Rough starting is getting worse...

[SHOBrad]

I've owned my 100% stock '97 SHO (60K miles) for exactly 30 days now and a rough starting problem I've intermittently noticed is getting worse. Today I went home for lunch (parked the car at home for 1 hr in 45°F weather) and when I went to restart it after lunch, it fired like it normally does then when I let off the key it immediately died. When I hit the key for the second time, it cranked for a moment and then fired roughly and smoothed out. It has fired up roughly several times but has never actually died. Once it is running, it runs perfectly smooth. This sometimes does not happen at all and the car starts smooth. If I was still in my Mustang I would do an Idle reset and change the plugs. Is there some procedure to resetting the idle (resetting the TPS to .998V on the Mustang) for the SHO's? I only have run Amoco ultimate in the car and have been fairly gentle on it. Is there anything I should look for?

Thanks,
Brad

<small>[ October 14, 2002, 01:42 PM: Message edited by: SHOBrad ]</small>

 

[SHOZ123]

Maybe your IAC is leaking or your throttle plate is sticking open a bit. At 60K I would put some new OEM Motorcraft plugs in it.

You don't need the ultimate stuff. Don't baby it either.

<small>[ October 14, 2002, 04:23 PM: Message edited by: SHOZ123 ]</small>

 

[Mr Anonymous]

Easiest first step would be to check for codes. If you don't have access to an OBD-II code scanner, most AutoZones do and will check the codes for free. Could save you some headaches.

 

[SHOBrad]

Had the codes pulled. Nothing. I guess that’s good and bad!

I'm going to take a shot in the dark here and continue on with my Mustang "Idle Reset" thoughts and see where that gets me. I checked the throttle plate motion and it was smooth and closed completely.

Check out this link

Mustang Idle Reset

I used to have problems with my 5.0 starting bad and I would follow those steps and the car would start perfect for quite a while. Does anyone know what the TPS voltage should be at idle for the SHO?

Thanks,
Brad

 

[stephen newberg]

At this point I would pull the plugs and replace them, just to be sure, and probably replace the fuel filter too. Sometimes it is the easy things,

pax, smn

 

[SHOZ123]

You have mail Brad

 

[SHOBrad]

Ok, I dug in and got my hands dirty for the first time with this problem.

I pulled the flexi-tube between the MAF and the T/B to get a good look at the situation. First thing I noticed was that the throttle plate closed all the way. I had always noticed a "catch" in the accelerator pedal when you first touched it but I thought it was a sticky cable or something of the sort. Turns out that the butterfly valve was closing so far that it was getting stuck closed in the bore. I went back to my 5.0 upbringing where the car should idle correctly with no accessories on and with the IAB unplugged. I pulled the plug on the IAB and adjusted the stop screw on the T/B until I got a steady 650-ish RPM idle. I then disconnected the battery for about 20 minutes to clear the tables in the computer, plugged the IAB back in, reconnected the battery and started the car. Seemed good so far. I have since been driving the car for 2 days with no notice of idle problems. It actually seems to be getting better since I did the work. SO far so good!

I wondered after I saw the throttle plate stuck if I did this by pressing the gas too hard. My 5.0 had a definite full-throttle feel to it whereas my SHO does not. The first time I floored it I didn't think I had it all the way down so I pressed a little harder and it felt like it was bending something. Could I have bent the T/B cable linkage or possibly twisted the throttle shaft? This could definitely explain it!

Thanks!
Brad

P.S. I would like to thank SHOZ123 for the TPS voltage chart. I gathered from the chart that the EEC-V in the Taurus is not as touchy as the EEC-IV that I am used to so no TPS adjustment was necessary.

<small>[ October 23, 2002, 09:43 AM: Message edited by: SHOBrad ]</small>

 

[SHOZ123]

You should not have to adjust the throttle stop. The idle air the V8 consumes comes completly from the IAC, fuel vapor purge and PCV systems. If the IAC is disconnected when the engine is at idle, it should die.

The proper way to set the idle if the throttle stop has been moved is this. With the car off set the throttle stop to 2mm clearance. Clear the PCM by disconnecting the battery for a minute or two then let the PCM re-learn idle by doing each of these steps until the idle is steady, usually 10 seconds or so. Idle in park, idle in drive, idle in drive with the MAX A/C on, idle in park with the MAX A/C on. That's it.

If you still have problems there is either a bad TPS which is usually the electrical connection or a vacuum leak.

If you had the TP sticking it may be from a buildup behind it. But what I found was this.

I use to have the throttle sticking coming just off idle and found it to be the throttle cable at the TB. If you look at the cable it has a plastic bushing that is free to move on the cable. This bushing will catch on the cable and cause the binding. What I did was to squirt some silicone up between the outer covering of the throttle cable end and the bushing. This will keep the bushing from moving and allow the cable to ride smoothly into the bushing. I also sprayed some cable **** on the cable betweeen it and the bushing. It has been fine for the last two years now.

<small>[ October 23, 2002, 10:56 AM: Message edited by: SHOZ123 ]</small>

 

[SHOBrad]

SHOZ123, Could you define 2mm clearance? Does this mean to back the throttle stop completely and then adjust it so that it hits the bracket and moves it 2mm? I'm going to completely take the T/B off this weekend and clean all carbon off of it and **** the connections. Sound like agood plan?

Thanks,
Brad

 

[SHOZ123]

There should be a 2 mm gap. At no time should the throttle be touching the stop. I wouldn't put any **** on it except on the cable.

I also wouldn't use any abrasives when cleaning the TB.

<small>[ October 23, 2002, 06:51 PM: Message edited by: SHOZ123 ]</small>