LS 5.3 in a YJ performace issue. - Great Lakes 4x4. The largest offroad forum in the Midwest

RADRICK · August 20th, 2012, 06:14 AM

A good friend of mine recently purchased a 91 yj with a 5.3 swap. He was told it was an 06 5.3, it has a manual trans, possibly an nv 4500, and a 8.8 rear. It is a DBW set up, factory ECM, still has MAF/IAT, EGR, and front O2 sensors. Anyway when driving holding steady pedal the rpm's start to surge and looses power. It seems that the engine is really loaded up, or is starving for fuel. When this happens the exhaust smells really rich. This occurs after driving for 2-3 min at opperating temp, when you cycle the key it will "reset" and run fine for the next 2-3 min then happen again, it will also occur when in neutral. It has plenty of top end power, just a wild surge under steady pedal- like 1500-2000 fluxuation. He had it scanned vin showes 4.8l, 2wd truck (prob for man trans), NO DTC's, shows that trans is in third gear always, IAT showed 150-160 when driving at opperating temp, TPS voltage in spec. When hooked to the scanner he perforemed a crank sensor variation relearn, just to rule that out. We tried driving with maf unplugged to see if anything changed, and it did not. He purchased the jeep from the previous owner who was from lansing area, it is orignally a red yj, but the jeep had a camo wrap when the p/o had bought it. We are both pretty mechanically inclined, having both turning wranches for a living, I spent 10 years in a gm service dept, and I cant think of another similar issue. Any help would be appreciated, on solving the issue or info from the previous owners or who put this rig together. I have a vid on my phone I can try to upload later if it helps.

liv2mx · August 20th, 2012, 09:05 AM

02 sensor.

RADRICK · August 20th, 2012, 09:38 AM

Thnaks for the reply Erin, why an o2 sensor and no code? I understand that when the o2's & engine are at opperating temp closed loop status is acheived. After key cycle does the ecm revert back to open loop for a pre-set amount of time till o2's are heated by the heater circut/exaust temp, IE the 2-3 min of time before it starts running poorly again? What else would reset after a key cycle, like open/closed loop?

liv2mx · August 20th, 2012, 09:47 AM

i'm not sure just been learning alot from going through some issues with my 5.3. what does the scanner say for temp on 02? pm joescamaro on here. he is real good with these motors. i was told it would not throw a code if it's just a o2. also depends on what was done to your computer.they can delete all codes or set it for 1,2,or 3 before a light or code will show.

redhead_823 · August 20th, 2012, 10:13 AM

They had to delete some O2 codes because the post-cat O2 sensors are gone. Maybe they deleted codes for the pre-cat sensors as well. Do you have the tools to monitor O2 voltage while it's running? Make sure it's cycling correctly.

Is it a manual or electronic throttle body? Maybe that's losing control.

Can you monitor the air flow (from the MAF) to see if that changes? If air flow is steady, it's probably fuel.

RADRICK · August 20th, 2012, 10:20 AM

Quote:

Originally Posted by liv2mx

i'm not sure just been learning alot from going through some issues with my 5.3. what does the scanner say for temp on 02? pm joescamaro on here. he is real good with these motors. i was told it would not throw a code if it's just a o2. also depends on what was done to your computer.they can delete all codes or set it for 1,2,or 3 before a light or code will show.

I will try to get some more info on o2 sensor switching & o2 heater temp. Ill try to pm joe later, is he back from rubicon yet? I wish we could track down the original builder to find out who & what the tune was done to computer.

Haggar · August 20th, 2012, 10:23 AM

Sometimes whoever tuned the ECU deletes out trouble codes from being reported.

Haggar · August 20th, 2012, 10:24 AM

ScOoTeR could probably give you some helpful info. He'll probably also cringe at IAT of 160 degrees (motor is probably pulling all kinds of timing)

RADRICK · August 20th, 2012, 10:25 AM

Quote:

Originally Posted by redhead_823

They had to delete some O2 codes because the post-cat O2 sensors are gone. Maybe they deleted codes for the pre-cat sensors as well. Do you have the tools to monitor O2 voltage while it's running? Make sure it's cycling correctly.

Is it a manual or electronic throttle body? Maybe that's losing control.

Can you monitor the air flow (from the MAF) to see if that changes? If air flow is steady, it's probably fuel.

I would have to say they deleted the post cat. o2's, He has access to a snap-on (solus) scanner, from what he said o2 & MAF readings were ok. It is an electric throttle body, most of the ones I have seen go bad will have a dead (no action) pedal.

RADRICK · August 20th, 2012, 10:37 AM

Quote:

Originally Posted by Haggar

Sometimes whoever tuned the ECU deletes out trouble codes from being reported.

Hope someone knows on here who bulit the jeep & who tuned it!

Quote:

Originally Posted by Haggar

ScOoTeR could probably give you some helpful info. He'll probably also cringe at IAT of 160 degrees (motor is probably pulling all kinds of timing)

I didn't think 160 was that bad, thought it got bad above 180.

Haggar · August 20th, 2012, 02:54 PM

Quote:

Originally Posted by RADRICK

Hope someone knows on here who bulit the jeep & who tuned it!

I didn't think 160 was that bad, thought it got bad above 180.

Here's some discussion about it:

need more HP out of my 6.0 - Great Lakes 4x4. The largest offroad forum in the Midwest

pigfat · August 22nd, 2012, 02:41 PM

try unplugging the 02 sensors and see if it goes away. Those systems dont like Bosch 02's and also if post flow 02's are in the upstream it could cause an issue. Intake air temp could be hot depending on where the mass airflow sensor is pulling the air.

August 20th, 2012, 06:14 AM	#1
RADRICK Senior Member Join Date: 04-28-09 Location: Galien, Mi Posts: 403 iTrader: (6)	LS 5.3 in a YJ performace issue. A good friend of mine recently purchased a 91 yj with a 5.3 swap. He was told it was an 06 5.3, it has a manual trans, possibly an nv 4500, and a 8.8 rear. It is a DBW set up, factory ECM, still has MAF/IAT, EGR, and front O2 sensors. Anyway when driving holding steady pedal the rpm's start to surge and looses power. It seems that the engine is really loaded up, or is starving for fuel. When this happens the exhaust smells really rich. This occurs after driving for 2-3 min at opperating temp, when you cycle the key it will "reset" and run fine for the next 2-3 min then happen again, it will also occur when in neutral. It has plenty of top end power, just a wild surge under steady pedal- like 1500-2000 fluxuation. He had it scanned vin showes 4.8l, 2wd truck (prob for man trans), NO DTC's, shows that trans is in third gear always, IAT showed 150-160 when driving at opperating temp, TPS voltage in spec. When hooked to the scanner he perforemed a crank sensor variation relearn, just to rule that out. We tried driving with maf unplugged to see if anything changed, and it did not. He purchased the jeep from the previous owner who was from lansing area, it is orignally a red yj, but the jeep had a camo wrap when the p/o had bought it. We are both pretty mechanically inclined, having both turning wranches for a living, I spent 10 years in a gm service dept, and I cant think of another similar issue. Any help would be appreciated, on solving the issue or info from the previous owners or who put this rig together. I have a vid on my phone I can try to upload later if it helps. Last edited by RADRICK; August 20th, 2012 at 06:57 AM.

August 20th, 2012, 09:05 AM	#2
liv2mx i like jungle gym's. Join Date: 11-10-05 Location: silver lake Posts: 10,380 iTrader: (4)	02 sensor.

August 20th, 2012, 09:38 AM	#3
RADRICK Senior Member Join Date: 04-28-09 Location: Galien, Mi Posts: 403 iTrader: (6)	Thnaks for the reply Erin, why an o2 sensor and no code? I understand that when the o2's & engine are at opperating temp closed loop status is acheived. After key cycle does the ecm revert back to open loop for a pre-set amount of time till o2's are heated by the heater circut/exaust temp, IE the 2-3 min of time before it starts running poorly again? What else would reset after a key cycle, like open/closed loop?

August 20th, 2012, 09:47 AM	#4
liv2mx i like jungle gym's. Join Date: 11-10-05 Location: silver lake Posts: 10,380 iTrader: (4)	i'm not sure just been learning alot from going through some issues with my 5.3. what does the scanner say for temp on 02? pm joescamaro on here. he is real good with these motors. i was told it would not throw a code if it's just a o2. also depends on what was done to your computer.they can delete all codes or set it for 1,2,or 3 before a light or code will show.

August 20th, 2012, 10:13 AM	#5
redhead_823 Senior Member Join Date: 05-10-09 Location: Sand Lake, MI Posts: 207 iTrader: (2)	They had to delete some O2 codes because the post-cat O2 sensors are gone. Maybe they deleted codes for the pre-cat sensors as well. Do you have the tools to monitor O2 voltage while it's running? Make sure it's cycling correctly. Is it a manual or electronic throttle body? Maybe that's losing control. Can you monitor the air flow (from the MAF) to see if that changes? If air flow is steady, it's probably fuel.

August 20th, 2012, 10:23 AM	#7
Haggar Covered in mud... Join Date: 11-06-05 Location: Oxford, MI Posts: 16,708 iTrader: (48)	Sometimes whoever tuned the ECU deletes out trouble codes from being reported.

August 20th, 2012, 10:24 AM	#8
Haggar Covered in mud... Join Date: 11-06-05 Location: Oxford, MI Posts: 16,708 iTrader: (48)	ScOoTeR could probably give you some helpful info. He'll probably also cringe at IAT of 160 degrees (motor is probably pulling all kinds of timing)

August 22nd, 2012, 02:41 PM	#12
pigfat GONE COMMANDO Join Date: 01-11-09 Location: West of Monroe Michigan Posts: 1,432 iTrader: (49)	try unplugging the 02 sensors and see if it goes away. Those systems dont like Bosch 02's and also if post flow 02's are in the upstream it could cause an issue. Intake air temp could be hot depending on where the mass airflow sensor is pulling the air.