# Car dies randomly after sustained constant cruising but then changing load causes semi-stall



## CDJetta (May 11, 2004)

Not really expecting anybody to have the... I KNOW IT'S THIS. 

1987 Rocco 16v. No vacuum leaks from what I can find unless my main huge plastic/rubber boot thing is leaking. All extra accessories vacuum lines have been disconnected and capped to eliminate any possible leaks to those. The whole ignition is new except for the actual distributor itself and ICM.

Roughly idles at 900-1k rpm. At cold the car may die at idle. It's a very jumpy idle when cold. Once warm it usually doesn't die except for recently it's been doing it more. After about 20 minutes, car fully warmed up, I can be cruising at 70mph on the highway and then give it the slightest more gas to increase speed and it'll lose all power and start engaging and disengaging power erratically as the gas pedal is just held down a little or a lot.

Usually what I do to enable me to increase my speed again is actually turn off the car then turn it back on. Once I do that I can press the gas pedal down all I want and it won't give me one shudder. It'll work fine for a few minutes and then go back again. it's quiet annoying.

Anybody have any clues or possible things for me to try out?


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## cuppie (May 4, 2005)

So many things that could be......

- intake leaks. Things oft forgotten about: brake booster (yes, it's part of the intake tract), and the engine itself (crankcase vent hose, oil dipstick & funnel, oil cap)
- wiring issues. Carefully inspect all engine grounds (both the ones on the rear of the intake, and the 'loose' ground wires at the battery negative clamp), and repair as needed. Also, run a ground wire from the intake ground stud to the battery negative clamp.
- power supply issues. Possibly a failing ignition switch. Can you verify voltage at, say, the coil + terminal when the car is misbehaving?
- fuel supply. Check your fuel pressure! And, verify that _both_ fuel pumps are functioning. Along those lines, it's not hard to pull the transfer (in-tank) pump, and inspect the pickup screen and pump hose.
- coolant temp sensor. It fails, and the engine management tends to go bat-isht crazy (personal experience here!) Cheap part, too. Aside from checking it (resistance chart is in the Bentley), there's a quick check, too: with key OFF, unplug it. Start engine (may be a little difficult, as fuelling won't be right....) - does it idle stable now? Get new temp sensor.
- cracks in intake boot. Don't bother "checking it for leaks" - just take it off (it's only 2 hose clamps), and carefully & thoroughly inspect it for cracks. Use a strong flashlight, and flex it a lot. _Any_ cracks = 'need new boot.' 

May be long-winded-sounding, yes, I know. But, like I said, there are a lot of things that could cause the issues that you're having. And, it wouldn't surprise me to hear that you end up fixing more than one problem. Be methodical. Be thorough. You'll get it.


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## CDJetta (May 11, 2004)

Thanks for the things to check. I've already been fixing things here and there.

Didn't know how to check the big boot for leaks. Thanks for that. I'll re-check everything for leaks again but the last three things you mentioned have already been fixed up. I've got the silicone MK1 Autohause front crankcase hose. Other two I know because I just did an oil change.

Wiring might be bad. O2 sensor is already replaced and hoses going to the knock sensor already replaced. New ground wire was already installed too. I made new ones out of double 0 gauge wiring I had laying around and soldered some ends on them.

Installed a new in tank pump but haven't checked the outer pump. I figured the car couldn't run with that one misbehaving. Fuel filter hasn't been checked which I am wondering if it's that but that wouldn't "reset" when shutting the car off.

Yesterday my coolant light on the coolant gauge went off when I first started the car. It was flashing. Got it to turn off when I cycled the car again. Might be coolant stuff.


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## CDJetta (May 11, 2004)

The car also seems to die when taking a right hand turn and not a left hand turn which is really weird.


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## ziddey (Apr 16, 2006)

CDJetta said:


> The car also seems to die when taking a right hand turn and not a left hand turn which is really weird.


Signature dead in-tank pump or associated pickup hoses. You below half a tank of gas too?


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## ellocolindo (Jan 15, 2010)

either a fuel pump in tnak; like it was suggested previously; or a wire about to break on the wiring harness somewhere.

how is the condition of the fusebox? any corrosion or leaky windshield?


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## CDJetta (May 11, 2004)

Fuse box is fine. I also already replaced the in tank fuel pump. I always hear the fuel pumps humming. I re-seated the in tank fuel pump to make sure it was positioned correctly.

This weekend I replaced all the fuel injector cups/holders and orings. Also cleaned out the injectors and restored the spray pattern. Runs a lot better but still have the stalling on load increase after it heats up. It doesn't really happen in the morning when going to work but happens a lot when going home from work. Don't know if it's the hotter temp outside towards the end of the day or what.

Made the multimeter to test the DPR reading and it's pulling a constant 20.01mA. On start up it starts lower around 10 and then builds up gradually till 20. No wavering or anything. Places online said it should go back and forth between 1-2mA and that my ECU is running in open loop because something isn't right. A sensor or something. I dunno. Anybody else have anything else?

O2 sensor is new too. ISV is humming and car runs worse when it's un-plugged.


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## ziddey (Apr 16, 2006)

87 should be cis-e. you should be oscillating around 10ma I believe. maybe 5ma since it's 16v? 20ma is max trim for enrichment. This is based on o2 sensor output. Does it run better with the o2 sensor unplugged? If everything is "right" and you end up at 20ma, you have a vacuum leak. Otherwise, your o2 sensor is not working properly / lazy. May as well get a long 3mm allen and richen the mixture to see where it gets you.

Check that your idle screw isn't all the way in. A lot of times with a bad oring, the screw will wander until it's fully tightened. Doesn't sound like your problem though.


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## CDJetta (May 11, 2004)

O2 sensor like I said I already replaced and it has less than 2k miles on it. When un-plugged it runs worse immediately, same with the coolant temp sensor. I bought a new one of those but haven't put it in yet. I've sprayed carb cleaner around the whole intake, TB, and the big boot. O-ring isn't leaking at the idle adjustment screw. Sprayed that down too and nothing happened. Today I'm going to check to fuel system pressure and make sure it's not dropping off. Haven't checked the fuel filter yet which that's today's adventure.


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