Odd Idling Issue -80 Fiat Spider FI

[esodu]

Hello everyone -

Any help would be much appreciated. Here's the issue: Basically, it won't hold the idle past 10-20 seconds.

I took it out for a long drive the prior weekend to this problem occurring. Then during a quick around the block run it died as I was coming back. It died as I downshifted and then tried to give it gas. I have replaced the air filter and fuel filter. The fuel pump seems to be fine. After replacing the filter it will hold an idle for close to a minute but as soon as the gas is pressed dies. Idle is rough at first then when it warms a bit it settles down to normal.

I am at a loss to what I should try next. I guess I could replace the FP and Fuel Regulator... Would the regulator cause this to happen? Could it be a FI issue and not a fuel line issue? If so, how do I test that or clean the FI's? Could this not be an engine issue but an electrical one??

Thx in advance!

[azruss]

check your throttle body air mix screw. It should have an O-ring on it. If it is closed all the way, it can create issues like you have having. Go see Brad's FI diagnostic pages to see how this all works.

[RRoller123]

The FI system gets makeup air to the fuel tank only through the opening with the cap on the top of the charcoal canister in the engine bay. If you pull the cap and hold your thumb over the opening to block air flow, the idle will slowly decrease and eventually the car dies out. (At least mine behaves this way). A clogged canister might explain these symptoms.

Pete

[76was124]

It could be a couple things, including the throttle plate sticking, or mis- adjusted Throttle Plate Switch (TPS). A quick test on the TPS is with the engine off, slowly lift the throttle cable from its normal idle position. You should hear a click when you first start to move the throttle plate position. If not, then likely it or the throttle plate stop screw is mis-adjusted.

Best thing would be to follow the idle setting FI diagnostic procedures in the maintenance manual AZRUSS mentioned.

The Links to Brad's manuals are at:http://www.artigue.com/fiat/

[esodu]

So I've done a few things to troubleshoot and here's the latest....

New (Known Good) AFM
New TPS and set properly
New (Known Good) Dual Relay Switch
New (Know Good) ECU
New Temperature Sensor

So with all of them in place and without the temperature sensor connected it starts and idles fine. Smooth. Can run up the RPM and no stall.

I replaced the TS and connected the wire and it immediately cuts out. I noticed that the connector to the TS is not perfect but will clamp (albeit not overly tight).

Could this be a situation where the TS is getting a misreading from the loose connector and thus it cuts out?? Is there a way to test the reading at the ECU for the TS?

[76was124]

Check the sensor with an ohmeter at the ECU connector. Pin 13 and ground (pin 5?)
Maybe have someone jiggle the connector/wires at the sensor while you look to see if the meter reading is jumpy. Also, depending on the orientation of the t-fitting and sensor, connector or up vs down, I've heard others say when the hood is closed it interferes a bit pushing on the connector causing intermittent connections.

In addition to Brad's maintenance manual that lists the proper ohm readings at various temperature, there is a graph showing the same in this threadhttp://www.fiatspider.com/f15/viewtopic ... 7s#p244569

[micbrody]

Ditto to 76was124 post. Check the resistance values at temp probe; AND again separately at terminal 13 of ECU:
Unplug the ECU and connect an ohmmeter between
terminals 13 and ground (vehicle body). The meter should read:
7,000 to 12,000 OHMS at 14 degrees F
2,000 to 3,000 OHMS at 68 degrees F
250 to 400 OHMS at 176 degrees F

The purpose of the engine temperature probe is to lengthen the time the fuel injectors are open when engine not warmed up. If engine is truly cold, and probe not sending reliable resistance to ECU, it could be hard to start. If, however, you have been running car and it's still on hot side, the engine will start (maybe with tiny help of cold start injector) regardless of temp resistance. However, if bad connection (high resistance), the ECU will think engine is cold, and enrich fuel mixture. I suspect this is what is happening. And when you hit throttle, you will essentially make mixture too rich and engine run horribly, and floods.


A great read on how l-jetronics works:
http://r.search.yahoo.com/_ylt=A0LEVv70 ... FZjLQtotI-

[RRoller123]

It occurs to me that if this higher resistance equates to a richer/leaner operation, then adding a resistor inline could be a way to adjust the mixture. (By effecting the injector open time). For example, if one believed the car to be running a little Lean, and the Resistance at the temp sensor at 176 deg-F is 250 ohms, adding a 150 ohm resistor to the line would push it up to 400 ohms and presumably enrichen the mixture.

[bradartigue]

So I've done a few things to troubleshoot and here's the latest....

New (Known Good) AFM
New TPS and set properly
New (Known Good) Dual Relay Switch
New (Know Good) ECU
New Temperature Sensor

So with all of them in place and without the temperature sensor connected it starts and idles fine. Smooth. Can run up the RPM and no stall.

I replaced the TS and connected the wire and it immediately cuts out. I noticed that the connector to the TS is not perfect but will clamp (albeit not overly tight).

Could this be a situation where the TS is getting a misreading from the loose connector and thus it cuts out?? Is there a way to test the reading at the ECU for the TS?

This is a common problem. You can test continuity and resistance at the ECU connector of the wiring harness, though you've already diagnosed the issue as being the temp sensor. Solution is to replace the pigtail, which will include about a foot of new wire and a new connector. Vendors sell them; buy the Bosch part.

The temp sensor failure state is typically to "tell" the ECU the engine is dead cold, which floods the engine. This is why they typically run fine until they warm up, then all hell breaks loose. Once you get it sorted out change your oil and filter, it will be fuel contaminated.

[esodu]

Answer - Ultimately this was a fuel injection problem. Replaced the injectors (and most of the
fI system's other parts...) and the problem went away.