Head temp sensor

Jbagel2 · 10-30-2006, 08:27 PM

what would cause you to need to put mass qualinty of resistance on the head temp sensor...

inline with the head temp sensor i have to have about 240K ohm of resistance to get the car to run very well.

what is this a sign of??

hardflex · 10-30-2006, 09:47 PM

is your car a 73 2.0 litre?

Jbagel2 · 10-30-2006, 10:14 PM

74 2.0

hardflex · 10-31-2006, 03:29 AM

Adding the resistance would richen the mixture. Some modifications like header exhaust and higher compression require a little richer mixture than factory settings. That could be it. But I'd bet some of your parts were replaced with mimatched items, most likely the MPS, because they're expensive and other models (such as from VW's or 1.7's) are more readily available.

Cross check your part numbers from P Banders site, to make sure what you have. If your MPS is good, but the wrong part No. you can have it reset to the proper specs. Bleyseng, on this board, can do it for you, maybe others will chime in.

You can check all the part no's, I suspect the most likely to affect your engine adversely are the MPS, ECU, Injectors (just look at the color), and CHT.

Jbagel2 · 10-31-2006, 07:50 AM

i"m positive that my mps is not adjusted properly, i have been desperatly searching for someone local that could adjust back for my. not even the porsche dealership here can do it. is Bleyseng his username because i didn't find him in the members list. and i really would like to have him adjust it for me..

hardflex · 10-31-2006, 08:49 AM

he's in this thread, look at his gallery page and email address.

When she's cold she runs real rough!

I'd still check all the other part no's, because he will set it per a standard MPS, and if your other parts don't match up it still won't be right.

I'd be willing to bet you have a 1.7 MPS. I had one in my car without knowing.

bowlsby · 10-31-2006, 11:28 AM

The ballast resistor on TS2 only richens the mixture when the engine is cold. After warmup, the ECU solely controls mixture because the TS2 has told the engine it is at operating temp.

Dave at Pelican Parts · Dave at Pelican Parts's Garage

If you really mean 240,000 ohms (240 K ohms) then something is really wrong. With that much resistance, the EFI will never think the engine is warmed up and will dump a lot of extra fuel in. Probably about as much as if the sensor is unplugged. That shows some fairly major problems...

--DD

Jbagel2 · 07:05 AM

yes i really mean 240K ohm... what kind of problems would that be sign of??? would it not mabey be because of mismatched parts??

Jbagel2 · 07:43 PM

i finaly got around to start checking part numbers... the mps that is in my car is VW# 0 208 100 003 Bosch # 22 906 51. acording to http://members.rennlist.com/pbanders/djetparts.htm#setups that isn't even supposed to be on a 914 i guess, anyone know what this might be off of?

hardflex · 09:24 AM

Probably a VW Beetle, 1600CC engine.

Well, replacing, or readjusting that, would be a good start.

Since it's basically a throw-away anyway, you might be able to drill out the end and readjust it yourself, if you can't find another good MPS. At least that's an option. Or trade it in towards the correct one. I think they all are basically the same mechanicals, just the adjusted settings are different.

The best thing would be to get a good one that's been checked and set for your car. If it's a just a matter of bolting it in, it's an easy fix.

Dave at Pelican Parts · Dave at Pelican Parts's Garage

240 K ohms should make the mixture very rich. Which means that your system without the resistance runs things very lean indeed. Check the fuel pressure; very low pressure will give you a very lean mixture.

I'm not sure what an incorrect MPS will do. The numbers you're quoting don't quite make sense to me; I'm used to the Bosch numbers being more like "0 280 100 101", and the VW numbers more like "022 905 105 A", or possibly without the letter suffix. Perhaps you swapped the Bosch and VW numbers and left off some zeros?

What else would cause a super lean condition? Hmm... Not sure off the top of my head.

But go through and check the basics--all the hoses and wires in good shape and connected correctly, valves in adjustment, good compression, fuel pressure in spec.

--DD

hardflex · 11-02-2006, 03:37 AM

I think the range on the CHT runs from around 3000 ohms to under 200, as it warms up. I would be surprised if the ECU could register the difference if the Ohms were up in the 240,000 range. I may be wrong, but I think he's not reading his Ohmeter right. It probably wouldn't run at all if it were running that lean.

Jbagel2 · 11-02-2006, 07:00 AM

i'm reading my ohmeter just fine. give me a little more credit than that please...

Jbagel2 · 11-02-2006, 08:19 AM

it is already some where around 240K-250K and i bought some more resistors to add because it is still running lean enough that it doesn't matter if the AAR is open or not. not untill the car warm up a little anyway. it is just a temporary fix untill i get my paycheck in a few days and bring it in to have the fuel pressure checked... another question i have been trying to check the part numbers on all of the fuel injection components to see if any of them are even the right ones for my car. and i can't find the number on the ecu, where is it supposed to be located, and do i need to take it out to find the part number..

hardflex · 11-02-2006, 08:45 AM

Hey, not being critical, it's difficult to understand the ranges on these things sometimes, that's all. been there done that.

Since your ohmeter skills are good, you should check the FI points in the distributor also to see if they are breaking fully. There are two, check each side.

pbanders · pbanders's Garage

The ECU sees a 240K ohm CHT as the car being ice cold - as rich a mixture as the CHT circuit in the ECU can deliver. Something is seriously screwed up. You need to do a complete diagnostic of your FI system. See my web pages for details on how to do this.