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1997 GMC Suburban P0301 Misfire After Intake Gasket Replacement - How to Fix Timing and Diagnose Cylinder 1 Issue

Model: 1997 GMC Suburban Fault Code: P0301 Posted: 2007-06-14 19:38

I recently replaced the intake gaskets on my 1997 GMC Suburban with a 350 engine. I took great care to document all vacuum lines, clean both upper and lower intake plenums, and torque all gasket connections according to manufacturer specifications. Before removal, I marked the distributor and reinstalled it so that all timing marks aligned properly. After starting the truck, it ran roughly and triggered a persistent P0301 diagnostic error (cylinder 1 misfire). I cleared the code multiple times, but it returned each time. I’ve reviewed several online resources about checking engine timing, particularly focusing on Cam R**ard Offset. However, my borrowed scan tool (Actron CP9180) does not display this parameter, so I cannot confirm if the distributor is properly timed. Additionally, I did not adjust the distributor gear during reassembly. I’ve performed the following checks: - Tested plug wire resistance: Plug 1 shows 1 ohm (good), and swapping it with plug 3 had no effect. - Observed that plug 1 appears dry, not wet. - Measured fuel pressure — it reads normal initially but drops to zero after a few minutes. Key questions: 1) Does P0301 specifically point to cylinder 1 only, or could it be a broader misfire? 2) With a dry plug and dropping fuel pressure, is this indicative of a sticking injector? There’s no black smoke observed. 3) Could the P0301 error be caused by improper cam r**ard offset timing? 4) Is running lean dangerous for long-term operation? I’m considering letting it warm up to check O2 sensor readings to determine if the mixture is lean or rich. 5) What should my next diagnostic steps be? I suspect that even a small timing error could interfere with misfire detection, especially after intake work. Given that many DIYers overlook cam timing during gasket replacements, I believe this may be a common but overlooked issue on 1997 GMC Suburans.

Related fault codes
P0301
Comments (5)
Anonymous 2007-06-15 06:25

The poppet injector line might be leaking or the vacuum lines could be crossed — this is a known issue after intake work and should be checked first.

Anonymous 2007-06-18 14:35

It's possible to reinstall a distributor correctly without using a scan tool, as long as you properly align the timing marks during installation.

Anonymous 2007-06-18 15:28

That’s true — it can be done. However, I don’t believe this is the root cause of the P0301 error in this case.

Anonymous 2007-06-18 15:39

No, but this has been raised four times about cam r**ard offset and the inability to read it on a $100 scan tool. That’s a basic misunderstanding — even a simple distributor installation requires proper timing setup to avoid recurring misfire codes. I know this isn’t his issue, but I felt compelled to point out how common this mistake is among DIYers.

Anonymous 2007-06-18 16:32

I completely agree — I’ve seen many older vehicles (like my 1975 Chevelle and 1980 GMC half-ton) with severely off timing after head gasket work, where wires were moved around the cap to compensate. The same issue occurs in older Chrysler engines post-head gasket jobs. Without proper cam timing, misfire monitors fail and performance suffers. I’ve personally seen turbo PT vehicles with persistent lean codes that only resolved when it was discovered the cam timing was off by nearly two teeth — right out of the factory! Timing and fuel delivery remain the top two issues people overlook. That’s likely why repair prices for these vehicles vary so widely.