1997 D1 Sputtering/Stalling

mrbieler

Active member
Sep 15, 2004
39
0
Lost Angeles
yes. that didn't change the idle issue. Something in the ECU connection appears to be wonky. At no point on the harness or at any connection is the voltage low, but at the TPS, it's under 0.5volts. We played with the fuel pump sensor, tps, and ICV. Anytime the TPS was plugged it, it would die no matter what we did with the other sensors. We're going to overlay a new wire from the ECU to the TPS.
 

mrbieler

Active member
Sep 15, 2004
39
0
Lost Angeles
Truck is now running great. Unfortunately, with all the work, battery disconnected, ECU swaps, etc I need to drive it for a few days to get the miles up and make sure the codes clear so I can get it smogged and registered for 2019.
 

robertf

Well-known member
Jan 22, 2006
3,913
4
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Truck is now running great. Unfortunately, with all the work, battery disconnected, ECU swaps, etc I need to drive it for a few days to get the miles up and make sure the codes clear so I can get it smogged and registered for 2019.

Just FYI, a battery disconnect has no impact on a GEMS ECU. They have no volatile memory, and the way they are wired effectively disconnects the ecu from the battery about 10 seconds after you turn off the car. Listen for the underhood relay click. Thats severing all power to the ECU
 

jymmiejamz

Well-known member
Callsign: KN4JHI
Dec 5, 2004
5,362
16
30
Los Angeles, Ca
Idling at 1500-2000 RPMs is pretty common with GEMS. The way I've always fixed it is reset the throttle adaptions. I'm not sure if you can do that with an aftermarket scan tool.
 

mrbieler

Active member
Sep 15, 2004
39
0
Lost Angeles
drove it about 100 miles and the codes cleared up and passed smog. still getting p0451. will check the cap and evap lines for leak, but it's running nicely otherwise.
 

mrbieler

Active member
Sep 15, 2004
39
0
Lost Angeles
Yes. The wire overlay restored the voltage to the TPS and our truck runs great. I’m still getting P0451 code, which leads me to believe I’m still having an issue with the fuel pump sensor or the evap system.

Now that I’ve passed smog and have the truck running properly, I can work on that.
 

jymmiejamz

Well-known member
Callsign: KN4JHI
Dec 5, 2004
5,362
16
30
Los Angeles, Ca
TPS is showing low voltage, but the ECU and all wiring connections, including wires that share leads with the TPS are showing good.
What was wrong with the wire if the wires were "showing good"
 

mrbieler

Active member
Sep 15, 2004
39
0
Lost Angeles
We're not sure. We were showing continuity along the harness, but with everything plugged in we were getting under 1volt at the tps.

The original TPS and the cleaned up original ICV are back in. Once we found the parts were functional, I put them back in rather than the aftermarket replacements.

I think the earlier comments pointing back to the fuel sensor are the issue. Taking the TPS off that wiring circuit appears to have cleared up the issue, but the error code is showing P0451 which I wasn't seeing before. Need some down time in the coming weeks to take look at that. No free weekend time coming up for bit though. Be nice if the fuel sensor wasn't molded into the fuel pump assembly... :(

Right now, all appears well. Good performance road and highway. Back to the regular 13MPG around town average.
 

Tugela

Well-known member
May 21, 2007
3,941
10
Seattle
On my first Disco I had P0451 for a while. If I recall, that is an evap code. After chasing my tail on it I finally figured out that the previous owner had installed a non-AEL fuel pump into an AEL truck. Symptoms were similar to what you describe. Might be worth a quick look to verify that you have the appropriate pump for your truck. I think 1997 was the changeover year (LR sold both) so it's possible you have an AEL fuel system with a mismatched pump. I don't know if the reverse mixup is problematic - AEL pump in a non-AEL truck.