Crossing stuff of the issues list little by little. Up to bat: the car is hard to start (lots of cranking, sometimes my stumble a bit) when cold, and idles rough when cold. Once car is warm it starts and runs perfectly.

Things I've tried or considered:

• Coolant temp sensor : This got replaced in Sept 2019 when I did some overhauling of the cooling bits. I disconnected and sprayed with QD electronic connection cleaner. I have a spare OEM one that I haven't tried putting in (just hate draining coolant).
• Smoke test for vaccum leaks. I thought maybe the intake manifold seals had gone bad, but there's no evidence of leaking from there (or anywhere else). I will may end up replacement the manifold gaskets anyway this summer as preventative maintenence.
• Fuel Cleaner: Ran techron through. No change. Fuel Filter is 2.5 years old.
• Weak Battery: I do have some suspicions of the battery. I think it's possible this has made the car slightly harder to start, but I'm not sure if this would have any explanation for the rough idle. I reconditioned and recharged the battery via trickle charger. This makes the cranking a bit healthier, but the cold start is still hard and the cold idle is still rough.
• MAF sensor: I cleaned mine and even replaced with a new one. No change.
• Spark plugs were replaced about 20,000 miles ago

I think the next culprit to explore might be the fuel injectors. If they're leaking, then this might explain the hard start. Not sure if it would explain the rough cold idle, but what do I know? I have a handful of spare injectors lying around, but they haven't been used in about 2.5 years, so I'm not sure if they'll be in appropriate condition to be put back in (I hear they can stick when not used for a while).

The car doesn't throw any codes. Any ideas of what I should check next? Need to make sure my game plan is sound.

 

I'd say spend some time with a cheap ELM327 first, and get the ECU's opinion as to the coolant temp. Also, get the fuel trims for a sense of air leaks.

 

yeah I have a bluedriver (unnecessarily expensive equivalent of ELM327). Maybe I'll take a drive today and record the fuel trims. Coolant temps have seemed accurate/normal though.

 

What is the fuel pressure?

 

for some reason my app doesn't support fuel pressure reading...alas. For what it's worth, by the seat of my pants, the fuel pressure has seemed consistent and fine. Goes from 40-140 without a hitch.

Just read the fuel trims at cold idle. I think there might be something wrong with the way my app is logging long term trims, but the short term fuel trims suggest I might not be out of the woods on air leaks. Bank 1 was between -2 and +3. Bank 2 was +4 and +11. Idle, in park.

 

Before you go to far, I would try and get a full set of DTCs, as they could point straight away to an obvious problem. There must be a friendly garage near you to just run a full scan.

In lieu of that, I would go get the injectors serviced, which is normally inexpensive for a garage to check and clean them. I remember doing that when I first got the Cat 2.5 years ago. I don't remember any serious issues in pulling the injectors and taking them for servicing.

 

I actually bought a set of used injectors a couple years ago, got them refurbished, and swapped them in on bank 2 when I was having misfire issues way back when. Maybe I'll send the others back out and swap them in just to cross it off the list. Real easy to do that.

FWIW, I'm probably gonna do the intake manifold gaskets regardless, as I didn't replace the valley hoses when I did the cooling overhaul a year or so back and I'd like to now.

I think the car will be going to my jag guy soon anyway to get the high pressure power steering line replaced (it started leaking maybe a year or two ago, and I did the DIY splicing repair, which has been good, but failed once, and I'd rather just get it over with). I don't feel like doing that myself. While its in there, maybe I'll have him do a full system scan. My scanner can do check engine lights the on-board data but can't do the full system scans.