Car is missing under slight load and dying on me when coming to a stop

[rsiwicki]

Well and interesting thing happened to me on the way home tonight. While cruising at 35mph I noticed as I tried to accelerate that the car seem hesitant to increase rpms and all of a sudden I noticed it was running rough so I shut it off immediately thinking it was my 4.08 rearend and came to a stop. I checked out the rearend...all looks good so I crank it up again and a puff of smoke (not a lot but some) comes out the rear which has never happened before. I then notice the car idling a little ruff so I give it the gas while in park and it increases the rpm but like the car is misfiring or something. I only live another 2miles down the road and so I proceeded to drive the car home for which it made it home but running somewhat rough....no smoke or anything...just the rpms keep jumping up and down. As I make a U-turn to pull into the condo the I give it a WOT run to see how it does....and it works fine with rpms increasing smoothly and power all there for the 40 yard sprint and then pull into the condo and the car is idling perfectly at 650rpms or so not a hint anything is wrong. I park it and come back 30 minutes later to check all the fluids and everything once over and all appears in good order. I crank it up and it cranks just fine and then I rev it a couple of times lightly to about 3,000rpm and there is not one thing wrong with the car. I come back in....eat dinner and then go fill it up with gas as I have a little less than 1/4 tank figuring maybe bad gas. Fill it up at Cheveron...no problem....fires up and drives fine so I proceed to take it around the block a couple of times to see if it was just a fluke...well a minute later it started acting up again with it acting like it was missing as when I give the car the gas the car would not go...it woudl be hesitant for a second and then finally take-off. I was then cruising and all seemed okay...not the best but the car was not running rough like befre and came to a stop light and the car idling perfectly so now I am like WTF? so at the light I hammer the throttle and the car hesitates (i think) for a split second and then takes off all seems perfect and then when I come to a stop the car completely dies on me. I start it up and it is idling a little funny and then proceed back to the condo where it continued running rough the the tach jumping up and down by a couple 100rpms and when I pull into the condo before I get it into park it dies again. I am really frustrated at this point....call my buddy Wes who thinks it is a MAF and I say it is the alternator that is shot again as it is acting almost like it did when the alternator blew in December. Well I go back out there turn on the lights, AC, etc and start it watching to see if the headlights start dimming. Well the car again is idling perfectly and lights are not dimming. So I wiggle the crap out of the MAF and the car does nothing at all except for idling perfectly like nothing is wrong. I rev the car to about 2,500rpms a couple of times lightly while in park and the car is running perfect with not a hint that something is wrong. I put it in drive, reverse, etc. and the car does not even stall and is laughing at me the whole time behaving like it should. I don't understand what the problem could be causing it to die like this whe coming to a stop and now missing or running rough when under a slight load. Under WOT it seems to be totally okay.

The only other thing weird with the car's engine in the past 9 months is that I have had a very low idle....around 550rpm consistently but the car runs perfectly smoothe so I have never bothered to complain about it figuring it can't be hurting anything. Sometimes on a rare occasion I have noticed it the rpms dip below 500rpm but only for a split second and never has caused any idling or rough running issues.

So what gives....does anybody have an idea of what all of a sudden could have broke on the car???

I think my car is trying to get even with me for looking at newer cars these past two weeks and the one time in several days I did not go looking at a newer car the car acts up on me. I can guarrantee that the car would have been traded in tonight if I had gone test driving a newer car tonight and this had happened.

[DAEDALUS]

My guess would be MAF too.

[rsiwicki]

would maf work when car is idling perfectly and then not work when car is moving under load?

Is there anyway to test this MAF wiithout buying a new one first or swaping a used one?

also will any of the MAF off of ebay or here in our classifieds work?

[DAEDALUS]

I wouldn't rule it out. I have had similar here-today-gone-tomorrow symptoms that I'm sure were MAF related. It's funny now, I thought I fixed it by changing the air filter. Obviously I fixed it by jiggling the MAF wire while changing the air filter.Take a voltage reading off the sensed wire...run a probe all the way back so you can watch the voltage when the MAF acts up. Voltage isn't linear, but it should change as smoothly as your RPMs.

[maxnix]

Well I wonder about the IAC since the instability occurs at idle. But that would not explain the stumble unless teh valve was sticking and not closing promptly. It should not affect anything above 2500 rpm.

Fix the Q45 and invest the rest of the cash and she will quit acting up.

[GreenQ45a]

Sounds like the issue I had with my 93.

It turned out to be the Fuel Pump Sending Unit 130.00-178.00

I replaced my ENTIRE fuel system on my old 93 the last thing to get fixed was the FPSU...

Thats where the issues was.

Has your Q45 ever failed to start?It is also a hint of a bad FPSU..

Just my 2 cents.

[96Qowner]

The MAFs on ebay tend to be about $100, while car-parts.com generally has 'em for $75 or less. The one I got for $75 through car-parts works great, and I know Jesda got his there. I bet a couple NICO guys who are parting their cars have 'em, too. There are two different connectors ... 90-94 and 95-96.

I never had idle issues with my bad one. And mine never ran rough - just bucked/stumbled on mild acceleration with occasional coughs at cruise speed.

One of these days I'm gonna take my old one apart and see if the internal wiring is bad. I wonder about those internal solder connections.

zerothread?id=92632http://forums.nicocl ... er...age=2
Modified by 96Qowner at 12:13 PM 8/10/2005

[rsiwicki]

bucked/stumbled on mild acceleration with occasional coughs at cruise speed.

yeah...in summary that is what mine did last night. It did die twice when coming to a sudden stop and it has never done that before or had trouble starting.

With the great help of you all....it appears it was the MAF. I replaced it with a used one from a junkyard hear in Miami (the only MAF that I could find out of calling every single junkyard here in Miami) and that seems to be the solution. After installing the new MAF this afternoon and driving the car twice for 20 minutes I have yet to experience the same type of problems. I was afraid to drive it any further in fear of getting stuck on the highway and needing a lift so I wanted to replace it ASAP. As I can't afford to be without my wheels this week or next week for both work and personal issues so I needed this fixed asap.

btw...the cut-off date build date is 10/94 for one type of connector and then 11/94 and onwards for the other type of connector. I got lucky with my car being built 5/94 so the MAF should be a little more easy to come by.

[elwesso]

The beast is back to terrorizing the streets of Miami beach!!

[maxnix]

With the great help of you all....it appears it was the MAF. I replaced it with a used one from a junkyard hear in Miami ..... After installing the new MAF this afternoon and driving the car twice for 20 minutes I have yet to experience the same type of problems.

SNAP! That's right, you are using the dreaded death to the MAF sensor K&N filter! Forgot about that.