'97 Deville, runs rough with A/C on
Thread Starter
Joined: Feb 2007
Posts: 13
'97 Deville, runs rough with A/C on
My '97 Deville runs great except when I have the A/C on. It idles smooth but while driving it runs rough and feels like it has a bad miss and occasionally backfires. As I said, with A/C off it runs great and the A/C itself works good and doesn't make any noise. Does anyone have a clue what this could be? Thanks.
Dave
Dave
Super Moderator
Joined: Dec 2006
Posts: 1,461
From: Toronto, CANADA
RE: '97 Deville, runs rough with A/C on
Hard to figure these things out from a distance but what is happening is that the AC is putting a load on the engine when the compressor cycles on. This load is uncovering a problem. If it feels like a miss and backfires that's what you have imo, a miss. . Do you have a code? I'd go through the standard items for a miss. Being a 1997 do you know if your spark plug wires have ever been changed? If not they probably need to be by now. Spark plugs, when changed last? Then there is the coils if problem still persists. I always suggest fuel and air filters too.
Thread Starter
Joined: Feb 2007
Posts: 13
RE: '97 Deville, runs rough with A/C on
ORIGINAL: Katzmans Caddy
Hard to figure these things out from a distance but what is happening is that the AC is putting a load on the engine when the compressor cycles on. This load is uncovering a problem. If it feels like a miss and backfires that's what you have imo, a miss. . Do you have a code? I'd go through the standard items for a miss. Being a 1997 do you know if your spark plug wires have ever been changed? If not they probably need to be by now. Spark plugs, when changed last? Then there is the coils if problem still persists. I always suggest fuel and air filters too.
Hard to figure these things out from a distance but what is happening is that the AC is putting a load on the engine when the compressor cycles on. This load is uncovering a problem. If it feels like a miss and backfires that's what you have imo, a miss. . Do you have a code? I'd go through the standard items for a miss. Being a 1997 do you know if your spark plug wires have ever been changed? If not they probably need to be by now. Spark plugs, when changed last? Then there is the coils if problem still persists. I always suggest fuel and air filters too.
Super Moderator
Joined: Jun 2006
Posts: 507
RE: '97 Deville, runs rough with A/C on
if you have been driving for a year with the SES light on, then you have no idea how many other codes may have set since the last time you had it scanned.
Step 1.
Scan for codes
Step 2.
Repair the obvious problem first then move on to the next issue.
Step 1.
Scan for codes
Step 2.
Repair the obvious problem first then move on to the next issue.
Thread Starter
Joined: Feb 2007
Posts: 13
RE: '97 Deville, runs rough with A/C on
Thanks. The SES light comes and goes. Sometimes it is off for a month at a time (I know about the gas cap so that isn't it) but your point is well taken. I'll get ahold of a scanner and go from there.
Tech Certified Members
Joined: Jun 2007
Posts: 2,701
RE: '97 Deville, runs rough with A/C on
something there does not like heat.
that points to electrical or electronic.
ORIGINAL: DeFormula
Additional info, it seems to occur once the engine is warmed up, not when I first start it up. Any additional ideas? Thanks.
Dave
Additional info, it seems to occur once the engine is warmed up, not when I first start it up. Any additional ideas? Thanks.
Dave
Super Moderator
Joined: Jun 2006
Posts: 507
RE: '97 Deville, runs rough with A/C on
The engine computer runs in open loop until it warms up. Uses a base program from the TPS CTS and MAF.
When it reaches operating temp it uses feedback from the o2 sensors for fuel control.
When it reaches operating temp it uses feedback from the o2 sensors for fuel control.
Super Moderator
Joined: Feb 2007
Posts: 3,945
RE: '97 Deville, runs rough with A/C on
going by FLCaddytech either that is it or the O2 sensors are off-line?
ORIGINAL: FLCaddytech
The engine computer runs in open loop until it warms up. Uses a base program from the TPS CTS and MAF.
When it reaches operating temp it uses feedback from the o2 sensors for fuel control.
The engine computer runs in open loop until it warms up. Uses a base program from the TPS CTS and MAF.
When it reaches operating temp it uses feedback from the o2 sensors for fuel control.