Sluggish performance

[Fridge]

After replacing the injectors and knock sensors on my 91 Q it runs a lot better on the top end. However crusing around town it feels a little sluggish and you have to really push on the pedal to get it to go. Also I can hear a little valve clatter at around 40 almost like bad gas however I always use premium and have tried different brands. There are no codes in the computor and it does not miss. Could this be the oxygen sensors? How can I test them? Thanks for all the help

[Q45tech]

Current US gasoline IS BAD in that it doesn't meet the standards that were in effect when the Q was designed. Don't be fooled by the pump octane stickers they don't mean much NOW other than premium is better than mid which is better than regular.

Using 4th gear around town under 50 mph is just asking for knock!

O2 sensor is not monitored at idle or during acceleration only at steady cruise speeds.

BG44k will clean intake valve stems and piston crowns of carbon build up, try that for a week in gasoline then report back on changes.

[goody90q45]

However crusing around town it feels a little sluggish and you have to really push on the pedal to get it to go.

Sorry to sound like a broken record in this forum but how's the fuel pump/FPCU?

[Fridge]

Yep replaced fuel pump and controller a while back. I ordered some bg off of ebay and I will try it out.Its time for a oil change to so I will flush the crankcase as well.

[Q451990]

Be gentle with that oil flush stuff... whatever you're using. Q45Tech has recommended a fresh oil change, half can of BG Quick Clean, followed by another oil change, other half can of quick clean - then a third oil change.

The carbon build-up that Q45Tech was mentioning is on the valves, intake components, plenum, throttle body, EGR etc. Not in the crankcase... so if that's the reason you're thinking of an oil flush, it's really not necessary... I tend to avoid oil flushes unless there's a specific issue i'm chasing - since the chance of loosening up something and redepositing it somewhere else is always a concern.

One other question... have you checked your EGR valve's function? It's not monitored by the ECU with the federal ECU, so you wouldn't see a code. Check it by feeling the bottom of the valve while reving the engine at the throttle body. It should rise and flutter between something like 1000 to 3000 RPMs. Then cut out at higher RPMs. You should also be able to manually push it up (open) at idle and cause the engine to choke down or almost choke down...

Good luck

Heath

[Fridge]

Ok,I ran the bg44k and it does seem to have more pick up but the clatter is still there. I believe it is coming from the pass side chains. When you start it up it rattles a little at first and them calms down. I have been flushing it at every oil change since I put the jdm engine in it and allways get brown stuff out. The lifters used to be noisy as hell but they are quiet now after all the flushes. I use mobil 1 and change it at 5k miles. I am going to pull the chain tensioner and check it for wear. Maybe the oil passage is stopped up? I probably should have changed them when I did the chain guides But they looked fine.

[maxnix]

the Nissan dealer in Bryan offers the envirolution crankcase flush for about $100. Perfect to top off with BG MOA.

[Fridge]

Got the tensioner out. What fun lol. I tried to blow through it but it seemed pluged so I soaked it for a while and tried pressure. I can now blow through it but there is a restriction feels like a very small orfice. Is that normal? Or is it supposed to have a straight through passage?

I have some bg moa but since I use mobil 1 I did not think it would help much. Would it be compatable?

[maxnix]

Yes, it is. When I do the crankcase flush, there is enough capacity left after the 6 qt. M1 refill to hold a can.
Modified by maxnix at 8:04 AM 12/17/2007

[Fridge]

Well its much better now. I think most of the noise was from the chains rattling. Also it is even quiet on start up. funny I thought that was normal

[Q451990]

Also it is even quiet on start up. funny I thought that was normal

Only on my truck, apparently. That's great news that you got it fixed!

Heath

[elwesso]

Be one of the cool kids and drive your Q in 3rd gear below 55mph. It likes 2000 RPM a lot more than 1200.

[Fridge]

Hmm 3rd gear all the time? I have done that before for a little while and the car does seem to enjoy it but what does that do to your mileage? I have noticed that mileage varies greatly depending on how I drive. The best I have gotten was almost 20 on the highway and the worst was 12 hotroding around town. Is that typical?