Need some input
Thread Starter
Racer
Joined: Apr 2010
Posts: 285
Likes: 0
From: New Prague MN
Need some input
I just finished my injector swap and have now developed the "idle" issue.
1986 L98
Bosch III injectors from FIC
After install I reset the IAC per manual (I have no scanner) and checked the TPS (.548 vdc at idle, 4.49 at WOT) settings to insure they were correct. I left the negative battery disconnected for at least 10 minutes to alow for reset and used a propane torch to sniff out any vac leaks.
Funny thing is, after a 10 minute drive the idle will hold steady at 700 rpm, but on initial startup it starts hunting from 600 to 800. I have suspected long before this that I was having IAC issues, and have cleaned it, but I notice when I let off the gas it takes several seconds for the engine to settle from say 1500 rpm to idle speed.
Anybody got any tips to throw out of what I may have missed?
TIA
Casket
1986 L98
Bosch III injectors from FIC
After install I reset the IAC per manual (I have no scanner) and checked the TPS (.548 vdc at idle, 4.49 at WOT) settings to insure they were correct. I left the negative battery disconnected for at least 10 minutes to alow for reset and used a propane torch to sniff out any vac leaks.
Funny thing is, after a 10 minute drive the idle will hold steady at 700 rpm, but on initial startup it starts hunting from 600 to 800. I have suspected long before this that I was having IAC issues, and have cleaned it, but I notice when I let off the gas it takes several seconds for the engine to settle from say 1500 rpm to idle speed.
Anybody got any tips to throw out of what I may have missed?
TIA
Casket
Le Mans Master
Joined: Aug 2010
Posts: 9,272
Likes: 17
did it hunt prior to the work? did you run it before you adjusted it and after the new injector install? and did you make a note of the readings prior to adjusting it, and can you get it back to where it was? and did you remove the runners and renew the gaskets or did you just loosen thing up so you could get the fuel rail out? did you replace all the o-rings? and on and on and on. I vote, put the settings back where they were and start from there.
Thread Starter
Racer
Joined: Apr 2010
Posts: 285
Likes: 0
From: New Prague MN
Removed runners and installed ALL new gaskets and o-rings.
Before injector install the idle would occasionally fluctuate between 600 and 800 rpm, but was smooth. Now it will fluctuate between 600 and 800 and is rough running.
I just pulled codes and got a code 44 (lean exhaust). I cleared the codes, verified there was no code 44 stored and took it for a 10 minute run. It set code 44 again. It seems to run worse with the MAF disconnected, I still need to get it jacked up and verify the O2 sensor as well, but It looks like it still has the original MAF in it. I am leaning toward a bad MAF, but am always open to the wise suggestions from the group here.
Before injector install the idle would occasionally fluctuate between 600 and 800 rpm, but was smooth. Now it will fluctuate between 600 and 800 and is rough running.
I just pulled codes and got a code 44 (lean exhaust). I cleared the codes, verified there was no code 44 stored and took it for a 10 minute run. It set code 44 again. It seems to run worse with the MAF disconnected, I still need to get it jacked up and verify the O2 sensor as well, but It looks like it still has the original MAF in it. I am leaning toward a bad MAF, but am always open to the wise suggestions from the group here.
Thread Starter
Racer
Joined: Apr 2010
Posts: 285
Likes: 0
From: New Prague MN
Thanks for the replies.
Casket
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
Thread Starter
Racer
Joined: Apr 2010
Posts: 285
Likes: 0
From: New Prague MN
My plan is to test fuel pressure in the morning. It is possible that with new injectors and what is probably a old scruddy plugged up fuel sock, I just might not be getting enough fuel. I know the pump is firing as I can hear it at key on.
Le Mans Master
Joined: Aug 2010
Posts: 9,272
Likes: 17
not to flog a dead horse, but if it ran fine before you did the work, there's a pretty good chance the problem is with something you did , didnt, or forgot. get some sleep, it will probably be starin right at you in the morning.
Thread Starter
Racer
Joined: Apr 2010
Posts: 285
Likes: 0
From: New Prague MN
Thanks for the input. It is appreciated.
Thread Starter
Racer
Joined: Apr 2010
Posts: 285
Likes: 0
From: New Prague MN
The symptom that really bugs me is it keeps setting a code 44 (lean exhaust) and after hovering over the engine while running you can definatley tell that the ecm is increasing fuel to compensate.
I have pulled and plugged vac lines all morning and nothing seems to make any difference. Re-ran the propane test 3 more times to no avail. Code 44 could be a fuel pressurre problem. I am going to have to locate a pressure tester. I just shut down and manually operated the schrader valve and got about an eight inch fuel shower, but that is not exactly scientific
. It could also be the o2 sensor, but that would be a heck of a coincindence. Still checking and rechecking every thing from yesterday.
Thanks for input guys!
Casket
I have pulled and plugged vac lines all morning and nothing seems to make any difference. Re-ran the propane test 3 more times to no avail. Code 44 could be a fuel pressurre problem. I am going to have to locate a pressure tester. I just shut down and manually operated the schrader valve and got about an eight inch fuel shower, but that is not exactly scientific
. It could also be the o2 sensor, but that would be a heck of a coincindence. Still checking and rechecking every thing from yesterday.Thanks for input guys!
Casket
Instructor
Joined: Jun 2011
Posts: 182
Likes: 0
From: Bowling Green Ky
The symptom that really bugs me is it keeps setting a code 44 (lean exhaust) and after hovering over the engine while running you can definatley tell that the ecm is increasing fuel to compensate.
I have pulled and plugged vac lines all morning and nothing seems to make any difference. Re-ran the propane test 3 more times to no avail. Code 44 could be a fuel pressurre problem. I am going to have to locate a pressure tester. I just shut down and manually operated the schrader valve and got about an eight inch fuel shower, but that is not exactly scientific. It could also be the o2 sensor, but that would be a heck of a coincindence. Still checking and rechecking every thing from yesterday.
Thanks for input guys!Casket
I have pulled and plugged vac lines all morning and nothing seems to make any difference. Re-ran the propane test 3 more times to no avail. Code 44 could be a fuel pressurre problem. I am going to have to locate a pressure tester. I just shut down and manually operated the schrader valve and got about an eight inch fuel shower, but that is not exactly scientific
. It could also be the o2 sensor, but that would be a heck of a coincindence. Still checking and rechecking every thing from yesterday.Thanks for input guys!Casket
would fuel pres affect idle only? does it affect lean -I realize it sounds like it should, but...?
I did the inj switch, no issues, but I sure saw a dozen opportunities! elec plugs, vac lines, even possible to switch inj plugs if not marked.
pcv?
jc
Thread Starter
Racer
Joined: Apr 2010
Posts: 285
Likes: 0
From: New Prague MN
no comment is useless if it triggers another idea, called "piggybacking."
would fuel pres affect idle only? does it affect lean -I realize it sounds like it should, but...?
I did the inj switch, no issues, but I sure saw a dozen opportunities! elec plugs, vac lines, even possible to switch inj plugs if not marked.
pcv?
jc
would fuel pres affect idle only? does it affect lean -I realize it sounds like it should, but...?
I did the inj switch, no issues, but I sure saw a dozen opportunities! elec plugs, vac lines, even possible to switch inj plugs if not marked.
pcv?
jc
Thanks again for all the replies.
Burning Brakes
Joined: May 2011
Posts: 838
Likes: 2
From: Louisville Ky
also, one bolt each side in cntr int manifold was only finger tight. never had leaked, which is a mystery.
egr pipe cracked under the heat shield? happened before.
if you look closely, you SHOULD be able to see all lines under plenum, all connecections. I'd make a mental list and check before removing plenum. in desperation would unhook batt cble, start over.
I'm guessing, but thinking at the same time.
joe
Thread Starter
Racer
Joined: Apr 2010
Posts: 285
Likes: 0
From: New Prague MN
During my slow teardown for inspection, I happened to find some debris (no idea what) pinched in the bottom of the passenger intake runner. Correcting this helped, but the idle still hunts when cold. After it warms up I get a high idle condition (1k in gear, 1200 in park) but it is stable. I replaced the IAC and did my IAC and TPS resets per manual. While inspecting the O2 sensor I noticed some flaking coming out of the slots in the pre-cats. I will clean those out when the car cools, but as always, I am open to other suggestions.
Thanks
Casket
Thanks
Casket
Le Mans Master
Joined: Aug 2010
Posts: 9,272
Likes: 17
back in the day, initial tune settings were used to get a engine running so you could make fine tuning adjustments to make it run good or better depending on the age of the parts. is it possible someone prior to you did that and you set it 'back' to initial settings?
you might also lower the idle down and see what that does