Miss after slight runaway

[blackbird82]

Hey I have a 94 AAZ Jetta. I was cleaning and re-sealing the intake top.(the upper half of the manifold, it was leaking at the gasket between the two halves.) And I guess some carb cleaner got in the intake, when I had it all done and fired it up. it ran and then a few seconds later sucked up the cleaner. hello revS!
It revved pretty high and then calmed down.  I shut it off and re-started it. And ever since it seems to have a slight miss at idle when cold.Although when hot, it stil has a slight stumble.  Rev it up and it runs great. Starts immediately.
Changed injectors and went from single spring to double spring. Didnt change it, although less smoke.
All glow plugs great. when I had the injectors out, i ran em and they got nice and cherry
Pete
Journeyman tech. John deere ag systems

[blackbird82]

on a side note. I thought it was injectors. Cause it would miss when cold, but hot idled fine with a bit of nailing.  I changed em out with a set of dual spring injectors rebuilt with 297 nozzles and 150 bar. now it doe sth estumble a bit when hot. only sometimes!

[Vincent Waldon]

How much liquid carb cleaner do you think the engine ingested??  I ask because anything more than 20cc could have bent a rod, giving you poor compression in 1 or more cylinders... smoke, starting issues, etc.

[blackbird82]

hmm could've been an amount close to that.  That is a possibility, although, it sure burned it good! I have rebuilt some small yanmars that did that, have low deck heiht after ingesting hydraulic, when a seal went
they smoked white all the time, and it was only one cylinder. I don't smoke white at all!

[Smokey Eddy]

Interesting. Have you tried advancing the timing a SMIDGE to see if that clears it up?
loosen your pump up a bit (keept it snug) and i like to take a very soft rubber mallet and gently knock the pump towards the head JUST until it idles fine. Very very touchy business. Be careful and patient.

[blackbird82]

never loosened the pump on these. are the bolts the ones on the inside that you get through the pump pulley?

[burn_your_money]

You put 294s in a dual spring body? That could be your problem, although I wouldn't expect it on just one cylinder.

[blackbird82]

I have to double check. i think they were 293's iput in there.  The old single springers had 297's in them. It didn't miss at idle with them when warm or even a little better than cold. they were a little weaker opening pressure (147 vs. 150). I just wonder if its all timing and fuel delivery.  I have always wondered if you have 2 springs(delivery and injectors)how if one is off it would afffect the other. 
Plus at what rpm should advance take over from the cold start handle. At like 1600rpm if I pull the handle it still advances it, and revs it up to 1800!

[Vincent Waldon]

Plus at what rpm should advance take over from the cold start handle. At like 1600rpm if I pull the handle it still advances it, and revs it up to 1800!

The cold start advance is ignored by around 2000 RPM... and it's only a couple of degrees of advance to begin with.

On many pumps however, the cold start lever is tied to a "fast idle" lever which ups the idle speed when you pull out the cold start handle... this may be what you're experiencing.

[blackbird82]

Mine never idles higher with cold start. Its newer than that. true at around 2000 spm it is not effective. But from what it does in the mids (1200-1400) it would suffice to me that the pump is not advancing fast enough. hmm, i need to get another out bolt for the pump and drill and tap and put a DR port on it.

[blackbird82]

after more testing last night! my cold start handle still advances the timing up to 2500rpm. i can tell from the sound. and it will make it speed up a hair. that to me is really high, pump should be advancing tiself before that.

[vanbcguy]

after more testing last night! my cold start handle still advances the timing up to 2500rpm. i can tell from the sound. and it will make it speed up a hair. that to me is really high, pump should be advancing tiself before that.

Definitely not a good sign...

Try hagar's "pull test" - find a fish scale and see how much force it takes to pull the cold start engine while the car is off, then try again after starting it, and once more at 2K RPM.  The force required to pull the cold start handle should decrease quite a bit if the pump's internal pressure is good, especially by 2K RPM.  A "good" pump should be a ratio of 5:1 or more (IE if it takes 5 lbs to pull the handle when the engine is off it should only take 1 lb when the engine is running, your numbers will be different).

If it's a low ratio (not much difference in force) then the pump's timing piston is either stuck or the pump's pressure is way down.  Just an easy test to get a "handle" on things!

[blackbird82]

yeah I can feel the difference when driving vs sittin with the motor off. I need to get myself the tools to test and check and set timing.

[blackbird82]

after more lookin into it, i can see that pump pressure is gonna be my main culprit. what is the best way to measure. i was thinking of gettting another out banjo bolt and drilling and tapping for a fitting. what have you guys done?

[vanbcguy]

The best solution I've seen is using the extension pedestal from an NA pump and tapping it for a gauge.  That way you have the same OUT bolt in use for your measurements, as it is part of the pressure regulation system.