1994 Q45 idle surge

[t61bh6o]

122K miles, and first problem.... All of a sudden (3 weeks now), the idle sporatically bounces from 400 to 750 and sometimes drops below (had 1 stall out). Disconnected the MAF sensor, and checked the connection, but everthing seemed clean and tight. New air filter, new fuel filter, always synthetic oil every 3K since 65K used throtle body cleaner and Outlaw fuel injector cleaner... Did not fix problem. Didn't know if I should check for error codes on the ECU because the check engine light never came on. Can the ECU register problems even if the check engine light is not lit? Also overdrive is acting weird since problem started, sometimes downshifting or upshifting on the highway... all other gears fine... Getting sporatic sulfur smell as well. Can the MAF cause these symptoms? Heard about MAF grounding... is that something I should try... Haven't read any posts on how to do this on a 94 Q... Need help determining next steps any help would be greatly appreciated... Thanks in advance.

[qship96]

these were the first symptoms that I experienced that progressed to weird shift points of the transmission,turned out to be defective throttle position sensor-cleared everything up to perfect running condition.good luck!

[Q45tech]

Remember the check engine light only comes on from Hard codes and open or shorts or lack of voltage from a sensor.The 90-95 ecu is not smart enough to tell if signals are just wrong [at that specific rpm] as long as they are within a wide range.

[t61bh6o]

Thanks for the tip on the ECU. I will follow the instructions on other posts to check the codes since I shouldn't expect that the check engine light will indicate an error that the ECU picked up.

Since my first post, I started the car and at an idle grabbed a hold of the large intake hose running from the maf to the throttle body, and slowly put pressure on it up and down... the car stalled.

I pulled the hose off, and all attached hoses, inspected for any cracks and re-attached all hoses TIGHT... Took the car for a 20 minute ride, stop and go and high speed, and all seems OK no surging no stalling.

Will report back after the morning commute.

Thanks.... Any recommendation about grounding the MAF?

[maxnix]

No, but check the connection and use dielectric grease to retard corrosion.

[Q451990]

Wiggle the connector at idle and see if the idle speed changes... that's the best test for the MAF connector. You're definately on to something with that flexing of the hose - now you need to isolate the problem - which I suspect is either a faulty MAF or it's connection.

Heath

[t61bh6o]

Car ran great... smoother acceleration... & idled at 750 on point no surging, no problem with the overdrive either.

Just tightened all the hose connections to the maf / throttle body / and all hoses in between.

Thanks for the help.