Will start and (sometimes) idle, but not rev

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nickj

Well-known member
Oct 21, 2010
77
0
Bozeman, MT
Hello, I just finished swapping a new (used) engine into my Disco II ('02 V8 SE, with SAI) -- the previous one looked as if it hadn't been oiled enough, and broke the camshaft (in three places, and likely had other issues).

Upon putting everything back together, every start after the very first one, the truck has started right up and idled at about 1200RPM. Sometimes it will almost die (dropping the tach to 0) and fire itself back up, and sometimes it'll idle along as long as we've cared to watch.

If I give it any gas at all, it will immediately try and quit, and if I get off of the gas, it'll return to idle (the rpm drops the more it warms up). Often, if I pump the gas (either via the throttle or the cam at the TB), I can get it to rev up into the 4-5000 rpm range.

Occasionally, there's a pop from the intake if I just pump it once. Does anyone have any ideas on this? I've asked the same question over at LRO, and I'm just looking for more eyes here.

I've already checked TPS, and swapped to a (seemingly) good MAF. I've got a few CkPSs between the old engine, new one, and a test one. I've put pressure into the intake and gotten no significant leaks -- it seems to hold pressure fine, and I've also checked fuel pressure -- pretty solid at 50psi.

Anyone seen this, and if so, what fixed it? Thank you!
 
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nickj

Well-known member
Oct 21, 2010
77
0
Bozeman, MT
KyleT said:
cam sensor plugged in? get all the injectors plugged in?

get all the engine ground straps on good?
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Pretty sure cam is in -- can double check (although why would it idle?). Injectors are along the same lines. Very sure those are all in.

Only saw one ground 'strap' -- driver's side, near firewall. It's on very well, and was cleaned first.
 
I HATE PONIES

I HATE PONIES

Well-known member
Aug 3, 2006
4,864
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nickj said:
Oh yeah -- no CELs (only a 1590 / rough road)
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Try driving it a bit. This will help light the CEL and store codes.

The 1590 will be stored if you have amigo problems but won't turn on the light.
 
no694terry

no694terry

Well-known member
Sep 29, 2009
989
0
pittsburgh, pa
Check cam sensor plug again, mine sent me for quite a loop when I did head gaskets. Started fine but ran like crap. Finally I got a code and it was cam sensor, dirty plug. And disconnect battery each time you try something, makes ecu recheck all sensors
 
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messar

Well-known member
Sep 11, 2010
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As far as I know, there is no way to reset adaptive values except with a T4, faultmate, hawkeye, etc.

When I switched out my ECU, the truck would start, but not idle or rev. Resetting the values made it work perfectly.

Matt
 
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nickj

Well-known member
Oct 21, 2010
77
0
Bozeman, MT
no694terry said:
Check cam sensor plug again, mine sent me for quite a loop when I did head gaskets. Started fine but ran like crap. Finally I got a code and it was cam sensor, dirty plug. And disconnect battery each time you try something, makes ecu recheck all sensors
Click to expand...
Dirty plug is definitely possible. We had to re-use the old harness, and it wasn't always the cleanest. Will also take the disconnect battery into consideration as I test.
 
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nickj

Well-known member
Oct 21, 2010
77
0
Bozeman, MT
messar said:
As far as I know, there is no way to reset adaptive values except with a T4, faultmate, hawkeye, etc.

When I switched out my ECU, the truck would start, but not idle or rev. Resetting the values made it work perfectly.

Matt
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Hmm. Closest LR dealer is very much not possible. I don't think there even is one in MT. I will try and find an Indie with one of those tools, and see if I can borrow, I guess.
 
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nickj

Well-known member
Oct 21, 2010
77
0
Bozeman, MT
D Chapman said:
It's the fuel pump
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D Chapman, What makes you think fuel pump? It seems to hold just fine at 50PSI, and if we release pressure while idling, it shoots right back to 50. Are you thinking it can't supply higher fuel rates for speeds above idle? Would that match with being able to 'pump' it to a higher rev?
 
D Chapman

D Chapman

1
Jan 3, 2005
11,746
73
On Kennith's private island
nickj said:
D Chapman, What makes you think fuel pump? It seems to hold just fine at 50PSI, and if we release pressure while idling, it shoots right back to 50. Are you thinking it can't supply higher fuel rates for speeds above idle? Would that match with being able to 'pump' it to a higher rev?
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50psi?? That seems like a lot. Is this while the truck is running?

Backfiring through the intake is a fuel starvation problem.

Take some starter fluid and spray into the intake to see if the engine revs as it should.

Just because a fuel pump runs does not mean it's good. It has to flow as well. Now it could be a clogged fuel filter or a dirty sock on the fuel pump itself. But I doubt it.

Your MAF or CKPS should throw a code if bad.

You could also check to make sure no teeth on the "tooth ring" bolted to the flywheel are bent. Usually this breaks the ckps, but maybe they're bent the other way.... Still, I doubt it.

My money is on the pump.

The only way to reset adaptive values is with either a T4 or a Autologic. I'm not familiar enough with the other Rovercom or Rovercom Lite computers to know if they do this or not. PT should know. But you should have it done.

The only other thing I can think of is the timing cogs not being timed correctly.
 
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nickj

Well-known member
Oct 21, 2010
77
0
Bozeman, MT
D Chapman said:
50psi?? That seems like a lot. Is this while the truck is running?

Backfiring through the intake is a fuel starvation problem.

Take some starter fluid and spray into the intake to see if the engine revs as it should.

Just because a fuel pump runs does not mean it's good. It has to flow as well. Now it could be a clogged fuel filter or a dirty sock on the fuel pump itself. But I doubt it.

Your MAF or CKPS should throw a code if bad.

You could also check to make sure no teeth on the "tooth ring" bolted to the flywheel are bent. Usually this breaks the ckps, but maybe they're bent the other way.... Still, I doubt it.

My money is on the pump.

The only way to reset adaptive values is with either a T4 or a Autologic. I'm not familiar enough with the other Rovercom or Rovercom Lite computers to know if they do this or not. PT should know. But you should have it done.

The only other thing I can think of is the timing cogs not being timed correctly.
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50PSI -- will check again tonight. Recall 42-50 while idling though.

Can try feeding it starting fluid.

Other (old) MAF throws several codes. 'New' used one throws no codes. No codes as far as CkPS (or anything else for that matter, aside from 1590 for the abs).
 
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