High idle and idle in motion . Not TPS, IAC. Need some ideas

[Axianator]

The TPS voltage requirement was directly from Ted B. and not as a means of TPS HP mod but for the LPM calculations.

I understand that Ted was the one who instructed you to adjust your TPS voltage. However, I still stand by my original post - if Ted (or anyone else) is encouraging you to adjust your TPS voltage or telling you that your TPS voltage "must be set as close to 1.0v as possible", then that person is woefully misinformed and is spreading a popular misconception. All EEC-IV computers, including the EEC-IV-equipped '89-'95 V6 SHO, use relative TP as the basis for their TP-based calculations, which may be explained thusly:

Relative TP = 'Absolute TP' - 'Closed Throttle TP'

where:

'Absolute TP' = Current absolute TP voltage (0-5v) as reported by the TPS
'Closed Throttle TP' = Last closed throttle TP voltage captured by the EEC from the TPS. On some models, this value is captured only at startup, while on other models, it is constantly being captured by the EEC in the background.

Example:

Say your absolute TP voltage at WOT is 4.5v and your closed throttle voltage reads the standard 0.74v. Subtract the two and you end up with a relative TP voltage of 3.76v. Now, if you adjust your TPS so that your closed throttle voltage reads around 1.0v, then your WOT voltage will automatically read higher by the same amount, effectively cancelling out the TPS adjustments you just made:

Old closed throttle voltage = 0.74v
New closed throttle voltage = 1.0v
Difference after adjustment = 0.26v

Old WOT voltage = 4.5v (before adjustment)
New WOT voltage = 4.76v (after adjustment)

As you can see, there is no need to adjust the TPS for a "higher" voltage reading on any EEC-IV-equipped vehicle since these adjustments will not make any difference. Yes, boys and girls, you heard correctly - the famed "TPS modification" that has long been touted by many Mustang owners is nothing but a hoax. The only time you should adjust your TPS is if you have a fully-functional sensor that is reading below the minimum range that the EEC expects to see when capturing the 'Closed Throttle TP' value above. Corporate range values for closed throttle TP are usually 0.45-1.2v, although actual values will vary between vehicle computer calibrations.

The ideal TPS idle voltage really is a mystery, as my TPS was at 0.74V stock. Bumping it up to .99V was a huge change but it worked well for 5 years.

As I have shown with my comments above, there is no mystery surrounding the "ideal" closed throttle TPS voltage.

Ted would be the right person to explain this.

Although I certainly have the utmost respect for Ted's prior tuning knowledge and experience, and while I would not presume to speak for him myself, I will say that Ted is not the only person who understands EEC theory and operation, nor is he the only person who can explain these particular operational facets of the V6 SHO EEC.

Maybe I overlooked the fact that my new car has way less miles and the bearing resistance on all the accessory pullies is less so the idle is higher than before?

Engine idle speed is governed completely by the EEC, which uses spark advance, fuel delivery, and the ISC assembly to control engine idle speed for specific situations. Unless you are ingesting large amounts of unmetered air into your intake through a vacuum leak, you should see the same idle speed at all times once the EEC has run through it's initial startup logic.

I'm still with Scott and RStalvey on this - pull the LPM first, then check again for leaks.

 

[zerg1024]

just a thought take out the chip then see where the idle is at it might even be the adjuster screw on the throttle body itself may have been set to high or maybe it loosened up.

 

[U_SHO?]

Sorry for the delay;

Axianator, I agree that TPS idle setting is relative, as a matter of fact, I proved it by relearning idle earlier on 3 different voltages (.99, .9, and .74V) for absolutely no changes. I always respected Ted's knowledge as much as Scott's and just did what I was told in this case knowing it can't hurt to adjust the TPS. If TP is relative, and my TPS works ok over the whole range, my TPS adjustment won't hurt the idle speed.

It is good to know that min range goes as high as 1.2V so that rules out ECU thinking that my foot is on the throttle at .99V. That was a good write up though. Do you know if there is an adjustment in the chip for how many RPMs to bump idle when in motion? I wish Ted chimes in but I had trouble getting in touch with him in the past week or so.

I haven't removed the chip yet because my base idle seemed to have dropped since I reconnected IMRC solenoid and relearned the idle and haven't used A/C the past week. The idle is lower but the tach reading is not as smooth as on the old car and the idle in motion is just not consistent and varies between the 1300 and 1450 now and it is related with outside temperature too. I also got 180F t-stat to put in soon as that is the last big difference between the two cars.


Likely I will have to take the ECU out to remove the chip because I taped it pretty tight in there and I am waiting just a bit on that because of my other responsibilites and the need for the running car. Besides, I don't have cats on my exhaust and with Ted's LPM, I noticed a difference in torque with and without the chip. Due to scavenging I'd say the chip, besides advancing the timing, makes my engine run a little richer to make it up for less backpressure in the exhaust so as long as I have no cats, I think I should keep it.

Zerg1024, the throttle stop is at factory setting. And when IAC valve is disconnected, I got no idle as the butterfly is completely closed.

Thanks all

Igor

 

[RStalveyARFF]

Personally, I'd throw that LPM as far as I possibly could. Your car will run absolutely fine without an LPM. I gained 2hp and lost 2 lb/ft of torque with a Ted B programmed LPM for my car. Not worth it.

 

[Axianator]

If TP is relative, and my TPS works ok over the whole range, my TPS adjustment won't hurt the idle speed.

Yep - so long as your closed throttle TP voltage remains within the expected aforementioned range and your TPS is functioning properly, then your TPS adjustments will not have any effect on your engine idle speed, throttle response or power output.

It is good to know that min range goes as high as 1.2V so that rules out ECU thinking that my foot is on the throttle at .99V. That was a good write up though. Do you know if there is an adjustment in the chip for how many RPMs to bump idle when in motion? I wish Ted chimes in but I had trouble getting in touch with him in the past week or so.

Most EEC calibrations contain adder functions or parameters that control the amount of base idle speed adjustments to apply while the vehicle is in motion. However, I have yet to see any Ted B.- or SHO Shop-based LPM program that modified any of these factory functions (and I have examined many of these programs).

 

[hawkeye18]

Well, all the simple solutions have been covered, so now we go into the ridiculous: have you checked your throttle body to see if there is something keeping it from completely closing? Is there a leak in the air tube between the MAF and the TB on the bottom, where carb cleaner wouldn't necessarily get in there? Is there something physically keeping the throttle cable from closing all the way? When my Cruise control cable retainer thingy snapped, it snagged the CC cable and wouldn't allow the engine to go below 4K rpms! boy was that interesting! You mentioned issues with the cruise control cable, try disconnecting it from the throttle body assembly and see if that helps. Look for kinks in the throttle cable that would keep it from closing all the way. It's gotta be something...

 

[U_SHO?]

Update: LPM removed, MAF replaced with stock - still the same

Allright guys, I'm losing my patience with this stupid problem.

Finally got back in town and got my old car back. I swapped my Pro-M Maf with stock unit, and took the LPM out. Initially I thought that was it , but idle and high idle are only about 100 or less RPMs down than with chip but still high. Idle when moving still goes to 1350 and on one hot day with A/C on it went as much as 1800 before it settled down after 10 secs or so. When A/C clutch kicks in, revs drop for about 200rpms then rise a 100 over the previous idle, so with A/C idle fluctuates a lot. A/C definitely makes it worse.

Also drove my old car for comparison (all stock now), and it idles at 900 rpm and just a tad over a grand while moving. Not only that, but also noticed that when first started cold, the old car barely revs over 1200. My new car revs at 2000rpms for about 4 secs, than drops to 1600 for the same time, than sits at about 1200 for a while to eventually settle at over a 1000. If I didn't use the same computer that was in old car, I would think that computer needs to relearn the idle everytime all over.

After driving my old car again, another difference I noticed is that at low rpms (1500-2000) my new car is not smooth at all and the gentle pull in 3rd or even keeping the steady throttle is somewhat jerky.

hawkeye18, I already took the cruise cable off, and checked for the gaps in the intake so that's ruled out. TB closes fully and you can hear it hitting against the throttle stop so the cable is not sticking. Air tube is nice and tight around maf. Thanks for the tips.

Axianator, after removing the chip, the idle dropped exactly by 100 rpms and that matches the idle change that I had when I used the chip in my old car. I ran a simple hp and tq test using a g-tech meter and the results were disappointing to me. There was a slight gain with the pro-m MAF only (1/4 mile @94.5 vs 92.3 stock) but after I added the chip to the mix, the performance dropped slightly (1/4 mile@93 in 6 runs). There was a little dip in tq at about 2800 rpms, but the secondaries kick in about 200rpms earlier which I like for a somewhat smoother HP delivery. I have enough graphs and gripe for a whole separate post on this so I will leave it as a separate topic.

What I have left is to put 180F thermostat and changing the DIS module I cracked...

I saw in alldata that there is a procedure to reset factory set idle as well. Has anybody done that successfully? Is it possible that when the computer had once before been replaced in this car, the dealer did this procedure and set the idle for the new computer? That computer is also L0S like the one I have in now, so the car should run the same with the same computer right? I also think my tach show little higher than in the old car and I wonder how acurrate those things are. G-tech showed RPMs in tune with the tach in my old car, but in the new one it is a little off (tach shows more than g-tech).

I almost wrote a book on this problem - what am I overlooking???

 

[NiNeTy Fo SHO]

Did you reset the idle after removing the aforementioned items?

 

[U_SHO?]

Did you reset the idle after removing the aforementioned items?

Yes, every time.

 

[93rev2sev]

You have a vacuum leak. It's gotta be...

Does your cruise control work? If not I would be the vacuum line to the canister(behind drivers fender) is cracked or disconnected...it's worth a look.

 

[U_SHO?]

You have a vacuum leak. It's gotta be...

Does your cruise control work? If not I would be the vacuum line to the canister(behind drivers fender) is cracked or disconnected...it's worth a look.

I agree, but where??? Cruise works fine. The only issue I had with cruise cable was that the bracket on the throttle plate was bent so the cruise cable would fall off under full throttle. I straightened that and checked for normal operation of both throttle and cruise cable.
The cruise canister is untouched. I checked for the leaks with the carb cleaner all around the intake... Is there any tool I can use to check for the vac leak? Thanks

 

[SHOZ123]

What happens when the IAC is disconnected when the engine is at a high idle?

 

[U_SHO?]

What happens when the IAC is disconnected when the engine is at a high idle?

It dies pretty quickly after that.

 

[NiNeTy Fo SHO]

I would think thats the solution to your problem then. If you had vac. leaks, the car would probably still run after disconnecting the IAB as the engine is still getting air.

 

[SHOZ123]

Should die immediately. You are getting extra air some where.

Is the throttle stop not hitting the throttle linkage when the engine is off. Is there a tiny gap between set screw and throttle stop?

 

[U_SHO?]

Should die immediately. You are getting extra air some where.

Is the throttle stop not hitting the throttle linkage when the engine is off. Is there a tiny gap between set screw and throttle stop?

I meant it dies immediately after IAC is unplugged.

The throttle stop is fully rested and the adjustment screw is at the factory position (with yellow paint on it). Looking at the throttle butterfly, it is closed when I let go of gas cable and you can hear the linkage hit the throttle stop...

 

[SHOZ123]

So where is the extra air coming in? If it is from the IAC then it is a programming issue but I think you ruled that out by going back to stock components.

Is the PCV system leak free?

 

[U_SHO?]

So where is the extra air coming in? If it is from the IAC then it is a programming issue but I think you ruled that out by going back to stock components.

Is the PCV system leak free?

Not a programming issue, it does the same without the chip. I do not see any dirt around the pcv hose around the TB if that is the way to tell if it's leak free. Would air leak cause the exhaust to smell a lot after putting catless pipe? I could not compare to my old car because I never kept the old one in the garage, but after I first start the car and the cold idle goes to its 2000(000) rpms CO gas can be smelled upstairs in the house...

Is it possible that ECU is trying to compensate for this air leak and runs richer? Would that explain big idle fluctuations after A/C kicks in and not so smooth 1500-2500 rpm range?

 

[U_SHO?]

Looked for a leak again with a whole can of B12 cleaner all around the intake and any air hose I could think of. Nada

I'm having trouble keeping steady speed when stuck in traffic, like 20 mph in 2nd at 1800 rpms... If I accelearate it pulls ok, if I back off it somewhat slows down but to keep it smooth right at 1800 is almost an art. It is all related I'm sure

Has anyone have success resetting idle by adjusting throttle screw? Will this affect both curb and fast idle?

 

[U_SHO?]

Ruled the vacuum out of the mix, as well as any sensors.

Is this a valid theory: When the previous owner replaced the water pump he changed the CPS. Is it possible to install CPS in a way to advance the timing a bit? Or CID sensor or timing belt a notch or two off? This would raise the idle speed and explain why I don't have as much gain in power with the chip. Advancing the base timing would effectively change the timing all over the rpm band, right?

How can I check the base timing on this motor? If this is the case, does this mean I am stuck until the next maintenance interval and the timing belt, CPS, CID, sensor replacement?