I have a 1990 Deville with the 4.5 Liter. I had a lot of problems with it so I took it to a dealership and they said I had six bad injectors. So, I replace those with remanufactured ones from www.rockauto.com and it runs much better but still not perfect.
It just falls flat on its face when you try to accelerate with more that 1/4 of the pedal down, it idles a little rough, and it dies at stop signs when the gas tank is less than a quarter full. It shows the codes 48, 49, 52, and 98.
I've replaced the plugs and wires recently, also, when I changed the injectors.
Can anyone help me out?
at the top of the 4.x board is a sticky with all the trouble codes in it, I'm assuming they're all engine (E) codes? if so here's your list:
E48 - EGR System Problem ~ clean or get a new EGR tube/valve...
E49 - A.I.R. Control Problem ~ don't know, maybe the MAF sensor?
E52 - PCM Memory Reset (See Note) ~ not important just means you or someone has reset the codes
E98 - High RPM P/N to D/R in ISC Range ~ ISC sounds like it's going or gone, do you have a high/unstable idle? If so time for a new ISC motor...
Definitely sounds like your computer is having trouble reading how much air is actually entering your engine, would explain some of your problems.
Your EGR valve is likely sticking open, causing your rough idle and hesitation. If you push up on the diaphram underneath it and it doesn't move freely, it must be replaced. While you're at it, clean out those tubes in the throttle body with carb. cleaner and a coat hanger or wire brush. This should solve the E48, E49, and E98 codes. The ISC code (E98) is probably out of range because it's trying to prevent a stall because of the stuck EGR.
Also, for $15, you may want to install a new MAP sensor--it's very easy. These tend to get lazy over time. Also, clean out the MAP port on the throttle body with intake cleaner.
1990 model PCM's were sensitive to shorted injectors. If the resistance got very low on any of those 6 bad injectors, the PCM probably suffered damage to one or more injector drivers. You may have an EGR problem, or you may have just created one by accident while doing the injectors.
E49 is A.I.R Control problem. its the goofy looking device on top of the rear vavlve cover with all the hoses coming off of it. that valve diverts air into the front exhaust manifold and into the cat. conveter under the car. this is for emissions and i have the same code. the vavle unit is about $400, so i suggest a salvaged vavle.
My car is acting the same except for the dieing, im think it may be the distributor cap, rotor, and possibly coil.
I haven't got around to doing anything to it yet and it's still running about the same. I'm averaging 9 mpg with it. The only thing different now is the only code I'm getting is the E49(A.I.R. Control Problem).
Also, the previous owner took hollowed out the catalytic converter and put it back on. Would this contribute to my problem?