1988 xjs starting issue
 

My '88 has been acting up for the past month. After it sits overnight when I go to start the car in the morning the gas pedal acts jammed until you press it pretty hard and then it releases and is fine after that.

When you go to actually crank it, the car won't start unless 100% throttle is being applied. After it finally starts (usually after 4-5 10 second cranks) you must keep the gas at full throttle as it stumbles at around 500 rpm and smoke dumps out the back. Release gas now, and it just dies.

After about 30 seconds of flooring it you can release the gas and it sort of idles but you have to rev it a couple times in park and suddenly it starts running fine! She smooths out and I don't have problems for the rest of the day.

It was an annoyance until yesterday the RH catalytic converter caught on fire during this ritual. Nothing really phases me anymore with these jags.. ehh fire? just another day in jag ownership! This particular xjs is such a POS compared to my others that after I put the fire out with my trusty extinguisher I just started it back up and drove to work!

PS. Car still won't pass smog duhhhh (documented in another thread)

Verdict? She's flooding overnight right? This morning start issue ties in with the fact that it can't pass smog I know it but how? Who knows.


Maybe I'll record a video of this tomorrow morning and post it..

Any diagnosis on these symptoms must be guesswork. BUT, if it were me, I would guess that this is a fuel injection problem or overfuelling problem, and start looking at that area. Just some suggestions:

• if your have Marelli ignition, these are symptoms of overfuelling caused by one bank not sparking or both banks not sparking properly (that is to say, injectors working OK but no spark). So I would do the Marelli dizzy fixes and test or change the Marelli amplifier units and inspect and renew (unless perfect) the amplifier to dizzy loom. Brake Buster and others have recently posted on this subject.
• it could be flooding caused by faulty injector operation (I believe this is quite likely as the car is trying to start), especially as a cat fire must be caused by loads of unburnt fuel making its way to the cat. This would also explain your smog results; If so, my guess would be that the injectors or staying open too long. Or even some of them are jamming partially open, or that intermittent injector loom grounding is causing some of them to stay open.
• pursuing this idea, I would detach the injector loom and inspect it very carefully for breaks and shorts. if it were me I would replace it.
• Next, with a new loom fitted, I would see if any change. If not, I would remove the injectors and have them cleaned or clean them myself. Also test them for spray pattern and proper operation and 100% closure.
• Clean up the injector loom plug to resistor pack connector (my latest bit of XJS learning, see maintenance tip of the day!), refit the injectors, try it and see what happens.

Greg

With the sticky pedal I would disconnect the rods between the pedestal and each throttle and see if that makes a difference. If it does not the trouble may be in the pedestal or maybe the throttle pot below it. I am not sure of the construction of the pots but maybe the winding has come adrift and binding the wiper. Just guesswork but it would account for both symptoms.
Another possibility is one or the other fuel pressure regulators, maybe one has a dodgy diaphragm and is allowing fuel to bleed into the manifold over night. This would not account for a sticking pedal though.

Marelli ignition didn't come in until later 89, so it shouldn't have Marelli. My experience with these cars is that they temp sensor is very critical. I use a ohm meter at the sensor (unpluged), and then connect it, and go back to the ECU plug, and check it there for the same resistance. And even if its the same, it will still need to be in spec, for the current temp. As far as the throttle sticking, removing the throttle rods first, is the best advice I could give as well. Remove those, and then check the binding. If the throttle pedal works freely, then you can check each side of the engine seperately. There is a reason throttle bushings are sold readily, lol.

On a fule injected vehicle, holding the throttle to the floor, pretty much only allows much more air. This tells me that the car is flooding. Check that temp sensor, and keep us posted.

Okay so finally I have an update. I pulled the injectors and had them rebuilt and flow/leak tested. They are all better than new now. I put the car back together and the problems remain. So the injectors are eliminated.

I am inclined to think that the injector loom is fine, otherwise why would the car run so well any other time other than the first start up of the day?

The only change now is that I can start her up without being at WOT. It takes a few cranks but it will start with no throttle applied now. However, it has no power whatsoever. If you give it any gas the engine loads up for several minutes.

My solution is to start the car, go inside and get my things and let her idle for 5 or so minutes and then I leave.

This whole thing bothers me though because as I said in a previous thread, my car still can't rev past four thousand RPM. At 4k it just hits a wall. Plus it won't pass smog. It leads me to believe there is one problem and it is manifesting in these 2 or 3 general issues.

I know my exhaust system is crap. The PO put on 2 aftermarket cats per side and the O2 sensors are most likely shot from the fires.

I have 2 good oem cats and O2 sensors from my parts car but am reluctant to install them until I know they aren't going to be ruined the first time I run the car.

Can you confirm if your car has Marelli or Lucas ignition?

Do you still have the jammed throttle pedal problem?

Greg

If this is lucas ignition check secondary coil for 4000 limit on rpms.

The throttle body butterflies could be sticking causing sticking of throttle check their setting.

Hey guys. The car has lucas ignition and both coils were replaced with new OEM ones about a year ago.

Do you still have the jamming throttle? This could be important.

Have you actually tested for a good blue spark, even though the coils are new?

Have you checked fuel pressure?

I know this is a recent 'discovery' of mine, but have you cleaned up the plug connector on the resistor pack?

Might as well do all these things before worrying about the exhaust, even though it does sound a bit like a blocked exhaust. One test you could do is, when the car is ticking over and warm, feel the exhausts to see if their flow is equal. Then get someone to turn the capstan and see when it revs if the flows are equal. Any noticeable inequality would point to a blockage.

Greg