1992 Q45 Loading up at idle

[livebaitdrifter]

Hello all I recently purchased a 1992 Q45 with 86k , motor replaced at 33k, ran fine for a little while, now it loads up (cold start) at idle and blows black smoke, erractic idle, runs ok under power except some bucking at 60 mph. I cleaned the maf and intake. What should I try next. Thanks The drifter

[goody90q45]

While the NICOnauts sleep in on a Sunday morning, how about going out to the Q and clean up the MAF connector as shown in the pic I've attached. Use electric parts cleaner, brake cleaner, or equivalent and a toothbrush and clean any dirt/green corrosion. Tighten up the pins with a small nail and coat with dielectric grease. Do the same cleaning/coating for the 3 pins on the MAF.

Have you pulled ECU codes? Is the CEL light on? Ohmed injectors? Fuel pump/FPCU been changed? Sound like a swarm of bees in your trunk? See if cleaning the MAF connector doesn't help and if not by your next post you'll get some help on checking the fuel system.

[elwesso]

Indeed, you shoudl think MAF but you also need to check your fuel pump before you continue.. Ive seen too many people ignore FP's and end up trying everything before they get to that.. Check your fuel pressure (do you hear a buzzing behind the rear seat) and go from there.. it could very well be MAF related but DEFINITLEY you want to make sure your fuel pump is not suspect.

[Haitian_King]

Hello all I recently purchased a 1992 Q45 with 86k , motor replaced at 33k, ran fine for a little while, now it loads up (cold start) at idle and blows black smoke, erractic idle, runs ok under power except some bucking at 60 mph. I cleaned the maf and intake. What should I try next. Thanks The drifter

Whoa. Nice buy. I got my 92 at 83k last January. Good luck with your Q!

[livebaitdrifter]

Thanks goody and othersIM going to go out and work on it now. I read a thread that talked about the acc valve needing to be cleaned or is it iac valve. WHat y aknow about that? This car was dealer maintained, I have a service history report from infinity.The damn thing is 8 pages long! It had alot of fuel system repairs in the past . No sounds coming from trunk. I can check fuel pressure, does anyone know what it should be?\Thanks to all who replied the drifter

[pabs324]

The pressure should be around 35PSI and it should increase to about 43PSI

[Q45tech]

All parameters are in FSM which requires a few weeks of study to memorize the concepts.

Totally useless to even contemplate trouble shooting before you know how everything works.

34 psi idle if plenum pressure is 19-20 " HG 43.4 psi at WOT and in between depending on accelerator pedal position/rpm.

[livebaitdrifter]

hey I checked the maf connector and the clip was pertuding into the inner part of the connector, i fixed that and tightened up on the pins a bit. I road tested it and it ran very good. No bucking and a nice smooth idle. I m guessing it had a bad connection because of the clip.But today is nice and dry , yesterday was horrrible rain. THanks to allThe Drifter