PAUL T Posted March 18, 2018 Report Share Posted March 18, 2018 I work on the Deville today changing the plenum to get rid of the P0171 & P0174. Now I have a new problem hesitation at idle. I removed the fuel rail to change the plenum and I think that’s where the problem is. Is there anyway to tell which cylinder is causing the problem? The only code is P0300 history. I noticed a wet spot on the bottom of one injector. Link to comment Share on other sites More sharing options...
rockfangd Posted March 18, 2018 Report Share Posted March 18, 2018 Did you replace the injector bottom o-rings. I typically replace them as they can dry out and get damaged when removed GM FAN FOREVER Nice, clean, luxury= fine automobile Link to comment Share on other sites More sharing options...
PAUL T Posted March 18, 2018 Author Report Share Posted March 18, 2018 No I didn’t. Link to comment Share on other sites More sharing options...
PAUL T Posted March 19, 2018 Author Report Share Posted March 19, 2018 My wife, who drives the car, informed me that it was missing before I changed the plenum. I changed the spark plugs, the rear coils and rear wiring harness a couple months ago. I was more careful with the front plugs and did not change the front wiring harness or the coils. I also changed the throttle position sensor then too. Could one of the front coils or front wiring harness be the problem? Can you unplug the coils without getting zapped while the car is running? Link to comment Share on other sites More sharing options...
BodybyFisher Posted March 19, 2018 Report Share Posted March 19, 2018 Did you delete the codes after you replaced the plenum? The long term trim probably has the computer adding fuel due to the large lean vacuum leak. Typically, a hesitation is related to the TPS, check the connector Is the vacuum hose off the fuel pressure regulator? Check fuel pressure Recheck that all connectors and vacuum are back on, IAC, TPS, MAF on the intake snorkel Those are COP coils no? Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
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