starts easy but in a few minutes it starts to miss ?? replaced the plugs with no change. after 5 minutes of idling it will stall
I did a post on a different thread āA slight Miss at Idleā (I donāt know how to link threads) on this very topic. Check it out. The tread explains how I addressed the issue. Over the weeks, months, years, Thereās been threads addressing this very topic.
I have a thread; that I started months back Another XJ6 that wonāt start and another one is ādied on a short driveā This car had many issues
Diagnostics
- check the spark plugs to determine the what the engine is receiving - fuel - too much, not enough, or just right.
- check the fuel pressure at the fuel rail - should be something around 35 PSI
-
NOIDS - very handy. If you donāt have them. Pick some up. I got mine at Harbored fraught
Possible culprits - Injectors not firing properly after the cold start injector does itās job.
- and as always check the ignition system.
Hope this helps
Cheers!
Vail,
Search the archives for my post from July 29 2018 where I had a similar problem in my 1987 XJ6 Vanden Plas. In my case it was due to a failing coil, fixed when I replaced the coil.
Similar symptoms can be due to fuel delivery (bad fuel pump, clogged fuel filter, bad fuel regulator) or other ignition related problems like the ignition amplifier.
My 29 July post provides additional information on what I did to sort out the source of my cars problem.
Paul
1 Like
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And will it then restart, Vail - and sort of repeat the performanceā¦?
How does the rpms vary - does it die off or stop suddenly? What temperature did the gauge read when it dies, and when it will restartā¦
The symptoms of increasing fuel starvation and increasing overfuelling is virtually similar - the engine will start missing, and eventually stall. Either as a function of time, or as a function of temperatureā¦
Starvation symptoms as described may be due to insufficient fuel delivery over time - and a fuel pressure test is necessary for confirmation either way. It eliminates guessworkā¦
Increasing overfuelling with temp may be caused by a failed CTS. When the engine stalls, disconnect CTS connector and short it with a metal paper clip - if the engine now continues to run; you have CTS issueā¦
Further testing; ohm between the two leads on the CTS plug - it should read some 2Kohm, verifying the connection between the CTS and the ECU. While wriggling the connector/wires there must be no variations in the resistance. As a failed CTS or a failed connection will give the same symptoms - both tests are necessaryā¦
Since the engine takes time to die; another variable is a heat sensitive ign amplifier or coil. So check, when the engine stalls, that you have ignition and injector action while crankingā¦
As Paul says, as similar symptoms may have different causes - identifying whether it is fuel or ignition that is involved. And take it from thereā¦
Frank
xj6 85 Sov Europe (UK/NZ)
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Paul thanks for your info. I found I had no spark at the plugs then traced douwn to the coil were i had no spark. I replaced the coil put still have no spark. I have 12 volts at the + terminal with the key on and using the ground from the battery, can the problem be with the - ground terminal on the coil. what cotrols that ???
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If you connect coil neg to bat neg, Vail - you defeat the whole set-upā¦
The coil ground is controlled by the ignition amplifier - which āmakesā and ābreaksā coil ground, just like the mechanical breaker points, but done electronically.
With permanent ground on coil neg there is no ignition - and a grave danger of burning out the coilā¦
The proper test for the ignition amplifier is to connect a test lamp between coil neg (no batt neg jump!!) and ground. Turn ignition āonā - the lamp should be fully lit indicating intact coil primary. Cranking the engine; the test lamp should dim and flickerā¦
The ign amp is indeed heat sensitive - and may be the casuse of the original troubleā¦
Frank
xj6 85 Sov Europe (UK/NZ)
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My '85 XJ6 had the very same issue, and it was the coil. The car would fire up. I could drive it just about anywhere; but if I pulled up to a stop light; or turned the car off to nip off for coffee; It wouldnāt start until the engine cooled down. I had replaced the coil with one I had kicking around and it work ya me! but it was a used coil; lord knows how old.
Anyway, there was performance shop across the street from the coffee shop. I ran in picked up a MSD coil hooked it up (in the parking lot - how embarrassing). and the car has been very reliable ever since. That was nearly 20,000 miles ago.
Good advice. That amplifier is everything.
Follow up to my previous post.
On another Series III same issue. This is from another post I did
Replaced the coil with aMSD blaster 2 coil. Downside is the MSD is significantly bigger around, so it doesnāt fit in the stock coil holder - you can purchase the holder from MSD or Amazon. or remove the bottom screw and one of the screws in the water rail, and have stay there with one screw - like I did. Itās a tight sqeeze so itās not going anywhere. Why you might ask would I do something half assed like that? The other #3 phillips screw holding the bracket on is stripped by the PO.
I also dumped the ballast resister because I accidentally grounded it against the water rail with my screw driver and let the smoke out. I priced the ignition module - which was the better part of 500.00 for an OEM Lucas module. It had screws, so I decided to take it apart. Low and behold and much to MY surprise
(not anybody else in the forum when I reported my findings) a GM HEI module - with GM embossed on the top of it, as you can see in the picture.
I replaced the GM ignition module with a MSD multi-spark ignition module that matched the coil 1 for the street fire HEI ignition.
The caveat to all of this is when I popped the distributor cap off to see if this addition caused any issues, I noticed the extra glob of something on the magnetic pick within the distributor - see below
Iām not sure if that was there before the ignition upgrade or not. I didnāt check it out first - I shouldāve. I adjusted the gap on the magnetic pick up to be with in specs. I checked the timing, and the RPMās all was still spot on.
The ignition upgrade was the ticket. Much to my surprise the XK6 fired up on the first click The car has great pick up - better than ANY of my other Series III with 1/2 the miles on the clock. Iām very pleased with the end result.
So there you have it. Something to ponder.
Mark