Hello-

I have a 1996 Disco 1 with 161k that starts up w/o issues from a cold start- idles around 700-900 rpm. However, as soon as the engine warms up and I make several short stop/start errands the "normal" idle changes; it turns over with no issues, but after 1-2 seconds the rpm's go from 700-900rpm to below 300 rpm's and the engine sounds very rough. This continues for 10-30 seconds until the idle stabilizes at 600 rpms then the vehicle seems "normal" and drives w/o issues. At worst/lowest idle I've seen faults for cylinder misfire; P0301-P0308, but only a day after having added Seafoam or Lucas injection cleaner.

I just purchased the vehicle and have been trying to fix this nagging issue for about three weeks.

I do have a reference vehicle to compare to and that is my OTHER 1996 D1 with 98k- it starts w/o idle issues hot/cold- idle always around 800-900 rpms- no faults, no codes- just a great running vehicle (so far).

What I've done so far; I've cleaned the MAF, IACV, changed air filter and bought new sparkplugs and cables for installation.

From this and other internet resources suspect components include: throttle position sensor, crankshaft position sensor, fuel pump, fuel temperature sensor.

I have not yet replaced/swapped anything from my 1996/98k D1 into my 1996/161k D1.

Can someone suggest other sensors/connections/valves to check, adjust or clean to help me troubleshoot this idle issue?


Thanks in advance.

Regards,

cmpeng

 

The issue may be your IACV, clean the port where it is mounted to on the plenum, if it is gunked up, you are better off cleaning it thoroughly. I would recommend to reset the adaptive value but I believe your truck is not OBDII.

 

All vehicles manufactured for the 1996 model year in the US are OBDII compliant (IIRC)

 

CkPS look at the wiring to the sensor from its connector onward, around/near the exhaust down-pipe. Cracked, flaking, missing insulation will cause funky running without throwing a code. Fuel pump should have an output @ 34 psi at the Schrader Valve on the fuel rail. Coolant temp sensor for the ECU can also cause a hot start idle issue as it can falsely read cold instead of hot and run rich for a few. Usually that sensor will toss a code. Whatever sensor is the actual problem it suffers from heat soak. I left the fuel temp sensor off the list because they rarely fail and they also will pop a code. Hows the cooling system? Many here have gone with an Ultra Gauge so they can pull the actual readings, it's worth it.

 

Thanks for the advice. I cleaned a bunch of gunk from the valve tip and reinstalled the valve. How do I reset the IACV??

Regards,

cmpeng

 

https://landroverforums.com/forum/di...acement-83233/

Make sure the port is also clean down to bare aluminum, the IACV tends to pound the carbon into asphalt in the port.

 

same thing happened to me with my 97 107k ,tried seafoam and also changed plugs and wires,what really helped was adding a bottle of techron and changing the coolant temp sensor {advice i got on this forum} so far so good,good luck {think ihscout was who gave advice so thanks!!} and it doesn't hurt to clean everything in throttlebody!also changed fuel rail sensor and vac line from fuel pressure regulator to plenum

 

Update:

I tried resetting the IACV by using the turn key "ON"; turn key "OFF"; unplug IACV connection to the ECU; turn key "ON"; reconnect IACV to ECU.

Drove the vehicle for more than a day w/o issue until just now after running some errands after 16 miles of Hwy driving from work. From ignition the idle started out at 900 rpms then dove below 300 rpms after 1-2 sec for a while. It took about 30-45 seconds for the idle to pop back to "normal".

The CEL came on and I got codes P1316 and P0300- misfire codes. Does this mean I need to make time to change my plugs/wires or was I not able to reset the IACV with the above method?

thanks,

cmpeng

 

Here's my update as of 6/22.

Replaced spark plugs and ignition wires due to misfire codes (gap was a 0.40-0.60 on the plugs)- still having issues.

Replaced battery (not sure how old it was when I bought the vehicle) after getting it checked at local auto shop- still having issues but I now have more detail to the rough idle/engine not firing issue and a question.

The last week the weather has been in the 90's in Colorado. I have no issues when first starting the vehicle up in the morning. One 90+ degree afternoon I drive to Home Depot (6-7 miles at Hwy speeds) and let the vehicle sit for 15-20 minutes; go to start her up and no go. Vehicle initially starts and the RPMs go from 900-1000 to 200 then the engine cuts out. Let the vehicle sit for 30 more minutes and it starts up, but very rough idle until I can give it some gas after 1-2 minutes of idling and then all seems normal.

This sequence happend 2x more this past week. The vehicle starts after sitting over night; re-starts after engine is hot and just let to sit for 1-5 minutes, but WON'T START after sitting between 15-30 minutes; will start after sitting for 1-2 hrs. WTF!

I'm going to replace my fuel filter- cheap to replace- and see if that helps. I've stumbled upon forum references to looking at the fuel filter, fuel pump and fuel relay.

My question is why will the vehicle start up right away with a hot engine after just 20-30 seconds of sitting but will not start after sitting for 10-15 minutes of sitting; and how can this quirky issue be fuel line related?

Thanks,

cmpeng

 

as i said my truck does this also,it just happened to me again after changing everything! try running a bottle of techron it will help,it could be a leaking fuel injector or valve stuck open a little,the techron will help{maybe 2 bottles,1 per full tank}fuel filter should be changed if it never has been,but just check fuel pressure at rail {probably ok if truck starts right up even hot}i.ve also been told it might be an o2 sensor,good luck!