mikez71
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My fuel pressure increases to 55psi when I hit 3900-4700 rpms..
(and some startups, coast down or engine shutoff but that's different)
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Acceleration hesitation
- Thread starter GCDenali
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(and some startups, coast down or engine shutoff but that's different)
mikez71
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Actually found another log it was hitting 55psi by 3900 rpms,
And usually on cold start, sometimes hot start...
And usually on cold start, sometimes hot start...
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here's a weird one for ya when I was troubleshooting the clogged cat, didn't know it was a clogged cat yet... it was doing to some bizzare stuff
stuck on +10 psi and flashing check engine light, 2nd restart and all back to normal
in park/neutral (no load on engine, no misfires) but as soon as there was a load, bam knock retard
stuck on +10 psi and flashing check engine light, 2nd restart and all back to normal
in park/neutral (no load on engine, no misfires) but as soon as there was a load, bam knock retard
Was it running fine on the highway before you changed the plugs, wires, cleaned MAF and TB?
What did you use to clean the MAF meter? If brake cleaner was used, it can possibly damage the sensor causing incorrect readings to the PCM. Double check your plug wires and makes sure they are fully seated, #8 can be a pita. Make sure the air filter doesn't have a rodents nest in it, both sides of the filter.
What did you use to clean the MAF meter? If brake cleaner was used, it can possibly damage the sensor causing incorrect readings to the PCM. Double check your plug wires and makes sure they are fully seated, #8 can be a pita. Make sure the air filter doesn't have a rodents nest in it, both sides of the filter.
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GCDenali
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How would one test the Nnock retard?
Was running fine 193,000 miles never had the plugs or wires changed so that’s why I did it. I used mass airflow cleaner to clean the sensor and throttlebody cleaner to clean throttle plate.
It has a slight rough idle now, no codes
You said you used AC Delco Iridiums but didn't mention brand of wires, were they OE? Did you try to gap the plugs? Reason I ask is that can break the tip off.
At cruising speed, are BOTH upstream sensors updating at the same speed and rapidly?
Is the gasket on the TB good, torqued to spec? Could introduce unmetered air if not.
At cruising speed, are BOTH upstream sensors updating at the same speed and rapidly?
Is the gasket on the TB good, torqued to spec? Could introduce unmetered air if not.
mikez71
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Should be in your scanner, under engine>ignition>advance/retard.. or something like that?
Make sure you hear the "click" on each coil pack when installing the wires, they can be stubborn.
I tried the aftermarket wires on my 2012 Yukon and ended up switching to the OE, had some erratic fuel trims but nothing too crazy.
I always try to replace the upstream sensors with the plugs, JMHO.
I tried the aftermarket wires on my 2012 Yukon and ended up switching to the OE, had some erratic fuel trims but nothing too crazy.
I always try to replace the upstream sensors with the plugs, JMHO.
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GCDenali
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Bosch plug wires were the only option at the parts store. No the plugs were pre gapped. I torqued to spec. Gasket looked fine. I’ll check the upstream sensors, you are referring to o2 sensors correct?
if you do not have a scanner yet, you could pull those plugs and check them visibly, if one is not is not gapped right, cracked or something that could be an issue.
some misfires are not going to throw a code but would show up on a scanner, it has to hit a certain count before a code is thrown.
some misfires are not going to throw a code but would show up on a scanner, it has to hit a certain count before a code is thrown.
Yes.
I'll find a screenshot or a short video to show what I look at using the Torque Pro app. You can watch the graph as they change voltages, they are lazy at idle but while driving it's a rapid sawtooth graph.
Something to consider, if this also started after you filled up... given the price of gas right now it's a safe bet more 93 is not being replaced as quickly as 87. To get 89, the pumps mix the 87 & 93. Not likely but you could have some older gas mixed in with the 87...not as likely but a consideration if you don't regularly use this station.
Here's a couple screenshot I took awhile ago showing the behavior of the O2 sensors and the fuel trims. This way I can see if a sensor is getting lazy.
This is at idle and the upstream sensor will naturally lag and have a slow response. Bank 1 Sensor 1 & 2 which are the top green graphs. The lower graphs are the downstream sensors and should be close to linear when warmed up and steady RPM's.
This is at cruise and the upstream sensors are reacting much faster as they should when warmed up.
If your engine is warmed up, and you're steady cruising, the upstream sensors should mimic the rapid changing and not what the idle graphs look like.
I just skimmed, but where did you buy the plugs.
I've seen more and more knock off plugs causing problems these days. since it didn't do this before the plug change. it's very easy to crack it's the porcelain. I've done it by accident myself.
I've seen more and more knock off plugs causing problems these days. since it didn't do this before the plug change. it's very easy to crack it's the porcelain. I've done it by accident myself.
ChevyChevy
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Hey all, I know this is super Mr Obvious answer so I feel silly.... and I tried to read every thread for this, but what about Fuel Filter, and next Fuel Pump.
My 145,000 mile 5.3 gas 2002 just failed for first time. It was an easy repair. But before replacing I had decent pressure at idle, but poor acceleration.
My 145,000 mile 5.3 gas 2002 just failed for first time. It was an easy repair. But before replacing I had decent pressure at idle, but poor acceleration.
There is no external fuel filter on this truck. It is all contained in the fuel pump assembly.
After I replaced my plugs/wires I ended up retaining misfires.
Found #8 had a bad coil, replaced that coil but still misfires. Same plug had cracked(I think from the bad coil arcing, had checked new plugs and careful to install), so replaced plug and wire again just to be sure.
Could've been opposite - cracked plug arcing the coil ruining the coil. Idk.
Misfire gone for 2 months then comes back. Loose wire,same spot, #8.
I usually give my wires a push every so often now.
Found #8 had a bad coil, replaced that coil but still misfires. Same plug had cracked(I think from the bad coil arcing, had checked new plugs and careful to install), so replaced plug and wire again just to be sure.
Could've been opposite - cracked plug arcing the coil ruining the coil. Idk.
Misfire gone for 2 months then comes back. Loose wire,same spot, #8.
I usually give my wires a push every so often now.
Do you still have your old plug wires? If so, I would swap them for a test.
FWIW, I did the good house brand wires at the parts store with the OE plugs, I ended up replacing those with OE wires about a year later. Not sure if it was a rough idle or fuel trims but all was good afterwards.
