240 EFI spark plug type

[WILakeBoating]

Long time lurker and I can't say enough how much this forum has helped me. Kudos to all of you.

I have a 2001 Challenger 1800, 240 EFI M2 and am on season two of owning it. Changed the plugs near the beginning of last season (along with port side temp sensor as a preemptive since I wasn't getting top speed) and top speed restored; it worked great all year. Was winterized and gone over by a pro in the fall of last year and he said I'd need to get it out on the water once this season (just did that two weeks ago) and then change the plugs since they'd be probably fouled from winterizing/fogging.

It ran okay that first time out this season but did this thing where it would rev to what I intended and then lose power a little, then get right back to the correct power - rinse and repeat for anything over about 3k RPMs while cruising. Almost like someone was jerking around with the throttle but VERY quickly. Felt like it was missing intermittently on one or two cylinders but I'm no mechanic. I do not think it's the TPS or Coils/Trigger since the most likely issue is just fouled plugs so that's what I'm doing first before digging more.

So anyway, I thought I was getting a deal when I bought new plugs mid-winter and made the bonehead move of buying NGK BP8HS-10's instead of BPZ8HS-10's. I didn't realize the Z was missing until I had them installed and was putting everything away (facepalm). Have not turned it over yet. I already ordered the correct ones to install for this season.

I understand from googling that the difference between the Z and not the Z is the resistor which reduces some EMI noise, possibly also a heat rating difference?

Questions are:
-If I fire this thing up with BP8HS-10's installed is that going to screw up my ECM or something else?
-If they don't damage the engine and just will foul faster, are these ok to keep as a spare on board?

Thanks in advance!

 

[phaugh]

Long time lurker and I can't say enough how much this forum has helped me. Kudos to all of you.

I have a 2001 Challenger 1800, 240 EFI M2 and am on season two of owning it. Changed the plugs near the beginning of last season (along with port side temp sensor as a preemptive since I wasn't getting top speed) and top speed restored; it worked great all year. Was winterized and gone over by a pro in the fall of last year and he said I'd need to get it out on the water once this season (just did that two weeks ago) and then change the plugs since they'd be probably fouled from winterizing/fogging.

It ran okay that first time out this season but did this thing where it would rev to what I intended and then lose power a little, then get right back to the correct power - rinse and repeat for anything over about 3k RPMs while cruising. Almost like someone was jerking around with the throttle but VERY quickly. Felt like it was missing intermittently on one or two cylinders but I'm no mechanic. I do not think it's the TPS or Coils/Trigger since the most likely issue is just fouled plugs so that's what I'm doing first before digging more.

So anyway, I thought I was getting a deal when I bought new plugs mid-winter and made the bonehead move of buying NGK BP8HS-10's instead of BPZ8HS-10's. I didn't realize the Z was missing until I had them installed and was putting everything away (facepalm). Have not turned it over yet. I already ordered the correct ones to install for this season.

I understand from googling that the difference between the Z and not the Z is the resistor which reduces some EMI noise, possibly also a heat rating difference?

Questions are:
-If I fire this thing up with BP8HS-10's installed is that going to screw up my ECM or something else?
-If they don't damage the engine and just will foul faster, are these ok to keep as a spare on board?

Thanks in advance!

 

[phaugh]

I don’t have an answer for you on the plugs (non-technical) but I’m intently interested in your issue and how to resolve it. I’ve got a 2002 utopia with the exact same problem. It sat winterized for two years so figured It might be bad gas..water in it?. Used some fuel additives and figured I need to run through a tank. Read it could also be sticky injector valves too…so maybe additive helps? We’ll see. Next steps were plugs, water separator and fuel filter. Hoping to find here that it is a common issue with Merc EFIs

 

[WILakeBoating]

New plugs fixed the issue completely for me. Power restored and has ran great all summer so far. I run rec gas (no eth) when I can find it but just 87 with ethanol and marine sta-bil per the bottle every time I have to fill with eth gas.

Unbelievable how much fuel these engines eat in a day of tubing... Especially this year.

I have not dared to try the incorrect plugs in my original post. Didn't even try to turn it over because I'm chicken I'll ruin something.

 

[phaugh]

Yup, you were spot on. Many thanks for your help. I replaced 6 spark plugs (BPZ8HS-10) and the intermittent power loss issue (losing 5-7mph with slight bogging sound) while driving is gone. It’s running great so far. 2002 Utopia 205 M2 240 EFI. Thanks also to the forum admins and members, awesome information and experience here.