My hand was forced to put the jag on the road. Defiantly a different vehicle to drive. Loving it though.

Starting up the RPM's revs from 1000 to dropping to 100 then back up and down until it's ready to go.

Is this how Jags of this era normally start or do I need to make adjustments. It does take longer to adjust when the weather is colder.

 

Hi Wewillbefree,

This is definitely not how your Jag should behave. My first suspicion would be a leak in the air intake plumbing and/or carbon buildup in the Idle Air Control Valve (IACV). The IACV on your '88 looks a little different than the one in our '93, but the operation is the same. Carbon builds up on the pintle or plunger of the stepper motor, preventing it from closing completely and allowing unmetered air into the intake manifold. See the photos at the link below:

Idle Air Control Valve

Take care not to damage the IACV gasket. If it is damaged, you can use RTV silicone but be certain to use a product that is guaranteed to be safe for oxygen sensors.

I can't recall, but on an '88 there may be a procedure for setting the idle speed after cleaning the IACV. Check the Workshop Manual.

To search for leaks in the intake plumbing, it's easiest to remove the large pipes between the MAF and the throttle body (TB) and inspect for cracks or deformation. A common place for a leak is at the joint between the elbow and the accordion hose that attaches to the TB. When the hose clamp is overtightened, it causes the end of the elbow to collapse, creating a leak.

Also check all the breather hoses and vacuum hoses for leaks.

Another thing worth checking is the fuel pressure regulator (FPR). Pull the vacuum hose off the fitting, crank the engine. Any wet fuel indicates failure of the FPR diaphragm, which allows unmetered fuel into the intake manifold, causing rich running.

Please keep us informed.

Cheers,

Don

 

So I avoided starting with the IACV only because on the homework sheet that you gave me, I was supposed to clean out the carb build up by the throttle but there was absolutely no carb build up inside the port..
Now when I did take the MAFS out the MAFS sensor threading was damaged in the elbow. The compound that I used dried up and didn't hold. So air was getting through. I plugged it up now with some JB weld.
Then I moved on to the feul pressure regulator. When I took off the hose and started the car the feul came out wet. Switched the FPR with a used one and now when I start up the Jag there are no longer any issues.