Circles

Hello,

I have a situation with a LS400 I hope someone has some input for. The symptom was while driving it would not handle acceleration. Code P0171 was showing. The tach rpm's increased but the engine RPM did not seem to change. It seemed like a Mass Flow issue. Cleaned MASS flow and no change. Here is what I have done so far.
1. Fuel Fulter Change
2. removed Fuel pump and tested in a bucket and seemed fine but did not pressure test
3. wired fuel pump back but outside of the tank and did pump. However it did not seem to pump during start but only when coming off of start mode for a few seconds. no continuous pumping.
4. Checked FP relay. looks good.
5. getting spark
6. FP resistor was at 7 ohms not the .75 from the service manual but do not think that is the issue.
7. FP is back in tank. disconnected fuel line fitting for Bank 1 and no gas is showing up.

I think my next move is the ECM computer. I cannot find where the 97 has a FP ECU so I assume the ECM is firing the signal for the FP. Could the TPS be implicated as well? Thanks for your help.

LScowboyLS

92-97 LS400 is especially prone to have failing ECU capacitors, I would read that thread

Circles

Thanks for the quick update. Is the ECU you are referring to the main once behind the glove box? Thanks again

LScowboyLS

yes, the ECU (ECM) is the only box in the car with 4 connectors and 100 wires going to it. There is a diagram on how to remove it in post 1 of the ECU thread

PureDrifter

iTrader: (10)

this is more commonly a vacuum leak issue, look for a leak specifically near the PCV valve and associated vacuum lines as they are on the driver's side. 2GS400 have the same issue.

shanjam

put key to on position leave for 6mins then turn off turn on start