New 4.6 Stroker Dies When Clutch Engaged - Help!
Posted: July 8th, 2022, 9:37 pm
Appreciate all the information this site has provided me, and encouraged me to build a 4.6L stroker! However after about 450 miles I started experiencing an issue that I have been unable to resolve. Most of my build was guided through information I gleaned from this site, Dino's writings and Russ Pottenger. Almost all of my build parts were sourced through Russ and designed to run off the 99 4.0 fuel injection system I have. He and I have talked quite a bit about the problem below and I appreciate all of his help to date…he has been awesome to work with!
The issue I have is when I depress the clutch to shift out of 2-5 gear, the engine will die almost immediately….acts like I switched the jeep off. At times I have been able to hit the accelerator with it in neutral and get it to stay running, although most times it will still die. I can start it back up right away and continue to drive. It does not do this when in 1rst gear, and only about half the time when in second…..second gear is where I can usually catch it and keep it from dying by hitting the gas pedal. Once in a while it will stay running if in one of the higher gears (3-5), but this is only about 1-3% of the time. After starting the engine again it will stay running even if I shift back into gear and then depress the clutch again to unload the engine from the transmission. It will do this regardless of the amount of acceleration prior to depressing the clutch or if I am coasting beforehand. It has been very frustrating and results in having to start the engine back up after every stop or if I am slowing down to prepare to stop at a light. Again, the mechanism the seems to trigger this issue is depressing the clutch and taking load off the engine this way…..shifting in and out of gear has no correlation.
Build and history: #2 piston skirt came apart in my 99 4.0. Was tempted to 5.3 swap, but wanted to keep it "pure"….besides never messed with a Jeep/Chrysler engine before. The 4.0 engine was "retrofitted" in my 1990 YJ by the prior owner, and was not running well when I bought it….turned out to be a combination of poor wiring practices and a bad crank sensor. The engine is mated to the 1990 AX15 that was in the jeep originally.
Engine build:
• Forged rods, pistons, rings, pump, lifters, timing chain, etc. from Russ.
○ Racetech pistons, dished 26cc's
• Crank is out of a 86 4.2
• Quench set at 0.038"
• Machine work done at my local race shop, Watson-Ruppel and included: rotating assembly balance, 0.030 bore, decking of heads and block, 3 angle valve job and blending, grinding & polish crank, machine spring seats so they were all the same height from the deck, clean and mag block and head (no cracks), install new cam bearings and hone/fit cam…..I am sure I am forgetting a few details at the moment but it was thorough work.
○ Crank centerline to deck = 9.450"
○ Piston deck height = 9.457"
○ Mahle head gasket, 0.40" compressed thickness
○ Quench 0.033" (if my math is right)
○ Is my quench too tight???
• I ported and polished the head including polishing the chambers. Watson-Ruppel touched up a few things and cc'd the head, but the comment was the work was done very well and they didn't really have much to add to improve (luck on my part). Intake slight work to port matched to the heads.
○ Stock valves (I know, I should have went to the larger valves…..big regret lol).
○ Chambers range: 59.8 - 60.6cc (60.2cc average)
○ 26cc dish, 60.6cc chamber, 2.14cc head gasket volume (accounting for piston 0.007" above deck), should be 9.2:1 static CR (again if my math is right).
• Cam was bought from Russ and is a Comp, ground to Russ's specs (see attachment) and nitride surface treated. Harland-Sharp 1.6 rockers from Russ as well.
• New pushrods from Jegs…I cannot recall the exact length but have it written down if someone needs that info to help.
• BBK 62MM throttle body
• McCleod streetpro clutch
• Crank sensor is 3 years old and Mopar brand, less than 15,000 miles on it.
• New Bosch O2 sensor….I am running the upper one only. This is how it was prior to the build and ran fine.
• New intake air sensor…I broke the old one by accident during engine removal.
• Injectors are 24# from fuel injection connection (via Russ).
• NGK Coil Rail
• NGK plugs: ZFR6F (see pics attached, I just pulled them).
○ Not quite sure what to make of them….the markings on the insulator make me think detonation, but I have not had any noise or other anomalies that would indicate that. Have run everything from 93 octane to 87 octane without an apparent issue. No apparent change in performance from either.
○ Also not sure what the deal is with the electrode having that little shelf on the one side.
• Banks Revovler header into 3" stainless welded exhaust, 2.5" Magnaflow muffler and 2.5" tailpipe.
• Flowcooler water pump & new AL radiator.
Things I have checked:
• Fuel pressure 49 - 50# at idle, decreases under hard acceleration to 44-46#, right back up as soon as I let off the accelerator.
• IAC is newer and has the correct amount of supply voltage according to the manual I have.
• TPS checks-out within the range given in my manual.
• MAP has correct supply voltage according to the manual and there do not appear to be any cracks in the boot.
• Fuel injectors all have the correct resistance according to the manual.
• Vacuum at idle is 16-17 inches
• Engine very briefly hesitates when the throttle is rapidly opened, but otherwise runs great at idle, under load and acceleration. Not sure if that brief hesitation is related somehow or not.
Regarding how the fuel injection system is retro'd in the older jeep:
• Fuel pump is electric in-tank and controlled via the ECM and relay.
• Crank & cam sensors are plugged in and function as they did in the 99 vehicle
• Only the upper O2 sensor is installed. I read the lower is only really for emissions.
• Temp sensor installed in the water neck as stock.
• No changes or alterations to those on the throttle body and the intake air temp sensor.
I appreciate any and all thoughts, suggestions and comments. I have run out of ideas on what is going and hope this community can help me resolve so I can enjoy this Jeep/motor. Everything else I have ever owned, modded & played with was GM so this has been a bit of a learning curve….I am weak when it comes to the Jeep/Chrysler ECM logic and programming. I have a whole pile of other improvements I am tripping over as I need to get this fixed before I move on with the rest of the work!
The issue I have is when I depress the clutch to shift out of 2-5 gear, the engine will die almost immediately….acts like I switched the jeep off. At times I have been able to hit the accelerator with it in neutral and get it to stay running, although most times it will still die. I can start it back up right away and continue to drive. It does not do this when in 1rst gear, and only about half the time when in second…..second gear is where I can usually catch it and keep it from dying by hitting the gas pedal. Once in a while it will stay running if in one of the higher gears (3-5), but this is only about 1-3% of the time. After starting the engine again it will stay running even if I shift back into gear and then depress the clutch again to unload the engine from the transmission. It will do this regardless of the amount of acceleration prior to depressing the clutch or if I am coasting beforehand. It has been very frustrating and results in having to start the engine back up after every stop or if I am slowing down to prepare to stop at a light. Again, the mechanism the seems to trigger this issue is depressing the clutch and taking load off the engine this way…..shifting in and out of gear has no correlation.
Build and history: #2 piston skirt came apart in my 99 4.0. Was tempted to 5.3 swap, but wanted to keep it "pure"….besides never messed with a Jeep/Chrysler engine before. The 4.0 engine was "retrofitted" in my 1990 YJ by the prior owner, and was not running well when I bought it….turned out to be a combination of poor wiring practices and a bad crank sensor. The engine is mated to the 1990 AX15 that was in the jeep originally.
Engine build:
• Forged rods, pistons, rings, pump, lifters, timing chain, etc. from Russ.
○ Racetech pistons, dished 26cc's
• Crank is out of a 86 4.2
• Quench set at 0.038"
• Machine work done at my local race shop, Watson-Ruppel and included: rotating assembly balance, 0.030 bore, decking of heads and block, 3 angle valve job and blending, grinding & polish crank, machine spring seats so they were all the same height from the deck, clean and mag block and head (no cracks), install new cam bearings and hone/fit cam…..I am sure I am forgetting a few details at the moment but it was thorough work.
○ Crank centerline to deck = 9.450"
○ Piston deck height = 9.457"
○ Mahle head gasket, 0.40" compressed thickness
○ Quench 0.033" (if my math is right)
○ Is my quench too tight???
• I ported and polished the head including polishing the chambers. Watson-Ruppel touched up a few things and cc'd the head, but the comment was the work was done very well and they didn't really have much to add to improve (luck on my part). Intake slight work to port matched to the heads.
○ Stock valves (I know, I should have went to the larger valves…..big regret lol).
○ Chambers range: 59.8 - 60.6cc (60.2cc average)
○ 26cc dish, 60.6cc chamber, 2.14cc head gasket volume (accounting for piston 0.007" above deck), should be 9.2:1 static CR (again if my math is right).
• Cam was bought from Russ and is a Comp, ground to Russ's specs (see attachment) and nitride surface treated. Harland-Sharp 1.6 rockers from Russ as well.
• New pushrods from Jegs…I cannot recall the exact length but have it written down if someone needs that info to help.
• BBK 62MM throttle body
• McCleod streetpro clutch
• Crank sensor is 3 years old and Mopar brand, less than 15,000 miles on it.
• New Bosch O2 sensor….I am running the upper one only. This is how it was prior to the build and ran fine.
• New intake air sensor…I broke the old one by accident during engine removal.
• Injectors are 24# from fuel injection connection (via Russ).
• NGK Coil Rail
• NGK plugs: ZFR6F (see pics attached, I just pulled them).
○ Not quite sure what to make of them….the markings on the insulator make me think detonation, but I have not had any noise or other anomalies that would indicate that. Have run everything from 93 octane to 87 octane without an apparent issue. No apparent change in performance from either.
○ Also not sure what the deal is with the electrode having that little shelf on the one side.
• Banks Revovler header into 3" stainless welded exhaust, 2.5" Magnaflow muffler and 2.5" tailpipe.
• Flowcooler water pump & new AL radiator.
Things I have checked:
• Fuel pressure 49 - 50# at idle, decreases under hard acceleration to 44-46#, right back up as soon as I let off the accelerator.
• IAC is newer and has the correct amount of supply voltage according to the manual I have.
• TPS checks-out within the range given in my manual.
• MAP has correct supply voltage according to the manual and there do not appear to be any cracks in the boot.
• Fuel injectors all have the correct resistance according to the manual.
• Vacuum at idle is 16-17 inches
• Engine very briefly hesitates when the throttle is rapidly opened, but otherwise runs great at idle, under load and acceleration. Not sure if that brief hesitation is related somehow or not.
Regarding how the fuel injection system is retro'd in the older jeep:
• Fuel pump is electric in-tank and controlled via the ECM and relay.
• Crank & cam sensors are plugged in and function as they did in the 99 vehicle
• Only the upper O2 sensor is installed. I read the lower is only really for emissions.
• Temp sensor installed in the water neck as stock.
• No changes or alterations to those on the throttle body and the intake air temp sensor.
I appreciate any and all thoughts, suggestions and comments. I have run out of ideas on what is going and hope this community can help me resolve so I can enjoy this Jeep/motor. Everything else I have ever owned, modded & played with was GM so this has been a bit of a learning curve….I am weak when it comes to the Jeep/Chrysler ECM logic and programming. I have a whole pile of other improvements I am tripping over as I need to get this fixed before I move on with the rest of the work!