OK. I lied. I do not have a surefire P0300 solution. What I DO have is a '98 Blazer LT 4X4 with the dreaded misfire and much time spent reading thru the Forum's 1000's of search results. Frequently, members give advice and the person never repends back to say whether it worked or not. My shop wanted to replace the "spider" fuel injector ***'y until I showed them a recpt from the previous owner's half-complete collection showing this was done 5/27/11 at about 140K miles. The car currently has only 147,500 miles on it. I bought it around 12/1/12. So about 7 months is all.

Many Threads recommend changing the plugs, dist cap, rotor and plug wires and that it will (might?) work but you must use AC Delco brand parts in all cases. No problem. Time for new plugs anyway I think. The Prev Owner says he changed the wires (but no recpt) so I looked to see if they said AC Delco on them but they do not. (Not even sure if "AC Delco" would be printed on them anywhere even if they were that brand) Recpts show Autolite Platinum plugs were installed a couple weeks prior to the "spider".

So I'll be taking her to the shop in the next 2-3 weeks to change the items I listed and specifying AC Delco all the way. Meantime, I'd like to hear from some of you long-term owners with any advice or other AC Delco bits (preferably inexpesive ones!) that I should also replace while it's there.

If it helps, I don't seem to have any of the other problems some members have describe in their P0300 Threads. Starts fine. Runs OK. Take away the Service Engine Soon lite and the crappy mpg (13.5), and one might conclude that everthing was fine.

Thanks. And sorry for lying. But I promise that I will update the Forum when it comes back from the shop.

 

Well like you have probably read, anything in the secondary ignition can cause a p30x code. Secondary ignition being plugs, wires, cap, rotor, coil, and the ignition control module. But if your truck runs fine when its raining outside then i would leave the coil and ignition control module alone for now. As for the spider, depending on what brand and what kind of injection they put in being CPI or MPI, the spider could be bad again but i doubt it. MPI is the injection type you want and brand Delphi or AC Delco, hopefully the receipt tells you. Now it could also be the electrical connection going to the spider injectors causing the code, that happened to me after i replaced my injectors and it took me forever to figure out the simple connection problem. But i think you're on the right track with spark given your description of the problem

 

P0300 is almost always caused by, as 97cherry blazer mentioned secondary ignition. Low fuel pressure, worn distributor bushings and gear, along with incorrect adjustment of camshaft retard can also cause it.

Fuel pressure is quick, easy, and free to check. Most auto parts stores rent the tester. When you have one handy, let us know and we can walk you through the procedure. Worn distributor bushings, worn driven gear, and checking camshaft retard, require some expensive equipment to diagnose.

 

Thanks "Hook" & "97 Cherry". I fear I left out an important detail. I also have another issue. When running, there are several Dash Lites & Symbols that are on: Battery, ABS, Security, Seat Belt (mostly, not always). In addition, the temp gauge doesn't work and the gear selector panel won't highlight what gear I'm in. It used to go away and work fine but now it is almost always this way. I read other threads and thought I narrowed it down to a faulty Ignition Cylinder. Today I read more posts and am getting confused between Ignition Cylinders and Ignition Control Modules. I nearly got stranded at the supermarket this AM. Turned the key, got lites and chimes, twisted it the last bit, then ... nothing. I loosened the re-tightened the battery cables 3-4 times. Sometimes I got the lites and chimes back, other times, nothing. Sometimes I jiggled the key and tried twice. Checked to see that it was firmly in Park too but always got the same result before the jiggling and checking. Finally, it started. The Battery and Alternator are nearly brand new. Any idea what is wrong?

)I'll probably post this as a New Thread too in hopes that more people will see it)

 

The ignition lock cylinder is what the key goes into. The ignition switch is what the lock cylinder turns to operate the ignition circuits and the starter. The ignition control module receives a signal from the PCM to fire the ignition coil.

 

So I got the D-Cap, Rotor and Plugs replaced (all AC Delco "exact fits") and the code went from P0300 to P0304. I guess that's progress. The plug wires are OK says the mechanic. He said one of the plugs was only hand-tight, too! He wants to replace the spider injection assembly coz he feels (a) the truck seems to need it and (b) based on his experience it usually solves the problem. He seems to know his stuff. But I read several other Forum Posts for P030X code solutions and other options seem to exist that are much less costly. Gonna mull it over.

 

P0304 indicates cylinder #4 is misfiring, (center cylinder on passenger side). That narrows things down considerably.

$200 for the injector assembly, plus a couple hours of labor, is an expensive gamble. It could very well be a problem with #4 injector or poppet valve/nozzle. It might be sticking open or closed, or the injector might not be working. Could even be a bad plug or plug wire. Or, it could be the intake gasket is leaking vacuum on #4 port. To a trained tech, monitoring fuel trim on a capable scan tool would tell if bank 2 is running lean or rich, which would determine where to start look for the problem.

 

OK. So now I'm searching posts related to Spider Fuel Injectors to see if AC Delco is the preferred product etc. This led to the idea that I could follow other's leads and upgrade to the Delphi #FJ10565 which converts the system from Sequential to an MFI type (eliminates poppets). One reply led me to an Amazon site where they are new-in-the-box and sell for $221.32 (supposedly, the list price is $670.33) It fits my '98, includes a necessary bracket, new fuel pressure regulator and a gasket for the upper intake plenum - but other gaskets may be needed. The reviews, nearly all 5-star, are like reading a list of what's wrong with my car and how this product fixed everything. No more SES lite. Better mileage, etc., etc., etc. Before I buy it, I'll speak with the shop to see if they know obout this upgrade/conversion or whether they were planning on just another OE type. Very encouraged about this. Will update this post with the results.

 

Before you spend money on anything, it needs to be correctly diagnosed, (check post #7 again). It might not be the injector, then you're out $200 needlessly. If it turns out that you need the injector assembly, the Delphi #FJ10565 includes the bracket which is $20 extra if you don't get a Delphi. My experience is none of them come with any gaskets. That may have changed recently though. The upper intake, or "plenum" gasket set is all that's necessary. The conversion is plug and play, no programming necessary. Your 98 is sequential now, all the conversion does is relocate the injectors to the intake ports and eliminate the poppet valves. Keep an eye on Amazon, I see them for under $200 at times, just gotta watch.

 

I can see your point about having testing done first. I asked my mechanic this AM about whether the injector swap he had in mind involved the Delphi FJ10565. He did not know for certain which brand he normally uses but says it will be the MFI-type and that it will cost about $700. Plus, he will not use bought-off-the-internet parts (?!) and the job will cost about $700. The Amazon site's Reviews section told of DIY-ers needing 2-4 hrs to do the swap. So 2-3 hours for a pro? I calculate a savings of $200 or so by taking the job and part to another. less -picky shop. I have never used Amazon (I thought they only sold books!) but I gather it would be in a factory-sealed box and it's described as "new". Exactly like what I'd get at Pep Boys/Advance Auto/Auto Zone/ Etc - only less expensive. So what's the problem? Geez! I guess more thinking on my part is needed. Maybe finding a reasonably-priced place to have the testing done, too. More later.