I'm having some trouble with my 89 GTUs and emissions. I'm currently not trying to pass a sniffer test, but I know my car will never pass. The exhaust smells like a car without a cat on. It runs very rich and makes my clothing reek of exhaust after a couple of seconds... It also backfires when shifting above 6500 RPM.

What I have done:
Removed the intake and replaced all vac lines.
Cleaned the injectors.
Adjusted the throttle body according to FSM
Adjusted the TPS
Replaced all intake manifold gaskets
Replaced the plugs. Wires are a year old.
Timing is set.

Verified operation/resistance of:
BAC
water thermo sensor
air intake sensor
AFM - Had to replace with a used one
ACV

What I have found:
(There are two things that don’t “Jive”.)

1st is when I pull the hose from the Air-Pump to the ACV, I can feel air coming FROM the ACV inlet. According to the FSM, I should not be able to feel anything coming from the ACV inlet. The test says when you rev the engine, you should feel air being sucked IN around 2600-3000 RPM, but not out. So I replaced the Anti-Afterburn check valve. No improvement. I exchanged the ACV with a known working one…no improvement.

2nd is a possible typo in the FSM? Page F1-63 “Testing the Relief Solenoid Valve”, the test says air should not be sucked in below 3600 RPM and have vacuum above 3600 RPM. My car is opposite. The solenoid is working, but the output is exactly the opposite of what the FMS says it should be. Below 3000 RPM, the solenoid sees 12V and it opens. Above 3000 RPM, the solenoid sees 0V and closes.

I’m kind of at a loss here. I’m trying to restore the car to 100% stock and this is bugging the hell out of me. Any help is greatly appreciated. Sorry about the long post.

PS: Please keep your “just remove all the emissions” comments to yourself. Thanks!

 

http://www.geocities.com/huguesdc1/secondary.html

for acv, you should have vacuum on both nipples at idle. If you don't, there's a problem with the solenoids or TPS.

If you are running rich, I would look into the water thermosensor first and make sure it's ok though.

hugues -

 

I'm not a guru because my birth certificate lists a father, but I have some ideas.

On the part about the air blowing out the ACV inlet....you should feel air being sucked in when you LET GO of the throttle after reving the engine. Thats when air should be sucked into the intake manifold. Not while being rev'd UP. And I would suspect that checkvalve (the spoked one) but that is not where the air is sucked into the intake manifold. It's sucked into the intake thru another passage DURING DECELERATION. If you feel air blowing back toward the airpump, while the engine is rev'd UP, then I'd suspect the checkvalve in the split air pipe. That somewhat mushroom looking one.

On the second thing you listed: Your manual seems to be wrong. The vacuum hose that leaves the Relief Solenoid should have a vacuum coming from the solenoid at idle and below 3600rpm. When above 3600 rpm there should be no vacuum.

I do that test a touch different than the manual. I pull the large hose off the bottom of the ACV. Then I reach across the engine while its idling and pull the Blue plug off the solenoid. When that is done a large volume of air should exaust out the large hose on the bottom of the ACV. Then I put the Blue plug back on the solenoid. Then I rev the engine moderatly until it gets above the 3600 rpm. Wnen 3600 is reached.....a large amount of air should exaust out the bottom of the ACV. I do it that way because of the difficulty of pulling the small vac hose off the solenoid.

You should also confirm that the Switching and the Relief vacuum hoses are not swapped above the Air Control Valve.

 

Thanks for the link. I'll be educating myself some more in a minute...

As for the solenoid test: I do have vacuum on both. So I guess my FSM has a typo. BTW: I'm using the manual found at FC3S.ORG!

So that answers one of my questions.

 

I'll take a closer look at the Split Air Pipe check valve. I know I tested it when I had the engine apart. I could only blow through it one way, but maybe my lungs weren't a very good test and it leaks with more pressure?

As for tesitng the ACV, it does appear to be functioning normally. The vac lines are not mixed and it passes all the FSM tests EXCEPT for the problem I've mentioned above with it blowing back towards the airpump.

At least I have something else to look into. Thanks for the tips.

 

Get a long piece of vacuum hose. Connect it to where each of the two vac hose for the acv are above it, one at a time. Suck on each one. The idea is to make sure that each will hold a vacuum. If the diaphram in the acv is bad, then you won't be able to hold a vacuum as you suck on the hose when it is attached to either of the nipples.

 

I'm already a step ahead of you here. I could get the diaphrams to move, but they wouldn't hold pressure for more than a second or two.

So now I'm "rebuilding" my ACV. The diaphrams are good, but they leak around the sides, so I'm going to use some high temp silicone on them. I'll let you know how it turns out.

My only problem is finding a new ACV gasket! I think I'm going to have to make a new one.

 

*UPDATE*

My ACV rebuild was a success. History: My car failed the ACV test. IE: Air was coming from the ACV->towards the Air-pump at idle.

I disassembled the ACV completely and cleaned it with carb cleaner. (Very easy to do) I checked the operation of the two electrical solenoids and they were fine. The two vacuum diaphragms were in good condition, however they leaked around the outside of the diaphragm seal. So I put a thin coating of silicone on the diaphragm seals and presto! The diaphragms held under vacuum.

I also had to make my own gasket since nobody stocks an ACV gasket. Luckily my old gasket survived long enough to make a template for the new one. *If anyone needs a template for the ACV gasket, I can scan it into PDF and email it to you.*

I guess that’s it. The car is running smoothly and the exhaust is no longer making my eyes water! Thanks for everyone's help.

Jeff

 

eeek! A success story. Scary

 

LOL! Tell me about it. Scary when things work.

I was really surprised how simple the ACV is once you get it apart.

 

About the ACV gasket, mazdatrix does have them, but they dont appear to be listed on the website. I had to call for a part number.

 

In the hope that someone reads this.........the acv can and will cause idling problems when old and grey. The ONLY way it can do this is if the antiafterburn diaphram/poppet/whatever goes bad. The fix is simple. Take the acv off. Get a tube of red rtv. Plug the small approx 3/16 hole that feeds from the acv to the intake air manifold.

I had this happen on the 86 non-turbo this weekend. Its not real hard to determine if the acv is leaking. Just warm up the engine and let it idle. Then remove the Blue plug from the Relief solenoid. If there is a definite change in the idle....then the diaphram/poppet is amiss.

I have no after effects of doing this. Never have had any backfiring etc with or without the thing plugged.

And no, Virginia, the rtv will not be sucked into the intake and destroy your engine. Let it set up for a hourl or so before idling the car again.

 

B@stards! I had the guy on the phone and he said they didn't carry it. Oh well, I found a piece of gasket material for $1.25 at Autozone. Took me about 15 minutes to trace and cut out. How much for the gasket from Mazdatrix?

 

Its been awhile, but I think it was like $5 or $7.

 

In the hope that someone reads this.........the acv can and will cause idling problems when old and grey. The ONLY way it can do this is if the antiafterburn diaphram/poppet/whatever goes bad. The fix is simple. Take the acv off. Get a tube of red rtv. Plug the small approx 3/16 hole that feeds from the acv to the intake air manifold.

I had this happen on the 86 non-turbo this weekend. Its not real hard to determine if the acv is leaking. Just warm up the engine and let it idle. Then remove the Blue plug from the Relief solenoid. If there is a definite change in the idle....then the diaphram/poppet is amiss.

I have no after effects of doing this. Never have had any backfiring etc with or without the thing plugged.

And no, Virginia, the rtv will not be sucked into the intake and destroy your engine. Let it set up for a hourl or so before idling the car again.