Sudden Rough Idle, Loss of Power

[TheSonn]

92' Q45 with all new plenum hoses, T-chain guides, filters, etc. Car gone over by Keith VanMeter in NJ when first bought 3 months ago. No problems then - 2K miles later, 9 am in the morning, car ran great. 3 pm in the afternoon, rough idle, loss of power. Distance between am and pm = 10 miles. Not too sure where to start. I have a spare MAF sensor, fuel pump control unit. THinking about trying to get my hands on a Consult. Anyone have any advise on buying a Consult? I believe I need a Consult 1. I see allot of Chinese made ones - I hesitate to buy one of those.

Any thoughts on all of this would be appreciated.

Thanks

[lino]

You should speak to Paul Wall. He's in Ipswitch. His email is in his profile.

Regarding the MAF, maybe you could swap out yours with Paul and see if that makes a difference.

Regarding the Consult, Consult 1 or Consult 2 will work on your car. For Consult 1 you will need the appropriate card. You can find these for sale from time-to-time on eBay and aren't very expensive since they have become obselete. Consult 2 are very expensive as they are still in use at Nissan and Infiniti dealers. On eBay new ones sell for over $6000. Used ones obviously much less but still quite expensive.

If you want to get a Consult cable there are many threads here discussing that subject. If you do a search you find them quite easily. The preferred brands seem to be blazt (http://www.blazt.biz/index.php) and ECUTalk (http://www.ecutalk.com/).

[Q451990]

I would start by swapping out the MAF and then ohm testing your injectors - although injectors tend to fail one by one and will exhibit a dead miss that feels like a "bounce" at idle. If I were betting I'd say it's the MAF.

How does the fuel pump sound? If you're getting a "bee hive in the trunk" sound at idle, especially below 1/2 a tank, is a sure sign that it's worn and pulling too much current - which will kill the controller.

Heath

[elwesso]

How does the fuel pump sound? If you're getting a "bee hive in the trunk" sound at idle, especially below 1/2 a tank, is a sure sign that it's worn and pulling too much current - which will kill the controller.

Heath

with no mention of the FP in the service history above, i would look at this first!

[Infinitiguy19]

92' Q45 with all new plenum hoses, T-chain guides, filters, etc. Car gone over by Keith VanMeter in NJ when first bought 3 months ago. No problems then - 2K miles later, 9 am in the morning, car ran great. 3 pm in the afternoon, rough idle, loss of power. Distance between am and pm = 10 miles. Not too sure where to start. I have a spare MAF sensor, fuel pump control unit. THinking about trying to get my hands on a Consult. Anyone have any advise on buying a Consult? I believe I need a Consult 1. I see allot of Chinese made ones - I hesitate to buy one of those.

Any thoughts on all of this would be appreciated.

Thanks

I might be able to meet you if you really need me but we would have to work some thing out, I also have my own laptop consult.

But I would check the MAF sensor and make sure its putting out the correct voltage. I would also clean it: http://www.q45.org/maf.html

Other than that it could be clogged injectors or maybe even a bad one if the idle is that bad: http://q45.org/ohminjectors.html. Its $100 to clean them with a BG flush.

Fuel pressure is also yet another possibilty, if you hear a buzzing noise its too late and you need a new pump.

Good luck.

[TheSonn]

Thanks for the help. The fuel pump is as quiet as a mouse. And I've run 3 cans of BG thru the tank over the past 2 months - all added to fuel tanks that were barely 1/2 empty with BG already in them. Plus, the engine ran fine in the morning, then, 6 hours later ran like crap. I'd think an injector problem might happen a bit more slowly?? Not sure . . .

So, the next step is the MAF. I'll be checking the voltage out this weekend, and swapping in a spare if need be.

Thanks again.

[Q451990]

I'd think an injector problem might happen a bit more slowly?? Not sure

Nope - normally with injectors it's a everything's fine one second, next second you feel a dead miss.

The easiest test for your MAF is just to swap your spare in, assuming you know that it's good...

Heath