Join Date: Sep 2008
Location: Oakbank, Manitoba
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Slightly low ICP when warm
This may take a while before it is easy to diagnose.
A few months ago I put in a new set of larger injectors. It ran very strong right out of the gate until the day I dynoed my truck about 3 weeks ago. Go figure... Outside of problems with loading the dyno that day, the truck seemed to run OK, but not quite as strong as normal. It seemed to have a slight miss about 1800rpm driving at 65mph. It only put down about 440hp and 770lb-ft and I attributed the lower drive pressure and ICP to the dyno loading. I later thought it was an injector harness connection, but today when I loaded Wildman's Extreme, this is what it did. Just after a cold start I pulled out of the yard the truck was running very strong and with little pedal the ICP was easy to get to 4000+ psi, almost too easy! However, after I was up to 65 mph, there was a definite miss as it was warming up, almost like stiction, but only at about 1800 rpm. All other parameters: FICM, EBP, MAP, Fuel Pressure, EGT, ICP and IPR were normal. After reaching normal operating temp there was no miss, but it took more pedal than normal to get the typical acceleration. The ICP would not go above 3000psi with the IPR commanding 82% at WOT.
I loaded the stock tune and a medium power tune and the ICP did reach 4000psi with the lower PW.
When I did the buzz and contribution tests (AE) cold it tested normal and did not miss. I will try to get a sample at 1800rpm cold tomorrow under slight load and see if the miss resurfaces.
My thoughts are I may have an injector to rail seal, standpipe, dummy plug STC leak or weak IPR, but they all looked very healthy when I put the injectors in (STC or IPR were not inspected). Of course, it could still be the HPOP. It has the original IPR, STC, HPOP, standpipes and dummy plugs. Yes I will replace the stand-pipes and dummy plugs for the updated ones during the next injector change in the next week or 2. I will also inspect or change IPR if it seems questionable. The STC will probably be changed out when I upgrade or pull the turbo.
My question is, "Can I get reliable air pressure test results with such a low pressure drop, or am I going to have to wait for more deterioration?"