Won't start, cranks fine, ....

When it finally does start, the engine runs up to around 5,000 RPMS, and then stays there! We have even had to pull the coil lead to shut it down, as it will NOT respond to the key being turned off if allowed to reach "idle". Is a fresh rebuild, timing is dead on (checked many times!) also, no fuel pressure in rail imediately after shutdown, while trying to start, will stutter/spit and then go racing for redline. Any ideas? TIA ( have been arguing with this think since last saturday)

ren said:

When it finally does start, the engine runs up to around 5,000 RPMS, and then stays there! We have even had to pull the coil lead to shut it down, as it will NOT respond to the key being turned off if allowed to reach "idle". Is a fresh rebuild, timing is dead on (checked many times!) also, no fuel pressure in rail imediately after shutdown, while trying to start, will stutter/spit and then go racing for redline. Any ideas? TIA ( have been arguing with this think since last saturday)

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Sounds like a big vacuum leak, manifold maybe. Are you sure it's all the way against the head? Is the IAC motor verified good?

Yes, head is fully seated and the mainfolds also, and the IAC has been exchanged with the one off a running, fully functioning motor. Am about ready to beat the owners' head against a wall until at least I feel better.

bump (I know, but I really need to fix this thing by Sat., so he can go wheeling with the rest of us.)

ren said:

We have even had to pull the coil lead to shut it down, as it will NOT respond to the key being turned off if allowed to reach "idle".

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This doesn't make sense. You said it goes to 5k and stays there. What is this about idle? If the key doesn't turn it off, you have a key switch problem or a power latch relay problem coupled with a bad computer. Make sure the leads on the starter solenoid by the battery is wired correctly.

The rpms and the not shutting off problems are most likely not related. A large vacuum leak will cause the high rpms but it has to be rather large. The only things that come to mind are a bad connection from the manifold to the head, a badly seated throttle body or a blown brake booster. Make sure the butterfly is closed in the throttle body when the accellerator is released.

Old Man: we have replaced the the entire relay bank with the ones from my XJ that I drive to his house, so we know that they are good. What I meant by "idle" is that the motor is wanting to stay at 5K, and not come down any at all. The few times that this XJ has tried to establish idle at a normal speed, it will spit and sputter with symptoms very similar to a clogged fuel filter on a carbed motor, then it will going screaming up to about 5k, and stay there. We have checked the manifold to head area several times, including with a propane torch, and a torque wrench to verifie the bolts are tight. The motor will not respond to key input to turn it off quite often when allowed to reach 5k, and we have tried to adjust the switch, and even have used a spare switch with screwdriver to try to confirm a bad switch. no luck. The comp. has been replaced with 2 of my known good spares, once with auto, then with manual comp. I have tried to choke the motor down by placing my hand over the butterfly in the T/B, but it will still maintain the 5k "idle". If the booster is allowing that much air to enter the motor, should we not be able to hear the leak under the dash? My friend's dad is convinced theat the cam is the trouble, but the timing is dead on, and the motor spins as easily as mine does. What are we missing?

bump again. We still have had no luck with this thing. Ideas anyone? TIA

If you can put your hand over the butterfly on the TB and not shut her down. you have an intake leak, (the air has to come in somewhere to keep it running that fast) Did you check the map to TB vacumn hose, That is one that gets forgotten.Check the Brake Booster vacumn line for cracks, You might be looking for a number of small / medium vacumn leaks. Your saying the manifold is on tight, so when you cover the TB where do you hear the whistle. that is where the leak will be when you are at 5000, and cover the TB. Good LUCK.

You have a leak I don't care what you think you installed correctly.

It can be a leaking in any of these places

tb-intake
intake-head
injector hole
vac lines
vac ports

Turns out that we had a cracked intake manifold. Simple R&R, now it runs great. Thanks to everyone that took the time for replying!