jproctor
Newbie
I put a new GM Replacement 5.7 long-block engine in my son’s pickup - 1990 Silverado --last summer. For the past 6 months, it has run great.
On the install, I had an local speed shop clean the intake. I replaced most of the sensors: IAC, MAP, CTS, Knock sensor and pigtail, O2, Coil, Distributor, wires/plugs, etc. I rebuilt the TBI and replaced the fuel pump (assembly) and inline filter. The original EGR held a vacuum so I did not replace it. Also, I didn’t want to drill out the TPS on the TBI. I had no reason to believe it needed replacing so it is original to the pickup.
All of the sensors are Delco except the IAC and CTS. I replaced the battery to intake ground and thoroughly cleaned all other grounds.
Last week the pickup stumbled and began to idle like crap. It was running very rich and smelled like fuel. It stumbles at stop lights and the idles in cycles from good to nearly dying.
I checked for vacuum leak to no avail. After 2 days it indicated a code (15). It began to be difficult to start as if the CTS was bad --- had happened on the old motor once. I found the pigtail for the CTS had a cut in it. I could also “wiggle” it and it would cause the engine to “react”. I replaced it last night.
Now, it starts up great and idles wonderful….UNTIL….it begins to cycle --- hear on video at :18, :38, 1:05, 1:23 -- engine was at operating temperature.
I don’t want to start chasing parts...practically everything is new.
1. Do I need to purchase the OBD1 ALDL cable to monitor the engine while running? I’m not sure what I would be looking for unless there is a resource for OEM operating parameters that I can compare. I don’t mind spending the $50 on a cable and learning a little more about that.
2. Will a OBD Scan Tool assist? Or, do they just “read codes”.
I can make just about any repair…but diagnosing these sensors is frustrating. I’ve read the forum (FCS and GMT400) for hours. A lot of people end up replacing part after part chasing similar idle issues and trouble codes.
Thanks for any help.
On the install, I had an local speed shop clean the intake. I replaced most of the sensors: IAC, MAP, CTS, Knock sensor and pigtail, O2, Coil, Distributor, wires/plugs, etc. I rebuilt the TBI and replaced the fuel pump (assembly) and inline filter. The original EGR held a vacuum so I did not replace it. Also, I didn’t want to drill out the TPS on the TBI. I had no reason to believe it needed replacing so it is original to the pickup.
All of the sensors are Delco except the IAC and CTS. I replaced the battery to intake ground and thoroughly cleaned all other grounds.
Last week the pickup stumbled and began to idle like crap. It was running very rich and smelled like fuel. It stumbles at stop lights and the idles in cycles from good to nearly dying.
I checked for vacuum leak to no avail. After 2 days it indicated a code (15). It began to be difficult to start as if the CTS was bad --- had happened on the old motor once. I found the pigtail for the CTS had a cut in it. I could also “wiggle” it and it would cause the engine to “react”. I replaced it last night.
Now, it starts up great and idles wonderful….UNTIL….it begins to cycle --- hear on video at :18, :38, 1:05, 1:23 -- engine was at operating temperature.
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I don’t want to start chasing parts...practically everything is new.
1. Do I need to purchase the OBD1 ALDL cable to monitor the engine while running? I’m not sure what I would be looking for unless there is a resource for OEM operating parameters that I can compare. I don’t mind spending the $50 on a cable and learning a little more about that.
2. Will a OBD Scan Tool assist? Or, do they just “read codes”.
I can make just about any repair…but diagnosing these sensors is frustrating. I’ve read the forum (FCS and GMT400) for hours. A lot of people end up replacing part after part chasing similar idle issues and trouble codes.
Thanks for any help.
