95 deville rough Idle, stalls

dave3999 · #1 (**permalink**) 07-05-08, 02:16 PM

I have a 95 Deville, 4.9 with a rough idle and stalling problem. Fuel pressure tests fine, vacume can be low (tested as high as 18 and steady, as low as 12 and steady. Current Codes are P053 and p012, sometimes history, sometimes current. Sounds like timing is off (knocks under a load), gettinf ISC code as well on and off. Have been through 3 ISC motors, replaced Hall effect swithc, ECM and PCM. New cap, rotor and coil (old looked awful). Sprayed starting fluid around intake, no noticable increase in RPM, Problem is much worse when warm. I'm thinking pick up coil, any suggestions?

dave3999 · #2 (**permalink**) 07-05-08, 03:08 PM

Just drove the car again, now code PO23 current and others history.

submariner409 · #3 (**permalink**) 07-05-08, 03:56 PM

Vacuum seems low, especially if idle is only 18".

dave3999 · #4 (**permalink**) 07-05-08, 05:51 PM

Could the vacume be causing the ignition codes? I cant seem to find a leak. Could an ignition broblem cause the vacume problem?

submariner409 · #5 (**permalink**) 07-05-08, 06:04 PM

Not sure about your particular ignition system, but a retarded spark at idle will sometimes cause a decrease in vacuum as well as a low-speed miss.

Lithorian · #6 (**permalink**) 07-05-08, 06:04 PM

my 95 deville pulls 22 in vacum at idle, i would start with your distributor seeing as you have p012 - no distributor signal and p053 - distributor signal interupt, change the pick up coil, search for a vacuum hose at the back of the motor near the driver's side corner, that damn hose ALWASY gets knocked off while doing the rear plugs, that will cause your low vacuum and is hard to get starting fluid in, as for the ISC you need to calibrate it or it wont work right, with the engine running, lift the throttle off the plunger and push the ISC in till it bottoms out, disconnect the ISC and adjust the plunger so that the gap between it and the throttle is .060, if i am correct, of course ranger will correct me if i am wrong:P, as for the knock under load it's PROBABLY spark knock, try rodding out the two EGR tubes in the throttle body. I had most of these problems with my deville as well, except for the distributor codes, so i have a few more tricks up my sleeve if this doesnt work. p023 - EST signal problem

dave3999 · #7 (**permalink**) 07-23-08, 12:10 AM

took it to the shop to have pick up coil replaced, put in new distributor and harness (wires were falling apart). No change, runs great cold, huge miss when warm. Mechanic is scratching his head. Fuel pressure fine according to him, he thinks vacume is also good.

Lithorian · #8 (**permalink**) 07-23-08, 02:37 AM

..... any other codes? i'd almost think that its would be a PCM problem...

ogbuehi · #9 (**permalink**) 07-23-08, 03:42 AM

Try cleaning out the EGR tubes. That always works for me.

dave3999 · #10 (**permalink**) 07-25-08, 05:40 PM

Car has been in the shop for 3 weeks, mechanic replaced dist & pick up coil, I cleaned out egr before taking it in. I replaced PCM before I took it in (problem with Idle speed motor went away), Mechanic says no codes now, fuel pressure and vacume test good. He is convinced it is an ignition problem but cant find it. Refering to dealer. Any ideas?