no change. it runs exactly as before. very rich, very poorly, shakes and jolts, backfires, and as soon as it gets up to about 160* it starts surging.

kind of like blower surge with a big cam and supercharger.

then it stalls and wont start again.


for those who dont know mods are:

modest top end rebuild, lots of new gaskets and such.
every wire vital to the engine management has been replaced with the highest quality.
new TPS
supposedly new CTS and IAT.
all new connectors.
all new plugs
new cap and rotor
firing order on the distributor is correct.


the only things i have yet to check are fuel pressure at the rail and distributor timing.

very dissapointing.

http://www.youtube.com/watch?v=pVkzO...ature=youtu.be

 

btw, i couldnt immediately tell that something was wrong with it for a minute or 2 the very first time i started it. and once it got warm, it started running very poorly.

there is definitely a correlation between the heat, and the way it runs. perhaps it is the CTS.

 

according to my Vacuum gauge, the V12 is drawing 6 in/hg at the ecu, at the fuel pressure regulator, and at the crossover.

to be honest, i was expecting something more along the lines of 16-20 in/hg

i was putting about 15in/hg on the ECU just to start it.

 

i just read this last;

man,, i feel bad for you, really, that damn car must be giving you nightmares.

ron

 

Your timing is off. Low manifold vacuum and the backfiring. Put a vacuum gauge on the engine and set the timing to the highest vacuum. Once you have that done it will be real close. Then you can get it dialed in with a timing light. You should see 20-25 in/hg. I would do this before anything else.

You are absolutely sure of the firing order?

Are the fuel injectors stock? I know you talked about using some GM ones.

What is your fuel pressure?

Also have you verified your wiring with resistance checks at the ECU connector?

Have you set the throttle plates?

Put a noid light or LED test light across all 12 injectors while the car is running.

You said "modest" top end rebuild. Does that include removing the timing chain or sprockets? If so are you absolutely sure the cam timing is correct?

The only way to fix any vehicle is a systematic and logical diagnostic approach. Random trying stuff is a good way to waste hours and get real frustrated. I am a field service engineer for a car manufacturer. I deal with this stuff on a daily basis. I see so many professional technicians just assuming the repairs they did are proper. The other big mistake is not using a plan. Out technical trainers like to reinforce, "Plan your work, work your plan".

My suggestion is to make a list of ALL the possible causes. Then work down the list eliminating them one at a time. Obviously some things are easy some are hard. Do all the easy ones first. Some are more likely and of course check those first. Some you may not have tools to do, save those for last. Trust me if you write it down and make notes you will find the cause. Trying to do it from memory and randomly you may never find the cause.

 

hmm. i thought the cam profile dictated the manifold vacuum.

so should i advance or retard the timing to draw more vacuum?


still havent checked the fuel pressure.
i bypassed the AAV and set the idle with the throttle plates, and adjusted my TPS accordingly.
injectors are stock and are all working once again.

i should have said light top end rebuild. i pretty much just replaced most of the rubber and paper from the cam covers, intakes,injectors, throttle bodies, crossovers, pipes, etc.
i didnt check the cam timing, but when i had the cam covers off, the tension on the chains was good.

 

You will have to try to see which way to turn it. Watch your vacuum gauge and of course listen. You will find that it will most likely be a bit too advanced once you do get to the point of setting it with a light but this will get you in the ball park. Of course providing the rest of the system is up to par.

Did you set the throttle plates?

 

.

 

100% agree, and I really feel for you and sympathise. If it was me, this is what I would do:

The symptoms are either too much fuel, which might be just tolerable cold, but as the car gets hotter is killing the spark, or the spark is mistimed.

Make sure the A1 cylinder is coming up to compression (by physically removing the plug and testing) and then ensure at this moment that the distributor rotor is pointing at the tiny "1" cast into the outside of the dizzy cap (roughly should point in the direction of B2/B3 cylinder).

Make sure the HT leads are in the right order going ANTI-clockwise round the cap viewed from the top.

Make sure there is a fat blue spark at the leads.

Then test the injectors trigger time and flowrate and fuel pressure.

Renew the coolant temp sensor, check the TPS output.

Then physically check all the loom from engine bay to ECU.

Try to borrow another ECU and try that AFTER everything else is checked.

Write yourself system notes of what to do and the results at each stage.

Greg

 

ive got a 16 cu and a 6 cu already.

 

the CTS is reading 2.3k ohms at ambient temperature.

 

i found the compression stroke and used a screwdriver to judge where TDC was. it appears as if the rotor is as advanced as it could possibly be, while still allowing the engine to run. its nearly contacting the next pole once it has reached TDC.

ive retarded the timing as far as the side adjustment will allow, and im going to see if it will run shortly.

unfortunately a few of my plug wires have come apart and are not worth repairing. theyre bosch and dont quite fit. found another set on rockauto for $22.99

 

alright. this is bullshit.

the engine seemed to straighten up quite a bit once i started advancing the timing. so i went full advance with about 20-25 in/hg on the ECU baffles (not connected to the engine) and it seemed to straighten up and even out.

heres where it gets weird. the intakes were reading 15 in/hg. i reconnected the ECU to the engine, and the rpm's died down to about 800 and the vacuum dropped to less than 5 in/hg, causing the engine to die.

the CTS is reading 220 ohms at about 190*


as soon as the engine gets hot, its like a freaking switch. BOOM. runs like ****.

 

adjusting the timing did very little to improve anything.

i played with the dristributor adjustment until i had it as good as i could get it. then i checked my reference marks only to realize it was in the EXACT SAME PLACE as when i started.

 

this ****ing turd will not run more than 5 minutes. as soon as it gets warm, it throws a switch and stalls. you cant start it again until it cools down.

at this point the ONLY thing keeping me from swapping in an L67 is that i would need a driveshaft thats 8 inches longer.

 

This could be an over heating coil. Try freeze spray on the coil when it dies to cool the coil and re-start.

Is the coil too hot to touch? and are you still running dual coils? if so how are they wired?

 

im still running dual coils, and theyre wired the same as factory, just fresh wires.

 

do you have an aftermarket rotor? that thing caused my car to run like **** for a while.

 

i do have an aftermarket rotor.

the coil is not getting hot.

 

ok. basically whats happening in this video is that i walk outside, release the vacuum on the ECU by accident, and the car dies. at that point it wont start.

85 XJS shuts off suddenly - YouTube