When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I have put a 2006 4.8 vortec with a 4l60 in a 92 YJ. I am having problems with lack of power. The vehicle accelerates like the old 2.5L; then seems to go flat and will upshift once I ease up on the throttle slightly. It runs smooth,revs fine with no load, will accerate slowly under light throttle but loses it on hills.
No codes come up.
I thought the MAF might be the problem and sprayed it with cleaner. It seemed the problem was gone on the first run, it accelerated and ran great! I shut it off and on a restart it was back to the same issue. I suspected a faulty MAF as it is likley original. Put in a new MAF and maybe a marginal improvement but not really much. The MAF is on the end of a 90 degree elbow immediately off the throttle body and a conical air cleaner on the MAF. Could the MAF being that close to the throttle body have that much impact? I am not finding any vacuum leaks.
I have tried with the MAF disconnected and it seemd to want to run better but was incredibly jerky, with the air filter off no change.
I have new Walbro gss341 fuel pump, a Delco Corvette return stye filter and 3/8"fuel line.
What am I missing?
Thanks
randy
ECM was tuned to the jeep specs. It has 4.10s and 35" tires
What baffles me is I got one good run and cant replicate it.
I will move the MAF furhter away as it appears it should be about 10"
Are you sure it's shifting through all gears? Not starting out in third or anything?
And you have a Park/Neutral switch to the pcm? And an operating VSS?
Is the MAF/IAT getting hot from being so short? (seems it would be close to the back of the radiator.
It can pull 10 degrees of timing at 120 degrees and pulls more as temp goes up. Thats enough to feel.
You need at least a 6" length of straight tubing between the filter and the MAF in order to reduce turbulent airflow. If your air filter is mounted directly to the MAF, it is going to have all kinds of driveability issues that you will not be able to tune out. You may want to look into getting a speed density tune and eliminating the MAF completely.
yep, Ive confirmed it is shifting through all gears.
It has a neutral switch and the VSS works.
I think I best get the MAF and air filter relocated as the next logical step.
Thx
You need at least a 6" length of straight tubing between the filter and the MAF in order to reduce turbulent airflow. If your air filter is mounted directly to the MAF, it is going to have all kinds of driveability issues that you will not be able to tune out. You may want to look into getting a speed density tune and eliminating the MAF completely.
I'll disagree with that.
I have two LS swaps with the filter right on the MAF and they tuned and run fine.
For reference look at most all trucks that come with LS engines, the MAF is connected right into the filter box. Also the LS1 4th gen cars have the MAF way close to the throttle body AND filter.
Here are mine, they tuned easy, one even has a big cam. Nearly stock should be even easier.
Check your fuel trims. That can tell you a lot on how the engine is running, such as not getting enough fuel, vacuum leak, running too rich, etc.
I'm assuming the CEL diagnostic code haven't been disabled from the tune?
I've been looking at a XJ for an off-road rig. Approximately, how much did you spend to convert yours to the LS, minus engine/transmission? If you don't mind me asking.
My .02.
My first 98 Wrangler LS swap was a 4.8/AX15 swap (16 years ago). Completely stock 4.8. I used a 255 Walbro and a C5 FFR. Ran great. I didn't even tune it. Pic below. Stock GM truck intake with the K&N air filter right in front of the mass air sensor.
Couple years later I changed it to a LS6/4L60E combo. Air filter right in front of the mass air sensor. 14 years no issues. I did have it tuned since I had a small cam in the LS6.
One thing about the oil type air filters when they are new they sometimes have a bit oil comes off the filter and coats the wires of the mass air filter. The oil coating messes up the mass air flow sensor reading. Maybe clean the mass air wires?
What I have read that the mass air should be more than 6" from the throttle body.
The black Nova was a 427 LS with the air filter right in front of the mass air. It did require a tune and it ran great.
Thanks for the ideas. I am going to connect with the fellow who did the tune as well to see what he can help with.
On costs I spent $150 for the rad., $500 for an NP241; $500 for super short Sye, $375 CV rear driveshaft $150 for a Lokar floor shifter, $1000 for a complete dual exhaust sytem, say about $500 for misc stuff
Recognize that I am in Canada and the SYE and some other smaller pieces came out of the US so duty and exxchange drove the price up. so ballpark $3500 or so
Yes, it can be done that way, but it's mostly recommended to have a straight length of tubing prior to the MAF. Not saying it can't be done otherwise, but it's possible on the OP's specific combo, there is turbulence that is causing the MAF to read incorrectly. I second the idea to get a scanner on there to read the fuel trims, it's much easier than guessing at what the root cause might be.
Yes, it can be done that way, but it's mostly recommended to have a straight length of tubing prior to the MAF. Not saying it can't be done otherwise, but it's possible on the OP's specific combo, there is turbulence that is causing the MAF to read incorrectly. I second the idea to get a scanner on there to read the fuel trims, it's much easier than guessing at what the root cause might be.
I think thats more true for a card type MAF sensor. The screen smooths out turbulence in a regular MAF.
I don't think either should be near a 90 or even 45 because the air can flow faster on one side of it. Like with the 90 the air will want to flow more on the outside (long radius side) and flow less in the short side. Unless the tube diameter is sufficiently small enough.
I was even hesitant to use that angled tube I have but it didn't change operation as far as the tune shows. It's not quite a 45.
The voltage checked well.
I did however, see that the butterfly on the throttle body was dirty. I cleaned what I could see and quite an improvement. I did some research on TB cleaning and am going to do that and see what happens but I am thinking this may be the problem. I am still going to extend the distance between the MAF and the TB but that doesnt seem be the main issue. does anyone have any expereince with a dirty throttle body affecting performance?
I tried that corvette filter/regulator and it gave me 65 psi, and very negative fuel trims. The internet swore it would be ok, but it never was. I got rid of that filter and installed a $5 regulated factory fuel rail. Problem solved.
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.
4.8 vortec swap problems 
