Running problem with a 7a

[mrtat2k9]

Running problem with a 7a
Hi all hope someone can help me I have a running problem with my 20valve. At wot from tick over car will rev. But if I try it after its bean revved and not returned to tick over the car just folts and will not pick up at all really getting frustrated with it now. Hope someone can shed a little light on the subject thanks

Rob

[sam80quattro]

tried pulling the fault codes?

[mrtat2k9]

do i need a vag com

[mcandmar]

Interested to hear what this turns outs to be. I've had those symptoms before with a broken valve spring. At exectly 6300rpms i got valve bounce and the ECU threw a wobbly. Second time was a missed gear shift and it pegged against the rev limiter. Both times it was as though the rev limiter was stuck on, and the only way to reset it was to allow the engine to idle for a second.

[mrtat2k9]

when it first started it would get throught it if i kept my foot planted but its got that bad now when i have to take it out on the road if i wont to change gear i have to dip the cluch let it idea for a second or 2 then hope it piks up when i try and let the cluch up

[mrtat2k9]

hi got code of it was a 2242 fixed it by turning maf screw down took batrie of for an hour looked to see if there was any more folt codes got 4444 but still runs the same any ideas. thanks

rob

[mcandmar]

2242 suggests a dodgy MAF, or emissions way off spec. I was going to say start by checking the Throttle Position Sensor and idle switch with a multimeter, i have had a few of them fail. Also check the rubber intake hose from airbox to throttle body, they can tear on the bottom where the metal crank case breather pipe connects.

[mrtat2k9]

hi i tested the Throttle Position Sensor but the 2 pin plug should i do the 3 pin to and how do i test the idle switch thanks

rob

[mcandmar]

Idle switch is the plug on the top of the throttle body, green on pre 1990 cars, black on post 1990 cars. Its a simple on/off circuit with a micro switch so check you have continuity at idle. You should also be able to hear it click as the throttle body closes.

The plug on the bottom is for the position sensor, measure resistance and you should see it steadily increase as you open the throttle body. Thats the theory but the pin outs are a little complicated as i think it has two separate outputs for each throttle body. And there are two different throttle bodys depending on the age of the car.

Let me know which one you have and i'll look up the details in the Bentley manual. As a general rule pre 1990 cars have the 5-1 tubular manifold, Hitachi Idle Valve, Green idle switch connector, and the two plug ECU. Post 1990 have the 5-3-1 cast manifold, Bosch Idle Valve, Black connector, and a four plug ecu.

[mrtat2k9]

its a 91-92 black connecters but i have put a tubular manifold thanks

rob

[mcandmar]

Right, post 1990 have a three pin connector,

Pin 1 & 2 must be between 1500-2600 ohms
Pin 2 & 3 must be between 750-1300 ohms

Full throttle value must not exceed 3600ohms.

From memory Pin 1 & 2 measures the first throttle body range, and Pin 2 & 3 measures the second larger throttle body which opens around half throttle.

P.S. When you fitted the 5-1 manifold did you fit the heatshield too? If you haven't the plastic body of the position sensor will melt and toast the sensor. BTDT

[mrtat2k9]

hi thanks i will cheque it when i get back to work and ye i did put the heat sheald on thanks

rob

[mrtat2k9]

tryed all that and nothing seams to be wrong. iv noticed a new problem. when i press the throttle pedal just a bit so its just started to open the car will start to rev then shut down and with out moving the pedal it will rev and shut down again and keep doing that untill i press the pedal a littal more. im confused more then ever with it now. hope someone can help me thank you

rob

[20Vcqdriver]

Very likely to be MAF or knock sensor problem. Once throttle off its stop it relies on the MAF signal, also knock sensor issues from experience do not always throw up a code ...

[Error404]

IME knock sensors really just stop the timing advancing so you end up with very flat and reduced power delivery.

Have you tried a different MAF & throttle pot?