A few things wrong with my 91 Q45

[TimLeary]

I have a 91 Q45, idles rough in drive or reverse. When in park idles fine. I also get heavy exaust smell. Could the cats be bad? Being a 91 how difficult would it be to put a performance exhaust on? I'm also trying to make it faster.

[qship96]

If a speedster is what you want,why did you buy a 4000 pound old LUXURY car? Maybe a camaro or trans-am would have been a beter platform to modify for speed?

aftermarke exhaust,intake,ecu,bla bla bla will still get you spanked by a new accord/altima/camry v6-so why bother?

[Q45tech]

Why do you think any performance exhaust will make a Q faster? It will make it louder and any unit that provides any partially useful gain will be very very loud indeed. The loudest painful units I've tested did indeed add 5HP and dropped quarter mile by 0.05 seconds.

NICO ecu will be the most effective power adder for $250 [see thread].

Probably a dirty throttle body housing along with misadjusted IAC [rpms drop too much in reverse].

Probably need to spend the $3,000 to get it right before upgrades are considered.

[maxnix]

If you restore your engine and drivetrain to as new OEM condition, it will be much faster. How is a "perofrmance" exhaust going to help a car that cannot run as designed due to deferred maintenance?

For starters, have you replaced the originaal plastic timing chain guides? Better think about that before even starting it again.
Modified by maxnix at 8:23 AM 2/29/2008

[Denver90Q]

I have a 91 Q45, idles rough in drive or reverse. When in park idles fine. I also get heavy exaust smell. Could the cats be bad? Being a 91 how difficult would it be to put a performance exhaust on? I'm also trying to make it faster.

What have you been smoking? Sorry, had to say that. I'd look at O2 sensor or fuel additives re. exhaust smell before cats as the OEM ones are pretty reliable but of course they need to be at operating temp to do their job.

If you don't mind loud you could get rid of the rear muffler and put in straight pipes.

[TimLeary]

aftermarke exhaust,intake,ecu,bla bla bla will still get you spanked by a new accord/altima/camry v6-so why bother?

I don't get smoked by those cars now. And my Q doesn't weigh 4000 lbs.

[qship96]

I don't get smoked by those cars now. And my Q doesn't weigh 4000 lbs.

Do your homework, and you will find otherwise

[Q451990]

I think that the point so far has been that you need to get the car running as designed before attempting mods... which are few and far between for the Q - at least ones that actually show documented gains in performance.

Alright... now that the beatdown is over (hopefully) - it sounds like your rough idle in reverse and drive is a dead miss. Does it feel like a "bouncing" sensation from the front of the car? That's how I would describe the injector failures I have experienced.

I would search for the instructions on ohm testing your injectors and go from there. I wouldn't suspect cats unless your fuel mixture has been off for a very long time... they typically don't fail on the Q.

Heath

[Haitian_King]

I don't get smoked by those cars now. And my Q doesn't weigh 4000 lbs.

You may be right about the not getting smoked. But unless you gutted your Q, curb weight is roughly 2 tons. I was surprised to find that out. I couldn't believe it. You'd never think it could move like that being that heavy. But it is.

There is no "performance" exhaust for the Q. The best option is custom headers, but they're pricey. Get the car fixed first and then worry about mods.

When I had a bad injector, I used to get a rough idle in Park as well. Ohm your injectors and let us know.

I take it that you're not the first owner. How much do you know about previous maintenance history?

Slightly off topic but is there a way to tell if the PO used 87-89 octane regularly? Is there any way to "repair" damage caused by improper fueling by the PO?

[Q451990]

Slightly off topic but is there a way to tell if the PO used 87-89 octane regularly? Is there any way to "repair" damage caused by improper fueling by the PO?

I can't think of a way you could tell. As far as damage, if the gas was really crappy, the damage that would have been done would be from spark knock.... which would probably be damage to hard parts... looseness in bearings or damage to the valves, valve seats, valve guides, etc. So no - no way to repair it without a rebuild.

The only possible thing to "repair" would be if the inferior fuel had more junk in it that caused injector clogging or more carbon build-up from a weaker additive package. Then you could do intake cleanings and injector flushes...

Heath

[Haitian_King]

Ok. Just curious. I had to replace one injector and from time to time, I can feel a slight "hiccup". Since I've owned the Q, I've filled it up with 87 once or twice. (This was when I first got the Q and I didn't "believe" the hype about Premium Fuel. I'm happy to say I now know better. Nothing less than 92!) I just wondered if an application or two of BG 44K would cure what ails me. I get regular oil changes and the rest. I think I might spring for a complete fuel rail flush when the weather gets warmer. It's looking like the President conversion will have to wait a bit.