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 am just finishing up a 02 LQ4 swap into my 89 K2500 with a NV4500. The engine had 120k on it when I pulled it. I replaced the coils with good used ones (that’s what I was told Atleast), plug wires and plugs. It has the stock PCM, and I used PCM Hammer and TunerPro to make the changes to the tune. I have been driving my LM7 swapped 944 for about a year now so I’m pretty confident I have the PCM in order.
the truck starts and idles fine, but it’s clearly lacking power. Once it’s out on the highway it’s really
noticeable. Watching the live stream, cylinder 2 consistently misfires. Looking at the history it shows all the cylinders misfiring. Before I go changing parts os there anything obvious I should look for?
All grounds have been landed. I use bare ring terminals, crimp and solder them. I’m pretty confident it’s not a ground issue, but I could be wrong?
Vacuum leak is something I’ve considered. Looking at the picture I took of the scan tool, it shows 11 inhg at idle. That’s pretty low and makes me think there’s a leak.
I will pull the plugs to put my eye on them to see how they look, that’s a sure way to tell.
I went out to look at the engine just now to see if I could find something obviously wrong, like a vacuum port left open. No luck there but I did see this and it make me think. I landed the drivers side grounds here in this picture. Would that cause me problems? I can easily get a 3/8 ring terminal and land them on the cylinder head if it matters that much.
Also, I got new Bosch O2 sensors, was that a bad idea? The style the engine had originally did not have a fused power source. Could they be causing these problems?
I moved the ground from the accessory bracket to the cylinder head with no change. Checked all the connections with the ignition and everything is tight.
I pulled plugs 1 and 2, 1 looked ok, maybe slightly rich and 2 looked lean.
I put a mechanical vacuum gauge on it and it shows 17inhg at idle, I didn’t have the scan tool on me but last time I looked at it, it read around 11. Couple a bad map sensor be the problem?
Some more information, I changed the map sensor, checked the vacuum with a od2 tool, it showed 11”, while mechanical gauge showed 17.5”. So I am unsure how to correct that problem? Unless a table is scaled wrong?
looking through the data stream while it’s running I am getting readings from all 4 O2 sensors, but I removed everything involved with the rears. I wonder if I had done something in correctly. It never went into closed loop either.
If you are running the factory fuel return style fuel rails , it looks like the pressures are correct. When manifold pressure is higher - fuel pressures will be lower. when manifold pressure is lower(throttle open) fuel pressure will be higher.
Could I have made a change in the tune that could of caused this? I didn’t get into any fuel or ignition tables. Outside of the VATS, emissions, and rear 02s the only other thing I did was change the abuse management settings. It wouldn’t let it go past 1400 rpm with them active.
With no vacuum to the FPR, should it stay at 58-60? Vacuum wouldn’t effect it in that situation would it?
Yes the fuel pressure regulator should be giving pressures around 58psi when it has little to no vacuum on it. While idling if the engine doesn't have any vacuum leaks I would think your stock engine should have around/above 15" of vacuum and lowering the fuel pressure below 58psi if it is a fuel return fuel type fuel rail.
Compression results don't look terrible.
thanks for the video Jetech, it really cleared that up for me.
So far
compression ok
fuel pressure ok
vacuum 17.5” with gauge
plugs verify running rich
took it for a spin, got some black smoke from the exhaust. It has power but cuts out hard when it misses, like it’s loosing everything and will randomly come back.
cam or crank sensor? Bad connection? All the grounds are tight and clean. Still shows p0300 and that’s it.
Last edited by tonyorlo; Apr 30, 2022 at 08:50 PM.
Yes it is, I dropped the tank and drained it before re installing it because I cleaned the frame up and ran all new stainless lines. Whatever fuel is in there was put in late Feb of this year.
Jetech you pointed me in the right direction. Luckily I used the right Intake gasket, I checked all the intake bolts and discovered one of those bolts was loose. By the #2 intake port which makes sense. Tightened it up and it runs great. My stupid fault.
It’s throwing a P0132 code and stays in open loop, the scan tool says OL_fault.
Well P0300 is sticking around. I thought for sure the loose intake bolt was the problem, and the truck ran great after I snugged it up. Jumped in today to take it to work and about a mile down the road it was acting like it did before. Severe loss of power. I had to limp it back home. Pulled the plugs and it’s running on the lean side now.
One thing I noticed when it looses power, the time is cut way back to between 7 and 16 degrees. Is that a sign of anything obvious.
Thinking about it, I’ve seen the knock sensor mentioned a few times in P0300 threads. Could it be cutting my timing way back? Would it throat a separate code?
Another update. I fired it up just now in the dark hoping to see some arching. Well it looked
like the 4th of July. The majority of the coils were arching in multiple places and a few plug wires were too.
I’m unsure of what I should do, do I change everything out? The wires were new parts store ones, nothing special. The coils were used ones I got off of eBay. The originals were in pretty poor condition.
Should I buy a certain type of wire? What kind of coil? Aftermarket like a MSD, or Delco only? I think I should avoid Duralast brand parts for the ignition.
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.
LQ4 swap multiple missfire problem 
More reading for you
