting via vice + piece of pipe is the hard part (without damaging electrical part). I gather locking pin has to be tack welded again, as to not fall out.

My mates GTR racecar engine is smooth as a factory engine when first start car (cold), but jab throttle and it starts to lump with aftermarket cams.

[93_jdm_fd]

I did find a tread about rebuilding or swapping the CAS from a Z32, or maybe he was installing an AEM electrical donut thing. Either way it didn't look to difficult but this is my daily driver right now and I need to drive it everyday. So if something went wrong I don't don't want to be stuck without a car.

I might just find another "known good" used one and try it. Maybe swap over and ecu and try that. I'm gonna pull the valve covers today and check again a little closer for any marks on the cam to indicate them being aftermarket. If they are I can live with it, at least I'll know it's suppost to idle like that.

[93_jdm_fd]

Swapped the CAS from my friends car and my lumpy idle is now smooth. Still have and idle issue but when warm the idle is smoot and doesn't sold live a corvette with a cam.