88turbotime

Hey guys, I'm having a problem with my TII.

I'll be driving down the road and all of a sudden the car just loses power. The engine cuts out and it just won't go anywhere. The engine doesn't actually die, and it idles fine, but when I give it throttle it just falls on its face and it won't rev up. Sometimes if I mess with it long enough it will start running right again, but usually I just shut the car off and then start it back up again and it runs right for a little while.

It will do this for a while, and then sometimes it runs just fine for a couple weeks at a time.

Here is what I know so far:
The computer was sending the code for the O2 sensor, so I replaced that along with the water temperature sender. My reasoning for that was that i've heard that the O2 code could be the water temp sender, if maybe it is telling the computer the engine is cold when its actually hot so it dumps more fuel to it to make it run rich. Either way, that didn't fix it.

If it matters, the engine mods the car has are streetport, removed emissions, racing beat turbo-back, K&N cone filter, 720cc seccondaries, walbro 255, and S-AFCII.

The next time it happens i will try leaning it way out to see if that helps, since it feels like it suddenly starts running super rich. But i don't know why that would be since i haven't messed with the settings on the S-AFC in a couple years or so. Plus I'm not sure if its getting way too much fuel, or not enough. I know it shoots flames under decelleration so i doubt its too little. Or maybe its something ignition going bad?


Thanks for any help

ifryrice

Does it do it under load, cruise, or all of the time once it hits this point? It'd be pretty hard to troubleshoot since there's so many different thing it could be if it's not a constant issue. It could be something shorting out, fuel delivery issue (fuel filters?), or a plug issue. There's a lot of ways it could go.

88turbotime

Yeah once it starts, it does it under all conditions except idle. It can be under power or cruising along and it happens, then it idles but doesn't want to rev up. The fuel filter is next on the list, but the plugs are new.

And yeah the inconsistency is a real problem. I wish it would just do it all the time so I can get some instant feedback. I thought I had it fixed because it went a couple weeks just fine but now its back with a vengence!

87 t-66

iTrader: (133)

try unplugging the tps and see if it goes away

arghx

iTrader: (3)

airflow meter hooked up tightly?

88turbotime

Ok I'll give that a try.

Yes, it is hooked up tightly, but one thing I was wondering is how critical is it that that thing is perfectly level? Like I said I have a K&N filter on the end of that thing and it really isn't secured by anything, it is just resting in there. It is close to level but it's not perfect, it does tilt downward toward the front of the car a little bit.

BDC

Check for cracks on the turbo inlet duct where it clamps to the compressor housing.

B

HAILERS

[QUOTE=88turbotime;9548304]Yeah once it starts, it does it under all conditions except idle. It can be under power or cruising along and it happens, then it idles but doesn't want to rev up.
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Like mentioned above........TPS. The plunger of the TPS is sticking. Been there, seen that. As in go to the store. Shop. Return to the car. Starts fine. PUt in gear to back up.........won't go over ?? 1100-1300 rpm.

ECU thinks it's in the fuel cut mode. The fuel cut mode I talk about is the same on where you drive along and let off the pedal all the way. The fuel injectors stop operating til your rpms return to approx 1300 rpm, whereupon they start injecting again and the car idles just fine and dandy.

You can prove/disprove this. Just disconnect the TPS and drive your heart out for??? hours? days? months. IF the problem does not return the problem was/is with a sticking TPS plunger.

Jpg attached does not explain it very well. But we all know that if your driving along and let off the pedal just a touch, then one primary will stop delivering. Then if you let off the pedal all the way both primary injectors quit injecting.............until you reach approx 1300 rpm and they work again. The ECU knows the pedal action thru the TPS.

Series five manual explains this better so you can read that if you want. Fuel and Emissions section.

88turbotime

Thanks HAILERS, that sounds like what my problem is. Earlier I checked the TPS as described in this link:
http://www.fc3spro.com/TECH/HOWTO/TPS/tps.html

and found that it reads 4k ohms in the idle position and around 12k with the throttle open. But as time goes by when i check it it has steadily gone down to about 8k ohms at WOT the last time i checked. Could this be related to the temperature of the engine? The engine was not hot the first time i checked, but it was probably still warm. That article says that you have to check it with the engine hot if you have the cold start assist still on, but I don't have that anymore so should it matter?
And since it was reading WAY over the 6.5k ohms that it talks about in that article does that mean i need a new TPS? At any rate that sounds like the TPS could be the reason my engine cuts out at 6500 RPMs regardles of engine load.

And my final question for now.... If I disconnect the TPS (which I will do right now) and the car runs fine as you say it should... why do I need it? Is there any reason to pay 150 bucks for a new TPS?

misterstyx69

iTrader: (142)

Get a wideband,and you will find out Why you should have a TPS.(not necessary,just read on..)
it tells the ECU what fuel to give out.
I have been screwing with a couple TPS's today.I found out that all FOUR of them will give my engine Different AFR"S at Idle,and rev..
sometimes good,sometimes WAY off the Meter(like 18:1 or higher).I am still Workin on it!
Get a Known Working TPS,from someone Reputable on Forum,rather than shell out 170 Bucks at the Dealer(or Mazdatrix).

88turbotime

Thanks misterstyx.

I drove it without the TPS plugged up and it worked fine. Its hard to say 100% that was the problem because it was so inconsistent, but think we can be fairly certain. It used to go a couple weeks at a time running fine but the last 2 times i tried to drive it I only made it about a mile or less away, until today.

And if nothing else, it DID fix my 6500 rpm cut out. She saw 7k today for the first time in over a year!


Edit: Oh and I have a wideband that i bought a couple years ago, I just can't figure out how I'm going to mount the guage so it looks nice. I already have a boost guage on the pillar, and I don't think I want to add anything else up there.

HAILERS

Uh, last time I looked the TPS default value when disconnected was.........................100%.

I think HEAT and dirt is effecting your TPS. Go to Radio Shack and buy a spray can of some sort of electical circuit board cleaner and with the TPS off the car, spray into the plunger area and shake it out. Then let it dry and reinstall in the near future.

TPS on a series four determines a ZONE the throttle is in so the ECU can make adjustments.

OR what you could do to PROVE it's the TPS, leave it connected and drive it. Then the next time you have this same problem, just lift the hood and disconnect the TPS plug and drive the car. Easier said than done on a turbII. Might just depin the wire at 2G on the ECU. Same effect.

I had a similar problem once. If the TPS was removed, the plunger would go in and out, but there was no resistance i.e. like the spring inside the TPS was hung up and just the outer shell of the plunger was moving, not the guts of the TPS. I mean gravity would make the plunger move in out just by tilting the TPS body. No spring resistance...not guts movement.

88turbotime

Cool man. I would love to plug it back in and just yank it the next time it acts up, but like you said, thats pretty tough with the TMIC. The plunger moves back and forth the way I would think it should, but I have no idea whats going on under there when it heats up and stuff. I'll try that with the circuit board cleaner.

Thanks guys, you all have been a tremendous help!

88turbotime

Hey guys, my hesitation showed up again today.

The TPS is still unplugged, and it ran fine for the little bit of driving i did, until today. I barely made it out of my subdivision when it started hesitating, but at least it wasn't as bad as it used to be. It made it to where I needed to go and back without me having stop the car and shut it off.

Do you think a new TPS would fix it entirely or am I dealing with something else?

slpin

iTrader: (9)

check TID
check AFM
bad wires by afm connector?
afm connector ripped out at one point?
fuel pump relay?
dirty/clogged fuel filters?
blew off hose on any intercooler couplings?

clokker

iTrader: (2)

Not sure it'll fix your problem but you should attend to this anyway.
Your S4 AFM is more sensitive than the S5's and wants to be level and secured.

afpreppie04

iTrader: (5)

Check grounds too. I had a hesitation problem on my S4 TII that was intermittent, went through a couple TPSs trying to figure it out, turned out to be iffy contact on the ECU ground to block. I guess under certain vibrations the ground would go out, causing the hesitation. It started out just like yours but eventually got to the point that it would actually stall at idle occasionally.