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Old 07-03-2008, 11:09 PM
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94 K Blazer weirdness..

I have built my race cars..built the XK120 with the SBC..restored and overhauled Jag XK engines..like a lot of folks here do all my maintianence..but now I am stumped.
I am vey much more capable with carbs..but I understand FI..and IF I HAD HAIR I'D PULL IT OUT..!

I have had this truck since new..160,000 excellent miles. It looks new..99.9% of the time runs excellent...everything works as new....EXCEPT...

About two years ago..coming to a stop from speed. Motor dies..brakes go to floor..check engine light comes on. Restart..motor missing badly. Rev motor a few times..returns to good..but idle is now a 1500 or so..rev a few times idle normal.

Got home checked the obvious..vacuum lines..fuel lines. No repeat for months. All is well..after months of no repeat..I'm figuring bad gas..something blocked fuel line..or Q radiation from planet X.

Re occurance..then more often..
I took TBI apart..cleaned. Replaced vacuum lines. Seemed better then a repeat..and more often.
Replaced MAP..had a defective Ign module (no start) so replaced that..raised idle sligthly.
Seemed much better for a several months.

As usual..when you think you have an intermitent problem solved..it REAPPEARS..!!
I have replaced fuel pump (in tank..it died) of course..fuel filter. I gas it at Costco and have for years as I do all my vehicles.

Now once every few months..it re-occurs.
I have since re cleaned the TBI. Replaced plugs and wires. Changed temp sensor (became in op). Replaced cat (holed) and muffler.

This is a completely stock 94 K Blazer 350 (NO OBD2)..routine filters etc done ALWAYS on schedule. It gets about 15mpg in town..about 19-20 open road..and has not changed these numbers since new.
No leaks..no noise..smooth as a baby's butt idle 99.9% of the time..

I love my red truck.

It goes months without a problem..then a few times in one week or so it re occurs..then dormant for long periods..
The most difficult thing for me diagnose.
I cannot re-produce the events at home to trouble shoot.

I still think it's vacuum related maybe in the ABS lines..something else..carbon canister.
I am at a loss..clutching at straws ??

But I AM NOW STUMPED.

Any ideas guys..?

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Old 07-03-2008, 11:49 PM
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EGR could cause this also check your dist for cracks in the magnet if so replace it. Hope this helps.
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Old 07-04-2008, 06:19 PM
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q radiation from planet X would only cause hesitations not a stalling condition. I thought everyone new this.
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Old 07-05-2008, 04:28 PM
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No ideas..anyone ?
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Old 07-05-2008, 07:58 PM
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Did you check the distributor for play in the shaft or cracks in the magnet??? IAC Counts? Manifold VAC readings? Fuel pressure???? should be 9-15 most average 11psi (fuel pressure regulator problem?) You stated that the check engine light came on. What code if any was set? What brand of ignition module did you install? Was it OE or after market? Only use OE. Will it stall with EGR disconected. Other potential areas: rubbed through wires on TBI unit, corrosion at the 4 pin connector at the distributor. A quick way to check the pickup coil is to unplug the est connector and if it starts and runs replace the distributor. Good luck....
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Old 07-06-2008, 12:14 AM
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I know it sounds obvious, but a bad plug wire will do what you are describing. Whens the last time it had new plug wires? Plugs would be my next guess.

Next up the list would be the throttle body, if its plugged up with carbon and goo from the pcv it will lead to very erratic operation intermittently. Where the idle bypass solenoid controls the airflow past the large butterfly to maintain the idle speed if where to start looking for gunk, use a whole can of carb cleaner to blow out those passages and get the gunge out. The throttle plate should be cleaned at the same time.

If the idle air bypass solenoid is still original equipment it could be operating intermittently, since cleaning it cost almost the same as replacing it I would just replace it.

Let us know what you find, pulling the throttle body for cleaning is a simple job and will only take a couple of hours to clean up and reinstall.
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