jumping idle/stalling

[ThatSHOkid]

ok here is my problem. the idle jumps somtimes and then goes to either the verge of stalling or stalling. Erik and i cleaned my IAB valve today and it is still doing it. i have also read that a performance chip can often cause these results. i do have a chip in (put it in today), but it does the jumping idle/stalling without a chip. any ideas? erik thinks it could be the throttle position sensor? thanks!

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1993 White/Tan SHO MTX 100k Miles
[*] Performance: Sho Shop Y Pipe * Coneless & Boxless * 80mm MAF * S & B Motorsports Concial Filter * Ted B Performance Chip
[*] Appearance: Colgan Custom Bra * Blacked Out "SHO" Lettering * Ventshade Sunroof Wind Deflector & Vent Guards * GTS Headlight Blackouts
[*] Audio: Sony 10 Disc Changer
[*] Lighting: Eagle Super White Headlights * American Products Company Super White Reverse & License Plate Lights * Blazertech Foglights
[*] Coming Soon: Tinted Windows, Sub Frame Connectors, Sway Bars, Front Strut Tower Braces, & A Sig Pic!
[*] The AIM Screename: KingPin641 (a NESHOC member)

"Drive it like you stole it!"

 

[whelen1]

You know, I had this problem last night. I would start it, and it would be fine. But when the RPM's started to come down, it would almost stall, jump up, stall, etc like 4/5 times or until I hit the gas..

Don't know what it is, but it scared me a little...

 

[94shoboy]

mine did that right before it died, it was the CPS. it may be other things, but thats a possibility

 

[Diameg]

Mine doesn't stall, but it hunts between 900 and 600 rpms.
It is very consistent. After idling for about 20 seconds, the tach goes down slightly, then up, then down slightly more...etc.
It continues between 600 and 900 very evenly back and forth until I give it gas (either driving away or just reving it).
Then, it will idle steady at 900 for a bit, then down, then up.......

I think I've solved it now though, I just sit at a red light with the tach at 6 grand the whole time.
Sure, everyone thinks I'm nuts and I'm killing my engine, but at least it doesn't hunt anymore.

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Mike

94 MTX (Rare Green model)
Hi Flow Y-Pipe, Dynomax, UDP's, 80mm MAF, K&N panel, Ted B LPM.

 

[whelen1]

It may be the CPS, but its not throwing a code either......i will try it...

 

[sdpatt]

It is unlikely that the cause of the hunting idle is the crankshaft position sensor. This sensor only signals the DIS and EEC when a spark event is due. The EEC adjusts the timing as it knows how to do for the cleanest emissions and most power. If the CPS does not provide the signal, there is simply no spark. The Hall effect sensor only knows ON and OFF. When this sensor fails, it results in an engine that not only doesn't idle, but one that shuts down as if you turned off the ignition key.

Check for a throttle position sensor signal problem by letting the engine idle, then moving the throttle plate, by hand, just off the set screw. If this corrects the hunting idle, then it could be the much cheaper and easier to replace TPS. Check out this site by Wells manufacturing, the maker of many of our cars sensors: http://www.wellsmfgcorp.com/counterpoints/Counterpoint2_1.pdf The top of page two explains how this situation can cause an unsteady idle without setting an error code.


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Scott

1991, 254K miles, glass hood, police grill, SVO shifter, Catz fogs,
K&N, 73mm MAF, Superchip, PP Y-pipe, Borla cat-back, 190 lph pump
Eibach/Tokico/polyurethane, Alum SFB, SS front/rear strut braces,
16x7.5" Moda R1, 225/55ZR16 Bridgestone RE730, -1 deg camber x 4,
6 disc CD, Class II hitch, Silver award at SHOklahoma Car Show

 

[ThatSHOkid]

i guess i will try and give it a whirl tomorrow. it is doing it all the time now. which is odd. how much does new CPS cost and how much would a tps cost? hey erik....u still have that extra one? where is the throttle plate? is it right near the throotle body? installed my 80mm maf today coudl this be oen of the problems depsite the fact i noticed it was doing it really bad last night before i put the 80mm maf on. just a coincidence it is doing it really bad now that i have the 80mm maf on?

 

[ThatSHOkid]

also when i put the 80 mm maf on, erik and i drilled a whole in a rubber part of my cone filter so that thign (sensor?) that plugs into the bottom of the stock MAF airbox can plug into the cone filter/80mm maf. could this be the problem?

[This message has been edited by ThatSHOkid (edited 02-01-2002).]

 

[ThatSHOkid]

where is the screw i have to offset? i know where the throttle is have operated it by hand

 

[RStalveyARFF]

it's on the opposite side of that Jay. I will look and try to find the TPS that I took off my car.

 

[ThatSHOkid]

hmmm.. i just checked otu autozone.com and unfortuantely the stores near me do not have the CPS or the TPS in stock but i can order them online. i wonder if i should just order them both and whatever fixes the problem, return the other? they don;t seem to be that bad of a price. well my questions is this, which do i choose
autozone lists 2 diff model #'s for the tps with only a dollar difference. here are the 2 part numbers
wells tps259 for 24.99 (O.E.M. #E9TF-9B989-BA) and wells tps39 for 23.99.(O.E.M. #F2DF-9B989-AA)

[This message has been edited by ThatSHOkid (edited 02-01-2002).]

 

[ThatSHOkid]

thanks erik? how much u want for it if u got it?

 

[sdpatt]

I show the TPS as Wells P/N TPS215 from AutoZone.com for $23.99. The TPS is on the forward side of the throttle body held on by two Phillips head screws. The cost and effort to install this part are insignificant compared to the crankshaft position sensor.

The lowest price part is the Wells SU242 from AutoZone for $42.99, but either your effort or the labor charge to replace it are not trivial. To get to the CPS, you basically have to do all the labor to remove the timing belt: remove the intake crossover tube, the battery, the battery tray, the accessory belts and pulleys, the timing belt covers and the crankshaft damper.

Once again, I'll say that it is highly unlikely that the CPS is causing your engine's condition. If the cause is not the TPS, you may need a new IAC valve. They do get old and slow and this can result in the surging idle condition. This part is also much easier to access than the CPS.

Scott

 

[twrsho]

I had the same problem as you when I installed my 80mm MAF/LPM and it would idle hunt terribly. I also found out that the car was running extremely lean with any more than 1/4 throttle and loosing 17hp at the wheels. I replace the TPS, O2's and swapped to a known working 80mm Maf to no avail.

Try the following - unplug the MAF and reset the computer - test drive the car with the LPM installed and the electrical connector at the MAF unplugged, If it no longer idle hunts I suspect the LPM is not programmed properly - I first thought that this clearly pointed to the MAF - but upon swapping to a known working 80mm maf, it still idle hunted.

I find it highly unlikely that any one of your sensors has mysteriously gone bad at the same time you installed the maf/lpm. Like a stated - I replaced a lot of sensors and almost bought another - nothing worked.

I got several different view points from people that are close to the industry - they
pointed out that I had not tried a different programmer - what did I have to lose? I had the chip reprogrammed by "hold your breath" the ShoShop - car has run beautifully since then - last trip to the dyno shows a 10hp/17lbs torque increase from stock - thats an increase of 27hp/26lbs torque increase over the previous LPM.

I don't like to name names - You can e-mail me directly and I will elaborate further if you like. [email protected]

[This message has been edited by twrsho (edited 02-01-2002).]

 

[pittsburghsho]

Are there 2 different iac's? One of them you can take apart and one of them you can't. I have cleaned mine 3 times and it is giving all the signs that I need to clean it again. It would be nice to replace it.

Originally posted by sdpatt:
I show the TPS as Wells P/N TPS215 from AutoZone.com for $23.99. The TPS is on the forward side of the throttle body held on by two Phillips head screws. The cost and effort to install this part are insignificant compared to the crankshaft position sensor.

The lowest price part is the Wells SU242 from AutoZone for $42.99, but either your effort or the labor charge to replace it are not trivial. To get to the CPS, you basically have to do all the labor to remove the timing belt: remove the intake crossover tube, the battery, the battery tray, the accessory belts and pulleys, the timing belt covers and the crankshaft damper.

Once again, I'll say that it is highly unlikely that the CPS is causing your engine's condition. If the cause is not the TPS, you may need a new IAC valve. They do get old and slow and this can result in the surging idle condition. This part is also much easier to access than the CPS.

Scott

 

[sdpatt]

There was an IAC valve that did not like being cleaned, I have read, but not seen with my own eyes. What I do know, is that if cleaning doesn't correct the problem, you may need to buy a new IAC valve to make the problem go away.

Scott

 

[DeaconBlue]

Again Scott hite the nail on the head, twice;

"If the cause is not the TPS, you may need a new IAC valve. They do get old and slow and this can result in the surging idle condition."

"...if cleaning (the IAC valve) doesn't correct the problem, you may need to buy a new IAC valve to make the problem go away."

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95 MTX
with a few mods

 

[Diameg]

DeaconBlue,

I've done both (new TPS and new IAC), neither helped.

Still the hunting idle, but at least I have 2 new parts......ugh...


------------------
Mike

94 MTX (Rare Green model)
Hi Flow Y-Pipe, Dynomax, UDP's, 80mm MAF, K&N panel, Ted B LPM.

 

[RStalveyARFF]

Okay, first, I want nothing for it, since I paid nothing for the other. Second, we can get a IAC that I know likes to be cleaned at Hollands some day, and third, just wait till your 60k for the CPS, it's only 20k away, and your car isn't exhibiting signs for needing one.

 

[Shoman94]

Originally posted by Diameg:
DeaconBlue,

I've done both (new TPS and new IAC), neither helped.

Still the hunting idle, but at least I have 2 new parts......ugh...

OK, My turn...I would have gone the same route at Scott but since thats been tried...I had this problem a while back (like 3 years ago) but I just remember what it was. The Cam Identification Sensor. This sensor doesn't throw a check engine light but it can pull a code, but in my case it didn't. Anyways...It fixed mine.

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'94 MTX Silver
Tokico Struts, Eibach Springs, Spmotorsports SubFrame Conn. 29mm ShoShop Rear sway bar, Shohop Cat back, Gutted box with K&N, '96 Brake Upgrade, White Face Guages.

[This message has been edited by Shoman94 (edited 02-02-2002).]
Fixed my post error.

[This message has been edited by Shoman94 (edited 02-02-2002).]