Cadillac Owners Forum banner
22K views 72 replies 13 participants last post by  dennis93coupe 
#1 ·
I did some searching but I still have some questions about replacing one or more injectors on a 94 Cadillac Deville with 4.9L engine and 140K miles. We want to get around 30-40K more miles out of this car and we only use it for road trips so this means about 10 years.

I recently replaced the head gaskets and also removed the fuel rails and cleaned the intake before reassembly. (PS thanks to everyone here who helped me, the suggestions from this website helped alot). The car runs great except I now notice that the fuel used is about 20% more than what the computer indicates. I kept careful records over a recent 1000 mile trip. It used to get 24-25 highway mpg's but on this trip it only got around 21. These mpg's are from my own calculations not the computer.

I checked the regulator with engine running and it does not leak. I will check the injectors this weekend by pulling the fuel rails up and energizing the pump. I suspect that one or more injectors will be dripping. So here are my questions:

1. Is it best to replace all injectors if one or more is leaking?

2. Do I need any special tools to take the injector off the rail? And to replace.

3. Do I need any other parts besides the injectors? I put new o-rings on when I did the head gasket job, can I reuse these?

4. What is the best price I can hope for and where do I get injectors at this best price!
 
See less See more
#52 ·
Stoneage_Caddy said:
why do i have a bad feeling thats the valvetrain noise im getting ....
They aren't a hard swap, probably harder to get the valve covers off...
 
#54 ·
I did all of them on my Olds 350, which I suspect is nearly an identical twin to the Cad HT series. Very easy. I would recommend making sure the arms are wet with oil and that you use an accurate torque wrench.

It looks like the only area to mess up is overtorqing or cross threading. Olds went into the head direct with a fine threaded bolt. Cadillac bolted more like a wood bolt into the alum arm support. So if you cross thread, you have to get a fatter bolt that can dig in or replace the support. The pivots are what wears. Olds had some issues with breakage (mainly 86-up when engines went to Mexico). But most really need replacing >100K just due to wear. Being it is a hydrailic lifter, it tends to keep quiet, but once you replace it, you will be amazed how much more quiet it is.

The catch the FSM says, and I would do it for sure.

"REMOVE THE ROCKER ARM SUPPORT WITH ROCKER ARMS AND PIVOTS ATTACHED AS AN ASSEMBLY AS THE PIVOT ASSEMBLIES OR SUPPORT BAR THREADS MAY BE DAMAGED IF PIVOT BOLT TORQUE IS REMOVED AGAINST VALVE SPRING PRESSURE"

This is likely where people have gone wrong on these engines.
 
#55 ·
N0DIH said:
I did all of them on my Olds 350, which I suspect is nearly an identical twin to the Cad HT series. Very easy. I would recommend making sure the arms are wet with oil and that you use an accurate torque wrench.

It looks like the only area to mess up is overtorqing or cross threading. Olds went into the head direct with a fine threaded bolt. Cadillac bolted more like a wood bolt into the alum arm support. So if you cross thread, you have to get a fatter bolt that can dig in or replace the support. The pivots are what wears. Olds had some issues with breakage (mainly 86-up when engines went to Mexico). But most really need replacing >100K just due to wear. Being it is a hydrailic lifter, it tends to keep quiet, but once you replace it, you will be amazed how much more quiet it is.

The catch the FSM says, and I would do it for sure.

"REMOVE THE ROCKER ARM SUPPORT WITH ROCKER ARMS AND PIVOTS ATTACHED AS AN ASSEMBLY AS THE PIVOT ASSEMBLIES OR SUPPORT BAR THREADS MAY BE DAMAGED IF PIVOT BOLT TORQUE IS REMOVED AGAINST VALVE SPRING PRESSURE"

This is likely where people have gone wrong on these engines.
Just set the rocker bridge on there and get the bolts started. They should thread easy once they start correctly. When they are started tighten each one in one turn increments switching back and forth. Like tighten the left one a turn and then the right and then the left again and so forth. They are known for stripping out or busting when someone runs the bolt down on one side and then cocks the whole bridge one way. Then they tighten the other side and snap, goes the bridge. Stick to that and you should be fine. IN Oldsmobile V-8's like 350's and 307's these are notorious for making a lifter sound. I heard one engine sounded like it was flat coming apart. Sounded like it had no oil and wouldnt make it another 5 minutes on idling and come to find out we replaced all the bridges and it was as quiet as a new one. It was my brothers car actually and it was a 83 Cutlass coupe with the 260 V-8. Same thing as a 307, just smaller.

Blaze
 
#56 ·
Im still leaning toward this injector because I did put a used 1 in and when i pull that plug it does smell of gas slightly right after i run it but its not dripping or anything but i dont know if it should be. Maybe its extremly weak or just bad. As far as checking the compression i dont think im able to correctly....I can barely get my hand in the back of the engine let alone take spark plugs out. I was told i need all of the plugs out to do a proper compression test. I did do 1 earlier in this thread i was informed it was incorrect but by the way i got 195 on that 1...lol. Since i changed the dist cap and rotor the car definatly runs better but still not 100% obviously. Now the idol seems to be high when i first start it up...it revs up a bit and then lowers down...rpms are around 1000 after it lowers down. any ideas?
 
#60 ·
devilleman1024 said:
Ok I pulled the spark plug and yes it does smell of gas and looks wet. I also put the plug wire right up next to a solid ground and no spark. I even switched 5 wire with 7 just to see if I got a bad wire and still no spark. I think im gonna run to the auto parts store and pick up a dist, cap and rotor.
Let's get back to the basics, fuel and fire. Seems like #5 plug is not getting spark and all the others are. You are sure #5 plug is good? If so pull #5 wire off the dist cap. Connect a battery jumper cable to a good ground, start the engine on 7 cylinders and hold the other end of the jumper near #5 on the cap. Any spark? If there is spark, the problem is a bad wire or bad plug. If no spark the problem is with the cap (unlikely because new cap made no change) or internal in the distributor. The only thing inside the distributor that is cylinder specific is the pick-up coil. Not likely but possible.
FWIW
YMMV
DFB
 
#61 ·
holy crap...ok at first there was not a spark but after about 3 or 4 secs of holding it there it started i dont know what happened but it did. So i looked at both ends of the wire and made sure it was ok so it could snap on....and the end of the plug that hooked to the spark plug was bent a little so i straightened it out. To make a long story short through the climate controls i shut off #5 and it did it.....but only a little compared to the others. The other 7 make a pretty big difference in the rpms and #5 does about half as much? Thanks everybody who helped me get this far. But what now....lol
 
#63 ·
the car ran great....thanks dfbonnet whatever you told me to do did something...i dont know what but i love the basics! LOL. I washed it while i was out there i have been neglecting it a little since it hasnt been running the greatest. i think im gonna replace the plug wires again just to make sure.
 
#66 ·
devilleman1024 said:
Should I try adjusting the idle speed control or should I just replace it? The idle was high and I unhooked the ISC and the idle dropped to normal. Is it bad to leave it unhooked?LOL
Here's what I've done based on my recollection of posts by him who's name may not be spoken. Remove the air horn and open the throttle and look down the bores. Dirty? Spray bores and throttle plates with carb cleaner and brush with old tooth brush. Do not use a metal brush. Spray again to rinse. Do you see those two tubes down in the bores? Are they clogged up? If they are, rod them out with a piece of coat hanger wire or such. No need to be immaculate, just mostly open. Those tubes are part of the EGR system. Not germane here but a good time to check them out. Don't worry about any crud falling into the manifold. It causes no problems.
Start the car. How is the idle? Still high? While still running, find where the wiring from the ISC motor plugs into the wiring harness and separate the connection just enough so the ISC still works but the retaining clip is not latched. This is so you can get it apart with one hand. With one hand, or with a helper, advance the throttle a bit while pressing in on the ISC plunger with your finger. It should retract fully under pressure. Now finish disconnecting the ISC wiring from the main harness with your third hand. That will freeze the ISC in the fully retracted position. Let the throttle return to closed and turn off the car. With the throttle closed and the ISC fully retracted you should have about .030" +/- clearance between the plunger and the throttle. If there is no clearance screw the ISC plunger in until there is about .030". Doesn't have to be exact. Sometimes they are tight and require a bit of force. Reconnect the ISC to the harness. Disconnect the negative battery terminal to reset the ISC settings to default. Reconnect the battery and start up. If the ISC is still advancing the throttle too much it is probably defective.
FWIW
YMMV
DFB
 
#67 ·
I have found that GM X-66A works best for cleaning the throttle bores. It is a carbon dissolver that GM developed for top cyl cleaning. Works well, very well. See your local GM dealer... They have X66P also, it is the POUR can, the X66A is Aerosol spray.
 
#72 ·
Procedure is a bit complicated. PM me with your email and I will forward scans of the pages from the FSM. In order to get into the diagnostics, hold down OFF and WARMER on the climate control until you see it come up on the dash. Then follow the instructions in the pages sent.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top