Simple Question About the TPS

[llll1l1ll]

Hi,

'88 325is here. Before I get flamed, I did a quick search but that yielded no results.

Anyway, would a bad TPS not allow the engine to turn over? I was driving on the highway and my car just stopped running altogether and wouldn't turn over. I did the stomp test and it gave code 1233 for the WOT TPS switch. Car will crank but will not turn over. Tried swapping DMEs from a 173 to a 153 in a vain attempt to see if it would work. Cleaned the connectors on the TPS and female connector. Cleaned all the relays. Still nothing.

The TPS is less than a year old. I just find it odd that the CEL comes on before starting (like normal) and the ICV is buzzing it's head off (like normal), but since the TPS WOT switch is bad it won't start. It just seems like that wouldn't matter.

Could it be something else that's causing this? All the fuses are in good shape, too, btw.

Best,

Peter

[DaveSmed]

Unplug the TPS and give it a shot. It might enter a "clear flood mode" or something along those lines. (not too sure if Motronic does that..) That would prevent the fuel injectors from firing.

I can tell you though that the TPS is not a critical sensor to the operation of the car, it only functions at idle and WOT, so disconnecting it is a good test.

[llll1l1ll]

No it still won't start with the TPS unplugged. That's why I'm so baffled.

If it makes any difference, when the car died (on 95 outside of D.C. in morning rush hour) the tach just dropped to zero while the car rolled in gear. Makes me think it's something a little more in-depth than a simple TPS.

For the record, the CPS is just now a year old. It's still connected. However, I've been having intermittent running problems but that has to do with the main relay or something.

[NC325iC]

check the cps wiring for any wear spots just to be sure

[jlevie]

The TPS won't interfere with starting the engine. A bad idle switch will cause problems at idle and a bad WOT switch will affect top end performance.

[llll1l1ll]

The CPS wiring is solid - I looked. I'll check again in the morning.

Jlevie further solidifies my idea since the TPS is really just all about idle vs. WOT. I don't believe it would affect starting.

I think I might start simple and get a new main relay. That was causing me issues in the past with engine management, in that the car would lose power and not run.

It's nice because I can let my car sit now because I take the Metro to work. In other words, I can take my time fixing it.

[DaveSmed]

Be sure you get the correct relay. It is not a generic 5 pin Bosch relay...

I would try jumping it first before you buy one though. The ICV is powered through one leg of the relay, and the DME through another. While it is possible one leg could die, usually the relay just stops working altogether.

[llll1l1ll]

Well, the relay I was looking at was on Bavauto.

To be perfectly honest, I'm a retard when it comes to wiring and electrical stuff. I might fry something if I try jumping this.

[Rigmaster]

Bad main relay will cause the car to just die like you described.

What seems to happen is that they "disconnect" internally and that cuts power to several things, the tach just drops to -0-. Might try tapping on the main relay while trying to start the car and see if that works- if so, it sounds for sure like a main relay.


OH, and when we say a car "turns over" it means that the engine spins. So in your case I would say your car turns over fine, but does not start or does not fire. I was confused when I first read your post saying the car does not turn over.

[m3michel]

I would check some simple things up front, also. I had a burned up rotor do the same thing to me one time.

[slammin.e28]

I had a burned up rotor do the same thing to me one time.

x2 on my e28. It looked like a freakin' rats nest, the thing just shredded itself.

[scrowner]

llll1l1ll - nice user name!

You are in Rockville, I am in Germantown MD. I have 3 E30s, you could borrow a main relay from me if you have not already bought one to see if it is your issue. Sounds like it is from the posts. I may even have one I lifted from the junk yard that you can have. PM me.

[llll1l1ll]

Haha thanks! I made my screen name up when I was drunk almost nine years ago.

Tomorrow when I get home from work, I'll try tapping on the main relay while I turn it over to see if I can get the engine to fire. : D

I don't think it's my rotor since it's not that old and the tach wouldn't drop with a bad rotor - it just wouldn't start. : D

Jokes aside, I'm leaning towards main relay. What I'm most worried about is a piece of wiring that has came apart somewhere down the line. I mean, it is 21 year old wiring...

[llll1l1ll]

Hokay, so:

I ordered a main relay off of Bavauto and swapped it out from the original. Although it didn't look much like the original one, it fit right in. However, the car still will not start. The ICV comes on and yadda yadda, except this time the DME relays back the 1444 code when I do the stomp test.

It's a cold day today but I think that has nothing to do with it.

I looked at all the spark plugs and they look the same except they don't smell too much like fuel like I thought they would. Granted, I don't think a busted fuel pump or pump relays would cause the tach to drop to 0 and the car to die.

Cliffs: replaced main relay, car still no start, 1444 code, ICV buzz still in effect

[jlevie]

Is there spark when cranking the engine?