90 Q45 Start-Sputter-Stall ...help

[OneTimePoster]

I have had an intermittent problem (it is a problem for a day...then it goes away...then it comes back for 2 days...then it goes away). Car seems to start but within a second the idle drops from around 1000 to 800 then 500 then sputter then stall .... If I give it gas on the start or pump the car will rev up to say 3000 rpm and then just die (as though its run out of fuel). Sometimes the sputter will be right around a stall and then it idles back up around 1000, then goes to 800, etc., and sputter and die (maybe it'll get through 3 cycles of this and die). This goes on over and over and over again for as long as 10 minutes. Then for no apparent reason it starts fine, I can give it gas, the idle stays steady.

Um, help.

[Q451990]

How's the idle when you wiggle the MAF connector? Other things that come to mind are the CAS connection, fuel pump & it's controller - but the MAF is my best guess. Run a search for MAF or Mass Air Flow Meter for more info...

Heath

[Chally]

Have you checked the Fuel Flow & pressure?Could be a Pump, PUMP CONTROLLER or even both.

[OneTimePoster]

It feels exactly like I assume a fuel pump/controller problem except for the following: 1) pump is 6 mos old (oem) and 2) controller is 9 mos. old. No whining from rear etc. And it keeps starting (it gets fuel at the start, it just feels like the fuel comes in pulses, ie, fuel/starvation (maybe stall)/fuel.......I can give it gas (revs up to say 3000 rpm and then just dies....if I give it less gas up to say 2500 and then dies....time to stall seems to be the constant variable) if this makes any sense. Finally, the thing I can't figure out is the spontaneous remission that just seems to occur for no reason after 10 mins of starting and stalling.

[Chally]

Connect the Fuel gauge & make sure!It's no use trying to figure what might be wrong if you don't eliminate the most likely.Fuel pumps CAN fail, even though they are new. I've had one fail just last week, on a Toyota, it failed immediately I fitted it.BTW is the Controller brand new or 2nd hand?

[OneTimePoster]

fyi, foot on the pedal on ignition revs straight up to just below 4000 and immediate stall.

Wiggling the MAF connection seems to have no impact. I do not own a fuel gauge. The controller was new. Any other quick dx suggestions?

I am guessing this doesn't sound like any specific known common problem ..... in which case I assume I'm screwed and off to the dealer?

[Chally]

Any mechanic shop will have a Fuel Pressure Gauge. If they don't, RUN!

It sounds like the pump is working on Full speed, (startup priming & WOT), & not on the other 2 slower speeds. (It's a 3 speed controller)Get the pressure/flow checked first, as it will give an accurate result as to if you have fuel pressure when the engine stalls.

Without this test first, you may be wasting your time & money. BTW, it does the engine NO good giving it a good rev at startup. (time of most engine wear!)

[maxnix]

BTW, it does the engine NO good giving it a good rev at startup. (time of most engine wear!)

I was cringing so intensely, I was hoping that is not what he meant.

[OneTimePoster]

If that was the problem what would cause the pump to ultimately come to life after 10 mins?

Since you mention it, it does feel to me like the fuel system works briefly (1-2 sec) then sort of jumps down and then again, and then if it doesn't stall back up, down, down, up.....etc. If the pump switches this quickly (1-2) secs this may be a good guess.

Is there any way I would be able to fool the pump so that I can get it started more easily (so's I can drive it to a fuel gauge)?

[DAEDALUS]

If that was the problem what would cause the pump to ultimately come to life after 10 mins?

A bad electrical connection...maybe a failed solder joint in the controller?

Quote »Is there any way I would be able to fool the pump so that I can get it started more easily (so's I can drive it to a fuel gauge)? [/quote]

You can splice into the pump wiring and send it 12V direct from one of the hot wires in the neighborhood. It would take a bit of invstigation with a multimeter. If you're going to do that, you can troubleshoot it to see if that's the problem. Only run the pump on 12v for as long as is really necessary. It's not made to run at that voltage all the time.

[#RealRiceGSR#]

I need you to update your e-mail adress, it is invalid, you can do so by using the user cp button at the top of the page; thanks.

[texasoil]

I recently experienced similar situation, and found the plug connector to the fuel pump controller had loose female contacts(not enough tension) and would not make good connection with the controller male plugs. It caused a 'no-start' once which 'cleared' on third try and then a 'stop while driving' . Diagnosis consisted of listening to pump speed jump around while wiggling the plug.

(also tried on known good spare pump controller with same results, verifying loose female clips in the plug.)

Also replaced fuel pump while in there (it was getting noisy, especially on high --had 130K miles)