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Update: The exhaust manifold has been removed from the vehicle, and the honeycomb structure has detached from the converter. This is the side misfiring on cylinders 1, 2, and 3. A new converter manifold seems to be in development. I wanted to inform you. The other side functioned properly and did not generate any misfiring codes.

Here is the update before I submit it to the store to ascertain the situation. Thank you for the information; it has been beneficial. After reviewing various materials. I have cleaned the mass airflow sensor; it was somewhat soiled. I have removed the injectors and cleaned them; a few damaged O-rings were there, but they are currently in fine condition.I have removed the leads from each injector to see whether it is firing, and the engine falters. I discovered fissures in the coil wire and rectified them with whole new terminals. Compression is satisfactory, and both the spark plugs and coil packs seem to be in excellent condition. However, I get a misfire on cylinders 1, 2, and 3. It idles well; but, as I increase the RPM, it stumbles, and the check engine light activates, resulting in significant stumbling and stalling. I brought it to my driveway, and it exhibits no power, as if the exhaust is obstructed or the catalytic converter on one side is blocked. I am contemplating whether the previous mechanic purchased a low-quality catalytic converter and exhaust manifold due to an issue from the prior owner. He may have replaced them but experienced persistent misfires that he could not diagnose. I discovered that he had tightened some exhaust bolts while leaving others loose, which ultimately caused the problem. Perhaps he installed inferior ones, which lasted just a year. I am only expressing my thoughts. I am perplexed; I had to replace an axle since the one purchased from O'Reilly failed at the joint. Incorporating a Volvo resolved the issue. Any other suggestions would be much appreciated. I will remove the exhaust manifold and catalytic converter to assess their condition. I have conducted a live scan, and all metrics are satisfactory. Therefore, I am now investigating farther downstream. The exhaust seems to be malfunctioning, so I will focus my attention there.



Thank you.

Apologies, yes, the pressure sensor. My subsequent action involves examining the coil wiring, which seems to be fractured at the terminus.Perhaps they are arcing over.I will keep you informed. Thank you once again.

Fuel trim is an average code, but misfire codes may occur rapidly under certain situations. Following the installation of the plugs and coils, the subsequent task is to address the wire harness connected to the coils. In earlier models, such as my son's 2000 S40, it is not unusual for the connectors to fracture, which may create the illusion of a defective coil. When you refer to a pressure regulator, are you indicating the fuel pressure sensor?

All plugs possess a uniform hue and have an aesthetically pleasing appearance. The fuel pressure is around 69 psi at startup and remains stable after warming up, indicating satisfactory performance. I cleaned the MAF some thousand miles ago, but that is not imply it is not contaminated. I will re-examine that; but, would it not also trigger a lean code associated with the MAF, in addition to the misfire in cylinders 1, 2, and 3? Cylinders 4 and 5 have consistently functioned well, although I previously had a misfire in cylinder 6, which has since resolved. The issue persists exclusively in cylinders 1, 2, and 3.Secured the ground connection on many wire harnesses, since just a few strands were maintaining the ground to the coil packs. I have not yet assessed the PCV, but I will do so as well. The gasoline pump, pressure regulator, and fuel filter have been replaced within the last week. Merely due of its mileage. New gaskets have been installed on the intake; however, exhaust leaks have not yet been inspected and will be addressed as well. Thank you.

Your compression is satisfactory (around 180 is OK for a naturally aspirated engine); your first low measurement may have been from a cold engine, among other factors. Have you inspected the plugs again after replacing the coils and plugs? Do they all exhibit the same coloration, or are there variations in the burn lines, especially at the tips of the electrodes compared to the bends around the base? Have you gathered runtime data on the O2 sensor's readings throughout a driving cycle? Numerous OBD2 readers are capable of performing this function; alternatively, a shop may do a diagnostic test. This raises concerns about fuel mix considerations. Are the MAF and intake components clean? A malfunctioning PCV oil separator might cause obstructions. What is the fuel pressure at startup and after the engine has warmed up? You own a variable pump, necessitating professional assessment of the pump's duty cycle. Have you examined for intake air or exhaust leaks, among other issues? You ultimately observed the quality of the gasoline. Consider using a brand name 93 octane gasoline or adding a can of Techron fuel injector cleaning to the tank. This may assist in cleaning the injectors and is a beneficial maintenance task. Your description suggests an investigation of the gasoline pump, pressure sensor, and pump controller. A professional equipped with a VIDA system can do this task more precisely (although purchasing your own VIDA/DICE on eBay is an option). Therefore, I believe it is worthwhile to invest $150 for a professional to conduct a diagnostic scan and road test for you.

Thank you one again.

I am experiencing misfire difficulties with a 2007 Volvo XC90 3.Currently, there are misfires in cylinders 1, 2, and 3. Previously, misfires were also detected in cylinder 6, however it seems there are no longer any misfires in that cylinder.I replaced the spark plugs and ignition coils due to high mileage and sluggish starting. However, if I turn the key and let it to remain in the on position for a few further seconds, the engine starts fine. I determined that the fuel pump was weakening due to the mileage, replaced it, and resolved the problem. I identified one faulty ground wire in the coil pack loom, which I believe resolved the misfire on cylinder 6. However, I also discovered a faulty wire affecting cylinders 1, 2, and 3, which I repaired, however the problem persisted. However, it is possible that the ground is disrupted farther ahead, and I shall investigate that tomorrow. Disconnected the wires on the injectors sequentially, resulting in a difference in motor performance; also, replaced the coil packs one at a time. The motor faltered in each instance. A compression test was conducted a few thousand miles ago, with a reading of 160 psi across all cylinders. The engine idles well; but, as I increase the RPMs, it misfires, and the check engine light activates. I am considering removing the fuel rail to inspect the condition of the injectors, since they may be the source of the problem. At this juncture, I am perplexed; the RPM remains constant at 650 when idling.Do you have any suggestions on where to search? I am attentive to your advice. I conducted a compression test, revealing that the peak cylinder pressure was 210 psi and the lowest was 185 psi. Everything seems OK; but, may there be a problem with the computer situated atop the air cleaner? I first considered poor fuel quality, although there are no indications of a lean situation in any of the cylinders. I have bought new connections to splice in and assess their impact, since they were very inexpensive and the existing connectors were cracked and opened at the ends, which seems to be a typical problem. However, I am depleting my list of items to verify. Thank you for any information and for your attention.