Can someone explain the conditions the ISCV Check Valve sees? Pics inside. Thanks!

teedoff00

teedoff00

14 psi boost
Dec 5, 2007
297
0
16
Selah, WA
A little history: I have a 1987 7MGTE that hasn't been driven much that last four years, which is probably most of the issue. I took it to Reno for Hot August Nights 2 years ago and it won't idle on its own. It trys to idle in the low 550-600 RPM range and tries to catch itself then dies. I have to hold my foot on the gas to keep it running. 2 years ago it obviously had new gas and new spark plugs before the trip and still had these symptoms.

I took it on a long road trip, around 90 miles last weekend and it still has the same symptoms even with fresh gas. I went ahead and changed the spark plugs to the NGK BKR7Es today and decided to remove the ISCV and see if it was gunked up. I had quite a bit of gunk and I decided to go ahead and clean it up. I soaked and scrubbed the apparatus (not the sensor) and the check valve in Dawn. The check valve doesn't have any tears etc but it doesn't seem all the way closed in a static position. See attached photos. Of course when I blow through the wagon wheel, air comes out the other side.

I am wondering if a new one is needed? It's a 40 dollar part and I don't want to order a new one to find out it looks the same. In my mind under boost, it would force the silicone seal shut and wouldn't leak and under vaccum it would flow through the iscv and check valve into the manifold. Meaning it would be ok as is.

Any ideas on whether or not a new one is needed?

For those still with me, I went ahead and tested the ISCV via the TSRM and am unable to get a lot of movement in either the open or closed direction. Hoping this is causing my idling issue. What's the best way to clean the motor? and ReLube? Can I just use electrical cleaner?

My AFPR was reading very high, and didn't change with the vac removed, so I decided to clean out my Aeromotive AFPR. I didn't see any gunk so I re assembled. I currently have vacuum coming from the stock location, and decided to switch to where I have my Zeitronix Map plumbed, it got much better. But I find I have to run almost 30psi with the vac connect to get it to run ok. At stock boost (wastegate crack pressure) AFRs are from 11.2-12.4. So that should be ok, no idea why the pressure needs to be so high though. I'd like to clean the vac lines etc but I don't know of the best way? Compressed air? Seafoam? What do you guys think?

Thanks for any help or advice! I will have more questions to come and am looking forward to returning to active status on this awesome forum!
Ucw3zh1.jpg
zHfGzVX.jpg
 
hvyman

hvyman

Dang Dude! No Way Man.
Staff member
Apr 17, 2007
12,568
1
0
Fullerton,CA
It's to prevent boost from blow I to the valve.

Cupped side should face inside the manifold.

The iac takes like 125 steps from open and closed so yes it will only go a small amount at a time.

You any to adjust the afpr with the vac line removed and capped. To about 35 psi.

Have you checked for codes?
 
teedoff00

teedoff00

14 psi boost
Dec 5, 2007
297
0
16
Selah, WA
Thank you for the reply.

My worry is that the rubber seal in the check valve isn't fully seated or doesn't appear to be. My thought is that this wouldn't matter as it be open under vacuum and forced shut under pressure. Is this the correct line of thinking? Anyone know what a new one looks like?

Thanks for explaining the stepping, it did make the noises etc when voltage was applied, but movement wasn't noticeable, so it must be a miniscule amount.

I checked for codes and got a 42 vehicle speed sensor. Not sure why I had this? It's a manual trans and I thought that was only for Auto???

I can try setting the afpr again with the vac disconnect and capped, thanks for the tip.

Is there any way to clean out the vac system?

Thanks again for the reply.
 
hvyman

hvyman

Dang Dude! No Way Man.
Staff member
Apr 17, 2007
12,568
1
0
Fullerton,CA
Have you followed the tsrm to fully test the iac?
And has the throttle stop , dash pot, and tps all been properly set?

Generally I've never seen them sit like that usually there always flat on mine. It should push shit during boost tho. And your problem is not during boost it's at idle. Was installed correctly with the black ring?
 
teedoff00

teedoff00

14 psi boost
Dec 5, 2007
297
0
16
Selah, WA
I did follow the tsrm to test resistance and then operation on the IAC, but I was unable to verify movement (maybe it only moves a little for each cycle, S1, S2, S3, S4, S1 example) but I did here the sound for both open and close.

Can you explain what I am looking for on the throttle stop? Also what is the best way to test the Dash Pot? With the car idling the way it is it is hard to verify as it is stated in the TSRM. On a side note, I get quite a bit of smoke (AFR reads 10.0) when I let off the gas after WOT. Could the Dash Pot be the culprit? It says it is involved with burning all the fuel...

This was the first time I have had the IAC off the car, so I will make sure to put the Check valve, the rubber gasket and then the IAC back on. My concern is if the check valve will leak seeing how the seal doesn't appear to be flush on the check valve. But I would assume this would only be an issue if boost/pressure could flow from manifold to IAC, which in this case (seal is intact, with no tears, but appears mushroomed toward the manifold) it would force the seal to shut completely.

zHfGzVX.jpg
 
teedoff00

teedoff00

14 psi boost
Dec 5, 2007
297
0
16
Selah, WA
A little update:
I traced all my Vac lines and low and behold, I had one disconnected on the valve atop the power steering! :Big Face Palm:... Serves me right for not starting there. The idle has returned to normal and now my AFPR is reading 28 with vac and 35 without.

I am still seeing a large amount of smoke on decel after WOT. Widebands show 10.0-10.5 while smoking. So I know it is fuel... Question is what could be causing this, I didn't have this condition when I built the motor back in 2008... But it has been present for the last 4 years or so (hasn't been driven much).

So... I will be making a thread on that as soon as I have some more details on what I have tested.

Here's a list of things I have thought of to test, some of which I have done. Please post if you have any advice or other things I can test out.

Thanks for the help guys!

Done:
High RPM Decel no boost: No smoke
HIgh RPM Decel with boost: Smoke when under about 4.5K rpm
Log AFR on decel to verify rich: WOT-->Clutch--> Upshift without boost. AFR: 11.5-->15-->10 for about 3 secs then back to ~15 cruise.
Check vac hoses: No vac leak detected
Boost Leak test: Holds pressure

Ideas:
Check PCV system for function: Blew out TB orfices, where else show I cleanout?
Check Dashpot
Leaky injector?

Basic info on my car:
Full re-build, HKS head gasket, ARP throughout, Walbro, 550 cc, lexus afm, Aeromotive AFPR, rebored ct-26, 3" stainless exhaust, 2.5" stainless intercooler pipes and driftmotion fmic, ACT stage 3 clutch, aem tru-boost and uego wideband, zeitronix for datalogging and rebuilt R154 by Marlin Crawler.
 
teedoff00

teedoff00

14 psi boost
Dec 5, 2007
297
0
16
Selah, WA
I did check the TPS per TSRM last weekend and it fit all the specs for resistance. It is also fairly new. I only had a code 42 registered.
Is there another way to check to see if its poorly adjusted?

Thanks again for the help guys, its much appreciated.
 
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