MK1 Golf - poor running for first 30 min
Discussion
Hi,
Anybody recognise these symptoms?
-Engine very rough on idle for the first 20-30 minutes (chugging, misfiring, stalling)
-Random but very frequent misfires/cut-outs holding a steady rpm from 1000-3000 in high gear or when letting foot off the accelerator and coasting (overrun)
-Revs fine in neutral and pulls fine under medium to hard acceleration
-Seems to be getting progressively worse over the last few months i.e. did not happen overnight
I've changed the leads and dizzy cap and checked the plugs but not the coil yet. I think the fact that the problem lasts for 20-30 min suggests that it's not the cold start bypass valve. The 5th injector /thermo-time switch works (would only affect running for a few seconds anyway).
I checked the voltage at the cig lighter and it's a bit low - 11V at idle, 12.5 during normal running but 11ish with the lights, heater etc on.
Any suggestions much apprecaited.
Cheers,
Duncan
Anybody recognise these symptoms?
-Engine very rough on idle for the first 20-30 minutes (chugging, misfiring, stalling)
-Random but very frequent misfires/cut-outs holding a steady rpm from 1000-3000 in high gear or when letting foot off the accelerator and coasting (overrun)
-Revs fine in neutral and pulls fine under medium to hard acceleration
-Seems to be getting progressively worse over the last few months i.e. did not happen overnight
I've changed the leads and dizzy cap and checked the plugs but not the coil yet. I think the fact that the problem lasts for 20-30 min suggests that it's not the cold start bypass valve. The 5th injector /thermo-time switch works (would only affect running for a few seconds anyway).
I checked the voltage at the cig lighter and it's a bit low - 11V at idle, 12.5 during normal running but 11ish with the lights, heater etc on.
Any suggestions much apprecaited.
Cheers,
Duncan
30 minutes is a long time, unless you are driving quite slowly in very cold weather, for things to take to warm up.
This is a CIS car, right? Check the 4 rubber donuts that hold the 4 injectors into the head, they tend to crack and make a vacuum leak. This may or may not be visible without pulling the injectors, which is not difficult. You can spray some WD-40 in the general area and see if that affects the idle.
If this is at all like the US spec car it has a fair bit of vacuum hose, all of which can create a vacuum leak. Overall this sounds like a vacuum leak, but check the "control pressure" between the warmup regulator on the front of the block and the fuel distributor, this takes a special gauge and hose setup that you may or may not want to invest in.
A long shot that I have never actually heard of - 30 minutes is about how long it takes for the engine to put a little heat into the gas tank, maybe a weak fuel pump? Check the amperage, it's easy to run the fuel pump by jumpering the correct 2 pins on the fuel pump relay.
You didn't say, but you should catch up on any deferred maintenance such as fuel filter, air filter (although I have never seen rough running from a dirty air filter)
Call me in the morning if this does not help
This is a CIS car, right? Check the 4 rubber donuts that hold the 4 injectors into the head, they tend to crack and make a vacuum leak. This may or may not be visible without pulling the injectors, which is not difficult. You can spray some WD-40 in the general area and see if that affects the idle.
If this is at all like the US spec car it has a fair bit of vacuum hose, all of which can create a vacuum leak. Overall this sounds like a vacuum leak, but check the "control pressure" between the warmup regulator on the front of the block and the fuel distributor, this takes a special gauge and hose setup that you may or may not want to invest in.
A long shot that I have never actually heard of - 30 minutes is about how long it takes for the engine to put a little heat into the gas tank, maybe a weak fuel pump? Check the amperage, it's easy to run the fuel pump by jumpering the correct 2 pins on the fuel pump relay.
You didn't say, but you should catch up on any deferred maintenance such as fuel filter, air filter (although I have never seen rough running from a dirty air filter)
Call me in the morning if this does not help
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