[Murry101]

Given the ignition system is in good repair, that sounds like a MAF problem to me, which could also explain the flat spot. Since the c900T has no way of sensing load, it relies on the MAF for pretty much everything.

This past summer I replaced the original MAF sensor with a spare I picked up. I reinstalled the original yesterday and the problem persists. I’m going to grab a can of CRC MAF cleaner and clean the “spare” and see what happens. I’m not expecting much.

I also picked up a cheap fuel rail/injector assembly off eBay. I’m going to modify the banjo bolt and add a schrader valve so I can run some fuel pressure checks.

 

[jvanabra]

Wow, this is a conundrum!

 

[Jim Mesthene]

Did your new spark plugs arrive?

 

[Murry101]

Did your new spark plugs arrive?

not yet. I didn’t pull the existing plugs to inspect them, although I thought about it. I figure why bother until the new plugs arrive. Given my luck with the USPS lately that might take a while, if they show up.

i did run the car for about 500 to 1,000 miles with the intermittent CEL. I’m wondering if that could have damaged the plug. Also worth noting, when I replaced the plugs a couple of years ago the one in the number 2 or 3 cylinder (2nd from the firewall) was visibly different. It had a white “patina”.

 

[Murry101]

The MAF sensor is a problem. When I swapped sensors a couple of nights ago it was snowing, so I did not go for a road test. I did manual actuate the throttle and the engine hesitated. Today I did a proper road test after the engine warmed up and their was no hesitation off idle or dip in power around 3700 rpm. However, the CEL came back on and has not extinguished. I tried to pull the error code, but I got a number that doesn't appear in the Bentley manual. I swear it blinked out 12411. I must have done something wrong or misread the code. When I started the car again the engine idled high (1000 rpm) for about 10 seconds, almost stalled, and then bounced high and low twice before settling back at normal idle speed. Hope I didn't do any damage. When I have more time I am going to pull the code again. This time with the Bentley manual close at hand.

 

[jvanabra]

I wouldn't swear to it, but to me it sounds like you have two, differently bad MAFs. I have a whole box of differently bad MAFs... Some are labeled "pulls good won't idle" and "runs bad passes smog" ...

 

[Murry101]

I wouldn't swear to it, but to me it sounds like you have two, differently bad MAFs. I have a whole box of differently bad MAFs... Some are labeled "pulls good won't idle" and "runs bad passes smog" ...

Ugh, I think you might be correct. I guess I role the dice and pick up another one off the internet and take my chances or call Goldwing.

 

[jvanabra]

Since you have two, I would personally take the crappier of them and send it to Injection Labs for a rebuild. It'll be $120 or so, but what you get back will be as new. In addition to the box of bad MAFs, I have one good one from IL that was in my SPG until I converted it to Trionic.

 

[Murry101]

Since you have two, I would personally take the crappier of them and send it to Injection Labs for a rebuild. It'll be $120 or so, but what you get back will be as new. In addition to the box of bad MAFs, I have one good one from IL that was in my SPG until I converted it to Trionic.

Thanks for the tip. I didn't know anyone was rebuilding these. I will definitely pursue that route.

 

[Murry101]

Price has gone up a bit. $256 for a rebuild. They said it will outlast the car afterwards.

 

[jvanabra]

Yikes! It's still a gamble as to whether it will fix your issue or not, but it won't hurt, and the point about it outlasting the car is solid. Given the prevalence of marginal MAFs in c900s I'd certainly consider it realistic yours is as well. I think you can read the MAF values with a Tech 2 on a -948 LH 2.4 ECM, if you have a Tech 2 and such an ECM kicking around.

 

[Murry101]

I received a call from Kevin at Injection Labs after he bench tested the MAF sensor. He told me the unit was out of calibration by 35 mV, and the symptoms I described are consistent with this level of drift. During a lengthy technical discussion he mentioned that 40 mV is typically the threshold were the ECU throws the car into limp mode..I guess I was pretty close. He sounded confident that this repair would resolve my issues. I'm keeping my fingers crossed.

Bench testing is a free service, so I may ship the original unit to them after I get the "spare" back.

 

[jvanabra]

I did not know they would do that.... I wonder how they'd feel about getting a whole box of 'em?

Glad that this seems a good path out.... hopefully it pans out!