Intermittent high idle after TPS replacement.

[green57]

The idle in my SVO has been sticking at 2000 rpms after the car warmed up. This has been happening for a few weeks, so I figured it was time for a new TPS. While installing the new TPS I also cleaned my IAC, throttle body and EGR. I put it all back together with new gaskets, and reset the base idle and timing. I set the new TPS at .984 volts at idle up to above 4.75 at WOT.

I took the car out for a test drive and everything seemed to be working fine except every now and then when I let off the throttle the idle would go up to about 2100 then come down and hold at 2000. A quick tap on the throttle and the idle would drop back to normal. Before the new TPS tapping on the throttle would not help…so at least now it will go back to idle, but it still is not correct.

I thought there might be something else wrong so I pulled these codes when I returned from the test drive.

I have an early 85 all stock except for a LA3 with after market 35 pound injectors, and a 3" down pipe.

KOEO

54 ACT or VAT sensor signal voltage is to high.
81 Boost solenoid - circuit failure. I have a manual boost controller so that would make sense.
82 Electro - Drive Fan: circuit failure. I did notice the fan did not turn on after the gauge was reading to the high side of normal.
83 could be EGR or fan. Not quite sure about that one.

KOER

24 ACT or VAT not at normal levels.
25 KS not detected during Engine Run Self-Test
34 EGR Pressure Feedback signal voltage out of limits or insufficient EGR flow
75 Brake on/off switch always closed circuit. No worries on this one.

Would the 54 and 24 VAT codes cause idle problems?

Not quite sure what to do, any help or ideas for a repair?

Thank you,

G57

[MikeFleming]

Throttle shaft/bores are probably worn. Set the base (CT) TPS lower to 0.900/0.920 VDC.

[green57]

Mike,

Thank you for the advice I'll give that a shot.

Should I be worried about the 54 and 24 codes? I was thinking that I might be getting these codes because the LA3 is not receiving a signal from the absent ACT sensor.

Is there a list of codes related to the LA3 swap that can be disregarded. Number 75 is understandable to me, some of the others I just don't know about.

Any suggestions about the codes related to the EGR? I have seen them the last few times I've checked for fault codes, and it made sense because the small green vacuum line was broke. I have replaced the line and was not expecting to see any codes related to the EGR after the repair. What else should I check?

Thanks again

G57

[MikeFleming]

Should I be worried about the 54 and 24 codes? I was thinking that I might be getting these codes because the LA3 is not receiving a signal from the absent ACT sensor. Since those sensors are not installed, the LA* EEC is merely telling you they are missing.

[green57]

Mike,

I Set the TPS to .902 but I still get the high idle every now and then. Its usually when I'm driving at slower speeds like in a school zone or parking lot. A blip to the throttle drops it back to normal, its just annoying. I don't know where to go from here, does some one make an after market throttle body that fits the SVO intake?


On a side note it seems that the milage is not back to where it should be. Normally I get around 280 miles a tank normal driving, around 305 highway. I thought with the new TPS it would go back to normal, but it looks like I'm coming up short again.


Is there another sensor that would effect the cars idle and gas milage? All the sensors are original except the O2 sensor and the fuel pressure regulator they were replaced in 2007.


Thanks again for any help.


G57

[dznj]

Subscribing, as I am in the same boat. I lubed up the throttle cables, and replaced wiring from the TPS connector to the connector on the passenger side. Improved, but still somewhat intermittent. As with green57, the idle will drop with a slight throttle blip.

[Chalky]

I chased one of these for a few months, turned out the ball that the accelerator cable snaps onto had worn formed a little burr which was causing the cable end to stick. Check for burrs, rub with some fine sandpaper and add some grease to the ball and socket in the cable end.

[dznj]

Sorry to bring this back from the dead, but my SVO has had this issue for a while now. I tried an experiment yesterday, with interesting results. I started the car and backed it out of the garage. It hadn't run for approximately 3 days. Let it sit in the driveway, and once it warmed up a little, I blipped the throttle and the idle dropped to just under 1K. I let the car sit until the temp gauge got up to the high side of normal and the fan kicked on. Drove the car. No issue.

When I drive the car normally, the temp gauge never comes up to the normal range. The needle just sits at the hash near the "C". Once I started driving the car yesterday (outside temp ~ 60F) the gauge dropped down almost to the "C".

I'm wondering, if I have a thermostat/thermostat housing issue where the T-stat is stuck open and or the housing is corroded internally and letting water past the T-stat. That could explain why the car is running so cold, and potentially explain the idle problem, since the car is not coming up to temp.

Thoughts?

[MikeFleming]

A thermostat issue is indeed possible but that won't have an effect on the idle speed after 5 minutes of running. The EEC will conclude that the coolant temp sensor is merely off and carry on as idf it's a warm/hot engine.

As usual check coolant quality/level and circulation rate (worn/rusted water pump impeller).

Then check for worn throttle shaft/bores. One way is to monitor the closed throttle TPC voltage then start and idle the enigne without touching the throttle. If the bores are perfect, the TPS voltage will not change.

[dznj]

A thermostat issue is indeed possible but that won't have an effect on the idle speed after 5 minutes of running. The EEC will conclude that the coolant temp sensor is merely off and carry on as idf it's a warm/hot engine.

As usual check coolant quality/level and circulation rate (worn/rusted water pump impeller).

Then check for worn throttle shaft/bores. One way is to monitor the closed throttle TPC voltage then start and idle the enigne without touching the throttle. If the bores are perfect, the TPS voltage will not change.

Thank you Mike for the fast response! I did add a spot of coolant to the overflow (not enough to matter, IMHO), and the water pump was new when the motor went back in the car less than 2 years (5K miles) ago.

How would I check the throttle shaft/bores?

D

[dznj]

Will do! Thanks again! The car is so much fun to drive without the annoying idle nonsense, and mildly infuriating when it won't behave.

Unfortunately, the 'season' is coming to a close here in MA, as we are supposed to get snow on Wed. Once they lay down the salt, the SVO goes to bed until Spring.

[MikeFleming]

Once they lay down the salt, ... Marguarita time? Or a circle of salt with candles?

[dznj]

Marguarita time? Or a circle of salt with candles? I wish ! The old salt on the roads to melt ice and car components.....

D

[svono50]

dznj, your idle issue is likely a throttle shaft/bore related issue, since you can get the idle back down with a blip of the pedal...but there could possibly another culprit. I have been blipping my throttle for years and know that there is some play in my throttle shaft/linkage...comes with age/wear no big deal. I would also get a 'jumpy' idle where the idle would blip on its own, no touching the pedal and just sitting and idling at a light. Kind of embarrassing when sitting next to a Viper or Corvette as you appear to be challenging them to a stoplight race.

I would invite you to try a simple test where you just need to manipulate/move/twist a couple of harness connections along the firewall. The two connectors that are in the harness that leads to the TPS/IAB/ECT sensors are the ones I am talking about. With the car warmed up and idling, start moving/manipulating the wires leading into the connectors and see if you get any idle blips. If you do, it could be the result of a loose pin connection in one or more of the pins of the connectors. I found mine after performing a 'wiggle' test with the EEC and working my way through the connections to find the culprit. One of the female pins in the 4-wire connector had opened up and was causing an intermittent 'break' that would cause the computer to pop out of closed loop mode and run my idle up based on its internal tables (see pic below). My ultimate fix was to replace the harness connectors with some Weather Pack connectors, but a temp fix of closing up the female pin did work for a couple of years. Once it came back, I simply decided not to fiddle with it again and move onto a more robust connector system. The location of the connectors above the downpipe combined with my track day participation is the most likely suspects of why the pins were opening up through heat cycling. YMMV.

Before:
7954

After:
7955

[dznj]

dznj, your idle issue is likely a throttle shaft/bore related issue, since you can get the idle back down with a blip of the pedal...but there could possibly another culprit. I have been blipping my throttle for years and know that there is some play in my throttle shaft/linkage...comes with age/wear no big deal. I would also get a 'jumpy' idle where the idle would blip on its own, no touching the pedal and just sitting and idling at a light. Kind of embarrassing when sitting next to a Viper or Corvette as you appear to be challenging them to a stoplight race.

I would invite you to try a simple test where you just need to manipulate/move/twist a couple of harness connections along the firewall. The two connectors that are in the harness that leads to the TPS/IAB/ECT sensors are the ones I am talking about. With the car warmed up and idling, start moving/manipulating the wires leading into the connectors and see if you get any idle blips. If you do, it could be the result of a loose pin connection in one or more of the pins of the connectors. I found mine after performing a 'wiggle' test with the EEC and working my way through the connections to find the culprit. One of the female pins in the 4-wire connector had opened up and was causing an intermittent 'break' that would cause the computer to pop out of closed loop mode and run my idle up based on its internal tables (see pic below). My ultimate fix was to replace the harness connectors with some Weather Pack connectors, but a temp fix of closing up the female pin did work for a couple of years. Once it came back, I simply decided not to fiddle with it again and move onto a more robust connector system. The location of the connectors above the downpipe combined with my track day participation is the most likely suspects of why the pins were opening up through heat cycling. YMMV.

Before:
http://www.svocop.com/forum/attachment.php?attachmentid=7909&stc=1

After:
http://www.svocop.com/forum/attachment.php?attachmentid=7910&stc=1


Thank you Ted. I will double check this again as well, and reply back as soon as I have some answers.

Happy Thanksgiving!

Doug

[Under Pressure]

I will have to check that . I think I have a bad connector one of the ones you're talking about. ThanksGiving

[svono50]

If you do replace your factory connectors with Weather Pack connectors and don't want to build them yourself (i.e.- purchase all sub-components and tools, etc) you can purchase connectors with pigtails. I found an online shop that sells them for very reasonable prices as compared to all the ala-carte components, it was Columbine Automotive Products in Colorado. I know I will be going back to them if/when I need other replacement connectors. I have a feeling I could have specified the wire gauge and colors for the pigtails, but didn't think of that till after I received mine...damn hindsight being 20-20 of course!?! I have a write up on my connector replacement over on the 'other' forum in my project thread for anyone wanting to see more details.

[dznj]

Well, it has been a while, but I think it is finally figured out! I replaced both the 3 wire (TPS stuff) and the 4 wire original factory connectors with the Weather Pack connectors from Columbine as svono50 suggested. I also replaced most of the ground wire from the TPS to where the grounds meet for the TPS/coolant temp (I think) and the ground that runs to the computer. I reset the base idle, reset the TPS voltage (again, and again, again!) with little to no improvement. Timing was perfect, so it left me scratching my head. JTurbo stopped over the other day and we turned down the idle screw and the hanging idle improved, but did not go away.

Finally, this past Sunday, I repeated everything again, except that I additionally turned down the idle screw so that the car idles at ~900 RPM with the IAC plugged in. VIOLA! It seems to be good now.

Those Weather Pak connectors with pigtails are the way go go! The old Ford barrels were worn out, and the clips had broken off eons ago anyway, so it was good to replace them. Finally, after 3 years, I can drive the car without the dreaded 2K idle!

Next, on to headlight/fog light relays. And then to get the AC working.

http://i1029.photobucket.com/albums/y356/dmoglin/1985%20Ford%20Mustang%20SVO/IMG_20160509_185314971_zpsynpi0wsc.jpg (http://s1029.photobucket.com/user/dmoglin/media/1985%20Ford%20Mustang%20SVO/IMG_20160509_185314971_zpsynpi0wsc.jpg.html)
http://i1029.photobucket.com/albums/y356/dmoglin/1985%20Ford%20Mustang%20SVO/IMG_20160509_185305175_zpsqzqxdi1c.jpg (http://s1029.photobucket.com/user/dmoglin/media/1985%20Ford%20Mustang%20SVO/IMG_20160509_185305175_zpsqzqxdi1c.jpg.html)
http://i1029.photobucket.com/albums/y356/dmoglin/1985%20Ford%20Mustang%20SVO/IMG_20160502_135027867_zps8kinb90s.jpg (http://s1029.photobucket.com/user/dmoglin/media/1985%20Ford%20Mustang%20SVO/IMG_20160502_135027867_zps8kinb90s.jpg.html)
http://i1029.photobucket.com/albums/y356/dmoglin/1985%20Ford%20Mustang%20SVO/IMG_20160502_135019150_zpsjdticonq.jpg (http://s1029.photobucket.com/user/dmoglin/media/1985%20Ford%20Mustang%20SVO/IMG_20160502_135019150_zpsjdticonq.jpg.html)

Cold Car: http://i1029.photobucket.com/albums/y356/dmoglin/1985%20Ford%20Mustang%20SVO/th_VID_20160516_173309643_zpsj314njn6.mp4 (http://i1029.photobucket.com/albums/y356/dmoglin/1985%20Ford%20Mustang%20SVO/VID_20160516_173309643_zpsj314njn6.mp4)

Warm Car: http://i1029.photobucket.com/albums/y356/dmoglin/1985%20Ford%20Mustang%20SVO/th_VID_20160516_180253955_zpsewzuh9ph.mp4 (http://i1029.photobucket.com/albums/y356/dmoglin/1985%20Ford%20Mustang%20SVO/VID_20160516_180253955_zpsewzuh9ph.mp4)



Thanks!

[JTurbo]

Glad it's running better - drive the wheels of if it!!!

Don't forget to get a new clamp for the VAM to turbo hose....

[dznj]

JT - I did the clamp the next day. Cross that one off the list!;)

D