Hi
I have a problem I find kinda puzzling, the hard starting is in part due to bad glowplugs that are ordered and most likely arrives tomorrow. But I think there is something else funny going on under my hood. It goes rabbitjumping at around 1600 rpms or so but is fine above and below this point. What could cause this to happen at only such a specific rpm point?

My SES light is on but I don't have a way of checking the codes. Can this be a PMD Issue?

I haven't done the full diagnostic checklist but Lift pump check is ok. Batteries and connections are fine(they wasn't but is now).
Fuel and Air filter are fine. (fuel filter has been changed twice since problem started).

Anyone have any ideas about this?

Changed the glowplugs today but she still doesn't start right. Haven't had the chance to try a cold start yet as it was still kinda warm when I tried..

Might this be the optic sensor in the pump causing this?

I forgot to mention in my original post that cruise control also died when this happened and I read in another thread that his cruise control died when he disconnected this sensor altogether.

This sensor is read at a certain sampling frequency am I right? Could this be the explanation why my problem seem to be worst at a certain RPM. If at this rpm the sampling rate is close to the frequency of what is to be sampled i guess some artifacts will occur in the output..? Anyone know the sampling frequency here?

Ordered a OBDII cable thingy for the computer yesterday, if it arrives before I get to pull the trigger on any action it might help clarify what the problem really is..

Any ideas anyone?

I've heard that cruise control goes out when PMD is going bad........

Louis

Yes the pmd is on my suspect list..

how is it once it warms up my suburban does the same thing but starts fine some times with alittle white smoke i installed new glows and injectors but it still does it once it warms up it is fine for the rest of the day

Warm or (summer)cold is only a slight difference in cranking time now that the new glowplugs are in and no difference in the other issue.

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The lines above were written yesterday before bed time and obviously never posted..
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Today I called the local stealer around here to hear about the extended warranty on the pump and had a chat. I think I know what the problem is now, its probably pulling air from a rusted tube on top of the tank.. He knew it right away when I told him about the symptoms! :) Guess I'll put them a little higher on my "places to call" list the next time something goes bad! :)