'98, 150K, this has become my daily driver because I love it and it has proven to be rock solid, no issues to speak of whatsoever until lately.... On a cold start it springs to life with a mighty roar, rev's up to about 1200 and after a few seconds settles right down to 700-800 and runs and idles smoooooooth for as long as it is running. On a warm start however, it still gives its roar and rev's up to about 1200 upon starting but then after a few seconds instead of dropping down to normal idle it drops down to zero, and either stalls or hunts and surges for around 30 sec before finding normal idle and settling in. From this point forward it runs and idles mint, until the next warm start cycle. Does it when I shut it off and immediately restart and also if I let the fuel pump spin up before starting, so not thinking fuel pressure is the issue. Crank position sensor ?? Seems odd that it would only show up on a warm start and never again while the car is running. No issues when I cycle the ignition when it is cold, definitely feels like it's temperature related and it is not intermittent, this bad behavior has become our new normal. If I prop up the RPMs during this period it tends to drop right in to normal idle. Any advice would be most appreciated, I am hoping that someone may have experienced this and can point me in the right direction before I start hacking away at it.

 

Take a look at the IACV. Your problem sounds similar to what I had. Clean throttle body and IACV. Be careful not to change the position of the pintel of the IACV while cleaning it.

 

mine [97] does the same thing,i agree cleaning iacv and maybe give the maf a shot of maf cleaner,it does help

 

Fuel Pump- I had the same issues until this weekend when I replaced mine (plus the fuel filter); 96 Disco 1 with 160k. Started cold but would leave me stranded when hot. Measure your fuel pressure at the fuel engine rail and see if its low- mine measured 21 psi- it should be 34-37 psi. The pump will overheat intermittently depending on gas level in tank and outside temperature and won't deliver enough fuel.

I kept getting spark plug/misfiring codes. I changed the air filter, fuel filter, battery, plugs (0.060 gap), ignition wires, cleaned IACV, cleaned MAF (all which needed to be done anyway after 160k!!??). Once I got a tip to measure the fuel pressure (from this forum) it all fell into place.

My tip is buy/borrow the fuel sender lock ring tool- don't think you can remove the pump with a screw driver and mallet/hammer with one gentle tap like all the guys in the u-tube videos do. Mine was stuck solid- I was afraid I'd break the plastic ring.

Also, replace the fuel filter too. Replacing the fuel filter is harder than replacing the pump (as long as you have the sender tool) due to location and nut corrosion. Mine took 2 hrs to replace and I almost rounded the nut edges on my fuel line connections- that would have been bad. Use anti-sieze on both fuel line connections to help prevent corrosion.

Good luck.

cmpeng

 

One more thing.......

The last thing I wanted my hot starting issue (search for my symptoms in a recent thread) to be was a weak fuel pump. Why?? Because it meant I'd have to open up the fuel tank: fuel + oxygen + ignition source = trouble.

I had no prior experience with replacing a fuel pump until this weekend. With the right tools and direction and being safe with cleaning up excess fuel from the lines you should have no issues- also remember to disconnect the negative battery lead before you start.

cmpeng

 

I gotta say God bless LR for putting that fuel pump access plate in the cargo hold of our Discos. It's rarely fun dropping a tank the hard way...

 

If you run down the fuel in your tank to a quarter tank it is less of a hassle to work on it.

 

when the key is in position 2, the fuel pump motor noise should be very noticeable for at least 5 seconds or so. I could not hear my original motor noise when the key was in position 2- I assumed this was due to a tired pump motor.

I got the vehicle with 160k so I'm not sure if the pump motor was failing due to age or clogged fuel filter- not sure when the filter was last changed. When I removed the filter and blew air through it I had a hard time getting anything through and when I did the filter barfed out a large chunk of dark matter plus fuel. When I exhaled through the new filter there was a big difference in the resistance I was feeling.

no doubt a clogged fuel filter can wear out a pump motor prematurely.

cmpeng

 

Thanks all, as it turns out cleaning the IACV and bore real good fixed that right up. I had myself convinced that IACV was not the issue as it idled perfectly once it got its act together, but there were some pretty good clumps of asphalt on the pintle and cleaning it up resolved this for me. Thinking now of putting an oil separator on the crankcase vent.