OK, I just replaced a hodge podge set of mixed glowplugs in my truck, and carefully plumbed new wires to them. I was hoping to have a dramatic improvement in startability. Now, the truck starts and definitely hits on all 8 right away which it wasn't doing before, you could hear it pick the last couple cyls up after a few seconds of idling. But it still smokes like a freight train on cold start, and now, I have a funny noise at idle when it warms up that wasn't there before. I don't really know how to describe it, There has always been a slight lub in the exhaust, but the oil consumption is very low and smoke is non existent once it warms up. This sound I can only hear while in the cab with the windows up. It sounds like a ....hmmm... a muffled 'whump, whump, whump' is the best I know how to describe it. I don't think I have a weak cylinder, but I'm going to do a compression test to make sure. I'm thinking this has something to do with the surging problem I was having, had to trim the fuel back to make it go away. Its definitely on the pass side, I though it might be a bad lifter, but as soon as I pop the hood to check, I can't hear anything anymore. Anyone had this problem or have an idea what it might be?

What's ambient up there, now?

I'd say 35F right now most mornings, but I only have the noise when the truck warms up.

TDG i had exactly the same noise as you describe with my 95 and i'm not sure if your 94 is the same but my noise was the vac pump, made that noise for 100,000km and then the pump went. I could only really notice it from within the cab. Try a stethascope on the pump. I could barely hear it outside the truck with the hood down and coudn't hear it with the hood up.

vacuum pump is new, just a month old now.

Still sounds like vac pump to me, when i put the new one on my truck it still had the noise, just less pronounced. Pump worked just fine.

Worth a double check for piece of mind.

Could be the denser cold air is transmitting the deeper low-frequency engine noises, hiding the higher freq ticking and tapping - you're hearing the intake pulses, and such after the cold advance rattle goes away.

Or, something else.............

what about the lub in the exhaust? somethings wrong somewhere because when I put the fuel back to stock it surges like a big dog.

That's the hi-flo hi-pops - PCM has no way to identify them - it's trying to correct for excess fuel with Cyl Balance routines. 35deg ambient, 35-50deg IAT ain't helping.

Those are 'hi-flo hi-pop' at idle, as well as 3500rpm - they're designed for mech IP Marine use, where the engine(s), in a yacht, fe, is at 75-90% full power clear across the bay.
Cap'n don't care 'bout no idle, when the babes-on-board lamp is lit..........

Warm weather you'll get xtremely low idle rpm 450-500-550, occasional surging...........

At those lo rpms, you'll swear the crank is fixin' to fall outta the main bearings, from all the injector rattles and such.

They're not hi-flows, just hi-pops, and I've had 3 completely different sets of injectors in this engine, none of them made a noticeable change in performance or affected the surge or idle speed/quality and it acts the same in Texas Summer heat and Canadian winter cold.

Mis-read the 'hi flo' muffler in your sig, and your rebuilt IP and first hi-pops went in last month, right?
Point is, you're doing things the PCM does not recognize, and has no way to compensate for, particularly in an EGR-based program.

You'd need the non-EGR eprom for better results - PCM is identical, but for that.

Still think the noise is related to what's been done and the cold ambients, but then, I cannot look, touch, and listen from here.....................

Could try temporarily replacing the K&N with an AC - see if that helps the noise

Compression test results?

I've had the pump in and out 6 times, changed every piece in it, tried a different pump, 3 sets of injectors, nothing changes the way it acts even with completely stock settings on pump and injectors.

It always, since the day I bought it, did the same thing. Completely normal operation until coolant temperature gets high enough for the PCM to drop L.I. speed to 560, its like that engine just cannot maintain that speed for some reason.

Ok - IP, injectors, timing chain, F manifold.

Leaves IAT and ECT sensors, which you can check with Tech-II, and idle Fuel Rate, and Desired and Measured Advance.

And History Cyl Balance DTC's.

Snapshot mode will catch problem if PCM knows it's doing it.

If Snapshot doesn't catch it, then PCM doesn't know it's doing it - time to replace PCM

Might try a complete '95 K30 PCM - no wiring\connector differences - non-EGR

considered that, the '95 PCM that is, I believe the 'F' engines don't idle as slow as the 'S' engines.
Never tripped a cyl contribution code, ECT and IAT sensors seem to be giving normal readings, timing is not the problem, I've even swapped the harmonic balancer out. Nothing makes any difference. I'm wondering if the torque converter is loose somehow or if the motor mounts are shot.

The "muffled whump-whump-whump" sound that you're hearing could be the wastegate door tapping against the turbo housing. I experienced this exact symptom on my '96 F engine when I had a bad WG actuator (and low vac from the pump). Without the force of the diaphragm rod pulling the WG shut at idle, the door sort of floats in response to the exhaust pulses. The turbo housing apparently dampens the tapping, and I was convinced that I had a rocker arm that was ready to fall off the stud! Replacing the vac pump and actuator solved both the lack of performance and the tapping immediately! The test is simple...at idle, you should not be able to pull the WG actuator arm down by hand...if you can, there's a vacuum problem.

Jim

New vacuum pump, new WG Solenoid, new actuator with custom long WG arm. WG is held very tightly shut, barely moveable by hand at idle. Noise doesn't change with vacuum line unplugged either.

Thanks TDG I read this post before traveling last weekend and I noticed a different sound in my truck too. I hadn't drove it for a long trip sense changing the pulley couple week ago, and now I can hear things I could n't before. I concluded that my noise was the new 3" catless, mufflerless exhaust system I have rumbbling in my cab. Anyway thats my story, sorry not much help with yours I guess.

I"m starting to wonder if they just 'forgot' to finish another weld somewhere on my exhaust. Sounds like it could be the downpipe or part of the exhaust hitting something.

easy to check for exhaust leaks is on a cold morning, start up truck and climb under while it's running, emer. brake set oh course, and then under hood all quick before it gets to warm.

I don't think its leaking, just a little loose on a hanger somewhere.