Rough running 95 SLS

FUQTodd · #1 (**permalink**) 06-16-09, 05:04 PM

Gentlemen - I have a 1995 Seville SLS with 141,000 miles on it. I bought it from a Benz dealership my brother in law works for (wholesale trade in) with a few codes. I replaced the EGR and one ABS sensors. Also, a TC code pops up occasionally if the car is forced to downshift while in OD (p0039 I think) which I immediately clear.

I love the car but it has issues accelerating and idling, especially with the AC running after it warms up. I checked the fuel pressure and it is fine. I also replaced the FP regulator.

A Cadillac mechanic out of Vegas I take it to told me over the phone it is probably a poor body ground located at the passenger side firewall which needs to be tightened, as this is common.? I can't seem to find the ground wire / cable he referred to, and I am in SLC. Please help???

**Ranger** · #2 (**permalink**) 06-16-09, 05:53 PM

Common? I've never heard of that. might be time for a set of plugs and wires (A/C Delco).

FUQTodd · #3 (**permalink**) 06-17-09, 12:46 AM

Thank you for the response. However, the car runs great when it is cold. Once it is about up to operating temperature is when the missing begins - and it is amplified with the use of the AC. The plug wires, I believe, are made from silicone or HCR which is impervious to the heat the car runs at. Plugs don't seem to make much more sense either. I have read about at least 1 other member experiencing the same issues, with no updated post as to how things turned out. If anyone has any ideas PLEASE post them. Thank you in advance! Todd

submariner409 · #4 (**permalink**) 06-17-09, 09:59 AM

If the plugs and wires are original, it's past time to replace them. Use ACDelco #41-950 Platinum plugs and an ACDelco wire set from www.rockauto.com or www.gmotors.com. or call Luke in Parts at Lindsay Cadillac, over there >>>>

Your symptoms of a warm load miss fit plugs/wires to a T. As soon as the injector timing changes from cold to warm, the mixture goes toward the lean side, and added loads place a real demand on the ignition system. While you're in there, you might as well remove the coils and ICM and clean every connection there, too, including the coil connector towers. If this turns out to be a ground fault, it will not be the first time, either.

Make sure the plug wires conform to the diagram. The coil to plug sequence is critical. Google "waste spark ignition".

cctgene · #5 (**permalink**) 06-17-09, 10:24 AM

Quote:

Originally Posted by FUQTodd

Gentlemen - I have a 1995 Seville SLS with 141,000 miles on it. I bought it from a Benz dealership my brother in law works for (wholesale trade in) with a few codes. I replaced the EGR and one ABS sensors. Also, a TC code pops up occasionally if the car is forced to downshift while in OD (p0039 I think) which I immediately clear.

I love the car but it has issues accelerating and idling, especially with the AC running after it warms up. I checked the fuel pressure and it is fine. I also replaced the FP regulator.

A Cadillac mechanic out of Vegas I take it to told me over the phone it is probably a poor body ground located at the passenger side firewall which needs to be tightened, as this is common.? I can't seem to find the ground wire / cable he referred to, and I am in SLC. Please help???

Don't know if this will be helpful or not but the FSM for the 92 model does reflect a key grounding point behind the right passenger kick panel. This point serves as a common body ground for a bunch of things including the Powertrain control module (PCM), Idle speed control (ISC) motor, Transaxle position switch, ect. Since the PCM controls the fuel injection system this could indeed cause major problems, if you had a loose connection, but I don't know how common it is. The ground location is to the right and below the PCM, itself, and is the smallest of the four connectors that comes out of the wiring loom.

As I said above, this is from the FSM for a 92, so your layout might be different, but it might be worth a look see.

FUQTodd · #6 (**permalink**) 06-17-09, 01:45 PM

Thank you to those who posted, and to the countless number of posts I read prior to posting my problem. Once I get it fixed I will update this thread. Thank you guys again! Todd

FUQTodd · #7 (**permalink**) 06-26-09, 03:19 AM

put in the OEM AC-Delco platinum plugs gapped at .050, and the car woke up! Thank you to all of you helped me out with your wisdon and insight. It was (and is) greatly appreciated. Todd

submariner409 · #8 (**permalink**) 06-26-09, 09:34 AM

If ANYONE can explain the reason for these engines liking AC plugs and AC plugs only, I sure would like to hear it. The idea defies all reason, but this thread is another example.

Soon as I bought my STS, in went a set of NGK Iridium plugs - just like in the Olds 455's I build. Lousy performance and a nagging low speed miss. Lurked in here and saw the "Use OEM plugs" thing, passed that off as hogwash. Got fed up in 03/06, in went the AC #41-987's and they're still in there. My engine had the original DENSO plugs, and the plugs that are in there now are AC, but marked "Made in Japan" so go figure..........

ghutchin · #9 (**permalink**) 06-26-09, 05:01 PM

I can say that the Delco wires hold up much longer than other brands. I had a set of Bosch wires in my car that started missing after about 40k. The AC's regularly go to 90k+.

I'm currently running Denso Iridium plugs. Those seem to be good.

I think in the end its a longevity thing, with the Delco products being designed to GM's spec of lasting 100k miles. In reality, I think this equates to them being of higher quality.

FUQTodd · #10 (**permalink**) 07-01-09, 09:29 PM

speaking of longevity I just changed both radiator hoses last night and both were original equipment. BTW the car is a 1995 with 141K - neither hose was bad either.