Rough Running Problems...

[V8Pete 0]

I've searched the forum high and low and can't seem to find a problem quite like mine...

 

I've got a 1900 GTI with LE2 Jetronic. When I start it cold, the idle oscillates at roughly 0.5-1 Hz between about 1000 rpm and just above stall speed. When it starts coughing and nearly stalls, the revs go back up, then come back down and the cycle repeats. When warm it idles around 700 rpm.

 

The other problem is it surges under load and feels underpowered below about 3500 rpm with low to moderate throttle percentage. It seems to improve when I nail the throttle.

 

I changed the plugs, leads, and ignition amp/module which made it run better and improved the surge problem a fair bit, but after a few days, it seemed to be back to its old tricks. The old plugs looked a bit carbon-fouled.

 

I was thinking of having a look inside the [newish looking] distributor cap, trying a different coil, and checking the timing, but it keeps raining when I have time to do it, hence I'm on the computer talking about it instead of doing it

 

Is surging an expected symptom of ignition problems? There are no cackles or backfires or anything. I tended to associate surging with fuel delivery problems, then saw the carboned up plugs, and don't really know what can be done about fuelling with EFI apart from pump and filter which are new. I did run some injector cleaner in it with a tank of petrol, but that didn't do anything.

 

Do dicky SADs give the cold idle symptoms I described? My searching seemed to give slightly different symptoms.

 

Any ideas not involving a can of petrol and matches would be appreciated...

[pugbliss 0]

My only help is search under the folowing headings...

 

clean throtal body

clean SAD

 

then go to mot station and ask them to check your exhuast emmisions as it may be running rich at idel. This can be corrected but only at idel, if its running rich through out the rev range whilst driving then it could be quite possible the AFM (air flow meter)

 

im not a great deal of help i know but its a start

[jackherer 543]

I've got a 1900 GTI with LE2 Jetronic. When I start it cold, the idle oscillates at roughly 0.5-1 Hz between about 1000 rpm and just above stall speed.

 

its known as 'hunting'.

 

pugbliss has given you the answers you need but you wont find much if you spell throttle like that :D

[GLPoomobile 958]

Sounds vaguely similar to mine.

 

My used to run absolutely spot on before I did anything to it. The only problem was the valve stem selas had gone big time and it was smoking burning loads of oil. Despite this it ran spot on.

 

So I refurbed my spare 1.9 head and swapped it over and since then it hasn't run right. I've heard of other people using the 1.9 cam in a 1.6 with out problems so I don't think it is this.

 

My thoughts are:

1 - inlet gasket causing a slight obstruction to the injectors. I actually trimmed the edges slightly when I fitted it as it was overlapping in to the ports, but maybe it wasn't enough.

2 - I know my valve clearances are way out. I don't think this would cause the problems, but maybe?

3 - possible that I didn't get the cam timing spot on when I fitted the belt. Never done one before and had a major struggle. I think this is the most likely cause.

 

My symptoms are that when cruising on light throttle the engine jerks really badly. It's like the 'kangarooing' you get in traffic, but much worse and makes it impossible to drive smoothly under 30 mph. Only gets better if you accelerate!

 

Also idle goes up and down but not as bad as yours. Oscillates by about 200-400rpm. I have it set to about 1100 rpm though as it just wasn't happier below this.

[pugbliss 0]

jackherer...cheers good job i can do other thing cos spelling int my strong point, and for once it seams like i have some advice rarther than me asking for it!!!!

[Martin@PRD 0]

Another few pointers that seam to be over looked quite regular.

 

1. Make sure the injector plugs pins havent been pushed out or damaged in any way, loose wiring course allsorts of "wavy" power

 

2. Check Afm for bad tracks on the circuit board, this also created flat spots and irregular running problems

 

3. Fuel pressure, if possible replace regulator and remove pump from tank for inspection of sludge/water and split or loose piping on pump.

 

4. Make sure Tps clicks before it rests on the idle speed screw

 

5. Replace Cold start device (2 pin) found on the side of the head 90> or on the water exchange unit found under the thermostat housing <90

[Richie-Van-GTi 70 2 Cars]

could also be the ECU temp sensor is dodgy.

[yorkshirekowboy 19 1 Cars]

i had the same probs with my 1.9, it was the doing the exact same, but 6/700 revs, i did the afm overhaul and it cured it but i need need to adjust the mixer screw on the afm abit!!!!

 

It was ok for about a month then my SAD started to act up, so fixed that too, try the plug/connectors for dirt and any signs of corrosion!! wd40!!!

 

also as Richie-Van-GTi says the ECU temp sensor also another common fault, this happened on my 1.6!!! check the wires again if all ok, take get a spanner and take it out look at the copper end/sensor and see if it needs cleaning!! i cleaned mine with very very fine wire wool!!

 

Edited January 17, 2007 by surferkid205

[Rob_the_Sparky 9]

The hunting seems to be a symptom of a rich idle mixture, hence there being a number of possible reasons for it. AFM and ECU temp sensor being the most likely.

 

Have you played with the ignition timing? If it is retarded then idle will be weak and you will be down on power, wil feel a bit "flat" for want of a better word.

 

In theory the fuel pressure regulator may also cause a rich mixture but TBH I've not heard of this being common. Although I guess this maybe because not many people measure the rail pressure...

 

Rob

 

P.S. What fuel do you use over there? Our 95RON unleaded requires 1.9s to be retarded to avoid pinking so better to use 98RON if you can get it andf then tune the ignition timing to match the fuel.