SHO is less peppy at first startup. Fine when its warm

[F-22 Raptor SHO]

trying to find out what may be wrong: My 95 ATX seems a bit slow under 3500 RPM in the morning on my way to work. In fact, if I lay on it it seems like im pulling a jet ski behind me. Once it goes over 3500 and the secondaries open up, it feels like the trailer was removed and the car really takes off. It does this whenever the car has sat for more than a couple hours and is cold.

Once it warms up a bit, the problem goes away. No CE lights or anything. I checked the codes for grins and no problems were found.

Suggestions?

 

[sdpatt]

The secondaries are closed by the vacuum valves. Double check to make sure that they are changing position when the engine is first started. When the engine is cold, note the position of the secondary linkage. Then start the engine or have someone else start it and note the position of the linkages. They should snap closed with the manifold vacuum as the engine is started. If they are not moving, there could be gummed residue in the shaft pivots or a vacuum leak.

 

[F-22 Raptor SHO]

Scott,

Wow, that was a fast reply, thanks....I neglected to mention that when I arrived at work this morning i did goose the engine to see if the secondaries were opening and closing properly. I did think that those may have been the problem. They were opening and closing then, but of course that was after the 4 mile drive. I will go check them at lunch to see if and they were, but I had not checked that at first start up.

I assume the residue problem is internal and not external? How does one clean out this residue? I am due to clean out the sludge in the intake.

Michael

 

[TwiceSHOwn]

Ok i am a little confused.

My 93 ATX will NOT open the secondaries in park. Something about keeping the Tq converter from overheating. Actually i think it wont rev over 4K at all...but i will have to verify that.

The reason i ask is how did you goose the engine to see if they were opening? Or were you saying WHILE you were driving?

 

[F-22 Raptor SHO]

Secondaries are fine....I popped the hood and watched as the engine was started...the valves closed as they should. They then open when you goose it as the should also.

As to Twice's question, yes the atx has a limiter, but if you quickly goose it from under the hood you will see the valves open as the revs go up. Secondaries open at 3500, rev limiter kicks in at 4000.

 

[SHODOGG]

Dude you shouldn't be beating on an engine while its cold anyway. I try to keep it under 4k until my engine is warmed up personally. The car will last much longer this way.

 

[TwiceSHOwn]

Unless you are chipped secondaries open at 4K, at least mine do.

 

[sdpatt]

Well, since the secondaries are closing when the engine is cold, the problem may have something to do with the "open-loop" operation dring the warmup period. In this mode, the EEC is using mapped parameters for the spark advance and fuel injector opening times without adjustment due to the rich or lean readings from the O2 sensors.

Try cleaning the filaments of the MAF sensor by spraying gently with intake cleaner. Also make sure the ACT has its normal red tip showing and is not covered by dirt. There may also be a slight vacuum leak that is overly leaning the mixture until the closed loop mode accounts for the lean condition.

Had there been any maintenace on the upper part of the engine before this problem began? That may give a clue to the cause.

Scott

 

[Milo]

Shodogg, that is exactly what I was going to say. I baby engines until they have warmed up to operating temp.

 

[F-22 Raptor SHO]

scott: the only maintenance I have performed is new plugs last summer and tranny flush last month...I am due for the 60K, but right now with the temps at 20F, Its way too cold.

I know what the MAF is, but dont know how to clean the filaments. Anything in that Exhaustive Auto Concordinance that you have which may shed some light on this procedure would be great.

The ACT acronym is a new one for me, but as u say it is a little red thing, Im guessing its that little red *** inside the air box and has something to do with incoming air temperature. Is my assumption correct?

I consider this board to be a great blessing as it allows other SHO owners to learn from each other and have a fun time.

Oh and Scott, thanks again