Idle Stumbles When Blip Throttle

[SHO#7]

The title pretty much sums it up. I park my 93 in my shop at work. Meaning that sometimes I have to move it around to get a car in the flat bay. This is what happens...

Right after I have started the car and begin to back out ( No warm up is necessary, the shop is 70 degrees ) upon the lightest throttle application the idle will stumble to maybe 700, from the normal 900. Then it quickly returns. It will only do this one or two times. Let it run for 20 seconds and it does not do it at all.

I know this is a stupid thing to be concerned about, but it bothers me. I have a few ideas, I am just looking for some advice. I had a situation like this that it would do it all the time, and I cleaned the MAF. That problem went away. It has only been a couple of hundered miles since then. Did I make a film on the MAF wire and now it has to get red hot again ( 20 seconds of run time ) before it can read correctly? Do I have to wait for the O2 sensor heaters to warm up ( they are older, 60k + ). Do I just let the car run for 20 seconds...

There are no codes. Almost every sensor is new on this thing. IAC, all the 120k parts are fresh, intake is clean, MAF wire looks fine, throttle plate is clean ( coolant is bypassed ), ECT is new.

Any suggestions?

Thanks
Mike

 

[Racer X]

I'm dealing with the same headache, but in my case it lasts longer than 20 seconds. More on the order of a couple of minutes, depending on how cold it is outside. Additionally, on cold start, there is an intermittant miss that I can't figure out, since I'm only a year into my 60k.

So far I have a new TPS, DIS, CID, CPS, and I cleaned the MAF thoroughly, and it still persists. It's done this every winter since I've owned the car, and so far I haven't been able to figure it out, though this winter was worse than last winter.

 

[Eliw]

My 89 does this as well, depending on how cold it is. When I can, I just let it warm up a little more than normal. It will do it till the temp needle moves up a notch or two. In the summer though, it doesnt do it for too long

 

[SHO#7]

I have no missfire at all. The plugs are 3k old. The Taylor wires are 3k old also. No oil in the wells. The car runs perfect ( In fact, she is pretty strong ). I think you may have other issues if you have some missfires going on. And again, the garage is 70 degrees. It is not cold. It does however only do it on a cold start ( IE. sitting overnight )

Maybe she just runs a little rich and is more noted during closed loop warm up cycle? O2 Heaters are slow to turn on?

Other thoughts?

Mike

 

[Eliw]

I dont have a mis neither. Racer X, Queens NY? What color SHO?

 

[rangerj]

The first place to look for cold idle issues is the idle air bypass. Clean it and the passage and see if the situation improves. If not, check codes for other possible sensor problems. Also check for any blockage, such as a dirty air filter or obstruction in the air flow. Also check the snorkle (large hose from the air cleaner to the throttle body) for any cuts or splits. An air leak in the snorkle can cause problems and often goes undetected.

 

[SHO#7]

The first place to look for cold idle issues is the idle air bypass. Clean it and the passage and see if the situation improves. If not, check codes for other possible sensor problems. Also check for any blockage, such as a dirty air filter or obstruction in the air flow. Also check the snorkle (large hose from the air cleaner to the throttle body) for any cuts or splits. An air leak in the snorkle can cause problems and often goes undetected.

Thanks for the imput. However, I did just replace the IAC valve. I had the intake off for a cleaning and had suspected that may have been the cause. I replaced it and there was no change. The intake is clean and, for the most part, oil free. I did check the snorkel, as I have had issues with it on customers cars, and all is well. Again, only 20 seconds or so, and then the condition goes away.

There are no codes, according to my scanner.

Mike

 

[projectSHO89]

Mike,

Check your TPS output voltage witht he switch in RUN and engine off.

Should be as close to +.99 VDC as possible without going over.

This is a popular adjustment among the Mustang crowd and is said to improve throttle tip-in. Who knows, it might help your tip-in at startup.

Steve

 

[Racer X]

I dont have a mis neither. Racer X, Queens NY? What color SHO?

Yeah, East Elmhurst right by LaGuardia airport. It's a red Gen 2 with the TCCA logo in the back window, and clear corners. Where in BK are you?

 

[Eliw]

Yeah, East Elmhurst right by LaGuardia airport. It's a red Gen 2 with the TCCA logo in the back window, and clear corners. Where in BK are you?

Im in bushwick right on the border of brooklyn and queens. I have seen your car. My bands drummer lives directly "across the street" (more like the grand central) from Lguardia airport. I usually take him home and his friends and I always see that red SHO. Small world, small world.

in anycase, ive got to check my TPS like stated above. I really hate it when my car does the whole Idle drop when its cold out.