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  #31  
Old 06-16-2016 | 09:32 PM
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Originally Posted by disc oh no
I'm not sure, but if it's heat related, it kind of sounds like an intake gasket leak. You could try having someone start it up and keep it running for you while you pour some water around the edges of the lower intake manifold. That's how I used to find leaks like that before I got a smoke machine.
Also, you can have a fairly big vacuum leak on startup and not get any trouble codes. This is because the fuel system is in open loop. So the computer isn't running the fuel trims and watching the O2 sensors until it goes into closed loop.
Okay so help me out here usually a gasket leak will leak when cold and once it heats up the gasket swells and seals. Am I backwards on this?. If the leak was there when hot would it not effect how it runs when warm. Once it is started it runs fine. Idles fine at stop lights everything. Only when you shut it down and then re try and start it while it's hot is there an issue.
 
  #32  
Old 06-16-2016 | 09:46 PM
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Oh, okay, I misread something there. Sorry about that. That sounds a lot like vapor lock. I would try checking the fuel pressure. If it's too low, or not holding rest pressure it will boil and will be very hard to start.
 
  #33  
Old 06-17-2016 | 06:35 AM
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Disc, what would cause that. Is that a fuel pump issue or is there something else which actually controls the fuel pressure?
 
  #34  
Old 06-17-2016 | 05:15 PM
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Originally Posted by Doc McCoy
Disc, what would cause that. Is that a fuel pump issue or is there something else which actually controls the fuel pressure?


It's a returnless system so anything relating to fuel pressure is controlled by the fuel pump assembly.
This is not the only possibility though. I would check the fuel pressure before replacing the pump.
I have seen coolant temp sensors do some strange things as well.
Checking either one of these things is pretty easy. There's a Schrader valve on the back of the fuel rail. Make sure the pressure is within spec and it holds fuel pressure for a while after shutting the engine off. If you don't have a fuel pressure tester Harbor Freight sells one for about $20.
The coolant temp sensor can be checked with a scan tool that has live data. The gauge is useless on these trucks.
 
  #35  
Old 06-17-2016 | 07:34 PM
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Thank you for your advice Disc. The sad thing was that when the wife and I bought this Discovery we thought we were buying a quality vehicle that would last us a long time. The three amigos hit right after the warranty ran out. It has just went downhill from there. I have a 1998 Ford Explorer that i have beat to sh*t hunting and fishing and skiing and have put less money into it in going on 18 years than I have put in the Discovery in a year at times.
 
  #36  
Old 06-17-2016 | 08:03 PM
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I hear you there man! That's why I never tell people to replace parts. I just tell people to check things out. I can't even tell you how many times I've seen lists and lists of parts that someone's replaced and they never fixed the problem!


I don't think I could handle the stress of using a Rover as an everyday driver. Sometimes they go for a long time without needing work, but then it all seems to go bad at once.
 
  #37  
Old 06-18-2016 | 09:58 AM
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Originally Posted by Doc McCoy
Okay so help me out here usually a gasket leak will leak when cold and once it heats up the gasket swells and seals. Am I backwards on this?. If the leak was there when hot would it not effect how it runs when warm. Once it is started it runs fine.
I can't wait to see the resolution of this.
The only thing I might add: at air conditioning equipment school, I learned that there is a big difference between a vacuum leak and a pressure leak.
There has been some great advice here, and I seriously doubt the following falls into that category, but: I would get a big cigar and do a smoke test for vacuum leaks.
 
  #38  
Old 10-19-2016 | 09:30 AM
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Sorry for letting this thread die but my best friend was diagnosed with glioblastoma cancer of the brain and that has been my focus for awhile. So back into the fray. The problem has changed just a bit. If the vehicle has sat overnight when i start it revs up to around 2000 for a second or two then drops toward 750 but shudders and dies like it's getting no gas. If I restart and work the throttle to keep it going for a bit then its fine. Once it's running it runs just fine, literally no issues. So here are some things I have replaced as potential problems and some due to age (13 years 130,000). Coil, plug wires, plugs, MAF sensor, engine idle control valve, throttle position sensor, fuel pump with new gasket and metal locking ring, throttle body heater plate. Again once it's up and running it runs fine and it seems to be only if the vehicle sits for a long period (overnight). I have crawled under when running and I cannot smell any gas and no check engine lights or codes so I don't think it's losing pressure but I haven't actually checked with a guage. So any help here will be appreciated. Thanks Doc
 
  #39  
Old 10-19-2016 | 12:17 PM
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Doc, Life intervened with me, too, and I was away from the forums for a long while; I am sorry read that you are still having problems.

The surge and then strange idle fits my experiment (on the first page; I unplugged TPS and drove around) perfectly, but you replaced the throttle position sensor, so are you POSITIVE that the TPS plug is firmly seated? That is precisely what mine did with the TPS unplugged. If that wire is an issue it is a real stinker because the goes under the upper intake (and is part of the injector harness). The only other time that I have had a massive surge at startup is when I stupidly (that is my job here, to try all of the stupid things and then report on myself), tried starting my truck with the upper intake off. It surged to maybe 5000 rpms in about 1-2 seconds, and I barely made it to the ignition to turn it off before it exploded. I couldn't wait to see how it would idle, or if it ever would pre-explosion. That was a fun time... I inferred that unlimited air into the engine was a bad thing, and further inferred than a massive air leak would cause a similar result. I think you would hear a massive air leak, though.

When someone says they have a rough start after a long sit, then fine running all day, I always jump to "check your coolant", not because I am a chicken little, but because almost every time that happened to me, chicken little was right... Coolant was dripping into a cylinder and it took all night to make enough of a puddle to interfere with startup, then it would run fine all day while happily and silently ruining my catalytic converter/y-pipe. But I was losing coolant and it wasn't going to the driveway wildlife... no puddles.

The other possibility (cracked fuel line or something allowing fuel pressure to escape) you seem to have addressed, but be sure you smell around the back of the truck, too, too. I had a similar symptom once and when I got the carpet out of the way of my fuel pump there was a nice pond of explosive liquid sitting on it, from a crack in the upper housing at the pressure line.

So I am at a little bit of a loss. But if you need someone to try something outlandish and possibly damaging to prove or disprove a theory, I am the guy to call.
 
  #40  
Old 10-19-2016 | 12:27 PM
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Whoa whoa...

I just re-read the thread. When you cleaned your idle air valve it was VERY dirty. Had alot of oil in it. Have you checked that again?

This comes to mind because there is a hose at the top of each valve cover that returns to the intake--in effect, it recirculates the "blow by" air from the top of the heads, to save the environment. On alot of diesels, those hoses go to a large oil separator then to the ground or maybe back to the intake. Anyway, on my rover, I have some neat little filters on those hoses and don't return the dirty air. Alex_M showed me that. There is supposed to be a crappy little oil separator at the top of each valve cover. But after a few months, on mine ONE SIDE is dripping with oil. My filter on the other side is clean. The difference? I dropped the oil separator on the dirty side, saw it on the ground, didn't know what it was, and kicked it away from me.

So I wonder if you have a dirty side or sides, too, and it is just fowling your idle air control valve. Mine doesn't get fowled because I don't return the pressure to the the intake, but I bet yours does. Have you checked it again since you cleaned it?

It is a little bit of a stretch, but your issues seem to defy the common fixes, so I am trying to think out of the normal box.
 

Last edited by CharlieV; 10-19-2016 at 12:31 PM.


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