tessicini

I seek the collective wisdom of the forum. It is my understanding that the secondary air injection pump works for a few seconds upon starting the engine. The purpose being to accelerate the catalytic converter heating. I just had my 1998 flushed using a variation of the conventional wisdom. The CEL is out and I am wondering what I can do to prevent or postpone a return of the problem. I have two thoughts for criticism:

1. Wire a switch to actuate the SAI pump relay every two or three starts when the engine is off.

2. Wire a switch as in 1. and a facility which will enable me to inject a small amount of Techron or equivalent and manually actuate the SAI pump while the engine is running (or while the engine is off).

It seems to me that there must be some process which can be applied to prevent or at least reduce the occurance of this problem.


Please comment.

chris walrod

First off and most importantly, welcome to Rennlist. We'll help you spend your hard earned money

Your SAI pump runs for ~30 seconds upon cold or colder startups. I dont feel running it longer will do anything to prevent these small ports from occluding.

Best would be to avoid driving the car very short distances, in other words, get her good and hot each drive, and drive it hard. Redlining these cars every once and a while is, what I believe, good for them. My car typically runs smoother and better after track events.

tessicini

If the carbon which plugs the SAI ports is generated during combustion, why don't you think that there is a possible benefit to some form of cleaning cycle with or without solvent and without combustion. This in essence would be a mini version of the way these plugged "guys" are unplugged by one of the recommended cleaning processes....isn't it?

I don't understand how running the engine hard can improve the plugging of the SAI ports. It can remove carbon buildup in the cylinders, but how does it help the SAI path?

chris walrod

More in terms of building heat in efforts to prevent further carbon build up. It will take more than running the air pump to periodically clean these ports. Better would be to introduce high pressure and high volumes of air like that of a shop air compressor.

I dont feel combustion is necessarily the sole cause, more so oil that has leaked past the valve seal and eventually finding its way into this small port at start up. Heat will help burn-off this oil residue. Again, I speak mostly in theory.

Phil

change your check valve at 5k......8k.....10k.....15....
in other words....change the check valve( do a search)...........do a search for a post by ME.....regarding check valves......, and ...........read my disclaimer....but most of all.....
have a great day!!

kkim

I'd like to add my .02 as I just had the "pleasure" of clearing a plugged port using a home flush method guided by Laura's (thank you!!) unsolicited advice.

https://rennlist.com/forums/showthre...&highlight=sai

First, I would agree with Phil that the SAI valve should be changed regularly... at what interval, that is for you to determine as there is no set schedule for it as a maintenance item. What I have found is a lot of moisture in the SAI passages from what I assume is from condensation. This leads to the SAI valve rusting quite badly. I installed a brand new valve a few months ago in hopes that it would help my CEL problem. It did not, so I went in again recently to do the flush. What I found of the recently installed valve was it was already starting to corrode from the moisture being caught in the SAI passages.

I too have thought of teeing in a piece of rubber hose above the valve so one could introduce some sort of cleaner, but have been warned that I would need to find a suitable hose able to withstand exhaust engine temps in the likelihood of a SAI one way valve failure. Not finding a suitable hose could lead to an engine fire, which I would like to avoid. There is the other problem of what injecting the cleaner would do to the cat. The results have been debated before w/ a majority siding on possible damage to some very expensive cats.

With regards to Chris's comments about clogged ports, I found the clogs in mine to be way up away from the hole in the exhaust port area. I ran a wire a good 3-4 inches up the passage and found no real buildup. It took blocking up the exhaust ports with rubber stoppers and pressurising the SAI passages to about 100psi to finally get some of the carbon out of the passages. When it did come out, I took a good look at the bits and they were solid, hard bits of black looking material which could very well be oil deposits that get mixed with the water in the SAI system and somehow hardens in those passages. I do believe the cleaners and solvents do work to break down and soften deposits which are relatively new, but if deposits are left to sit for many miles, they tend to harden and be very resistant to cleaners breaking them down. Better not to wait for that stage to occur, which is why I would recommend doing the flush on a regular basis. If someone could invent a SAI passage "rotor rooter", they would make a million dollars and even more friends.

My advice would be to change the valve and do the DIY flush at regular 30k intervals, which I feel is a conservative estimate, but takes into account the infrequent nature some of the "garage queens" get run good and hard.

Just be thankful there is a DIY for the flush... prior to this, the fix was an top end rebuild at $6K!!

More and more shops are starting to offer the flush at about $1k, which is not that bad, considering the parts alone ran me about $200 and the flush itself is very time consuming, including actual waiting time for the deposits to "loosen" up, can run into the days or weeks. You can't "hurry" the process.

tessicini

Thanks for the discussiion. Is it possible that the plugging of these passages is CAUSED by the premature failure of the check valve? Has anybody had to clear these passages and noted that the check valve was still OK?

kkim

My original 60k mile valve that I removed was rusty, but was still functional as a one way valve.

Lorenfb

"I don't understand how running the engine hard can improve the plugging of the SAI ports. It can remove carbon buildup in the cylinders, but how does it help the SAI path?" - tessicini -

You are correct in that high revving of the engine will NOT reduce the clogging of
the SAI ports but will likely increase the carbon buildup if the engine has excessive
oil consumption. Also, the high revving further increases the valve guide wear causing
more oil burning & thus a greater likelihood of clogged SAI passages.

For additional SAI info check here ( www.systemsc.com/pictures.htm ).

tessicini

Loren,

My understanding is that these passages are rough (as cast). Has anyone considered; or is it even possible to clean them out with a drill or reamer? What is your opinion of teeing in a line to occasionally bleed in a small amount of solvent (techron et al ) into the SAI manifold before the check valve.

Tony

Lorenfb

"My understanding is that these passages are rough (as cast). Has anyone considered; or is it even possible to clean them out with a drill or reamer?" - tessicini -

Not really possible given the orientation of the passages as they go thru the
cam housing, cylinder head, & etc. Adding an access port for a cleaning solution
may not achieve much versus just removing the air check valve.

tessicini

I don't understand...I assumed the check valve was to keep the "higher pressure" exhaust gas from flowing back into the SAI blower. What do you think would be accomplished by removing it?

The teeing idea would be to accomodate an occasional cleansing upon start up when the blower runs or on other occasions when one would want to force a small amount of solvent through the passages.

Lorenfb

"What do you think would be accomplished by removing it?" - tessicini -

Sorry, I meant to say that the check valve is removed, as many have done,
to allow entry of the solvent cleaner which obviates the need for an additional
port.