Injector seals / Hesitation at light throttle ?

[schoward]

Hi all

I have been having an issue with my SC lately whereby it runs decent but it has been starting to bog or hesitate under light throttle. Car is stock 81 SC with CIS / O2 all setup stock.

While cruising along it wants to bog a bit but if i give it more throttle it smooths out. Overall performance and idle seem a little weaker but car runs and drives. Seems to slowly be getting progressively worse or maybe I am now just aware of it. The problem came on kind of quickly in late July.

Ruled out
-I tried changing out old spark plug wires - no change
-Swapped in my spare O2 relay
-Timing is dead on spec / Idle and mixture were perfect before this started happening
-Checked ignition operation (1 year old permatune CDI and coil) light is flashing 'normal' - have not checked voltage etc as I do not know how.

Car is/was in good tune otherwise and was running great prior to this with last major service done 5k miles ago.

I did a few reads (different days) on my CIS test port with a dwell meter at warm idle and it seemed to be reading around 50 dwell when it usually reads around 40. Observed this on at least two different days and I interpreted as car may be running leaner than usual (Air leak?).

So, this morning after driving the kids to school in the car, I poked around with some carb cleaner after car was all warmed up.

When I sprayed carb cleaner on the injector bases/injector seals on cylinders 1-2-3 the engine would temporarily bog slightly (rpm drop) with every spray. Injector/cylinder 2 especially reactive to this - every spritz of the carb cleaner at the injector base instantly caused a slight rpm drop/bog. Doing the same on cylinders 4-5-6 gave absolutely no change (I had seal replaced on cylinder 4 a few years back).

Have I gotten close here you think? I would say based on above, seems like injector seals are getting done on the 1-2-3 side.

Does this add up pointing to seals as the likely cause of my hesitation? I would have thought with leaks the rpm would perk up or increase when I sprayed fluid, but not sure or perhaps its because I was spraying at the injectors.

Thanks in advance.

[deguitars]

Sounds like you're onto it. I changed out the seals, sleeves, and the injectors and it solved a myriad of issues with cold starting and hesitations. The injectors themselves are not that expensive so if you're going to the hassle of pulling them out I'd just change them, they don't owe you anything at this point.

cheers

[schoward]

Thanks for the reply - luckily these parts are cheap and the 1-2-3 side looks very accessible to start with.

If any other comments, I'm all ears - appreciate the brainpower.



thanks.

[Bob Kontak]

With spray,engine will bog if o-rings are leaking. Engine will increase in RPM if intake runners are leaking at heads. Don't know why.

You are on the right track.

[schoward]

Thanks, Bob - glad you are back

[gazzerr]

Have you checked the condition of your WUR with a fuel pressure test and a test on the resistance of the heater coil?

[schoward]

Checked pressures and WUR electrical plug connection resistance about a year ago. If no luck with seals, I am going to have to do (or have shop do if I don't have time) the full procedure (pressures, leaks, ignition, etc) from scratch. Now that you made me think of it, yeah pressures are possibly highly relevant here (possible cause). May be time to get out my gauge kit.

[gazzerr]

Yep i would start there first. Changing the injector seals and seats is definitely worth it. Big job but rewarding.