I have owned and loved my 1988 Deville for 6-7 years now, and it has around 135,000 miles on it. Recently I have been having troubles with the engine stuttering while driving, and stalling out once. I have replaced the plugs and wires, and had the car gone over, but haven't fixed the problem. It hasn't had any troubles within the last 2 weeks, but I was wondering if anyone could shed any light on the potential problem? When brought in to my mechanic, he found a code for the TPS and adjusted it, but it happened again after he worked on it. I tried using the onboard code reader and only got the system to bring up F48 7.0 and after hitting another button an adjustment from 100 degrees came on. Any help would be appreciated I love this car and hope to not have to get rid of it. I have also had to replace the waterpump and alternator in the past year and the roughness started a little while after replacing the alternator. This has the 5.0 273 motor.

 

Hey Ming; Some of the things to check for the stuttering would be Map sensor vac. hose leaking, poor connection at the EGR valve solenoid (cold engine only) intermittent malfunction of the speed sensor trigger at the distributor. Check all of your vacuum hoses for leaks/cracks. If performance is poor then maybe you need the Throttle body overhauled. The kit is about $60-80. Good luck.

 

F48 is not related to problem. Being condition started after alternator / water replacement, look at ground wires at alternator bracket. Early DFI cars are picky about grounds. Grounds wires should be on stud, eyelets clean, and nut all silverish / not rusted. Cadillac used cadium plated bolts, star washers, and nuts for grounds because DFI was ground sensitive, meaning any old fastener won't work. DFI is unique to Cadillac what works on other EFI cars doesn't always apply to Cadillacs. 273ci is 4.5 not 5.0 which can lead to inaccurate info or parts. brougham1 is correct about MAP sensor T in vac gauge watch how it reacts as throttle is popped to wot. Get factory manual to be able to get the most out of onboard systems. Make sure wires going to injectors are not pinched under air cleaner or spacer for it. Monitor fuel pressure should not fall under 9psi when engine is rev'ed or under load.

 

Hey guys thanks for the info, and any more suggestions are welcomed... My mistake on calling it a 5.0 motor, it was late and I typed wrong, you're definately correct on the 4.5 motor. Also, where would be a decent place to purchase a factory manual, all I can usually find are the no-help at home manuals.