EGR issue with Jaguar XJS
Discussion
After months of trying to find a 'miss' on my 1994 Jaguar XJS 4.0 I am closer to finding the root cause,but maybe you can help.
On a light throttle at about 30mph the car misses and stutters, but never cuts out or dies etc. Get on the gas and it goes without really missing a beat. Its been driving me crazy.
Work I have done:
New plugs, coil, cap, rotor arm, injectors all cleaned and flow/vol balanced, new crank speed sensor, compressor and leak down test (all excellent), new O2 sensor, new EGR valve and EGR solenoid, and even a new ECU (actually available from Jaguar Heritage NOS and very reasonable) Still no change. Yes, I know, keep throwing new parts isn't the best approach but even 2 garages were a bit stumped. I took it to a rolling road dyno and all checked out too.
BUT, this weekend I disconnected the hose from the EGR valve to the EGR solenoid and it appears to have stopped the 'missing'. It runs smooth with the EGR valve take off port open or blocked off, but as soon as I reconnect the complete system it runs bad.
The hose goes from the EGR valve to the EGR solenoid, then another hose goes from another orifice on the solenoid to the inlet manifold, which pulls a vacuum on the EGR system. This hose also tees off to somewhere on the firewall. If I disconnect the inlet manifold port the car idles a little rougher, block it off and it smooths out.
What could be the problem? The EGR valve is brand new and so is the Denso solenoid. Another EGR was tried and they didn't change the miss. No check engine light is coming on either. With the car idling, if I push up the underside of the EGR valve diaphragm the engine coughs and will stall.
FWIW, the car is a US spec one.
Thanks for anyone with input on EGR systems and how they should work.
On a light throttle at about 30mph the car misses and stutters, but never cuts out or dies etc. Get on the gas and it goes without really missing a beat. Its been driving me crazy.
Work I have done:
New plugs, coil, cap, rotor arm, injectors all cleaned and flow/vol balanced, new crank speed sensor, compressor and leak down test (all excellent), new O2 sensor, new EGR valve and EGR solenoid, and even a new ECU (actually available from Jaguar Heritage NOS and very reasonable) Still no change. Yes, I know, keep throwing new parts isn't the best approach but even 2 garages were a bit stumped. I took it to a rolling road dyno and all checked out too.
BUT, this weekend I disconnected the hose from the EGR valve to the EGR solenoid and it appears to have stopped the 'missing'. It runs smooth with the EGR valve take off port open or blocked off, but as soon as I reconnect the complete system it runs bad.
The hose goes from the EGR valve to the EGR solenoid, then another hose goes from another orifice on the solenoid to the inlet manifold, which pulls a vacuum on the EGR system. This hose also tees off to somewhere on the firewall. If I disconnect the inlet manifold port the car idles a little rougher, block it off and it smooths out.
What could be the problem? The EGR valve is brand new and so is the Denso solenoid. Another EGR was tried and they didn't change the miss. No check engine light is coming on either. With the car idling, if I push up the underside of the EGR valve diaphragm the engine coughs and will stall.
FWIW, the car is a US spec one.
Thanks for anyone with input on EGR systems and how they should work.
you may already know but its an exhaust gas recurculation valve, it will open to allow exhaust gases into the combustion chamber to help lower emissions.
As suggested it may be possible to disable it either by removing the vacuum line or making a blanking plate, it may or may not bring on the engine check light but its worth a go.
A lot of people choose to blank it off completely
As suggested it may be possible to disable it either by removing the vacuum line or making a blanking plate, it may or may not bring on the engine check light but its worth a go.
A lot of people choose to blank it off completely
Edited by ch427 on Tuesday 24th September 19:52
I would really like the system to be working, because the car is very original etc.
So, I am figuring there must be a sensor that when the engine is to temp and running in a certain way the solenoid is switched open, that allows the vacuum from the inlet manifold to pull on the EGR valve and open it to allow the exhaust gasses to be drawng into the inlet manifold again.
I will check the system over again. Seems odd that with the 2 main components replaced it runs bad.
Any other input appreciated.
With the vacuum hose disconnected and the EGR blocked it is not triggering the check engine light.
So, I am figuring there must be a sensor that when the engine is to temp and running in a certain way the solenoid is switched open, that allows the vacuum from the inlet manifold to pull on the EGR valve and open it to allow the exhaust gasses to be drawng into the inlet manifold again.
I will check the system over again. Seems odd that with the 2 main components replaced it runs bad.
Any other input appreciated.
With the vacuum hose disconnected and the EGR blocked it is not triggering the check engine light.
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